+N1548 Committee Draft -- December 2, 2010 ISO/IEC 9899:201x @@ -40,11 +40,11 @@ relevant patent rights of which they are aware and to provide supporting documen Changes from the previous draft (N1256) are indicated by ''diff marks'' in the right margin: deleted text is marked with ''*'', new or changed text with '' ''. - - + +-Contents
+Contents
+
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are member of ISO or IEC participate in the @@ -573,20 +573,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. -
+
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. This International Standard was drafted in accordance with the fifth edition (2004). -
+
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75% of the national bodies casting a vote. -
+
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. -
+
This International Standard was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 22, Programming languages, their environments and system software interfaces. The Working Group responsible for this @@ -594,7 +594,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. std.org/JTC1/SC22/WG14/ containing additional information relevant to this standard such as a Rationale for many of the decisions made during its preparation and a log of Defect Reports and Responses. -
+
This third edition cancels and replaces the second edition, ISO/IEC 9899:1999, as corrected by ISO/IEC 9899:1999/Cor 1:2001, ISO/IEC 9899:1999/Cor 2:2004, and ISO/IEC 9899:1999/Cor 3:2007. Major changes from the previous edition include: @@ -608,7 +608,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
Major changes in the second edition included:
+
Annexes D, F, G, K, and L form a normative part of this standard; annexes A, B, C, E, H, *
I, J, the bibliography, and the index are for information only. In accordance with Part 2 of
the ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples
are also for information only.
-
+
-Introduction
-
+
With the introduction of new devices and extended character sets, new features may be added to this International Standard. Subclauses in the language and library clauses warn implementors and programmers of usages which, though valid in themselves, may conflict with future additions. -
+
Certain features are obsolescent, which means that they may be considered for withdrawal in future revisions of this International Standard. They are retained because of their widespread use, but their use in new implementations (for implementation features) or new programs (for language [6.11] or library features [7.30]) is discouraged. -
+
This International Standard is divided into four major subdivisions:
+
Examples are provided to illustrate possible forms of the constructions described. Footnotes are provided to emphasize consequences of the rules described in that subclause or elsewhere in this International Standard. References are used to refer to @@ -719,20 +719,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementors. Annexes provide additional information and summarize the information contained in this International Standard. A bibliography lists documents that were referred to during the preparation of the standard. -
+
The language clause (clause 6) is derived from ''The C Reference Manual''. -
+
The library clause (clause 7) is based on the 1984 /usr/group Standard. - - + +
+
This International Standard specifies the form and establishes the interpretation of programs written in the C programming language.1) It specifies
+
This International Standard does not specify
+
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. -
+
ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and symbols for use in the physical sciences and technology. -
+
ISO/IEC 646, Information technology -- ISO 7-bit coded character set for information interchange. -
+
ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1: Fundamental terms. -
+
ISO 4217, Codes for the representation of currencies and funds. -
+
ISO 8601, Data elements and interchange formats -- Information interchange -- Representation of dates and times. -
+
ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded Character Set (UCS). -
+
IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems (previously
designated IEC 559:1989).
-
+
-3. Terms, definitions, and symbols
-
+
For the purposes of this International Standard, the following definitions apply. Other
terms are defined where they appear in italic type or on the left side of a syntax rule.
Terms explicitly defined in this International Standard are not to be presumed to refer
@@ -803,184 +803,184 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Standard are to be interpreted according to ISO/IEC 2382-1. Mathematical symbols not
defined in this International Standard are to be interpreted according to ISO 31-11.
-3.1
-
- access +
+ access
<execution-time action> to read or modify the value of an object
-
+
NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used. -
+
NOTE 2 ''Modify'' includes the case where the new value being stored is the same as the previous value. -
+
NOTE 3 Expressions that are not evaluated do not access objects.
-3.2
-
- alignment +
+ alignment
requirement that objects of a particular type be located on storage boundaries with
addresses that are particular multiples of a byte address
-3.3
-
- argument +
+ argument
actual argument
actual parameter (deprecated)
expression in the comma-separated list bounded by the parentheses in a function call
expression, or a sequence of preprocessing tokens in the comma-separated list bounded
by the parentheses in a function-like macro invocation
-3.4
-
- behavior +
+ behavior
external appearance or action
-3.4.1
-
- implementation-defined behavior +
+ implementation-defined behavior
unspecified behavior where each implementation documents how the choice is made
-
+
EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
when a signed integer is shifted right.
-3.4.2
-
- locale-specific behavior +
+ locale-specific behavior
behavior that depends on local conventions of nationality, culture, and language that each
implementation documents
-
-
+ +
EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
characters other than the 26 lowercase Latin letters.
-3.4.3
-
- undefined behavior +
+ undefined behavior
behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
for which this International Standard imposes no requirements
-
+
NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable results, to behaving during translation or program execution in a documented manner characteristic of the environment (with or without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic message). -
+
EXAMPLE An example of undefined behavior is the behavior on integer overflow.
-3.4.4
-
- unspecified behavior +
+ unspecified behavior
use of an unspecified value, or other behavior where this International Standard provides
two or more possibilities and imposes no further requirements on which is chosen in any
instance
-
+
EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
evaluated.
-3.5
-
- bit +
+ bit
unit of data storage in the execution environment large enough to hold an object that may
have one of two values
-
+
NOTE It need not be possible to express the address of each individual bit of an object.
-3.6
-
- byte +
+ byte
addressable unit of data storage large enough to hold any member of the basic character
set of the execution environment
-
+
NOTE 1 It is possible to express the address of each individual byte of an object uniquely. -
+
NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
bit.
-3.7
-
- character +
+ character
<abstract> member of a set of elements used for the organization, control, or
representation of data
-3.7.1
-
- character +
+ character
single-byte character
<C> bit representation that fits in a byte
-
+
-3.7.2
-
- multibyte character +
+ multibyte character
sequence of one or more bytes representing a member of the extended character set of
either the source or the execution environment
-
+
NOTE The extended character set is a superset of the basic character set.
-3.7.3
-
- wide character +
+ wide character
bit representation that fits in an object of type wchar_t, capable of representing any
character in the current locale
-3.8
-
- constraint +
+ constraint
restriction, either syntactic or semantic, by which the exposition of language elements is
to be interpreted
-3.9
-
- correctly rounded result +
+ correctly rounded result
representation in the result format that is nearest in value, subject to the current rounding
mode, to what the result would be given unlimited range and precision
-3.10
-
- diagnostic message +
+ diagnostic message
message belonging to an implementation-defined subset of the implementation's message
output
-3.11
-
- forward reference +
+ forward reference
reference to a later subclause of this International Standard that contains additional
information relevant to this subclause
-3.12
-
- implementation +
+ implementation
particular set of software, running in a particular translation environment under particular
control options, that performs translation of programs for, and supports execution of
functions in, a particular execution environment
-3.13
-
- implementation limit +
+ implementation limit
restriction imposed upon programs by the implementation
-3.14
-
- memory location +
+ memory location
either an object of scalar type, or a maximal sequence of adjacent bit-fields all having
nonzero width
-
-
+ +
NOTE 1 Two threads of execution can update and access separate memory locations without interfering with each other. -
+
NOTE 2 A bit-field and an adjacent non-bit-field member are in separate memory locations. The same applies to two bit-fields, if one is declared inside a nested structure declaration and the other is not, or if the two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field member @@ -988,91 +988,92 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. members declared between them are also (non-zero-length) bit-fields, no matter what the sizes of those intervening bit-fields happen to be. -
+
EXAMPLE A structure declared as
struct {
char a;
int b:5, c:11, :0, d:8;
struct { int ee:8; } e;
- }
+ }
+
contains four separate memory locations: The member a, and bit-fields d and e.ee are each separate
memory locations, and can be modified concurrently without interfering with each other. The bit-fields b
and c together constitute the fourth memory location. The bit-fields b and c cannot be concurrently
modified, but b and a, for example, can be.
-- object +
+ object
region of data storage in the execution environment, the contents of which can represent
values
-
+
NOTE When referenced, an object may be interpreted as having a particular type; see 6.3.2.1.
-3.16
-
- parameter +
+ parameter
formal parameter
formal argument (deprecated)
object declared as part of a function declaration or definition that acquires a value on
entry to the function, or an identifier from the comma-separated list bounded by the
parentheses immediately following the macro name in a function-like macro definition
-3.17
-
- recommended practice +
+ recommended practice
specification that is strongly recommended as being in keeping with the intent of the
standard, but that may be impractical for some implementations
-3.18
-
- runtime-constraint +
+ runtime-constraint
requirement on a program when calling a library function
-
+
NOTE 1 Despite the similar terms, a runtime-constraint is not a kind of constraint as defined by 3.8, and need not be diagnosed at translation time. -
+
NOTE 2 Implementations that support the extensions in annex K are required to verify that the runtime-
constraints for a library function are not violated by the program; see K.3.1.4.
-
+
-3.19
-
- value +
+ value
precise meaning of the contents of an object when interpreted as having a specific type
-3.19.1
-
- implementation-defined value +
+ implementation-defined value
unspecified value where each implementation documents how the choice is made
-3.19.2
-
- indeterminate value +
+ indeterminate value
either an unspecified value or a trap representation
-3.19.3
-
- unspecified value +
+ unspecified value
valid value of the relevant type where this International Standard imposes no
requirements on which value is chosen in any instance
-
+
NOTE An unspecified value cannot be a trap representation.
-3.19.4
-
- trap representation +
+ trap representation
an object representation that need not represent a value of the object type
-3.19.5
-
- perform a trap +
+ perform a trap
interrupt execution of the program such that no further operations are performed
-
+
NOTE In this International Standard, when the word ''trap'' is not immediately followed by
''representation'', this is the intended usage.2)
@@ -1082,50 +1083,50 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
representation might perform a trap but is not required to (see 6.2.6.1).
-3.20
-
- [^ x^] +
+ [^ x^]
ceiling of x: the least integer greater than or equal to x
-
+
EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
-3.21
-
- [_ x_] +
+ [_ x_]
floor of x: the greatest integer less than or equal to x
-
+
EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
-
+
-4. Conformance
-
+
In this International Standard, ''shall'' is to be interpreted as a requirement on an implementation or on a program; conversely, ''shall not'' is to be interpreted as a prohibition. -
+
If a ''shall'' or ''shall not'' requirement that appears outside of a constraint or runtime- constraint is violated, the behavior is undefined. Undefined behavior is otherwise indicated in this International Standard by the words ''undefined behavior'' or by the omission of any explicit definition of behavior. There is no difference in emphasis among these three; they all describe ''behavior that is undefined''. -
+
A program that is correct in all other aspects, operating on correct data, containing unspecified behavior shall be a correct program and act in accordance with 5.1.2.3. -
+
The implementation shall not successfully translate a preprocessing translation unit containing a #error preprocessing directive unless it is part of a group skipped by conditional inclusion. -
+
A strictly conforming program shall use only those features of the language and library specified in this International Standard.3) It shall not produce output dependent on any unspecified, undefined, or implementation-defined behavior, and shall not exceed any minimum implementation limit. -
+
The two forms of conforming implementation are hosted and freestanding. A conforming hosted implementation shall accept any strictly conforming program. A conforming freestanding implementation shall accept any strictly conforming program that does not @@ -1138,10 +1139,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
A conforming program is one that is acceptable to a conforming implementation.5) -
+
An implementation shall be accompanied by a document that defines all implementation- defined and locale-specific characteristics and all extensions.
Forward references: conditional inclusion (6.10.1), error directive (6.10.5), @@ -1153,7 +1154,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
3) A strictly conforming program can use conditional features (see 6.10.8.3) provided the use is guarded @@ -1164,7 +1165,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. /* ... */ fesetround(FE_UPWARD); /* ... */ - #endif + #endif +
4) This implies that a conforming implementation reserves no identifiers other than those explicitly
@@ -1175,8 +1177,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
implementation.
-5. Environment
-
+
An implementation translates C source files and executes C programs in two data- processing-system environments, which will be called the translation environment and the execution environment in this International Standard. Their characteristics define and @@ -1185,12 +1187,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: In this clause, only a few of many possible forward references
have been noted.
-5.1 Conceptual models
+
+
A C program need not all be translated at the same time. The text of the program is kept in units called source files, (or preprocessing files) in this International Standard. A source file together with all the headers and source files included via the preprocessing @@ -1204,8 +1206,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: linkages of identifiers (6.2.2), external definitions (6.9),
preprocessing directives (6.10).
-5.1.1.2 Translation phases
-
+
The precedence among the syntax rules of translation is specified by the following phases.6)
6) Implementations shall behave as if these separate phases occur, even though many are typically folded
@@ -1269,18 +1271,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character.
-5.1.1.3 Diagnostics
-
+
A conforming implementation shall produce at least one diagnostic message (identified in an implementation-defined manner) if a preprocessing translation unit or translation unit contains a violation of any syntax rule or constraint, even if the behavior is also explicitly specified as undefined or implementation-defined. Diagnostic messages need not be produced in other circumstances.9) -
+
EXAMPLE An implementation shall issue a diagnostic for the translation unit:
char i;
- int i;
+ int i;
+
because in those cases where wording in this International Standard describes the behavior for a construct
as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
@@ -1291,8 +1294,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
valid program is still correctly translated. It may also successfully translate an invalid program.
-+
Two execution environments are defined: freestanding and hosted. In both cases, program startup occurs when a designated C function is called by the execution environment. All objects with static storage duration shall be initialized (set to their @@ -1301,39 +1304,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. environment.
Forward references: storage durations of objects (6.2.4), initialization (6.7.9).
-5.1.2.1 Freestanding environment
-
+
In a freestanding environment (in which C program execution may take place without any benefit of an operating system), the name and type of the function called at program startup are implementation-defined. Any library facilities available to a freestanding program, other than the minimal set required by clause 4, are implementation-defined. -
+
The effect of program termination in a freestanding environment is implementation-
defined.
-5.1.2.2 Hosted environment
-
+
A hosted environment need not be provided, but shall conform to the following
specifications if present.
-
+
-5.1.2.2.1 Program startup
-
+
The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int and with no parameters:
- int main(void) { /* ... */ }
+ int main(void) { /* ... */ }
+
or with two parameters (referred to here as argc and argv, though any names may be
used, as they are local to the function in which they are declared):
- int main(int argc, char *argv[]) { /* ... */ }
+ int main(int argc, char *argv[]) { /* ... */ }
+
or equivalent;10) or in some other implementation-defined manner.
-+
If they are declared, the parameters to the main function shall obey the following constraints:
+
In a hosted environment, a program may use all the functions, macros, type definitions,
and objects described in the library clause (clause 7).
-
+
-5.1.2.2.3 Program termination
-
+
If the return type of the main function is a type compatible with int, a return from the
initial call to the main function is equivalent to calling the exit function with the value
returned by the main function as its argument;11) reaching the } that terminates the
@@ -1385,17 +1390,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
will have ended in the former case, even where they would not have in the latter.
-5.1.2.3 Program execution
-
+
The semantic descriptions in this International Standard describe the behavior of an abstract machine in which issues of optimization are irrelevant. -
+
Accessing a volatile object, modifying an object, modifying a file, or calling a function that does any of those operations are all side effects,12) which are changes in the state of the execution environment. Evaluation of an expression in general includes both value computations and initiation of side effects. Value computation for an lvalue expression includes determining the identity of the designated object. -
+
Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations executed by a single thread, which induces a partial order among those evaluations. Given any two evaluations A and B, if A is sequenced before B, then the execution of A @@ -1406,20 +1411,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. between the evaluation of expressions A and B implies that every value computation and side effect associated with A is sequenced before every value computation and side effect associated with B. (A summary of the sequence points is given in annex C.) -
+
In the abstract machine, all expressions are evaluated as specified by the semantics. An actual implementation need not evaluate part of an expression if it can deduce that its value is not used and that no needed side effects are produced (including any caused by - + calling a function or accessing a volatile object). -
+
When the processing of the abstract machine is interrupted by receipt of a signal, the values of objects that are neither lock-free atomic objects nor of type volatile sig_atomic_t are unspecified, and the value of any object that is modified by the handler that is neither a lock-free atomic object nor of type volatile sig_atomic_t becomes undefined. -
+
The least requirements on a conforming implementation are:
+
What constitutes an interactive device is implementation-defined. -
+
More stringent correspondences between abstract and actual semantics may be defined by each implementation. -
+
EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual semantics: at every sequence point, the values of the actual objects would agree with those specified by the abstract semantics. The keyword volatile would then be redundant. -
+
Alternatively, an implementation might perform various optimizations within each translation unit, such that the actual semantics would agree with the abstract semantics only when making function calls across translation unit boundaries. In such an implementation, at the time of each function entry and function @@ -1453,29 +1458,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. would require explicit specification of volatile storage, as well as other implementation-defined restrictions. -
+
EXAMPLE 2 In executing the fragment
char c1, c2;
/* ... */
- c1 = c1 + c2;
+ c1 = c1 + c2;
+
the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
produce the same result, possibly omitting the promotions.
-
-+ +
EXAMPLE 3 Similarly, in the fragment
float f1, f2;
double d;
/* ... */
- f1 = f2 * d;
+ f1 = f2 * d;
+
the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
were replaced by the constant 2.0, which has type double).
-+
EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate semantics. Values are independent of whether they are represented in a register or in memory. For example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load @@ -1485,10 +1492,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. double d1, d2; float f; d1 = f = expression; - d2 = (float) expression; + d2 = (float) expression; + the values assigned to d1 and d2 are required to have been converted to float. -
+
EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in precision as well as range. The implementation cannot generally apply the mathematical associative rules for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of @@ -1501,37 +1509,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. x = (x * y) * z; // not equivalent to x *= y * z; z = (x - y) + y ; // not equivalent to z = x; z = x + x * y; // not equivalent to z = x * (1.0 + y); - y = x / 5.0; // not equivalent to y = x * 0.2; + y = x / 5.0; // not equivalent to y = x * 0.2; + -
+
EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
int a, b;
/* ... */
- a = a + 32760 + b + 5;
+ a = a + 32760 + b + 5;
+
the expression statement behaves exactly the same as
- a = (((a + 32760) + b) + 5);+ a = (((a + 32760) + b) + 5); + due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in which overflows produce an explicit trap and in which the range of values representable by an int is [-32768, +32767], the implementation cannot rewrite this expression as
- a = ((a + b) + 32765);+ a = ((a + b) + 32765); + since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap while the original expression would not; nor can the expression be rewritten either as - +
- a = ((a + 32765) + b);+ a = ((a + 32765) + b); + or
- a = (a + (b + 32765));+ a = (a + (b + 32765)); + since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine in which overflow silently generates some value and where positive and negative overflows cancel, the above expression statement can be rewritten by the implementation in any of the above ways because the same result will occur. -
+
EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the following fragment
@@ -1539,10 +1553,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int sum;
char *p;
/* ... */
- sum = sum * 10 - '0' + (*p++ = getchar());
+ sum = sum * 10 - '0' + (*p++ = getchar());
+
the expression statement is grouped as if it were written as
- sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));+ sum = (((sum * 10) - '0') + ((*(p++)) = (getchar()))); + but the actual increment of p can occur at any time between the previous sequence point and the next sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned value. @@ -1562,31 +1578,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. cannot interleave, but can be executed in any order. -
+
Under a hosted implementation, a program can have more than one thread of execution (or thread) running concurrently. The execution of each thread proceeds as defined by the remainder of this standard. The execution of the entire program consists of an execution of all of its threads.14) Under a freestanding implementation, it is implementation-defined whether a program can have more than one thread of execution. -
+
The value of an object visible to a thread T at a particular point is the initial value of the object, a value stored in the object by T , or a value stored in the object by another thread, according to the rules below. -
+
NOTE 1 In some cases, there may instead be undefined behavior. Much of this section is motivated by the desire to support atomic operations with explicit and detailed visibility constraints. However, it also implicitly supports a simpler view for more restricted programs. -
+
Two expression evaluations conflict if one of them modifies a memory location and the other one reads or modifies the same memory location. - -
+ +
The library defines a number of atomic operations (7.17) and operations on mutexes (7.25.4) that are specially identified as synchronization operations. These operations play a special role in making assignments in one thread visible to another. A synchronization @@ -1596,7 +1612,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. either an acquire fence, a release fence, or both an acquire and release fence. In addition, there are relaxed atomic operations, which are not synchronization operations, and atomic read-modify-write operations, which have special characteristics. -
+
NOTE 2 For example, a call that acquires a mutex will perform an acquire operation on the locations composing the mutex. Correspondingly, a call that releases the same mutex will perform a release operation on those same locations. Informally, performing a release operation on A forces prior side effects @@ -1604,43 +1620,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operation on A. We do not include relaxed atomic operations as synchronization operations although, like synchronization operations, they cannot contribute to data races. -
+
All modifications to a particular atomic object M occur in some particular total order, called the modification order of M. If A and B are modifications of an atomic object M, and A happens before B, then A shall precede B in the modification order of M, which is defined below. -
+
NOTE 3 This states that the modification orders must respect the ''happens before'' relation. -
+
NOTE 4 There is a separate order for each atomic object. There is no requirement that these can be combined into a single total order for all objects. In general this will be impossible since different threads may observe modifications to different variables in inconsistent orders. -
+
A release sequence on an atomic object M is a maximal contiguous sub-sequence of side effects in the modification order of M, where the first operation is a release and every subsequent operation either is performed by the same thread that performed the release or is an atomic read-modify-write operation. -
+
Certain library calls synchronize with other library calls performed by another thread. In particular, an atomic operation A that performs a release operation on an object M synchronizes with an atomic operation B that performs an acquire operation on M and reads a value written by any side effect in the release sequence headed by A. -
+
NOTE 5 Except in the specified cases, reading a later value does not necessarily ensure visibility as described below. Such a requirement would sometimes interfere with efficient implementation. -
+
NOTE 6 The specifications of the synchronization operations define when one reads the value written by another. For atomic variables, the definition is clear. All operations on a given mutex occur in a single total order. Each mutex acquisition ''reads the value written'' by the last mutex release. -
+
An evaluation A carries a dependency 15) to an evaluation B if: - +
+
An evaluation A is dependency-ordered before16) an evaluation B if:
+
An evaluation A inter-thread happens before an evaluation B if A synchronizes with B, A is dependency-ordered before B, or, for some evaluation X:
+
NOTE 7 The ''inter-thread happens before'' relation describes arbitrary concatenations of ''sequenced before'', ''synchronizes with'', and ''dependency-ordered before'' relationships, with two exceptions. The first exception is that a concatenation is not permitted to end with ''dependency-ordered before'' followed @@ -1687,14 +1703,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. transitively closed and (2) the ''happens before'' relation, defined below, provides for relationships consisting entirely of ''sequenced before''. -
+
An evaluation A happens before an evaluation B if A is sequenced before B or A inter- thread happens before B. - -
+ +
A visible side effect A on an object M with respect to a value computation B of M satisfies the conditions:
+
NOTE 8 If there is ambiguity about which side effect to a non-atomic object is visible, then there is a data race and the behavior is undefined. -
+
NOTE 9 This states that operations on ordinary variables are not visibly reordered. This is not actually detectable without data races, but it is necessary to ensure that data races, as defined here, and with suitable restrictions on the use of atomics, correspond to data races in a simple interleaved (sequentially consistent) execution. -
+
The visible sequence of side effects on an atomic object M, with respect to a value computation B of M, is a maximal contiguous sub-sequence of side effects in the modification order of M, where the first side effect is visible with respect to B, and for @@ -1725,23 +1741,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the value computed by A corresponds to the value stored by side effect X, then the value computed by B shall either equal the value computed by A, or be the value stored by side effect Y , where Y follows X in the modification order of M. -
+
NOTE 10 This effectively disallows compiler reordering of atomic operations to a single object, even if both operations are ''relaxed'' loads. By doing so, we effectively make the ''cache coherence'' guarantee provided by most hardware available to C atomic operations. -
+
NOTE 11 The visible sequence depends on the ''happens before'' relation, which in turn depends on the values observed by loads of atomics, which we are restricting here. The intended reading is that there must exist an association of atomic loads with modifications they observe that, together with suitably chosen modification orders and the ''happens before'' relation derived as described above, satisfy the resulting constraints as imposed here. -
+
The execution of a program contains a data race if it contains two conflicting actions in different threads, at least one of which is not atomic, and neither happens before the other. Any such data race results in undefined behavior. -
+
NOTE 12 It can be shown that programs that correctly use simple mutexes and memory_order_seq_cst operations to prevent all data races, and use no other synchronization operations, behave as though the operations executed by their constituent threads were simply interleaved, @@ -1750,8 +1766,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. race-free programs cannot observe most program transformations that do not change single-threaded program semantics. In fact, most single-threaded program transformations continue to be allowed, since any program that behaves differently as a result must contain undefined behavior. - -
+ +
NOTE 13 Compiler transformations that introduce assignments to a potentially shared memory location that would not be modified by the abstract machine are generally precluded by this standard, since such an assignment might overwrite another assignment by a different thread in cases in which an abstract machine @@ -1760,13 +1776,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. reordering of atomic loads in cases in which the atomics in question may alias, since this may violate the "visible sequence" rules. -
+
NOTE 14 Transformations that introduce a speculative read of a potentially shared memory location may not preserve the semantics of the program as defined in this standard, since they potentially introduce a data race. However, they are typically valid in the context of an optimizing compiler that targets a specific machine with well-defined semantics for data races. They would be invalid for a hypothetical machine that is not tolerant of races or provides hardware race detection. - +
14) The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of
@@ -1780,10 +1796,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
release/consume in place of release/acquire.
-5.2 Environmental considerations
+
+
Two sets of characters and their associated collating sequences shall be defined: the set in which source files are written (the source character set), and the set interpreted in the execution environment (the execution character set). Each set is further divided into a @@ -1791,29 +1807,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. locale-specific members (which are not members of the basic character set) called extended characters. The combined set is also called the extended character set. The values of the members of the execution character set are implementation-defined. -
+
In a character constant or string literal, members of the execution character set shall be represented by corresponding members of the source character set or by escape sequences consisting of the backslash \ followed by one or more characters. A byte with all bits set to 0, called the null character, shall exist in the basic execution character set; it is used to terminate a character string. -
+
Both the basic source and basic execution character sets shall have the following members: the 26 uppercase letters of the Latin alphabet
A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
+ N O P Q R S T U V W X Y Z
+
the 26 lowercase letters of the Latin alphabet
a b c d e f g h i j k l m
- n o p q r s t u v w x y z
+ n o p q r s t u v w x y z
+
the 10 decimal digits
- 0 1 2 3 4 5 6 7 8 9+ 0 1 2 3 4 5 6 7 8 9 + the following 29 graphic characters
! " # % & ' ( ) * + , - . / :
- ; < = > ? [ \ ] ^ _ { | } ~
+ ; < = > ? [ \ ] ^ _ { | } ~
+
the space character, and control characters representing horizontal tab, vertical tab, and
form feed. The representation of each member of the source and execution basic
character sets shall fit in a byte. In both the source and execution basic character sets, the
@@ -1824,42 +1844,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
control characters representing alert, backspace, carriage return, and new line. If any
other characters are encountered in a source file (except in an identifier, a character
constant, a string literal, a header name, a comment, or a preprocessing token that is never
-
+
converted to a token), the behavior is undefined.
-+
A letter is an uppercase letter or a lowercase letter as defined above; in this International Standard the term does not include other characters that are letters in other alphabets. -
+
The universal character name construct provides a way to name other characters.
Forward references: universal character names (6.4.3), character constants (6.4.4.4),
preprocessing directives (6.10), string literals (6.4.5), comments (6.4.9), string (7.1.1).
-5.2.1.1 Trigraph sequences
-
+
Before any other processing takes place, each occurrence of one of the following sequences of three characters (called trigraph sequences17)) is replaced with the corresponding single character.
??= # ??) ] ??! |
??( [ ??' ^ ??> }
- ??/ \ ??< { ??- ~
+ ??/ \ ??< { ??- ~
+
No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
above is not changed.
-+
EXAMPLE 1
- ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)+ ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??) + becomes
- #define arraycheck(a, b) a[b] || b[a]+ #define arraycheck(a, b) a[b] || b[a] + -
+
EXAMPLE 2 The following source line
- printf("Eh???/n");
+ printf("Eh???/n");
+
becomes (after replacement of the trigraph sequence ??/)
- printf("Eh?\n");
+ printf("Eh?\n");
+
+
The source character set may contain multibyte characters, used to represent members of the extended character set. The execution character set may also contain multibyte characters, which need not have the same encoding as for the source character set. For @@ -1879,7 +1904,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
For source files, the following shall hold:
+
The active position is that location on a display device where the next character output by the fputc function would appear. The intent of writing a printing character (as defined by the isprint function) to a display device is to display a graphic representation of @@ -1907,37 +1932,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. position on the current line. The direction of writing is locale-specific. If the active position is at the final position of a line (if there is one), the behavior of the display device is unspecified. -
+
Alphabetic escape sequences representing nongraphic characters in the execution character set are intended to produce actions on display devices as follows: \a (alert) Produces an audible or visible alert without changing the active position. \b (backspace) Moves the active position to the previous position on the current line. If
the active position is at the initial position of a line, the behavior of the display
- device is unspecified.
+ device is unspecified.
+
\f ( form feed) Moves the active position to the initial position at the start of the next
- logical page.+ logical page. + \n (new line) Moves the active position to the initial position of the next line. \r (carriage return) Moves the active position to the initial position of the current line. \t (horizontal tab) Moves the active position to the next horizontal tabulation position
on the current line. If the active position is at or past the last defined horizontal
- tabulation position, the behavior of the display device is unspecified.
+ tabulation position, the behavior of the display device is unspecified.
+
\v (vertical tab) Moves the active position to the initial position of the next vertical
-
-+
tabulation position. If the active position is at or past the last defined vertical
- tabulation position, the behavior of the display device is unspecified.
+ tabulation position, the behavior of the display device is unspecified.
+
+Each of these escape sequences shall produce a unique implementation-defined value which can be stored in a single char object. The external representations in a text file need not be identical to the internal representations, and are outside the scope of this International Standard.
Forward references: the isprint function (7.4.1.8), the fputc function (7.21.7.3).
-5.2.3 Signals and interrupts
-
+
Functions shall be implemented such that they may be interrupted at any time by a signal,
or may be called by a signal handler, or both, with no alteration to earlier, but still active,
invocations' control flow (after the interruption), function return values, or objects with
@@ -1945,15 +1974,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
image (the instructions that compose the executable representation of a function) on a
per-invocation basis.
-5.2.4 Environmental limits
-
+
Both the translation and execution environments constrain the implementation of
language translators and libraries. The following summarizes the language-related
environmental limits on a conforming implementation; the library-related limits are
discussed in clause 7.
-5.2.4.1 Translation limits
-
+
The implementation shall be able to translate and execute at least one program that contains at least one instance of every one of the following limits:18)
universal character name specifying a short identifier of 00010000 or more is
considered 10 characters, and each extended source character is considered the same
- number of characters as the corresponding universal character name, if any)19)
+ number of characters as the corresponding universal character name, if any)19)
+
19) See ''future language directions'' (6.11.3).
-5.2.4.2 Numerical limits
-
+
An implementation is required to document all the limits specified in this subclause, which are specified in the headers <limits.h> and <float.h>. Additional limits are specified in <stdint.h>.
Forward references: integer types <stdint.h> (7.20).
-5.2.4.2.1 Sizes of integer types
-
+
The values given below shall be replaced by constant expressions suitable for use in #if preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the following shall be replaced by expressions that have the same type as would an @@ -2015,7 +2045,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. promotions. Their implementation-defined values shall be equal or greater in magnitude - + (absolute value) to those shown, with the same sign.
+
If the value of an object of type char is treated as a signed integer when used in an expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of @@ -2070,27 +2100,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
20) See 6.2.5.
-5.2.4.2.2 Characteristics of floating types
-
+
The characteristics of floating types are defined in terms of a model that describes a representation of floating-point numbers and values that provide information about an implementation's floating-point arithmetic.21) The following parameters are used to define the model for each floating-point type: -
s sign ((+-)1)
b base or radix of exponent representation (an integer > 1)
e exponent (an integer between a minimum emin and a maximum emax )
p precision (the number of base-b digits in the significand)
- fk nonnegative integers less than b (the significand digits)
+ fk nonnegative integers less than b (the significand digits)
+
+A floating-point number (x) is defined by the following model:
p
x = sb e (Sum) f k b-k ,
k=1
- emin <= e <= emax
+ emin <= e <= emax
+
-+
In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be able to contain other kinds of floating-point numbers, such as subnormal floating-point numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0, @@ -2100,35 +2132,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. signaling NaN generally raises a floating-point exception when occurring as an - + arithmetic operand.22) -
+
An implementation may give zero and values that are not floating-point numbers (such as infinities and NaNs) a sign or may leave them unsigned. Wherever such values are unsigned, any requirement in this International Standard to retrieve the sign shall produce an unspecified sign, and any requirement to set the sign shall be ignored. -
+
The minimum range of representable values for a floating type is the most negative finite floating-point number representable in that type through the most positive finite floating- point number representable in that type. In addition, if negative infinity is representable in a type, the range of that type is extended to all negative real numbers; likewise, if positive infinity is representable in a type, the range of that type is extended to all positive real numbers. -
+
The accuracy of the floating-point operations (+, -, *, /) and of the library functions in <math.h> and <complex.h> that return floating-point results is implementation- defined, as is the accuracy of the conversion between floating-point internal representations and string representations performed by the library functions in <stdio.h>, <stdlib.h>, and <wchar.h>. The implementation may state that the accuracy is unknown. -
+
All integer values in the <float.h> header, except FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing directives; all floating values shall be constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX, and FLT_ROUNDS have separate names for all three floating-point types. The floating- point model representation is provided for all values except FLT_EVAL_METHOD and FLT_ROUNDS. -
+
The rounding mode for floating-point addition is characterized by the implementation- defined value of FLT_ROUNDS:23)
@@ -2136,13 +2168,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
0 toward zero
1 to nearest
2 toward positive infinity
- 3 toward negative infinity
+ 3 toward negative infinity
+
All other values for FLT_ROUNDS characterize implementation-defined rounding
behavior.
-
-+ +
Except for assignment and cast (which remove all extra range and precision), the values yielded by operators with floating operands and values subject to the usual arithmetic conversions and of floating constants are evaluated to a format whose range and precision @@ -2157,18 +2190,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operations and constants to the range and precision of the long double type; 2 evaluate all operations and constants to the range and precision of the - long double type. + long double type. + All other negative values for FLT_EVAL_METHOD characterize implementation-defined behavior. -
+
The presence or absence of subnormal numbers is characterized by the implementation- defined values of FLT_HAS_SUBNORM, DBL_HAS_SUBNORM, and LDBL_HAS_SUBNORM: -
-1 indeterminable25)
0 absent26) (type does not support subnormal numbers)
- 1 present (type does support subnormal numbers)
+ 1 present (type does support subnormal numbers)
+
+The values given in the following list shall be replaced by constant expressions with implementation-defined values that are greater or equal in magnitude (absolute value) to those shown, with the same sign: @@ -2179,7 +2214,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
{ p log10 b if b is a power of 10
{
- { [^1 + p log10 b^] otherwise
+ { [^1 + p log10 b^] otherwise
+
FLT_DECIMAL_DIG 6
DBL_DECIMAL_DIG 10
LDBL_DECIMAL_DIG 10
@@ -2200,7 +2236,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{ pmax log10 b if b is a power of 10
{
- { [^1 + pmax log10 b^] otherwise
+ { [^1 + pmax log10 b^] otherwise
+
DECIMAL_DIG 10
{ p log10 b if b is a power of 10
{
- { [_( p - 1) log10 b_] otherwise
+ { [_( p - 1) log10 b_] otherwise
+
FLT_DIG 6
DBL_DIG 10
LDBL_DIG 10
@@ -2217,11 +2255,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
FLT_MIN_EXP
DBL_MIN_EXP
LDBL_MIN_EXP
-
+
- [ ]+ [ ] + FLT_MIN_10_EXP -37 DBL_MIN_10_EXP -37 LDBL_MIN_10_EXP -37 @@ -2230,25 +2269,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
FLT_MAX_EXP
DBL_MAX_EXP
- LDBL_MAX_EXP
+ LDBL_MAX_EXP
+
FLT_MAX_10_EXP +37
DBL_MAX_10_EXP +37
- LDBL_MAX_10_EXP +37
+ LDBL_MAX_10_EXP +37
+
+
+The values given in the following list shall be replaced by constant expressions with implementation-defined values that are greater than or equal to those shown:
FLT_MAX 1E+37
DBL_MAX 1E+37
- LDBL_MAX 1E+37
+ LDBL_MAX 1E+37
+
+
+The values given in the following list shall be replaced by constant expressions with implementation-defined (positive) values that are less than or equal to those shown:
FLT_EPSILON 1E-5
DBL_EPSILON 1E-9
- LDBL_EPSILON 1E-9
+ LDBL_EPSILON 1E-9
+
FLT_MIN 1E-37
DBL_MIN 1E-37
- LDBL_MIN 1E-37
+ LDBL_MIN 1E-37
+
+
Conversion from (at least) double to decimal with DECIMAL_DIG digits and back should be the identity function. -
+
EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum requirements of this International Standard, and the appropriate values in a <float.h> header for type float: @@ -2281,7 +2325,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 6 x = s16e (Sum) f k 16-k , k=1 - -31 <= e <= +32 + -31 <= e <= +32 +
FLT_RADIX 16
@@ -2294,9 +2339,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
FLT_MIN_10_EXP -38
FLT_MAX_EXP +32
FLT_MAX 3.40282347E+38F
- FLT_MAX_10_EXP +38
+ FLT_MAX_10_EXP +38
+
-+
EXAMPLE 2 The following describes floating-point representations that also meet the requirements for single-precision and double-precision numbers in IEC 60559,28) and the appropriate values in a <float.h> header for types float and double: @@ -2304,13 +2350,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 24 x f = s2e (Sum) f k 2-k , k=1 - -125 <= e <= +128 + -125 <= e <= +128 +
53
x d = s2e (Sum) f k 2-k ,
k=1
- -1021 <= e <= +1024
+ -1021 <= e <= +1024
+
FLT_RADIX 2
@@ -2318,10 +2366,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
FLT_MANT_DIG 24
FLT_EPSILON 1.19209290E-07F // decimal constant
FLT_EPSILON 0X1P-23F // hex constant
- FLT_DECIMAL_DIG 9
+ FLT_DECIMAL_DIG 9
+
-
+
FLT_DIG 6
FLT_MIN_EXP -125
@@ -2350,7 +2399,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
DBL_MAX_EXP +1024
DBL_MAX 1.7976931348623157E+308 // decimal constant
DBL_MAX 0X1.fffffffffffffP1023 // hex constant
- DBL_MAX_10_EXP +308
+ DBL_MAX_10_EXP +308
+
If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
precision), then DECIMAL_DIG would be 21.
@@ -2359,7 +2409,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
<complex.h> (7.3), extended multibyte and wide character utilities <wchar.h>
(7.28), floating-point environment <fenv.h> (7.6), general utilities <stdlib.h>
(7.22), input/output <stdio.h> (7.21), mathematics <math.h> (7.12).
-
+
21) The floating-point model is intended to clarify the description of each floating-point characteristic and
@@ -2390,28 +2440,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
limits are one less than shown here.
-6. Language
+
+
In the syntax notation used in this clause, syntactic categories (nonterminals) are indicated by italic type, and literal words and character set members (terminals) by bold type. A colon (:) following a nonterminal introduces its definition. Alternative definitions are listed on separate lines, except when prefaced by the words ''one of''. An optional symbol is indicated by the subscript ''opt'', so that
- { expressionopt }
+ { expressionopt }
+
indicates an optional expression enclosed in braces.
-+
When syntactic categories are referred to in the main text, they are not italicized and words are separated by spaces instead of hyphens. -
+
A summary of the language syntax is given in annex A.
-6.2 Concepts
+
+
An identifier can denote an object; a function; a tag or a member of a structure, union, or enumeration; a typedef name; a label name; a macro name; or a macro parameter. The same identifier can denote different entities at different points in the program. A member @@ -2419,17 +2470,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. parameters are not considered further here, because prior to the semantic phase of program translation any occurrences of macro names in the source file are replaced by the preprocessing token sequences that constitute their macro definitions. -
+
For each different entity that an identifier designates, the identifier is visible (i.e., can be used) only within a region of program text called its scope. Different entities designated by the same identifier either have different scopes, or are in different name spaces. There are four kinds of scopes: function, file, block, and function prototype. (A function prototype is a declaration of a function that declares the types of its parameters.) -
+
A label name is the only kind of identifier that has function scope. It can be used (in a goto statement) anywhere in the function in which it appears, and is declared implicitly by its syntactic appearance (followed by a : and a statement). -
+
Every other identifier has scope determined by the placement of its declaration (in a declarator or type specifier). If the declarator or type specifier that declares the identifier appears outside of any block or list of parameters, the identifier has file scope, which @@ -2437,7 +2488,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. declares the identifier appears inside a block or within the list of parameter declarations in a function definition, the identifier has block scope, which terminates at the end of the associated block. If the declarator or type specifier that declares the identifier appears - + within the list of parameter declarations in a function prototype (not part of a function definition), the identifier has function prototype scope, which terminates at the end of the function declarator. If an identifier designates two different entities in the same name @@ -2445,20 +2496,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. strictly before the scope of the other entity (the outer scope). Within the inner scope, the identifier designates the entity declared in the inner scope; the entity declared in the outer scope is hidden (and not visible) within the inner scope. -
+
Unless explicitly stated otherwise, where this International Standard uses the term ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the entity in the relevant name space whose declaration is visible at the point the identifier occurs. -
+
Two identifiers have the same scope if and only if their scopes terminate at the same point. -
+
Structure, union, and enumeration tags have scope that begins just after the appearance of the tag in a type specifier that declares the tag. Each enumeration constant has scope that begins just after the appearance of its defining enumerator in an enumerator list. Any other identifier has scope that begins just after the completion of its declarator. -
+
As a special case, a type name (which is not a declaration of an identifier) is considered to
have a scope that begins just after the place within the type name where the omitted
identifier would appear were it not omitted.
@@ -2466,40 +2517,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(6.9.1), identifiers (6.4.2), macro replacement (6.10.3), name spaces of identifiers (6.2.3),
source file inclusion (6.10.2), statements (6.8).
-6.2.2 Linkages of identifiers
-
+
An identifier declared in different scopes or in the same scope more than once can be made to refer to the same object or function by a process called linkage.29) There are three kinds of linkage: external, internal, and none. -
+
In the set of translation units and libraries that constitutes an entire program, each declaration of a particular identifier with external linkage denotes the same object or function. Within one translation unit, each declaration of an identifier with internal linkage denotes the same object or function. Each declaration of an identifier with no linkage denotes a unique entity. -
+
If the declaration of a file scope identifier for an object or a function contains the storage- class specifier static, the identifier has internal linkage.30) - -
+ +
For an identifier declared with the storage-class specifier extern in a scope in which a prior declaration of that identifier is visible,31) if the prior declaration specifies internal or external linkage, the linkage of the identifier at the later declaration is the same as the linkage specified at the prior declaration. If no prior declaration is visible, or if the prior declaration specifies no linkage, then the identifier has external linkage. -
+
If the declaration of an identifier for a function has no storage-class specifier, its linkage is determined exactly as if it were declared with the storage-class specifier extern. If the declaration of an identifier for an object has file scope and no storage-class specifier, its linkage is external. -
+
The following identifiers have no linkage: an identifier declared to be anything other than an object or a function; an identifier declared to be a function parameter; a block scope identifier for an object declared without the storage-class specifier extern. -
+
If, within a translation unit, the same identifier appears with both internal and external linkage, the behavior is undefined.
Forward references: declarations (6.7), expressions (6.5), external definitions (6.9), @@ -2514,8 +2565,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
31) As specified in 6.2.1, the later declaration might hide the prior declaration.
-6.2.3 Name spaces of identifiers
-
+
If more than one declaration of a particular identifier is visible at any point in a translation unit, the syntactic context disambiguates uses that refer to different entities. Thus, there are separate name spaces for various categories of identifiers, as follows: @@ -2533,29 +2584,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. structure and union specifiers (6.7.2.1), structure and union members (6.5.2.3), tags (6.7.2.3), the goto statement (6.8.6.1). - +
32) There is only one name space for tags even though three are possible.
-6.2.4 Storage durations of objects
-
+
An object has a storage duration that determines its lifetime. There are four storage durations: static, thread, automatic, and allocated. Allocated storage is described in 7.22.3. -
+
The lifetime of an object is the portion of program execution during which storage is guaranteed to be reserved for it. An object exists, has a constant address,33) and retains its last-stored value throughout its lifetime.34) If an object is referred to outside of its lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when the object it points to (or just past) reaches the end of its lifetime. -
+
An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class specifier static, has static storage duration. Its lifetime is the entire execution of the program and its stored value is initialized only once, prior to program startup. -
+
An object whose identifier is declared with the storage-class specifier _Thread_local has thread storage duration. Its lifetime is the entire execution of the thread for which it is created, and its stored value is initialized when the thread is started. There is a distinct @@ -2563,12 +2614,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. associated with the thread evaluating the expression. The result of attempting to indirectly access an object with thread storage duration from a thread other than the one with which the object is associated is implementation-defined. -
+
An object whose identifier is declared with no linkage and without the storage-class specifier static has automatic storage duration, as do some compound literals. The result of attempting to indirectly access an object with automatic storage duration from a thread other than the one with which the object is associated is implementation-defined. -
+
For such an object that does not have a variable length array type, its lifetime extends from entry into the block with which it is associated until execution of that block ends in any way. (Entering an enclosed block or calling a function suspends, but does not end, @@ -2580,13 +2631,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
For such an object that does have a variable length array type, its lifetime extends from the declaration of the object until execution of the program leaves the scope of the declaration.35) If the scope is entered recursively, a new instance of the object is created each time. The initial value of the object is indeterminate. -
+
A non-lvalue expression with structure or union type, where the structure or union contains a member with array type (including, recursively, members of all contained structures and unions) refers to an object with automatic storage duration and temporary @@ -2610,8 +2661,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
36) The address of such an object is taken implicitly when an array member is accessed.
-6.2.5 Types
-
+
The meaning of a value stored in an object or returned by a function is determined by the type of the expression used to access it. (An identifier declared to be an object is the simplest such expression; the type is specified in the declaration of the identifier.) Types @@ -2619,28 +2670,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. that describe functions). At various points within a translation unit an object type may be incomplete (lacking sufficient information to determine the size of objects of that type) or complete (having sufficient information).37) -
+
An object declared as type _Bool is large enough to store the values 0 and 1. -
+
An object declared as type char is large enough to store any member of the basic execution character set. If a member of the basic execution character set is stored in a char object, its value is guaranteed to be nonnegative. If any other character is stored in a char object, the resulting value is implementation-defined but shall be within the range of values that can be represented in that type. -
+
There are five standard signed integer types, designated as signed char, short int, int, long int, and long long int. (These and other types may be designated in several additional ways, as described in 6.7.2.) There may also be implementation-defined extended signed integer types.38) The standard and extended signed integer types are collectively called signed integer types.39) - -
+ +
An object declared as type signed char occupies the same amount of storage as a ''plain'' char object. A ''plain'' int object has the natural size suggested by the architecture of the execution environment (large enough to contain any value in the range INT_MIN to INT_MAX as defined in the header <limits.h>). -
+
For each of the signed integer types, there is a corresponding (but different) unsigned integer type (designated with the keyword unsigned) that uses the same amount of storage (including sign information) and has the same alignment requirements. The type @@ -2649,71 +2700,71 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. correspond to the extended signed integer types are the extended unsigned integer types. The standard and extended unsigned integer types are collectively called unsigned integer types.40) -
+
The standard signed integer types and standard unsigned integer types are collectively called the standard integer types, the extended signed integer types and extended unsigned integer types are collectively called the extended integer types. -
+
For any two integer types with the same signedness and different integer conversion rank (see 6.3.1.1), the range of values of the type with smaller integer conversion rank is a subrange of the values of the other type. -
+
The range of nonnegative values of a signed integer type is a subrange of the corresponding unsigned integer type, and the representation of the same value in each type is the same.41) A computation involving unsigned operands can never overflow, because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting type. -
+
There are three real floating types, designated as float, double, and long double.42) The set of values of the type float is a subset of the set of values of the type double; the set of values of the type double is a subset of the set of values of the type long double. - -
+ +
There are three complex types, designated as float _Complex, double _Complex, and long double _Complex.43) (Complex types are a conditional feature that implementations need not support; see 6.10.8.3.) The real floating and complex types are collectively called the floating types. -
+
For each floating type there is a corresponding real type, which is always a real floating type. For real floating types, it is the same type. For complex types, it is the type given by deleting the keyword _Complex from the type name. -
+
Each complex type has the same representation and alignment requirements as an array type containing exactly two elements of the corresponding real type; the first element is equal to the real part, and the second element to the imaginary part, of the complex number. -
+
The type char, the signed and unsigned integer types, and the floating types are collectively called the basic types. The basic types are complete object types. Even if the implementation defines two or more basic types to have the same representation, they are nevertheless different types.44) -
+
The three types char, signed char, and unsigned char are collectively called the character types. The implementation shall define char to have the same range, representation, and behavior as either signed char or unsigned char.45) -
+
An enumeration comprises a set of named integer constant values. Each distinct enumeration constitutes a different enumerated type. -
+
The type char, the signed and unsigned integer types, and the enumerated types are collectively called integer types. The integer and real floating types are collectively called real types. -
+
Integer and floating types are collectively called arithmetic types. Each arithmetic type belongs to one type domain: the real type domain comprises the real types, the complex type domain comprises the complex types. -
+
The void type comprises an empty set of values; it is an incomplete object type that cannot be completed. - -
+ +
Any number of derived types can be constructed from the object and function types, as follows:
+
Arithmetic types and pointer types are collectively called scalar types. Array and structure types are collectively called aggregate types.46) -
+
An array type of unknown size is an incomplete type. It is completed, for an identifier of that type, by specifying the size in a later declaration (with internal or external linkage). A structure or union type of unknown content (as described in 6.7.2.3) is an incomplete - + type. It is completed, for all declarations of that type, by declaring the same structure or union tag with its defining content later in the same scope. -
+
A type has known constant size if the type is not incomplete and is not a variable length array type. -
+
Array, function, and pointer types are collectively called derived declarator types. A declarator type derivation from a type T is the construction of a derived declarator type from T by the application of an array-type, a function-type, or a pointer-type derivation to T. -
+
A type is characterized by its type category, which is either the outermost derivation of a derived type (as noted above in the construction of derived types), or the type itself if the type consists of no derived types. -
+
Any type so far mentioned is an unqualified type. Each unqualified type has several qualified versions of its type,47) corresponding to the combinations of one, two, or all three of the const, volatile, and restrict qualifiers. The qualified or unqualified versions of a type are distinct types that belong to the same type category and have the same representation and alignment requirements.48) A derived type is not qualified by the qualifiers (if any) of the type from which it is derived. -
+
Further, there is the _Atomic qualifier. The presence of the _Atomic qualifier designates an atomic type. The size, representation, and alignment of an atomic type need not be the same as those of the corresponding unqualified type. Therefore, this @@ -2784,24 +2835,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. atomic version of a type is permitted along with the other qualified versions of a type. The phrase ''qualified or unqualified type'', without specific mention of atomic, does not include the atomic types. -
+
A pointer to void shall have the same representation and alignment requirements as a - pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of + pointer to a character type.48) Similarly, pointers to qualified or unqualified versions of compatible types shall have the same representation and alignment requirements. All pointers to structure types shall have the same representation and alignment requirements as each other. All pointers to union types shall have the same representation and alignment requirements as each other. Pointers to other types need not have the same representation or alignment requirements. -
+
EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is pointer, not a floating type. The const-qualified version of this type is designated as ''float * const'' whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const- - + qualified float'' and is a pointer to a qualified type. -
+
EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
function returning struct tag''. The array has length five and the function has a single parameter of type
float. Its type category is array.
@@ -2846,19 +2897,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
arguments to functions, return values from functions, and members of unions.
-6.2.6 Representations of types
+
+
The representations of all types are unspecified except as stated in this subclause. -
+
Except for bit-fields, objects are composed of contiguous sequences of one or more bytes, the number, order, and encoding of which are either explicitly specified or implementation-defined. -
+
Values stored in unsigned bit-fields and objects of type unsigned char shall be represented using a pure binary notation.49) -
+
Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT bits, where n is the size of an object of that type, in bytes. The value may be copied into an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is @@ -2867,33 +2918,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. bits the bit-field comprises in the addressable storage unit holding it. Two values (other than NaNs) with the same object representation compare equal, but values that compare equal may have different object representations. -
+
Certain object representations need not represent a value of the object type. If the stored value of an object has such a representation and is read by an lvalue expression that does not have character type, the behavior is undefined. If such a representation is produced by a side effect that modifies all or any part of the object by an lvalue expression that does not have character type, the behavior is undefined.50) Such a representation is called a trap representation. -
+
When a value is stored in an object of structure or union type, including in a member object, the bytes of the object representation that correspond to any padding bytes take unspecified values.51) The value of a structure or union object is never a trap - + representation, even though the value of a member of the structure or union object may be a trap representation. -
+
When a value is stored in a member of an object of union type, the bytes of the object representation that do not correspond to that member but do correspond to other members take unspecified values. -
+
Where an operator is applied to a value that has more than one object representation, which object representation is used shall not affect the value of the result.52) Where a value is stored in an object using a type that has more than one object representation for that value, it is unspecified which representation is used, but a trap representation shall not be generated. -
+
Loads and stores of objects with atomic types are done with memory_order_seq_cst semantics.
Forward references: declarations (6.7), expressions (6.5), lvalues, arrays, and function @@ -2908,7 +2959,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
CHAR_BIT
- - 1.
+ - 1.
+
50) Thus, an automatic variable can be initialized to a trap representation without causing undefined
behavior, but the value of the variable cannot be used until a proper value is stored in it.
@@ -2922,15 +2974,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
on values of type T may distinguish between them.
-6.2.6.2 Integer types
-
+
For unsigned integer types other than unsigned char, the bits of the object representation shall be divided into two groups: value bits and padding bits (there need not be any of the latter). If there are N value bits, each bit shall represent a different power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of representing values from 0 to 2 N - 1 using a pure binary representation; this shall be known as the value representation. The values of any padding bits are unspecified.53) -
+
For signed integer types, the bits of the object representation shall be divided into three groups: value bits, padding bits, and the sign bit. There need not be any padding bits; signed char shall not have any padding bits. There shall be exactly one sign bit. @@ -2938,7 +2990,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. representation of the corresponding unsigned type (if there are M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit is zero, it shall not affect - + the resulting value. If the sign bit is one, the value shall be modified in one of the following ways:
+
If the implementation supports negative zeros, they shall be generated only by:
+
If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<, and >> operators with operands that would produce such a value is undefined. -
+
The values of any padding bits are unspecified.54) A valid (non-trap) object representation of a signed integer type where the sign bit is zero is a valid object representation of the corresponding unsigned type, and shall represent the same value. For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type. -
+
The precision of an integer type is the number of bits it uses to represent values, excluding any sign and padding bits. The width of an integer type is the same but including any sign bit; thus for unsigned integer types the two values are the same, while @@ -2979,7 +3031,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
53) Some combinations of padding bits might generate trap representations, for example, if one padding
@@ -2995,8 +3047,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
bits.
-6.2.7 Compatible type and composite type
-
+
Two types have compatible type if their types are the same. Additional rules for determining whether two types are compatible are described in 6.7.2 for type specifiers, in 6.7.3 for type qualifiers, and in 6.7.6 for declarators.55) Moreover, two structure, @@ -3011,10 +3063,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. with the same name. For two structures, corresponding members shall be declared in the same order. For two structures or unions, corresponding bit-fields shall have the same widths. For two enumerations, corresponding members shall have the same values. -
+
All declarations that refer to the same object or function shall have compatible type; otherwise, the behavior is undefined. -
+
A composite type can be constructed from two types that are compatible; it is a type that is compatible with both of the two types and satisfies the following conditions:
+
For an identifier with internal or external linkage declared in a scope in which a prior declaration of that identifier is visible,56) if the prior declaration specifies internal or external linkage, the type of the identifier at the later declaration becomes the composite type.
Forward references: array declarators (6.7.6.2). -
+
EXAMPLE Given the following two file scope declarations:
int f(int (*)(), double (*)[3]);
- int f(int (*)(char *), double (*)[]);
+ int f(int (*)(char *), double (*)[]);
+
The resulting composite type for the function is:
- int f(int (*)(char *), double (*)[3]);+ int f(int (*)(char *), double (*)[3]); +
56) As specified in 6.2.1, the later declaration might hide the prior declaration.
-6.2.8 Alignment of objects
-
+
Complete object types have alignment requirements which place restrictions on the addresses at which objects of that type may be allocated. An alignment is an implementation-defined integer value representing the number of bytes between successive addresses at which a given object can be allocated. An object type imposes an alignment requirement on every object of that type: stricter alignment can be requested using the _Alignas keyword. -
+
A fundamental alignment is represented by an alignment less than or equal to the greatest alignment supported by the implementation in all contexts, which is equal to alignof(max_align_t). -
+
An extended alignment is represented by an alignment greater than alignof(max_align_t). It is implementation-defined whether any extended alignments are supported and the contexts in which they are supported. A type having an extended alignment requirement is an over-aligned type.57) -
+
Alignments are represented as values of the type size_t. Valid alignments include only those values returned by an alignof expression for fundamental types, plus an additional implementation-defined set of values, which may be empty. Every valid alignment value shall be a nonnegative integral power of two. - -
+ +
Alignments have an order from weaker to stronger or stricter alignments. Stricter alignments have larger alignment values. An address that satisfies an alignment requirement also satisfies any weaker valid alignment requirement. -
+
The alignment requirement of a complete type can be queried using an alignof expression. The types char, signed char, and unsigned char shall have the weakest alignment requirement. -
+
Comparing alignments is meaningful and provides the obvious results:
+
Several operators convert operand values from one type to another automatically. This subclause specifies the result required from such an implicit conversion, as well as those that result from a cast operation (an explicit conversion). The list in 6.3.1.8 summarizes the conversions performed by most ordinary operators; it is supplemented as required by the discussion of each operator in 6.5. -
+
Conversion of an operand value to a compatible type causes no change to the value or the representation.
Forward references: cast operators (6.5.4).
-6.3.1 Arithmetic operands
+
+
Every integer type has an integer conversion rank defined as follows:
+
The following may be used in an expression wherever an int or unsigned int may be used: - +
+
The integer promotions preserve value including sign. As discussed earlier, whether a ''plain'' char is treated as signed is implementation-defined.
Forward references: enumeration specifiers (6.7.2.2), structure and union specifiers
@@ -3177,8 +3231,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
shift operators, as specified by their respective subclauses.
-6.3.1.2 Boolean type
-
+
When any scalar value is converted to _Bool, the result is 0 if the value compares equal to 0; otherwise, the result is 1.59) @@ -3186,15 +3240,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
59) NaNs do not compare equal to 0 and thus convert to 1.
-6.3.1.3 Signed and unsigned integers
-
+
When a value with integer type is converted to another integer type other than _Bool, if the value can be represented by the new type, it is unchanged. -
+
Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or subtracting one more than the maximum value that can be represented in the new type until the value is in the range of the new type.60) -
+
Otherwise, the new type is signed and the value cannot be represented in it; either the result is implementation-defined or an implementation-defined signal is raised. @@ -3202,15 +3256,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
60) The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
-6.3.1.4 Real floating and integer
-
+
When a finite value of real floating type is converted to an integer type other than _Bool, the fractional part is discarded (i.e., the value is truncated toward zero). If the value of the integral part cannot be represented by the integer type, the behavior is undefined.61) - -
+ +
When a value of integer type is converted to a real floating type, if the value being
converted can be represented exactly in the new type, it is unchanged. If the value being
converted is in the range of values that can be represented but cannot be represented
@@ -3226,8 +3280,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
range of portable real floating values is (-1, Utype_MAX+1).
-6.3.1.5 Real floating types
-
+
When a value of real floating type is converted to a real floating type, if the value being
converted can be represented exactly in the new type, it is unchanged. If the value being
converted is in the range of values that can be represented but cannot be represented
@@ -3237,23 +3291,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
conversions (6.3.1.8, 6.8.6.4) may be represented in greater precision and range than that
required by the new type.
-6.3.1.6 Complex types
-
+
When a value of complex type is converted to another complex type, both the real and
imaginary parts follow the conversion rules for the corresponding real types.
-6.3.1.7 Real and complex
-
+
When a value of real type is converted to a complex type, the real part of the complex result value is determined by the rules of conversion to the corresponding real type and the imaginary part of the complex result value is a positive zero or an unsigned zero. -
+
When a value of complex type is converted to a real type, the imaginary part of the
complex value is discarded and the value of the real part is converted according to the
conversion rules for the corresponding real type.
-6.3.1.8 Usual arithmetic conversions
-
+
Many operators that expect operands of arithmetic type cause conversions and yield result types in a similar way. The purpose is to determine a common real type for the operands and result. For the specified operands, each operand is converted, without change of type @@ -3261,8 +3315,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. explicitly stated otherwise, the common real type is also the corresponding real type of the result, whose type domain is the type domain of the operands if they are the same, and complex otherwise. This pattern is called the usual arithmetic conversions: - -
+
First, if the corresponding real type of either operand is long double, the other
operand is converted, without change of type domain, to a type whose
@@ -3288,7 +3341,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the operand with unsigned integer type is converted to the type of the
operand with signed integer type.
Otherwise, both operands are converted to the unsigned integer type
- corresponding to the type of the operand with signed integer type.
+ corresponding to the type of the operand with signed integer type.
+
+The values of floating operands and of the results of floating expressions may be represented in greater precision and range than that required by the type; the types are not changed thereby.63) @@ -3296,7 +3351,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
62) For example, addition of a double _Complex and a float entails just the conversion of the @@ -3305,10 +3360,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
63) The cast and assignment operators are still required to remove extra range and precision.
-6.3.2 Other operands
+
+
An lvalue is an expression (with an object type other than void) that potentially designates an object;64) if an lvalue does not designate an object when it is evaluated, the behavior is undefined. When an object is said to have a particular type, the type is @@ -3317,7 +3372,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. qualified type, and if it is a structure or union, does not have any member (including, recursively, any member or element of all contained aggregates or unions) with a const- qualified type. -
+
Except when it is the operand of the sizeof operator, the unary & operator, the ++ operator, the -- operator, or the left operand of the . operator or an assignment operator, an lvalue that does not have array type is converted to the value stored in the designated @@ -3330,19 +3385,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. storage class (never had its address taken), and that object is uninitialized (not declared with an initializer and no assignment to it has been performed prior to use), the behavior is undefined. -
+
Except when it is the operand of the sizeof operator or the unary & operator, or is a string literal used to initialize an array, an expression that has type ''array of type'' is converted to an expression with type ''pointer to type'' that points to the initial element of the array object and is not an lvalue. If the array object has register storage class, the behavior is undefined. -
+
A function designator is an expression that has function type. Except when it is the operand of the sizeof operator65) or the unary & operator, a function designator with type ''function returning type'' is converted to an expression that has type ''pointer to - + function returning type''.
Forward references: address and indirection operators (6.5.3.2), assignment operators
(6.5.16), common definitions <stddef.h> (7.19), initialization (6.7.9), postfix
@@ -3361,36 +3416,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
designator and violates the constraint in 6.5.3.4.
-6.3.2.2 void
-
+
The (nonexistent) value of a void expression (an expression that has type void) shall not
be used in any way, and implicit or explicit conversions (except to void) shall not be
applied to such an expression. If an expression of any other type is evaluated as a void
expression, its value or designator is discarded. (A void expression is evaluated for its
side effects.)
-6.3.2.3 Pointers
-
+
A pointer to void may be converted to or from a pointer to any object type. A pointer to any object type may be converted to a pointer to void and back again; the result shall compare equal to the original pointer. -
+
For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to the q-qualified version of the type; the values stored in the original and converted pointers shall compare equal. -
+
An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant.66) If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function. -
+
Conversion of a null pointer to another pointer type yields a null pointer of that type. Any two null pointers shall compare equal. -
+
An integer may be converted to any pointer type. Except as previously specified, the result is implementation-defined, might not be correctly aligned, might not point to an entity of the referenced type, and might be a trap representation.67) -
+
Any pointer type may be converted to an integer type. Except as previously specified, the result is implementation-defined. If the result cannot be represented in the integer type, the behavior is undefined. The result need not be in the range of values of any integer @@ -3399,15 +3454,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
A pointer to an object type may be converted to a pointer to a different object type. If the resulting pointer is not correctly aligned68) for the referenced type, the behavior is undefined. Otherwise, when converted back again, the result shall compare equal to the original pointer. When a pointer to an object is converted to a pointer to a character type, the result points to the lowest addressed byte of the object. Successive increments of the result, up to the size of the object, yield pointers to the remaining bytes of the object. -
+
A pointer to a function of one type may be converted to a pointer to a function of another type and back again; the result shall compare equal to the original pointer. If a converted pointer is used to call a function whose type is not compatible with the referenced type, @@ -3418,7 +3473,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
66) The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.19.
@@ -3431,9 +3486,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
correctly aligned for a pointer to type C.
-6.4 Lexical elements
+
+
token:
keyword
@@ -3448,13 +3503,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character-constant
string-literal
punctuator
- each non-white-space character that cannot be one of the above
+ each non-white-space character that cannot be one of the above
+
+
Each preprocessing token that is converted to a token shall have the lexical form of a keyword, an identifier, a constant, a string literal, or a punctuator.
+
A token is the minimal lexical element of the language in translation phases 7 and 8. The categories of tokens are: keywords, identifiers, constants, string literals, and punctuators. A preprocessing token is the minimal lexical element of the language in translation @@ -3472,8 +3528,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
If the input stream has been parsed into preprocessing tokens up to a given character, the next preprocessing token is the longest sequence of characters that could constitute a preprocessing token. There is one exception to this rule: header name preprocessing @@ -3481,14 +3537,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation-defined locations within #pragma directives. In such contexts, a sequence of characters that could be either a header name or a string literal is recognized as the former. -
+
EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or not E is a macro name. -
+
EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
increment operators, even though the parse x ++ + ++ y might yield a correct expression.
@@ -3503,9 +3559,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
occur in source files.
-6.4.1 Keywords
+
+
keyword: one of
alignof goto union
@@ -3522,23 +3578,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
enum static _Noreturn
extern struct _Static_assert
float switch _Thread_local
- for typedef
+ for typedef
+
+
The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for - + specifying imaginary types.70)
70) One possible specification for imaginary types appears in annex G.
-6.4.2 Identifiers
+
+
identifier:
identifier-nondigit
@@ -3554,14 +3611,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
digit: one of
- 0 1 2 3 4 5 6 7 8 9
+ 0 1 2 3 4 5 6 7 8 9
+
+
An identifier is a sequence of nondigit characters (including the underscore _, the lowercase and uppercase Latin letters, and other characters) and digits, which designates one or more entities as described in 6.2.1. Lowercase and uppercase letters are distinct. There is no specific limit on the maximum length of an identifier. -
+
Each universal character name in an identifier shall designate a character whose encoding in ISO/IEC 10646 falls into one of the ranges specified in D.1.71) The initial character shall not be a universal character name designating a character whose encoding falls into @@ -3571,19 +3629,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
When preprocessing tokens are converted to tokens during translation phase 7, if a preprocessing token could be converted to either a keyword or an identifier, it is converted to a keyword. - Implementation limits -
+
As discussed in 5.2.4.1, an implementation may limit the number of significant initial characters in an identifier; the limit for an external name (an identifier that has external linkage) may be more restrictive than that for an internal name (a macro name or an identifier that does not have external linkage). The number of significant characters in an identifier is implementation-defined. -
+
Any identifiers that differ in a significant character are different identifiers. If two identifiers differ only in nonsignificant characters, the behavior is undefined.
Forward references: universal character names (6.4.3), macro replacement (6.10.3).
@@ -3595,19 +3653,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Extended characters may produce a long external identifier.
-6.4.2.2 Predefined identifiers
+
+
The identifier __func__ shall be implicitly declared by the translator as if, immediately following the opening brace of each function definition, the declaration
- static const char __func__[] = "function-name";+ static const char __func__[] = "function-name"; + appeared, where function-name is the name of the lexically-enclosing function.72) -
+
This name is encoded as if the implicit declaration had been written in the source character set and then translated into the execution character set as indicated in translation phase 5. -
+
EXAMPLE Consider the code fragment:
#include <stdio.h>
@@ -3615,44 +3674,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{
printf("%s\n", __func__);
/* ... */
- }
+ }
+
Each time the function is called, it will print to the standard output stream:
- myfunc+ myfunc +
Forward references: function definitions (6.9.1). - +
72) Since the name __func__ is reserved for any use by the implementation (7.1.3), if any other
identifier is explicitly declared using the name __func__, the behavior is undefined.
-6.4.3 Universal character names
+
+
universal-character-name:
\u hex-quad
\U hex-quad hex-quad
hex-quad:
hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
+ hexadecimal-digit hexadecimal-digit
+
+
A universal character name shall not specify a character whose short identifier is less than 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through DFFF inclusive.73)
+
Universal character names may be used in identifiers, character constants, and string literals to designate characters that are not in the basic character set.
+
The universal character name \Unnnnnnnn designates the character whose eight-digit short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.74) Similarly, the universal character name \unnnn designates the character whose four-digit short identifier is nnnn @@ -3661,7 +3723,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
73) The disallowed characters are the characters in the basic character set and the code positions reserved @@ -3672,32 +3734,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
74) Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
-6.4.4 Constants
+
+
constant:
integer-constant
floating-constant
enumeration-constant
- character-constant
+ character-constant
+
+
Each constant shall have a type and the value of a constant shall be in the range of representable values for its type.
+
Each constant has a type, determined by its form and value, as detailed later.
-6.4.4.1 Integer constants
+
- +
+
integer-constant:
- decimal-constant integer-suffixopt
- octal-constant integer-suffixopt
- hexadecimal-constant integer-suffixopt
+ decimal-constant integer-suffixopt
+ octal-constant integer-suffixopt
+ hexadecimal-constant integer-suffixopt
decimal-constant:
nonzero-digit
decimal-constant digit
@@ -3718,36 +3781,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
a b c d e f
A B C D E F
integer-suffix:
- unsigned-suffix long-suffixopt
+ unsigned-suffix long-suffixopt
unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
+ long-suffix unsigned-suffixopt
+ long-long-suffix unsigned-suffixopt
unsigned-suffix: one of
u U
long-suffix: one of
l L
long-long-suffix: one of
- ll LL
+ ll LL
+
+
An integer constant begins with a digit, but has no period or exponent part. It may have a prefix that specifies its base and a suffix that specifies its type. -
+
A decimal constant begins with a nonzero digit and consists of a sequence of decimal digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed by a sequence of the decimal digits and the letters a (or A) through f (or F) with values 10 through 15 respectively.
+
The value of a decimal constant is computed base 10; that of an octal constant, base 8; that of a hexadecimal constant, base 16. The lexically first digit is the most significant. -
+
The type of an integer constant is the first of the corresponding list in which its value can be represented. - +
- Octal or Hexadecimal+ Octal or Hexadecimal + Suffix Decimal Constant Constant none int int @@ -3756,29 +3821,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. long long int long int unsigned long int long long int - unsigned long long int + unsigned long long int + u or U unsigned int unsigned int
unsigned long int unsigned long int
- unsigned long long int unsigned long long int
+ unsigned long long int unsigned long long int
+
l or L long int long int
long long int unsigned long int
long long int
- unsigned long long int
+ unsigned long long int
+
Both u or U unsigned long int unsigned long int
and l or L unsigned long long int unsigned long long int
ll or LL long long int long long int
- unsigned long long int+ unsigned long long int + Both u or U unsigned long long int unsigned long long int and ll or LL -
+
If an integer constant cannot be represented by any type in its list, it may have an
extended integer type, if the extended integer type can represent its value. If all of the
types in the list for the constant are signed, the extended integer type shall be signed. If
@@ -3786,49 +3855,50 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
unsigned. If the list contains both signed and unsigned types, the extended integer type
may be signed or unsigned. If an integer constant cannot be represented by any type in
its list and has no extended integer type, then the integer constant has no type.
-
+
-6.4.4.2 Floating constants
+
- +
+
floating-constant:
decimal-floating-constant
hexadecimal-floating-constant
decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt
- digit-sequence exponent-part floating-suffixopt
+ fractional-constant exponent-partopt floating-suffixopt
+ digit-sequence exponent-part floating-suffixopt
hexadecimal-floating-constant:
hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
+ binary-exponent-part floating-suffixopt
hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
+ binary-exponent-part floating-suffixopt
fractional-constant:
- digit-sequenceopt . digit-sequence
+ digit-sequenceopt . digit-sequence
digit-sequence .
exponent-part:
- e signopt digit-sequence
- E signopt digit-sequence
+ e signopt digit-sequence
+ E signopt digit-sequence
sign: one of
+ -
digit-sequence:
digit
digit-sequence digit
hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
+ hexadecimal-digit-sequenceopt .
hexadecimal-digit-sequence
hexadecimal-digit-sequence .
binary-exponent-part:
- p signopt digit-sequence
- P signopt digit-sequence
+ p signopt digit-sequence
+ P signopt digit-sequence
hexadecimal-digit-sequence:
hexadecimal-digit
hexadecimal-digit-sequence hexadecimal-digit
floating-suffix: one of
- f l F L
+ f l F L
+
+
A floating constant has a significand part that may be followed by an exponent part and a suffix that specifies its type. The components of the significand part may include a digit sequence representing the whole-number part, followed by a period (.), followed by a @@ -3837,7 +3907,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Either the whole-number part or the fraction part has to be present; for decimal floating constants, either the period or the exponent part has to be present.
+
The significand part is interpreted as a (decimal or hexadecimal) rational number; the digit sequence in the exponent part is interpreted as a decimal integer. For decimal floating constants, the exponent indicates the power of 10 by which the significand part is @@ -3848,26 +3918,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. adjacent to the nearest representable value, chosen in an implementation-defined manner. For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is correctly rounded. -
+
An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has type float. If suffixed by the letter l or L, it has type long double. -
+
Floating constants are converted to internal format as if at translation-time. The conversion of a floating constant shall not raise an exceptional condition or a floating- point exception at execution time. All floating constants of the same source form75) shall convert to the same internal format with the same value. - Recommended practice -
+
The implementation should produce a diagnostic message if a hexadecimal constant cannot be represented exactly in its evaluation format; the implementation should then proceed with the translation of the program. -
+
The translation-time conversion of floating constants should match the execution-time conversion of character strings by library functions, such as strtod, given matching inputs suitable for both conversions, the same result format, and default execution-time rounding.76) - +
75) 1.23, 1.230, 123e-2, 123e-02, and 1.23L are all different source forms and thus need not
@@ -3877,21 +3947,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
floating constants (see 7.22.1.3).
-6.4.4.3 Enumeration constants
+
+
enumeration-constant:
- identifier
+ identifier
+
+
An identifier declared as an enumeration constant has type int.
Forward references: enumeration specifiers (6.7.2.2).
-6.4.4.4 Character constants
+
- +
+
character-constant:
' c-char-sequence '
@@ -3919,51 +3990,53 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
\ octal-digit octal-digit octal-digit
hexadecimal-escape-sequence:
\x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
+ hexadecimal-escape-sequence hexadecimal-digit
+
+
An integer character constant is a sequence of one or more multibyte characters enclosed in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the letter L, u, or U. With a few exceptions detailed later, the elements of the sequence are any members of the source character set; they are mapped in an implementation-defined manner to members of the execution character set. -
+
The single-quote ', the double-quote ", the question-mark ?, the backslash \, and arbitrary integer values are representable according to the following table of escape sequences: -
single quote ' \'
double quote " \"
question mark ? \?
backslash \ \\
octal character \octal digits
- hexadecimal character \x hexadecimal digits
+ hexadecimal character \x hexadecimal digits
+
+The double-quote " and question-mark ? are representable either by themselves or by the escape sequences \" and \?, respectively, but the single-quote ' and the backslash \ shall be represented, respectively, by the escape sequences \' and \\. -
+
The octal digits that follow the backslash in an octal escape sequence are taken to be part of the construction of a single character for an integer character constant or of a single wide character for a wide character constant. The numerical value of the octal integer so formed specifies the value of the desired character or wide character. -
+
The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape sequence are taken to be part of the construction of a single character for an integer character constant or of a single wide character for a wide character constant. The numerical value of the hexadecimal integer so formed specifies the value of the desired character or wide character. -
+
Each octal or hexadecimal escape sequence is the longest sequence of characters that can constitute the escape sequence. -
+
In addition, characters not in the basic character set are representable by universal character names and certain nongraphic characters are representable by escape sequences consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t, and \v.77) - +
+
The value of an octal or hexadecimal escape sequence shall be in the range of representable values for the corresponding type:
@@ -3971,9 +4044,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
none unsigned char
L the unsigned type corresponding to wchar_t
u char16_t
- U char32_t
+ U char32_t
+
+
An integer character constant has type int. The value of an integer character constant containing a single character that maps to a single-byte execution character is the numerical value of the representation of the mapped character interpreted as an integer. @@ -3983,7 +4057,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. a single character or escape sequence, its value is the one that results when an object with type char whose value is that of the single character or escape sequence is converted to type int. -
+
A wide character constant prefixed by the letter L has type wchar_t, an integer type defined in the <stddef.h> header; a wide character constant prefixed by the letter u or U has type char16_t or char32_t, respectively, unsigned integer types defined in the @@ -3996,10 +4070,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. members of the extended execution character set, or containing a multibyte character or escape sequence not represented in the extended execution character set, is implementation-defined. -
+
EXAMPLE 1 The construction '\0' is commonly used to represent the null character. -
+
EXAMPLE 2 Consider implementations that use two's complement representation for integers and eight bits for objects that have type char. In an implementation in which type char has the same range of values as signed char, the integer character constant '\xFF' has the value -1; if type char has the @@ -4008,8 +4082,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123' specifies an integer character constant containing only one character, since a hexadecimal escape sequence is terminated only by a non-hexadecimal character. To specify an integer character constant containing the @@ -4017,7 +4091,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. escape sequence is terminated after three octal digits. (The value of this two-character integer character constant is implementation-defined.) -
+
EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
L'\1234' specifies the implementation-defined value that results from the combination of the values
0123 and '4'.
@@ -4030,12 +4104,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the result is not a token and a diagnostic is required. See ''future language directions'' (6.11.4).
-6.4.5 String literals
+
+
string-literal:
- encoding-prefixopt " s-char-sequenceopt "
+ encoding-prefixopt " s-char-sequenceopt "
encoding-prefix:
u8
u
@@ -4047,25 +4121,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
s-char:
any member of the source character set except
the double-quote ", backslash \, or new-line character
- escape-sequence
+ escape-sequence
+
+
A sequence of adjacent string literal tokens shall not include both a wide string literal and a UTF-8 string literal.
+
A character string literal is a sequence of zero or more multibyte characters enclosed in double-quotes, as in "xyz". A UTF-8 string literal is the same, except prefixed by u8. A wide string literal is the same, except prefixed by the letter L, u, or U. -
+
The same considerations apply to each element of the sequence in a string literal as if it were in an integer character constant (for a character or UTF-8 string literal) or a wide character constant (for a wide string literal), except that the single-quote ' is representable either by itself or by the escape sequence \', but the double-quote " shall - + be represented by the escape sequence \".
+
In translation phase 6, the multibyte character sequences specified by any sequence of adjacent character and identically-prefixed string literal tokens are concatenated into a single multibyte character sequence. If any of the tokens has an encoding prefix, the @@ -4073,7 +4148,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. is treated as a character string literal. Whether differently-prefixed wide string literal tokens can be concatenated and, if so, the treatment of the resulting multibyte character sequence are implementation-defined. -
+
In translation phase 7, a byte or code of value zero is appended to each multibyte character sequence that results from a string literal or literals.78) The multibyte character sequence is then used to initialize an array of static storage duration and length just @@ -4091,41 +4166,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. its type, with an implementation-defined current locale. The value of a string literal containing a multibyte character or escape sequence not represented in the execution character set is implementation-defined. -
+
It is unspecified whether these arrays are distinct provided their elements have the appropriate values. If the program attempts to modify such an array, the behavior is undefined. -
+
EXAMPLE 1 This pair of adjacent character string literals
- "\x12" "3"+ "\x12" "3" + produces a single character string literal containing the two characters whose values are '\x12' and '3', because escape sequences are converted into single members of the execution character set just prior to adjacent string literal concatenation. -
+
EXAMPLE 2 Each of the sequences of adjacent string literal tokens - +
"a" "b" L"c"
"a" L"b" "c"
L"a" "b" L"c"
- L"a" L"b" L"c"
+ L"a" L"b" L"c"
+
is equivalent to the string literal
- L"abc"+ L"abc" + Likewise, each of the sequences
"a" "b" u"c"
"a" u"b" "c"
u"a" "b" u"c"
- u"a" u"b" u"c"
+ u"a" u"b" u"c"
+
is equivalent to
- u"abc"+ u"abc" +
Forward references: common definitions <stddef.h> (7.19), the mbstowcs
function (7.22.8.1), Unicode utilities <uchar.h> (7.27).
@@ -4135,9 +4215,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
\0 escape sequence.
-6.4.6 Punctuators
+
+
punctuator: one of
[ ] ( ) { } . ->
@@ -4146,22 +4226,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
? : ; ...
= *= /= %= += -= <<= >>= &= ^= |=
, # ##
- <: :> <% %> %: %:%:
+ <: :> <% %> %: %:%:
+
+
A punctuator is a symbol that has independent syntactic and semantic significance. Depending on context, it may specify an operation to be performed (which in turn may yield a value or a function designator, produce a side effect, or some combination thereof) in which case it is known as an operator (other forms of operator also exist in some contexts). An operand is an entity on which an operator acts. - -
+ +
In all aspects of the language, the six tokens79)
- <: :> <% %> %: %:%:+ <: :> <% %> %: %:%: + behave, respectively, the same as the six tokens
- [ ] { } # ##
+ [ ] { } # ##
+
except for their spelling.80)
Forward references: expressions (6.5), declarations (6.7), preprocessing directives
(6.10), statements (6.8).
@@ -4173,9 +4256,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
interchanged.
-6.4.7 Header names
+
+
header-name:
< h-char-sequence >
@@ -4191,34 +4274,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
q-char-sequence q-char
q-char:
any member of the source character set except
- the new-line character and "
+ the new-line character and "
+
+
The sequences in both forms of header names are mapped in an implementation-defined manner to headers or external source file names as specified in 6.10.2. -
+
If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters, the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the - + sequence between the " delimiters, the behavior is undefined.81) Header name preprocessing tokens are recognized only within #include preprocessing directives and in implementation-defined locations within #pragma directives.82) -
+
EXAMPLE The following sequence of characters:
0x3<1/a.h>1e2
#include <1/a.h>
- #define const.member@$
+ #define const.member@$
+
forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
by a { on the left and a } on the right).
{0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
{#}{include} {<1/a.h>}
- {#}{define} {const}{.}{member}{@}{$}
+ {#}{define} {const}{.}{member}{@}{$}
+
Forward references: source file inclusion (6.10.2). @@ -4228,9 +4314,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
82) For an example of a header name preprocessing token used in a #pragma directive, see 6.10.9.
-6.4.8 Preprocessing numbers
+
+
pp-number:
digit
@@ -4241,34 +4327,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pp-number E sign
pp-number p sign
pp-number P sign
- pp-number .
+ pp-number .
+
+
A preprocessing number begins with a digit optionally preceded by a period (.) and may be followed by valid identifier characters and the character sequences e+, e-, E+, E-, p+, p-, P+, or P-. -
+
Preprocessing number tokens lexically include all floating and integer constant tokens.
+
A preprocessing number does not have type or a value; it acquires both after a successful
conversion (as part of translation phase 7) to a floating constant token or an integer
constant token.
-
+
-6.4.9 Comments
-
+
Except within a character constant, a string literal, or a comment, the characters /* introduce a comment. The contents of such a comment are examined only to identify multibyte characters and to find the characters */ that terminate it.83) -
+
Except within a character constant, a string literal, or a comment, the characters // introduce a comment that includes all multibyte characters up to, but not including, the next new-line character. The contents of such a comment are examined only to identify multibyte characters and to find the terminating new-line character. -
+
EXAMPLE
"a//b" // four-character string literal
@@ -4283,46 +4370,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
glue(/,/) k(); // syntax error, not comment
/*//*/ l(); // equivalent to l();
m = n//**/o
- + p; // equivalent to m = n + p;
+ + p; // equivalent to m = n + p;
+
-
+
83) Thus, /* ... */ comments do not nest.
-6.5 Expressions
-
+
An expression is a sequence of operators and operands that specifies computation of a value, or that designates an object or a function, or that generates side effects, or that performs a combination thereof. The value computations of the operands of an operator are sequenced before the value computation of the result of the operator. -
+
If a side effect on a scalar object is unsequenced relative to either a different side effect on the same scalar object or a value computation using the value of the same scalar object, the behavior is undefined. If there are multiple allowable orderings of the subexpressions of an expression, the behavior is undefined if such an unsequenced side effect occurs in any of the orderings.84) -
+
The grouping of operators and operands is indicated by the syntax.85) Except as specified later, side effects and value computations of subexpressions are unsequenced.86) * -
+
Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |, collectively described as bitwise operators) are required to have operands that have integer type. These operators yield values that depend on the internal representations of integers, and have implementation-defined and undefined aspects for signed types. -
+
If an exceptional condition occurs during the evaluation of an expression (that is, if the result is not mathematically defined or not in the range of representable values for its type), the behavior is undefined. - -
+ +
The effective type of an object for an access to its stored value is the declared type of the object, if any.87) If a value is stored into an object having no declared type through an lvalue having a type that is not a character type, then the type of the lvalue becomes the @@ -4333,7 +4421,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. value is the effective type of the object from which the value is copied, if it has one. For all other accesses to an object having no declared type, the effective type of the object is simply the type of the lvalue used for the access. -
+
An object shall have its stored value accessed only by an lvalue expression that has one of the following types:88)
+
A floating expression may be contracted, that is, evaluated as though it were a single operation, thereby omitting rounding errors implied by the source code and the expression evaluation method.89) The FP_CONTRACT pragma in <math.h> provides a @@ -4356,19 +4444,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: the FP_CONTRACT pragma (7.12.2), copying functions (7.23.2). - +
84) This paragraph renders undefined statement expressions such as
i = ++i + 1;
- a[i++] = i;
+ a[i++] = i;
+
while allowing
i = i + 1;
- a[i] = i;
+ a[i] = i;
+
85) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
@@ -4399,27 +4489,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
documented.
-6.5.1 Primary expressions
+
+
primary-expression:
identifier
constant
string-literal
( expression )
- generic-selection
+ generic-selection
+
+
An identifier is a primary expression, provided it has been declared as designating an object (in which case it is an lvalue) or a function (in which case it is a function designator).91) -
+
A constant is a primary expression. Its type depends on its form and value, as detailed in 6.4.4. -
+
A string literal is a primary expression. It is an lvalue with type as detailed in 6.4.5. -
+
A parenthesized expression is a primary expression. Its type and value are identical to those of the unparenthesized expression. It is an lvalue, a function designator, or a void expression if the unparenthesized expression is, respectively, an lvalue, a function @@ -4430,9 +4521,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
91) Thus, an undeclared identifier is a violation of the syntax.
-6.5.1.1 Generic selection
+
+
generic-selection:
_Generic ( assignment-expression , generic-assoc-list )
@@ -4441,49 +4532,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
generic-assoc-list , generic-association
generic-association:
type-name : assignment-expression
- default : assignment-expression
+ default : assignment-expression
+
+
A generic selection shall have no more than one default generic association. The type name in a generic association shall specify a complete object type other than a variably - + modified type. No two generic associations in the same generic selection shall specify compatible types. The controlling expression of a generic selection shall have type compatible with at most one of the types named in its generic association list. If a generic selection has no default generic association, its controlling expression shall have type compatible with exactly one of the types named in its generic association list.
+
The controlling expression of a generic selection is not evaluated. If a generic selection has a generic association with a type name that is compatible with the type of the controlling expression, then the result expression of the generic selection is the expression in that generic association. Otherwise, the result expression of the generic selection is the expression in the default generic association. None of the expressions from any other generic association of the generic selection is evaluated. -
+
The type and value of a generic selection are identical to those of its result expression. It is an lvalue, a function designator, or a void expression if its result expression is, respectively, an lvalue, a function designator, or a void expression. -
+
EXAMPLE The cbrt type-generic macro could be implemented as follows:
#define cbrt(X) _Generic((X), \
long double: cbrtl, \
default: cbrt, \
float: cbrtf \
- )(X)
+ )(X)
+
-- +
+
postfix-expression:
primary-expression
postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
+ postfix-expression ( argument-expression-listopt )
postfix-expression . identifier
postfix-expression -> identifier
postfix-expression ++
@@ -4492,22 +4585,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
( type-name ) { initializer-list , }
argument-expression-list:
assignment-expression
- argument-expression-list , assignment-expression
+ argument-expression-list , assignment-expression
+
-+
One of the expressions shall have type ''pointer to complete object type'', the other expression shall have integer type, and the result has type ''type''.
+
A postfix expression followed by an expression in square brackets [] is a subscripted designation of an element of an array object. The definition of the subscript operator [] is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th element of E1 (counting from zero). -
+
Successive subscript operators designate an element of a multidimensional array object. If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with @@ -4515,10 +4609,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implicitly as a result of subscripting, the result is the referenced (n - 1)-dimensional array, which itself is converted into a pointer if used as other than an lvalue. It follows from this that arrays are stored in row-major order (last subscript varies fastest). -
+
EXAMPLE Consider the array object defined by the declaration
- int x[3][5];+ int x[3][5]; + Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually @@ -4530,33 +4625,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: additive operators (6.5.6), address and indirection operators
(6.5.3.2), array declarators (6.7.6.2).
-6.5.2.2 Function calls
+
+
The expression that denotes the called function92) shall have type pointer to function returning void or returning a complete object type other than an array type. -
+
If the expression that denotes the called function has a type that includes a prototype, the number of arguments shall agree with the number of parameters. Each argument shall - + have a type such that its value may be assigned to an object with the unqualified version of the type of its corresponding parameter.
+
A postfix expression followed by parentheses () containing a possibly empty, comma- separated list of expressions is a function call. The postfix expression denotes the called function. The list of expressions specifies the arguments to the function. -
+
An argument may be an expression of any complete object type. In preparing for the call to a function, the arguments are evaluated, and each parameter is assigned the value of the corresponding argument.93) -
+
If the expression that denotes the called function has type pointer to function returning an object type, the function call expression has the same type as that object type, and has the value determined as specified in 6.8.6.4. Otherwise, the function call has type void. * -
+
If the expression that denotes the called function has a type that does not include a prototype, the integer promotions are performed on each argument, and arguments that have type float are promoted to double. These are called the default argument @@ -4573,7 +4668,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
If the expression that denotes the called function has a type that does include a prototype, the arguments are implicitly converted, as if by assignment, to the types of the corresponding parameters, taking the type of each parameter to be the unqualified version @@ -4583,28 +4678,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
No other conversions are performed implicitly; in particular, the number and types of arguments are not compared with those of the parameters in a function definition that does not include a function prototype declarator. -
+
If the function is defined with a type that is not compatible with the type (of the expression) pointed to by the expression that denotes the called function, the behavior is undefined. -
+
There is a sequence point after the evaluations of the function designator and the actual arguments but before the actual call. Every evaluation in the calling function (including other function calls) that is not otherwise specifically sequenced before or after the execution of the body of the called function is indeterminately sequenced with respect to the execution of the called function.94) -
+
Recursive function calls shall be permitted, both directly and indirectly through any chain of other functions. -
+
EXAMPLE In the function call
- (*pf[f1()]) (f2(), f3() + f4())+ (*pf[f1()]) (f2(), f3() + f4()) + the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before the function pointed to by pf[f1()] is called. @@ -4622,33 +4718,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
94) In other words, function executions do not ''interleave'' with each other.
-6.5.2.3 Structure and union members
+
+
The first operand of the . operator shall have an atomic, qualified, or unqualified structure or union type, and the second operand shall name a member of that type. -
+
The first operand of the -> operator shall have type ''pointer to atomic, qualified, or unqualified structure'' or ''pointer to atomic, qualified, or unqualified union'', and the second operand shall name a member of the type pointed to.
+
A postfix expression followed by the . operator and an identifier designates a member of a structure or union object. The value is that of the named member,95) and is an lvalue if the first expression is an lvalue. If the first expression has qualified type, the result has the so-qualified version of the type of the designated member. - -
+ +
A postfix expression followed by the -> operator and an identifier designates a member of a structure or union object. The value is that of the named member of the object to which the first expression points, and is an lvalue.96) If the first expression is a pointer to a qualified type, the result has the so-qualified version of the type of the designated member. -
+
Accessing a member of an atomic structure or union object results in undefined behavior.97) -
+
One special guarantee is made in order to simplify the use of unions: if a union contains several structures that share a common initial sequence (see below), and if the union object currently contains one of these structures, it is permitted to inspect the common @@ -4656,17 +4752,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. is visible. Two structures share a common initial sequence if corresponding members have compatible types (and, for bit-fields, the same widths) for a sequence of one or more initial members. -
+
EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or union, f().x is a valid postfix expression but is not an lvalue. -
+
EXAMPLE 2 In:
struct s { int i; const int ci; };
struct s s;
const struct s cs;
- volatile struct s vs;
+ volatile struct s vs;
+
the various members have the types:
s.i int
@@ -4674,13 +4771,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
cs.i const int
cs.ci const int
vs.i volatile int
- vs.ci volatile const int
+ vs.ci volatile const int
+
-
-+ +
EXAMPLE 3 The following is a valid fragment:
union {
@@ -4701,7 +4799,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* ... */
if (u.n.alltypes == 1)
if (sin(u.nf.doublenode) == 0.0)
- /* ... */
+ /* ... */
+
The following is not a valid fragment (because the union type is not visible within function f):
struct t1 { int m; };
@@ -4720,11 +4819,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
} u;
/* ... */
return f(&u.s1, &u.s2);
- }
+ }
+
Forward references: address and indirection operators (6.5.3.2), structure and union specifiers (6.7.2.1). - +
95) If the member used to read the contents of a union object is not the same as the member last used to
@@ -4740,13 +4840,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
can be safely accessed using a non-atomic object which is assigned to or from the atomic object.
-6.5.2.4 Postfix increment and decrement operators
+
+
The operand of the postfix increment or decrement operator shall have atomic, qualified, or unqualified real or pointer type, and shall be a modifiable lvalue.
+
The result of the postfix ++ operator is the value of the operand. As a side effect, the value of the operand object is incremented (that is, the value 1 of the appropriate type is added to it). See the discussions of additive operators and compound assignment for @@ -4756,7 +4856,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. function call, the operation of postfix ++ is a single evaluation. Postfix ++ on an object with atomic type is a read-modify-write operation with memory_order_seq_cst memory order semantics.98) -
+
The postfix -- operator is analogous to the postfix ++ operator, except that the value of
the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
it).
@@ -4771,50 +4871,52 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
T result = E;
do {
tmp = result + 1;
- } while (!atomic_compare_exchange_strong(&E, &result, tmp));
+ } while (!atomic_compare_exchange_strong(&E, &result, tmp));
+
with result being the result of the operation.
-6.5.2.5 Compound literals
+
+
The type name shall specify a complete object type or an array of unknown size, but not a variable length array type. -
+
All the constraints for initializer lists in 6.7.9 also apply to compound literals.
+
A postfix expression that consists of a parenthesized type name followed by a brace- enclosed list of initializers is a compound literal. It provides an unnamed object whose value is given by the initializer list.99) - -
+ +
If the type name specifies an array of unknown size, the size is determined by the initializer list as specified in 6.7.9, and the type of the compound literal is that of the completed array type. Otherwise (when the type name specifies an object type), the type of the compound literal is that specified by the type name. In either case, the result is an lvalue. -
+
The value of the compound literal is that of an unnamed object initialized by the initializer list. If the compound literal occurs outside the body of a function, the object has static storage duration; otherwise, it has automatic storage duration associated with the enclosing block. -
+
All the semantic rules for initializer lists in 6.7.9 also apply to compound literals.100) -
+
String literals, and compound literals with const-qualified types, need not designate distinct objects.101) -
+
EXAMPLE 1 The file scope definition
- int *p = (int []){2, 4};
+ int *p = (int []){2, 4};
+
initializes p to point to the first element of an array of two ints, the first having the value two and the
second, four. The expressions in this compound literal are required to be constant. The unnamed object
has static storage duration.
-+
EXAMPLE 2 In contrast, in
void f(void)
@@ -4823,58 +4925,65 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/*...*/
p = (int [2]){*p};
/*...*/
- }
+ }
+
p is assigned the address of the first element of an array of two ints, the first having the value previously
pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
unnamed object has automatic storage duration.
-+
EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects created using compound literals can be passed to functions without depending on member order:
drawline((struct point){.x=1, .y=1},
- (struct point){.x=3, .y=4});
+ (struct point){.x=3, .y=4});
+
Or, if drawline instead expected pointers to struct point:
-
+
drawline(&(struct point){.x=1, .y=1},
- &(struct point){.x=3, .y=4});
+ &(struct point){.x=3, .y=4});
+
-+
EXAMPLE 4 A read-only compound literal can be specified through constructions like:
- (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
+ (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
+
-+
EXAMPLE 5 The following three expressions have different meanings:
"/tmp/fileXXXXXX"
(char []){"/tmp/fileXXXXXX"}
- (const char []){"/tmp/fileXXXXXX"}
+ (const char []){"/tmp/fileXXXXXX"}
+
The first always has static storage duration and has type array of char, but need not be modifiable; the last
two have automatic storage duration when they occur within the body of a function, and the first of these
two is modifiable.
-+
EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory and can even be shared. For example,
- (const char []){"abc"} == "abc"
+ (const char []){"abc"} == "abc"
+
might yield 1 if the literals' storage is shared.
-+
EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly linked object. For example, there is no way to write a self-referential compound literal that could be used as the function argument in place of the named object endless_zeros below:
struct int_list { int car; struct int_list *cdr; };
struct int_list endless_zeros = {0, &endless_zeros};
- eval(endless_zeros);
+ eval(endless_zeros);
+
-+
EXAMPLE 8 Each compound literal creates only a single object in a given scope:
struct s { int i; };
@@ -4886,15 +4995,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
q = p, p = &((struct s){ j++ });
if (j < 2) goto again;
return p == q && q->i == 1;
- }
+ }
+
The function f() always returns the value 1.
-+
Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would have an indeterminate value, which would result in undefined behavior.
Forward references: type names (6.7.7), initialization (6.7.9). - +
99) Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
@@ -4906,9 +5016,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the same or overlapping representations.
-6.5.3 Unary operators
+
+
unary-expression:
postfix-expression
@@ -4919,44 +5029,45 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
sizeof ( type-name )
alignof ( type-name )
unary-operator: one of
- & * + - ~ !
+ & * + - ~ !
+
-+
The operand of the prefix increment or decrement operator shall have atomic, qualified, or unqualified real or pointer type, and shall be a modifiable lvalue.
+
The value of the operand of the prefix ++ operator is incremented. The result is the new value of the operand after incrementation. The expression ++E is equivalent to (E+=1). See the discussions of additive operators and compound assignment for information on constraints, types, side effects, and conversions and the effects of operations on pointers. -
+
The prefix -- operator is analogous to the prefix ++ operator, except that the value of the operand is decremented.
Forward references: additive operators (6.5.6), compound assignment (6.5.16.2).
-6.5.3.2 Address and indirection operators
+
+
The operand of the unary & operator shall be either a function designator, the result of a [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is not declared with the register storage-class specifier. -
+
The operand of the unary * operator shall have pointer type.
+
The unary & operator yields the address of its operand. If the operand has type ''type'', the result has type ''pointer to type''. If the operand is the result of a unary * operator, neither that operator nor the & operator is evaluated and the result is as if both were omitted, except that the constraints on the operators still apply and the result is not an - + lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. Otherwise, the result is a pointer to the object or function designated by its operand. -
+
The unary * operator denotes indirection. If the operand points to a function, the result is
a function designator; if it points to an object, the result is an lvalue designating the
object. If the operand has type ''pointer to type'', the result has type ''type''. If an
@@ -4975,84 +5086,87 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
end of its lifetime.
-6.5.3.3 Unary arithmetic operators
+
+
The operand of the unary + or - operator shall have arithmetic type; of the ~ operator, integer type; of the ! operator, scalar type.
+
The result of the unary + operator is the value of its (promoted) operand. The integer promotions are performed on the operand, and the result has the promoted type. -
+
The result of the unary - operator is the negative of its (promoted) operand. The integer promotions are performed on the operand, and the result has the promoted type. -
+
The result of the ~ operator is the bitwise complement of its (promoted) operand (that is, each bit in the result is set if and only if the corresponding bit in the converted operand is not set). The integer promotions are performed on the operand, and the result has the promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent to the maximum value representable in that type minus E. -
+
The result of the logical negation operator ! is 0 if the value of its operand compares
unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
The expression !E is equivalent to (0==E).
-
+
-6.5.3.4 The sizeof and alignof operators
+
+
The sizeof operator shall not be applied to an expression that has function type or an incomplete type, to the parenthesized name of such a type, or to an expression that designates a bit-field member. The alignof operator shall not be applied to a function type or an incomplete type.
+
The sizeof operator yields the size (in bytes) of its operand, which may be an expression or the parenthesized name of a type. The size is determined from the type of the operand. The result is an integer. If the type of the operand is a variable length array type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an integer constant. -
+
The alignof operator yields the alignment requirement of its operand type. The result is an integer constant. When applied to an array type, the result is the alignment requirement of the element type. -
+
When sizeof is applied to an operand that has type char, unsigned char, or signed char, (or a qualified version thereof) the result is 1. When applied to an operand that has array type, the result is the total number of bytes in the array.103) When applied to an operand that has structure or union type, the result is the total number of bytes in such an object, including internal and trailing padding. -
+
The value of the result of both operators is implementation-defined, and its type (an unsigned integer type) is size_t, defined in <stddef.h> (and other headers). -
+
EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to allocate and return a pointer to void. For example:
extern void *alloc(size_t);
- double *dp = alloc(sizeof *dp);
+ double *dp = alloc(sizeof *dp);
+
The implementation of the alloc function should ensure that its return value is aligned suitably for
conversion to a pointer to double.
-+
EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
- sizeof array / sizeof array[0]+ sizeof array / sizeof array[0] + -
+
EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a function:
- #include <stddef.h>+ #include <stddef.h> + - +
size_t fsize3(int n)
{
@@ -5064,7 +5178,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
size_t size;
size = fsize3(10); // fsize3 returns 13
return 0;
- }
+ }
+
Forward references: common definitions <stddef.h> (7.19), declarations (6.7),
structure and union specifiers (6.7.2.1), type names (6.7.7), array declarators (6.7.6.2).
@@ -5074,29 +5189,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
size of the adjusted (pointer) type (see 6.9.1).
-6.5.4 Cast operators
+
+
cast-expression:
unary-expression
- ( type-name ) cast-expression
+ ( type-name ) cast-expression
+
+
Unless the type name specifies a void type, the type name shall specify atomic, qualified, or unqualified scalar type, and the operand shall have scalar type. -
+
Conversions that involve pointers, other than where permitted by the constraints of 6.5.16.1, shall be specified by means of an explicit cast. -
+
A pointer type shall not be converted to any floating type. A floating type shall not be converted to any pointer type.
+
Preceding an expression by a parenthesized type name converts the value of the expression to the named type. This construction is called a cast.104) A cast that specifies no conversion has no effect on the type or value of an expression. -
+
If the value of the expression is represented with greater precision or range than required by the type named by the cast (6.3.1.8), then the cast specifies a conversion even if the type of the expression is the same as the named type and removes any extra range and @@ -5104,36 +5220,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: equality operators (6.5.9), function declarators (including prototypes) (6.7.6.3), simple assignment (6.5.16.1), type names (6.7.7). - +
104) A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
unqualified version of the type.
-6.5.5 Multiplicative operators
+
+
multiplicative-expression:
cast-expression
multiplicative-expression * cast-expression
multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
+ multiplicative-expression % cast-expression
+
+
Each of the operands shall have arithmetic type. The operands of the % operator shall have integer type.
+
The usual arithmetic conversions are performed on the operands. -
+
The result of the binary * operator is the product of the operands. -
+
The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. -
+
When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded.105) If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is @@ -5143,26 +5260,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
105) This is often called ''truncation toward zero''.
-6.5.6 Additive operators
+
+
additive-expression:
multiplicative-expression
additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
+ additive-expression - multiplicative-expression
+
+
For addition, either both operands shall have arithmetic type, or one operand shall be a pointer to a complete object type and the other shall have integer type. (Incrementing is equivalent to adding 1.) -
+
For subtraction, one of the following shall hold: - +
+
If both operands have arithmetic type, the usual arithmetic conversions are performed on them. -
+
The result of the binary + operator is the sum of the operands. -
+
The result of the binary - operator is the difference resulting from the subtraction of the second operand from the first. -
+
For the purposes of these operators, a pointer to an object that is not an element of an array behaves the same as a pointer to the first element of an array of length one with the type of the object as its element type. -
+
When an expression that has integer type is added to or subtracted from a pointer, the result has the type of the pointer operand. If the pointer operand points to an element of an array object, and the array is large enough, the result points to an element offset from @@ -5200,7 +5318,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. element of the array object, the evaluation shall not produce an overflow; otherwise, the behavior is undefined. If the result points one past the last element of the array object, it shall not be used as the operand of a unary * operator that is evaluated. -
+
When two pointers are subtracted, both shall point to elements of the same array object, or one past the last element of the array object; the result is the difference of the subscripts of the two array elements. The size of the result is implementation-defined, @@ -5208,16 +5326,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. If the result is not representable in an object of that type, the behavior is undefined. In other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of an array object, the expression (P)-(Q) has the value i-j provided the value fits in an - + object of type ptrdiff_t. Moreover, if the expression P points either to an element of an array object or one past the last element of an array object, and the expression Q points to the last element of the same array object, the expression ((Q)+1)-(P) has the same value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the expression P points one past the last element of the array object, even though the expression (Q)+1 does not point to an element of the array object.106) -
+
EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types. -
{
int n = 4, m = 3;
@@ -5226,7 +5343,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
p += 1; // p == &a[1]
(*p)[2] = 99; // a[1][2] == 99
n = p - a; // n == 1
- }
+ }
+
+
If array a in the above example were declared to be an array of known constant size, and pointer p were
declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
the same.
@@ -5245,48 +5364,50 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
element'' requirements.
-6.5.7 Bitwise shift operators
+
+
shift-expression:
additive-expression
shift-expression << additive-expression
- shift-expression >> additive-expression
+ shift-expression >> additive-expression
+
+
Each of the operands shall have integer type.
+
The integer promotions are performed on each of the operands. The type of the result is that of the promoted left operand. If the value of the right operand is negative or is - + greater than or equal to the width of the promoted left operand, the behavior is undefined. -
+
The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo one more than the maximum value representable in the result type. If E1 has a signed type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is the resulting value; otherwise, the behavior is undefined. -
+
The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
or if E1 has a signed type and a nonnegative value, the value of the result is the integral
part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
resulting value is implementation-defined.
-6.5.8 Relational operators
+
+
relational-expression:
shift-expression
relational-expression < shift-expression
relational-expression > shift-expression
relational-expression <= shift-expression
- relational-expression >= shift-expression
+ relational-expression >= shift-expression
+
+
One of the following shall hold:
+
If both of the operands have arithmetic type, the usual arithmetic conversions are performed. -
+
For the purposes of these operators, a pointer to an object that is not an element of an array behaves the same as a pointer to the first element of an array of length one with the type of the object as its element type. -
+
When two pointers are compared, the result depends on the relative locations in the address space of the objects pointed to. If two pointers to object types both point to the same object, or both point one past the last element of the same array object, they @@ -5309,12 +5430,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pointers to structure members declared later compare greater than pointers to members declared earlier in the structure, and pointers to array elements with larger subscript values compare greater than pointers to elements of the same array with lower subscript - + values. All pointers to members of the same union object compare equal. If the expression P points to an element of an array object and the expression Q points to the last element of the same array object, the pointer expression Q+1 compares greater than P. In all other cases, the behavior is undefined. -
+
Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
(greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is
false.107) The result has type int.
@@ -5324,16 +5445,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
-6.5.9 Equality operators
+
+
equality-expression:
relational-expression
equality-expression == relational-expression
- equality-expression != relational-expression
+ equality-expression != relational-expression
+
+
One of the following shall hold:
+
The == (equal to) and != (not equal to) operators are analogous to the relational operators except for their lower precedence.108) Each of the operators yields 1 if the specified relation is true and 0 if it is false. The result has type int. For any pair of operands, exactly one of the relations is true. -
+
If both of the operands have arithmetic type, the usual arithmetic conversions are performed. Values of complex types are equal if and only if both their real parts are equal and also their imaginary parts are equal. Any two values of arithmetic types from @@ -5357,20 +5479,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a null pointer constant, the null pointer constant is converted to the type of the pointer. If one operand is a pointer to an object type and the other is a pointer to a qualified or unqualified version of void, the former is converted to the type of the latter. -
+
Two pointers compare equal if and only if both are null pointers, both are pointers to the same object (including a pointer to an object and a subobject at its beginning) or function, both are pointers to one past the last element of the same array object, or one is a pointer to one past the end of one array object and the other is a pointer to the start of a different array object that happens to immediately follow the first array object in the address space.109) -
+
For the purposes of these operators, a pointer to an object that is not an element of an
array behaves the same as a pointer to the first element of an array of length one with the
type of the object as its element type.
@@ -5385,20 +5507,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
behavior.
-6.5.10 Bitwise AND operator
+
+
AND-expression:
equality-expression
- AND-expression & equality-expression
+ AND-expression & equality-expression
+
+
Each of the operands shall have integer type.
+
The usual arithmetic conversions are performed on the operands. -
+
The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
the result is set if and only if each of the corresponding bits in the converted operands is
set).
@@ -5406,97 +5529,102 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-6.5.11 Bitwise exclusive OR operator
+
+
exclusive-OR-expression:
AND-expression
- exclusive-OR-expression ^ AND-expression
+ exclusive-OR-expression ^ AND-expression
+
+
Each of the operands shall have integer type.
+
The usual arithmetic conversions are performed on the operands. -
+
The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
in the result is set if and only if exactly one of the corresponding bits in the converted
operands is set).
-6.5.12 Bitwise inclusive OR operator
+
+
inclusive-OR-expression:
exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
+ inclusive-OR-expression | exclusive-OR-expression
+
+
Each of the operands shall have integer type.
+
The usual arithmetic conversions are performed on the operands. -
+
The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
the result is set if and only if at least one of the corresponding bits in the converted
operands is set).
-
+
-6.5.13 Logical AND operator
+
+
logical-AND-expression:
inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
+ logical-AND-expression && inclusive-OR-expression
+
+
Each of the operands shall have scalar type.
+
The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0. The result has type int. -
+
Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
if the second operand is evaluated, there is a sequence point between the evaluations of
the first and second operands. If the first operand compares equal to 0, the second
operand is not evaluated.
-6.5.14 Logical OR operator
+
+
logical-OR-expression:
logical-AND-expression
- logical-OR-expression || logical-AND-expression
+ logical-OR-expression || logical-AND-expression
+
+
Each of the operands shall have scalar type.
+
The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0. The result has type int. -
+
Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; if the
second operand is evaluated, there is a sequence point between the evaluations of the first
and second operands. If the first operand compares unequal to 0, the second operand is
not evaluated.
-
+
-6.5.15 Conditional operator
+
+
conditional-expression:
logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
+ logical-OR-expression ? expression : conditional-expression
+
+
The first operand shall have scalar type. -
+
One of the following shall hold for the second and third operands:
+
The first operand is evaluated; there is a sequence point between its evaluation and the evaluation of the second or third operand (whichever is evaluated). The second operand is evaluated only if the first compares unequal to 0; the third operand is evaluated only if the first compares equal to 0; the result is the value of the second or third operand (whichever is evaluated), converted to the type described below.110) * -
+
If both the second and third operands have arithmetic type, the result type that would be determined by the usual arithmetic conversions, were they applied to those two operands, is the type of the result. If both the operands have structure or union type, the result has that type. If both operands have void type, the result has void type. -
+
If both the second and third operands are pointers or one is a null pointer constant and the other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers of the types referenced by both operands. Furthermore, if both operands are pointers to @@ -5529,12 +5657,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. is a pointer to void or a qualified version of void, in which case the result type is a pointer to an appropriately qualified version of void. - -
+ +
EXAMPLE The common type that results when the second and third operands are pointers is determined in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two pointers have compatible types. -
+
Given the declarations
const void *c_vp;
@@ -5542,7 +5670,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
const int *c_ip;
volatile int *v_ip;
int *ip;
- const char *c_cp;
+ const char *c_cp;
+
the third column in the following table is the common type that is the result of a conditional expression in
which the first two columns are the second and third operands (in either order):
@@ -5551,27 +5680,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
c_ip v_ip const volatile int *
vp c_cp const void *
ip c_ip const int *
- vp ip void *
+ vp ip void *
+
110) A conditional expression does not yield an lvalue.
-6.5.16 Assignment operators
+
+
assignment-expression:
conditional-expression
unary-expression assignment-operator assignment-expression
assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
+ = *= /= %= += -= <<= >>= &= ^= |=
+
+
An assignment operator shall have a modifiable lvalue as its left operand.
+
An assignment operator stores a value in the object designated by the left operand. An assignment expression has the value of the left operand after the assignment,111) but is not an lvalue. The type of an assignment expression is the type the left operand would have @@ -5582,16 +5713,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
111) The implementation is permitted to read the object to determine the value but is not required to, even
when the object has volatile-qualified type.
-6.5.16.1 Simple assignment
+
+
One of the following shall hold:112)
+
In simple assignment (=), the value of the right operand is converted to the type of the assignment expression and replaces the value stored in the object designated by the left operand. -
+
If the value being stored in an object is read from another object that overlaps in any way the storage of the first object, then the overlap shall be exact and the two objects shall have qualified or unqualified versions of a compatible type; otherwise, the behavior is undefined. -
+
EXAMPLE 1 In the program fragment - +
int f(void);
char c;
/* ... */
if ((c = f()) == -1)
- /* ... */
+ /* ... */
+
the int value returned by the function may be truncated when stored in the char, and then converted back
to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
values as unsigned char (and char is narrower than int), the result of the conversion cannot be
negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
variable c should be declared as int.
-+
EXAMPLE 2 In the fragment:
char c;
int i;
long l;
- l = (c = i);
+ l = (c = i);
+
the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
that is, long int type.
-+
EXAMPLE 3 Consider the fragment:
const char **cpp;
@@ -5660,7 +5793,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
const char c = 'A';
cpp = &p; // constraint violation
*cpp = &c; // valid
- *p = 0; // valid
+ *p = 0; // valid
+
The first assignment is unsafe because it would allow the following valid code to attempt to change the
value of the const object c.
@@ -5672,24 +5806,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
not volatile from the type int volatile * const).
-+
For the operators += and -= only, either the left operand shall be an atomic, qualified, or unqualified pointer to a complete object type, and the right shall have integer type; or the left operand shall have atomic, qualified, or unqualified arithmetic type, and the right shall have arithmetic type. -
+
For the other operators, the left operand shall have atomic, qualified, or unqualified arithmetic type, and (considering the type the left operand would have after lvalue conversion) each operand shall have arithmetic type consistent with those allowed by the corresponding binary operator.
+
A compound assignment of the form E1 op = E2 is equivalent to the simple assignment
expression E1 = E1 op (E2), except that the lvalue E1 is evaluated only once, and with
respect to an indeterminately-sequenced function call, the operation of a compound
-
+
assignment is a single evaluation. If E1 has an atomic type, compound assignment is a
read-modify-write operation with memory_order_seq_cst memory order
semantics.113)
@@ -5703,29 +5837,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
T result;
do {
result = tmp op (E2);
- } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
+ } while (!atomic_compare_exchange_strong(&E1, &tmp, result));
+
with result being the result of the operation.
-6.5.17 Comma operator
+
+
expression:
assignment-expression
- expression , assignment-expression
+ expression , assignment-expression
+
+
The left operand of a comma operator is evaluated as a void expression; there is a sequence point between its evaluation and that of the right operand. Then the right operand is evaluated; the result has its type and value.114) * -
+
EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists of initializers). On the other hand, it can be used within a parenthesized expression or within the second expression of a conditional operator in such contexts. In the function call
- f(a, (t=3, t+2), c)+ f(a, (t=3, t+2), c) + the function has three arguments, the second of which has the value 5.
Forward references: initialization (6.7.9). @@ -5733,44 +5870,45 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
114) A comma operator does not yield an lvalue.
-6.6 Constant expressions
+
+
constant-expression:
- conditional-expression
+ conditional-expression
+
+
A constant expression can be evaluated during translation rather than runtime, and accordingly may be used in any place that a constant may be.
+
Constant expressions shall not contain assignment, increment, decrement, function-call, or comma operators, except when they are contained within a subexpression that is not evaluated.115) -
+
Each constant expression shall evaluate to a constant that is in the range of representable values for its type.
+
An expression that evaluates to a constant is required in several contexts. If a floating expression is evaluated in the translation environment, the arithmetic precision and range shall be at least as great as if the expression were being evaluated in the execution environment.116) -
+
An integer constant expression117) shall have integer type and shall only have operands that are integer constants, enumeration constants, character constants, sizeof expressions whose results are integer constants, and floating constants that are the immediate operands of casts. Cast operators in an integer constant expression shall only convert arithmetic types to integer types, except as part of an operand to the sizeof operator. -
+
More latitude is permitted for constant expressions in initializers. Such a constant expression shall be, or evaluate to, one of the following:
+
An arithmetic constant expression shall have arithmetic type and shall only have operands that are integer constants, floating constants, enumeration constants, character constants, and sizeof expressions. Cast operators in an arithmetic constant expression shall only convert arithmetic types to arithmetic types, except as part of an operand to a sizeof operator whose result is an integer constant. -
+
An address constant is a null pointer, a pointer to an lvalue designating an object of static storage duration, or a pointer to a function designator; it shall be created explicitly using the unary & operator or an integer constant cast to pointer type, or implicitly by the use of @@ -5798,9 +5936,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and -> operators, the address & and indirection * unary operators, and pointer casts may be used in the creation of an address constant, but the value of an object shall not be accessed by use of these operators. -
+
An implementation may accept other forms of constant expressions. -
+
The semantic rules for the evaluation of a constant expression are the same as for nonconstant expressions.118)
Forward references: array declarators (6.7.6.2), initialization (6.7.9). @@ -5808,7 +5946,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
115) The operand of a sizeof operator is usually not evaluated (6.5.3.4). @@ -5824,44 +5962,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
118) Thus, in the following initialization,
- static int i = 2 || 1 / 0;
+ static int i = 2 || 1 / 0;
+
the expression is a valid integer constant expression with value one.
-6.7 Declarations
+
+
declaration:
- declaration-specifiers init-declarator-listopt ;
+ declaration-specifiers init-declarator-listopt ;
static_assert-declaration
declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
- alignment-specifier declaration-specifiersopt
+ storage-class-specifier declaration-specifiersopt
+ type-specifier declaration-specifiersopt
+ type-qualifier declaration-specifiersopt
+ function-specifier declaration-specifiersopt
+ alignment-specifier declaration-specifiersopt
init-declarator-list:
init-declarator
init-declarator-list , init-declarator
init-declarator:
declarator
- declarator = initializer
+ declarator = initializer
+
+
A declaration other than a static_assert declaration shall declare at least a declarator (other than the parameters of a function or the members of a structure or union), a tag, or the members of an enumeration. -
+
If an identifier has no linkage, there shall be no more than one declaration of the identifier (in a declarator or type specifier) with the same scope and in the same name space, except that a typedef name can be redefined to denote the same type as it currently does and tags may be redeclared as specified in 6.7.2.3. -
+
All declarations in the same scope that refer to the same object or function shall specify compatible types.
+
A declaration specifies the interpretation and attributes of a set of identifiers. A definition of an identifier is a declaration for that identifier that:
+
The declaration specifiers consist of a sequence of specifiers that indicate the linkage, storage duration, and part of the type of the entities that the declarators denote. The init- declarator-list is a comma-separated sequence of declarators, each of which may have additional type information, or an initializer, or both. The declarators contain the identifiers (if any) being declared. -
+
If an identifier for an object is declared with no linkage, the type for the object shall be complete by the end of its declarator, or by the end of its init-declarator if it has an initializer; in the case of function parameters (including in prototypes), it is the adjusted @@ -5892,9 +6032,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
119) Function definitions have a different syntax, described in 6.9.1.
-6.7.1 Storage-class specifiers
+
+
storage-class-specifier:
typedef
@@ -5902,33 +6042,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
static
_Thread_local
auto
- register
+ register
+
+
At most, one storage-class specifier may be given in the declaration specifiers in a declaration, except that _Thread_local may appear with static or extern.120) -
+
In the declaration of an object with block scope, if the declaration specifiers include _Thread_local, they shall also include either static or extern. If _Thread_local appears in any declaration of an object, it shall be present in every declaration of that object.
+
The typedef specifier is called a ''storage-class specifier'' for syntactic convenience only; it is discussed in 6.7.8. The meanings of the various linkages and storage durations were discussed in 6.2.2 and 6.2.4. - -
+ +
A declaration of an identifier for an object with storage-class specifier register suggests that access to the object be as fast as possible. The extent to which such suggestions are effective is implementation-defined.121) -
+
The declaration of an identifier for a function that has block scope shall have no explicit storage-class specifier other than extern. -
+
If an aggregate or union object is declared with a storage-class specifier other than
typedef, the properties resulting from the storage-class specifier, except with respect to
linkage, also apply to the members of the object, and so on recursively for any aggregate
@@ -5946,9 +6087,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
register is sizeof.
-6.7.2 Type specifiers
+
+
type-specifier:
void
@@ -5965,14 +6106,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atomic-type-specifier
struct-or-union-specifier
enum-specifier
- typedef-name
+ typedef-name
+
+
At least one type specifier shall be given in the declaration specifiers in each declaration, and in the specifier-qualifier list in each struct declaration and type name. Each list of - + type specifiers shall be one of the following multisets (delimited by commas, when there is more than one multiset per item); the type specifiers may occur in any order, possibly intermixed with the other declaration specifiers. @@ -6002,28 +6144,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
The type specifier _Complex shall not be used if the implementation does not support complex types (see 6.10.8.3). - +
+
Specifiers for structures, unions, enumerations, and atomic types are discussed in 6.7.2.1 through 6.7.2.4. Declarations of typedef names are discussed in 6.7.8. The characteristics of the other types are discussed in 6.2.5. -
+
Each of the comma-separated multisets designates the same type, except that for bit- fields, it is implementation-defined whether the specifier int designates the same type as signed int or the same type as unsigned int.
Forward references: atomic type specifiers (6.7.2.4), enumeration specifiers (6.7.2.2),
structure and union specifiers (6.7.2.1), tags (6.7.2.3), type definitions (6.7.8).
-6.7.2.1 Structure and union specifiers
+
+
struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
+ struct-or-union identifieropt { struct-declaration-list }
struct-or-union identifier
struct-or-union:
struct
@@ -6032,66 +6174,67 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
struct-declaration
struct-declaration-list struct-declaration
struct-declaration:
- specifier-qualifier-list struct-declarator-listopt ;
+ specifier-qualifier-list struct-declarator-listopt ;
static_assert-declaration
specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt
- type-qualifier specifier-qualifier-listopt
+ type-specifier specifier-qualifier-listopt
+ type-qualifier specifier-qualifier-listopt
struct-declarator-list:
struct-declarator
struct-declarator-list , struct-declarator
struct-declarator:
declarator
- declaratoropt : constant-expression
+ declaratoropt : constant-expression
+
+
A struct-declaration that does not declare an anonymous structure or anonymous union shall contain a struct-declarator-list. - -
+ +
A structure or union shall not contain a member with incomplete or function type (hence, a structure shall not contain an instance of itself, but may contain a pointer to an instance of itself), except that the last member of a structure with more than one named member may have incomplete array type; such a structure (and any union containing, possibly recursively, a member that is such a structure) shall not be a member of a structure or an element of an array. -
+
The expression that specifies the width of a bit-field shall be an integer constant expression with a nonnegative value that does not exceed the width of an object of the type that would be specified were the colon and expression omitted.122) If the value is zero, the declaration shall have no declarator. -
+
A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed int, unsigned int, or some other implementation-defined type. It is implementation-defined whether atomic types are permitted.
+
As discussed in 6.2.5, a structure is a type consisting of a sequence of members, whose storage is allocated in an ordered sequence, and a union is a type consisting of a sequence of members whose storage overlap. -
+
Structure and union specifiers have the same form. The keywords struct and union indicate that the type being specified is, respectively, a structure type or a union type. -
+
The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type, within a translation unit. The struct-declaration-list is a sequence of declarations for the members of the structure or union. If the struct-declaration-list contains no named members, no anonymous structures, and no anonymous unions, the behavior is undefined. The type is incomplete until immediately after the } that terminates the list, and complete thereafter. -
+
A member of a structure or union may have any complete object type other than a variably modified type.123) In addition, a member may be declared to consist of a specified number of bits (including a sign bit, if any). Such a member is called a bit-field;124) its width is preceded by a colon. -
+
A bit-field is interpreted as having a signed or unsigned integer type consisting of the specified number of bits.125) If the value 0 or 1 is stored into a nonzero-width bit-field of - + type _Bool, the value of the bit-field shall compare equal to the value stored; a _Bool bit-field has the semantics of a _Bool. -
+
An implementation may allocate any addressable storage unit large enough to hold a bit- field. If enough space remains, a bit-field that immediately follows another bit-field in a structure shall be packed into adjacent bits of the same unit. If insufficient space remains, @@ -6099,39 +6242,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation-defined. The order of allocation of bit-fields within a unit (high-order to low-order or low-order to high-order) is implementation-defined. The alignment of the addressable storage unit is unspecified. -
+
A bit-field declaration with no declarator, but only a colon and a width, indicates an unnamed bit-field.126) As a special case, a bit-field structure member with a width of 0 indicates that no further bit-field is to be packed into the unit in which the previous bit- field, if any, was placed. -
+
An unnamed member of structure type with no tag is called an anonymous structure; an unnamed member of union type with no tag is called an anonymous union. The members of an anonymous structure or union are considered to be members of the containing structure or union. This applies recursively if the containing structure or union is also anonymous. -
+
Each non-bit-field member of a structure or union object is aligned in an implementation- defined manner appropriate to its type. -
+
Within a structure object, the non-bit-field members and the units in which bit-fields reside have addresses that increase in the order in which they are declared. A pointer to a structure object, suitably converted, points to its initial member (or if that member is a bit-field, then to the unit in which it resides), and vice versa. There may be unnamed padding within a structure object, but not at its beginning. -
+
The size of a union is sufficient to contain the largest of its members. The value of at most one of the members can be stored in a union object at any time. A pointer to a union object, suitably converted, points to each of its members (or if a member is a bit- field, then to the unit in which it resides), and vice versa. -
+
There may be unnamed padding at the end of a structure or union. -
+
As a special case, the last element of a structure with more than one named member may have an incomplete array type; this is called a flexible array member. In most situations, - + the flexible array member is ignored. In particular, the size of the structure is as if the flexible array member were omitted except that it may have more trailing padding than the omission would imply. However, when a . (or ->) operator has a left operand that is @@ -6142,7 +6285,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. from that of the replacement array. If this array would have no elements, it behaves as if it had one element but the behavior is undefined if any attempt is made to access that element or to generate a pointer one past it. -
+
EXAMPLE 1 The following illustrates anonymous structures and unions:
struct v {
@@ -6154,81 +6297,95 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
} v1;
v1.i = 2; // valid
v1.k = 3; // invalid: inner structure is not anonymous
- v1.w.k = 5; // valid
+ v1.w.k = 5; // valid
+
-+
EXAMPLE 2 After the declaration:
- struct s { int n; double d[]; };
+ struct s { int n; double d[]; };
+
the structure struct s has a flexible array member d. A typical way to use this is:
int m = /* some value */;
- struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
+ struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));
+
and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
p had been declared as:
- struct { int n; double d[m]; } *p;
+ struct { int n; double d[m]; } *p;
+
(there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
not be the same).
-+
Following the above declaration:
struct s t1 = { 0 }; // valid
struct s t2 = { 1, { 4.2 }}; // invalid
t1.n = 4; // valid
- t1.d[0] = 4.2; // might be undefined behavior
+ t1.d[0] = 4.2; // might be undefined behavior
+
The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
- sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)+ sizeof (struct s) >= offsetof(struct s, d) + sizeof (double) + in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming code. - -
+ +
After the further declaration:
- struct ss { int n; };
+ struct ss { int n; };
+
the expressions:
sizeof (struct s) >= sizeof (struct ss)
- sizeof (struct s) >= offsetof(struct s, d)
+ sizeof (struct s) >= offsetof(struct s, d)
+
are always equal to 1.
-+
If sizeof (double) is 8, then after the following code is executed:
struct s *s1;
struct s *s2;
s1 = malloc(sizeof (struct s) + 64);
- s2 = malloc(sizeof (struct s) + 46);
+ s2 = malloc(sizeof (struct s) + 46);
+
and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
purposes, as if the identifiers had been declared as:
-
struct { int n; double d[8]; } *s1;
- struct { int n; double d[5]; } *s2;
+ struct { int n; double d[5]; } *s2;
+
+Following the further successful assignments:
s1 = malloc(sizeof (struct s) + 10);
- s2 = malloc(sizeof (struct s) + 6);
+ s2 = malloc(sizeof (struct s) + 6);
+
they then behave as if the declarations were:
- struct { int n; double d[1]; } *s1, *s2;
+ struct { int n; double d[1]; } *s1, *s2;
+
and:
-
double *dp;
dp = &(s1->d[0]); // valid
*dp = 42; // valid
dp = &(s2->d[0]); // valid
- *dp = 42; // undefined behavior
+ *dp = 42; // undefined behavior
+
+The assignment:
- *s1 = *s2;+ *s1 = *s2; + only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes of the structure, they might be copied or simply overwritten with indeterminate values.
Forward references: declarators (6.7.6), tags (6.7.2.3). - +
122) While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and
@@ -6247,26 +6404,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
layouts.
-6.7.2.2 Enumeration specifiers
+
+
enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
+ enum identifieropt { enumerator-list }
+ enum identifieropt { enumerator-list , }
enum identifier
enumerator-list:
enumerator
enumerator-list , enumerator
enumerator:
enumeration-constant
- enumeration-constant = constant-expression
+ enumeration-constant = constant-expression
+
+
The expression that defines the value of an enumeration constant shall be an integer constant expression that has a value representable as an int.
+
The identifiers in an enumerator list are declared as constants that have type int and may appear wherever such are permitted.127) An enumerator with = defines its enumeration constant as the value of the constant expression. If the first enumerator has @@ -6275,7 +6433,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. adding 1 to the value of the previous enumeration constant. (The use of enumerators with = may produce enumeration constants with values that duplicate other values in the same enumeration.) The enumerators of an enumeration are also known as its members. -
+
Each enumerated type shall be compatible with char, a signed integer type, or an unsigned integer type. The choice of type is implementation-defined,128) but shall be capable of representing the values of all the members of the enumeration. The @@ -6285,8 +6443,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
EXAMPLE The following fragment:
enum hue { chartreuse, burgundy, claret=20, winedark };
@@ -6294,7 +6452,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
col = claret;
cp = &col;
if (*cp != burgundy)
- /* ... */
+ /* ... */
+
makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
@@ -6308,90 +6467,100 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
been seen.
-+
A specific type shall have its content defined at most once. -
+
Where two declarations that use the same tag declare the same type, they shall both use the same choice of struct, union, or enum. -
+
A type specifier of the form
- enum identifier+ enum identifier + without an enumerator list shall only appear after the type it specifies is complete.
+
All declarations of structure, union, or enumerated types that have the same scope and use the same tag declare the same type. Irrespective of whether there is a tag or what other declarations of the type are in the same translation unit, the type is incomplete129) until immediately after the closing brace of the list defining the content, and complete thereafter. -
+
Two declarations of structure, union, or enumerated types which are in different scopes or use different tags declare distinct types. Each declaration of a structure, union, or enumerated type which does not include a tag declares a distinct type. -
+
A type specifier of the form - +
- struct-or-union identifieropt { struct-declaration-list }
+ struct-or-union identifieropt { struct-declaration-list }
+
or
- enum identifieropt { enumerator-list }
+ enum identifieropt { enumerator-list }
+
or
- enum identifieropt { enumerator-list , }
+ enum identifieropt { enumerator-list , }
+
declares a structure, union, or enumerated type. The list defines the structure content,
union content, or enumeration content. If an identifier is provided,130) the type specifier
also declares the identifier to be the tag of that type.
-+
A declaration of the form
- struct-or-union identifier ;+ struct-or-union identifier ; + specifies a structure or union type and declares the identifier as a tag of that type.131) -
+
If a type specifier of the form
- struct-or-union identifier+ struct-or-union identifier + occurs other than as part of one of the above forms, and no other declaration of the identifier as a tag is visible, then it declares an incomplete structure or union type, and - declares the identifier as the tag of that type.131) -
+ declares the identifier as the tag of that type.131) +
If a type specifier of the form
- struct-or-union identifier+ struct-or-union identifier + or
- enum identifier+ enum identifier + occurs other than as part of one of the above forms, and a declaration of the identifier as a tag is visible, then it specifies the same type as that other declaration, and does not redeclare the tag. -
+
EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
struct tnode {
int count;
struct tnode *left, *right;
- };
+ };
+
specifies a structure that contains an integer and two pointers to objects of the same type. Once this
declaration has been given, the declaration
-
+
- struct tnode s, *sp;+ struct tnode s, *sp; + declares s to be an object of the given type and sp to be a pointer to an object of the given type. With these declarations, the expression sp->left refers to the left struct tnode pointer of the object to which sp points; the expression s.right->count designates the count member of the right struct tnode pointed to from s. -
+
The following alternative formulation uses the typedef mechanism:
typedef struct tnode TNODE;
@@ -6399,19 +6568,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int count;
TNODE *left, *right;
};
- TNODE s, *sp;
+ TNODE s, *sp;
+
-+
EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential structures, the declarations
struct s1 { struct s2 *s2p; /* ... */ }; // D1
- struct s2 { struct s1 *s1p; /* ... */ }; // D2
+ struct s2 { struct s1 *s1p; /* ... */ }; // D2
+
specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
D2. To eliminate this context sensitivity, the declaration
- struct s2;+ struct s2; + may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then completes the specification of the new type. @@ -6431,57 +6603,59 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
131) A similar construction with enum does not exist.
-6.7.2.4 Atomic type specifiers
+
+
atomic-type-specifier:
- _Atomic ( type-name )
+ _Atomic ( type-name )
+
+
Atomic type specifiers shall not be used if the implementation does not support atomic types (see 6.10.8.3). -
+
The type name in an atomic type specifier shall not refer to an array type, a function type, an atomic type, or a qualified type.
+
The properties associated with atomic types are meaningful only for expressions that are
lvalues. If the _Atomic keyword is immediately followed by a left parenthesis, it is
interpreted as a type specifier (with a type name), not as a type qualifier.
-
+
-6.7.3 Type qualifiers
+
+
type-qualifier:
const
restrict
volatile
- _Atomic
+ _Atomic
+
+
Types other than pointer types whose referenced type is an object type shall not be restrict-qualified. -
+
The type modified by the _Atomic qualifier shall not be an array type or a function type.
+
The properties associated with qualified types are meaningful only for expressions that are lvalues.132) -
+
If the same qualifier appears more than once in the same specifier-qualifier-list, either directly or via one or more typedefs, the behavior is the same as if it appeared only once. If other qualifiers appear along with the _Atomic qualifier in a specifier-qualifier- list, the resulting type is the so-qualified atomic type. -
+
If an attempt is made to modify an object defined with a const-qualified type through use of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is made to refer to an object defined with a volatile-qualified type through use of an lvalue with non-volatile-qualified type, the behavior is undefined.133) -
+
An object that has volatile-qualified type may be modified in ways unknown to the implementation or have other unknown side effects. Therefore any expression referring to such an object shall be evaluated strictly according to the rules of the abstract machine, @@ -6491,10 +6665,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - + unknown factors mentioned previously.134) What constitutes an access to an object that has volatile-qualified type is implementation-defined. -
+
An object that is accessed through a restrict-qualified pointer has a special association with that pointer. This association, defined in 6.7.3.1 below, requires that all accesses to that object use, directly or indirectly, the value of that particular pointer.135) The intended @@ -6502,21 +6676,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. optimization, and deleting all instances of the qualifier from all preprocessing translation units composing a conforming program does not change its meaning (i.e., observable behavior). -
+
If the specification of an array type includes any type qualifiers, the element type is so- qualified, not the array type. If the specification of a function type includes any type qualifiers, the behavior is undefined.136) -
+
For two qualified types to be compatible, both shall have the identically qualified version of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers does not affect the specified type. -
+
EXAMPLE 1 An object declared
- extern const volatile int real_time_clock;+ extern const volatile int real_time_clock; + may be modifiable by hardware, but cannot be assigned to, incremented, or decremented. -
+
EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers modify an aggregate type:
@@ -6531,15 +6706,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pi = &ncs.mem; // valid
pi = &cs.mem; // violates type constraints for =
pci = &cs.mem; // valid
- pi = a[0]; // invalid: a[0] has type ''const int *''
+ pi = a[0]; // invalid: a[0] has type ''const int *''
+
-
-+ +
EXAMPLE 3 The declaration
- _Atomic volatile int *p;+ _Atomic volatile int *p; + specifies that p has the type ''pointer to volatile atomic int'', a pointer to a volatile-qualified atomic type. @@ -6563,21 +6740,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
136) Both of these can occur through the use of typedefs.
-6.7.3.1 Formal definition of restrict
-
+
Let D be a declaration of an ordinary identifier that provides a means of designating an object P as a restrict-qualified pointer to type T. -
+
If D appears inside a block and does not have storage class extern, let B denote the block. If D appears in the list of parameter declarations of a function definition, let B denote the associated block. Otherwise, let B denote the block of main (or the block of whatever function is called at program startup in a freestanding environment). -
+
In what follows, a pointer expression E is said to be based on object P if (at some sequence point in the execution of B prior to the evaluation of E) modifying P to point to a copy of the array object into which it formerly pointed would change the value of E.137) Note that ''based'' is defined only for expressions with pointer types. -
+
During each execution of B, let L be any lvalue that has &L based on P. If L is used to access the value of the object X that it designates, and X is also modified (by any means), then the following requirements apply: T shall not be const-qualified. Every other lvalue @@ -6587,34 +6764,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. object P2, associated with block B2, then either the execution of B2 shall begin before the execution of B, or the execution of B2 shall end prior to the assignment. If these requirements are not met, then the behavior is undefined. -
+
Here an execution of B means that portion of the execution of the program that would correspond to the lifetime of an object with scalar type and automatic storage duration associated with B. -
+
A translator is free to ignore any or all aliasing implications of uses of restrict. -
+
EXAMPLE 1 The file scope declarations
int * restrict a;
int * restrict b;
- extern int c[];
+ extern int c[];
+
assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
program, then it is never accessed using either of the other two.
-
-+ +
EXAMPLE 2 The function parameter declarations in the following example
void f(int n, int * restrict p, int * restrict q)
{
while (n-- > 0)
*p++ = *q++;
- }
+ }
+
assert that, during each execution of the function, if an object is accessed through one of the pointer
parameters, then it is not also accessed through the other.
-+
The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence analysis of function f without examining any of the calls of f in the program. The cost is that the programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the @@ -6626,9 +6805,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. extern int d[100]; f(50, d + 50, d); // valid f(50, d + 1, d); // undefined behavior - } + } + -
+
EXAMPLE 3 The function parameter declarations
void h(int n, int * restrict p, int * restrict q, int * restrict r)
@@ -6636,17 +6816,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int i;
for (i = 0; i < n; i++)
p[i] = q[i] + r[i];
- }
+ }
+
illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
modified within function h.
-+
EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments between restricted pointers declared in nested blocks have defined behavior. - -
+
{
int * restrict p1;
@@ -6658,7 +6838,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
p1 = q2; // undefined behavior
p2 = q2; // undefined behavior
}
- }
+ }
+
+The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For example, this permits new_vector to return a vector. @@ -6670,7 +6852,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. t.n = n; t.v = malloc(n * sizeof (float)); return t; - } + } +
+
function-specifier:
inline
- _Noreturn
+ _Noreturn
+
+
Function specifiers shall be used only in the declaration of an identifier for a function. -
+
An inline definition of a function with external linkage shall not contain a definition of a modifiable object with static or thread storage duration, and shall not contain a reference to an identifier with internal linkage. -
+
In a hosted environment, no function specifier(s) shall appear in a declaration of main.
+
A function specifier may appear more than once; the behavior is the same as if it appeared only once. -
+
A function declared with an inline function specifier is an inline function. Making a * function an inline function suggests that calls to the function be as fast as possible.138) The extent to which such suggestions are effective is implementation-defined.139) @@ -6708,8 +6892,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
Any function with internal linkage can be an inline function. For a function with external linkage, the following restrictions apply: If a function is declared with an inline function specifier, then it shall also be defined in the same translation unit. If all of the @@ -6720,17 +6904,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. provides an alternative to an external definition, which a translator may use to implement any call to the function in the same translation unit. It is unspecified whether a call to the function uses the inline definition or the external definition.140) -
+
A function declared with a _Noreturn function specifier shall not return to its caller. - Recommended practice -
+
The implementation should produce a diagnostic message for a function declared with a _Noreturn function specifier that appears to be capable of returning to its caller. -
+
EXAMPLE 1 The declaration of an inline function with external linkage can result in either an external definition, or a definition available for use only within the translation unit. A file scope declaration with extern creates an external definition. The following example shows an entire translation unit. -
inline double fahr(double t)
{
@@ -6745,26 +6928,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{
/* A translator may perform inline substitutions */
return is_fahr ? cels(temp) : fahr(temp);
- }
+ }
+
+Note that the definition of fahr is an external definition because fahr is also declared with extern, but the definition of cels is an inline definition. Because cels has external linkage and is referenced, an external definition has to appear in another translation unit (see 6.9); the inline definition and the external definition are distinct and either may be used for the call. -
+
EXAMPLE 2 - +
_Noreturn void f () {
abort(); // ok
}
_Noreturn void g (int i) { // causes undefined behavior if i <= 0
if (i > 0) abort();
- }
+ }
+
Forward references: function definitions (6.9.1).
@@ -6785,35 +6971,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
duration are also distinct in each of the definitions.
-6.7.5 Alignment specifier
+
+
alignment-specifier:
_Alignas ( type-name )
- _Alignas ( constant-expression )
+ _Alignas ( constant-expression )
+
+
An alignment attribute shall not be specified in a declaration of a typedef, or a bit-field, or a function, or a parameter, or an object declared with the register storage-class specifier. -
+
The constant expression shall be an integer constant expression. It shall evaluate to a valid fundamental alignment, or to a valid extended alignment supported by the implementation in the context in which it appears, or to zero. -
+
The combined effect of all alignment attributes in a declaration shall not specify an alignment that is less strict than the alignment that would otherwise be required for the type of the object or member being declared.
+
The first form is equivalent to _Alignas(alignof(type-name)). -
+
The alignment requirement of the declared object or member is taken to be the specified alignment. An alignment specification of zero has no effect.141) When multiple alignment specifiers occur in a declaration, the effective alignment requirement is the strictest specified alignment. -
+
If the definition of an object has an alignment specifier, any other declaration of that object shall either specify equivalent alignment or have no alignment specifier. If the definition of an object does not have an alignment specifier, any other declaration of that @@ -6822,31 +7009,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
141) An alignment specification of zero also does not affect other alignment specifications in the same
declaration.
-6.7.6 Declarators
+
+
declarator:
- pointeropt direct-declarator
+ pointeropt direct-declarator
direct-declarator:
identifier
( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
+ direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
+ direct-declarator [ static type-qualifier-listopt assignment-expression ]
direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
+ direct-declarator [ type-qualifier-listopt * ]
direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
+ direct-declarator ( identifier-listopt )
pointer:
- * type-qualifier-listopt
- * type-qualifier-listopt pointer
+ * type-qualifier-listopt
+ * type-qualifier-listopt pointer
type-qualifier-list:
type-qualifier
type-qualifier-list type-qualifier
@@ -6858,83 +7045,90 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
parameter-list , parameter-declaration
parameter-declaration:
declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
+ declaration-specifiers abstract-declaratoropt
identifier-list:
identifier
- identifier-list , identifier
+ identifier-list , identifier
+
+
Each declarator declares one identifier, and asserts that when an operand of the same form as the declarator appears in an expression, it designates a function or object with the scope, storage duration, and type indicated by the declaration specifiers. -
+
A full declarator is a declarator that is not part of another declarator. The end of a full declarator is a sequence point. If, in the nested sequence of declarators in a full - + declarator, there is a declarator specifying a variable length array type, the type specified by the full declarator is said to be variably modified. Furthermore, any type derived by declarator type derivation from a variably modified type is itself variably modified. -
+
In the following subclauses, consider a declaration
- T D1+ T D1 + where T contains the declaration specifiers that specify a type T (such as int) and D1 is a declarator that contains an identifier ident. The type specified for the identifier ident in the various forms of declarator is described inductively using this notation. -
+
If, in the declaration ''T D1'', D1 has the form
- identifier+ identifier + then the type specified for ident is T . -
+
If, in the declaration ''T D1'', D1 has the form
- ( D )+ ( D ) + then ident has the type specified by the declaration ''T D''. Thus, a declarator in parentheses is identical to the unparenthesized declarator, but the binding of complicated declarators may be altered by parentheses. - Implementation limits -
+
As discussed in 5.2.4.1, an implementation may limit the number of pointer, array, and function declarators that modify an arithmetic, structure, union, or void type, either directly or via one or more typedefs.
Forward references: array declarators (6.7.6.2), type definitions (6.7.8).
-6.7.6.1 Pointer declarators
+
+
If, in the declaration ''T D1'', D1 has the form
- * type-qualifier-listopt D+ * type-qualifier-listopt D + and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer. -
+
For two pointer types to be compatible, both shall be identically qualified and both shall be pointers to compatible types. -
+
EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer to a constant value'' and a ''constant pointer to a variable value''. - +
const int *ptr_to_constant;
- int *const constant_ptr;
+ int *const constant_ptr;
+
The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
same location.
-+
The declaration of the constant pointer constant_ptr may be clarified by including a definition for the type ''pointer to int''.
typedef int *int_ptr;
- const int_ptr constant_ptr;
+ const int_ptr constant_ptr;
+
declares constant_ptr as an object that has type ''const-qualified pointer to int''.
-+
In addition to optional type qualifiers and the keyword static, the [ and ] may delimit an expression or *. If they delimit an expression (which specifies the size of an array), the expression shall have an integer type. If the expression is a constant expression, it shall @@ -6942,33 +7136,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. type. The optional type qualifiers and the keyword static shall appear only in a declaration of a function parameter with an array type, and then only in the outermost array type derivation. -
+
If an identifier is declared as having a variably modified type, it shall be an ordinary identifier (as defined in 6.2.3), have no linkage, and have either block scope or function prototype scope. If an identifier is declared to be an object with static or thread storage duration, it shall not have a variable length array type.
+
If, in the declaration ''T D1'', D1 has one of the forms:
- D[ type-qualifier-listopt assignment-expressionopt ]
- D[ static type-qualifier-listopt assignment-expression ]
+ D[ type-qualifier-listopt assignment-expressionopt ]
+ D[ static type-qualifier-listopt assignment-expression ]
D[ type-qualifier-list static assignment-expression ]
- D[ type-qualifier-listopt * ]
+ D[ type-qualifier-listopt * ]
+
and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.142)
(See 6.7.6.3 for the meaning of the optional type qualifiers and the keyword static.)
-+
If the size is not present, the array type is an incomplete type. If the size is * instead of being an expression, the array type is a variable length array type of unspecified size, which can only be used in declarations or type names with function prototype scope;143) - + such arrays are nonetheless complete types. If the size is an integer constant expression and the element type has a known constant size, the array type is not a variable length array type; otherwise, the array type is a variable length array type. (Variable length arrays are a conditional feature that implementations need not support; see 6.10.8.3.) -
+
If the size is an expression that is not an integer constant expression: if it occurs in a declaration at function prototype scope, it is treated as if it were replaced by *; otherwise, each time it is evaluated it shall have a value greater than zero. The size of each instance @@ -6976,27 +7171,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. expression is part of the operand of a sizeof operator and changing the value of the size expression would not affect the result of the operator, it is unspecified whether or not the size expression is evaluated. -
+
For two array types to be compatible, both shall have compatible element types, and if both size specifiers are present, and are integer constant expressions, then both size specifiers shall have the same constant value. If the two array types are used in a context which requires them to be compatible, it is undefined behavior if the two size specifiers evaluate to unequal values. -
+
EXAMPLE 1
- float fa[11], *afp[17];+ float fa[11], *afp[17]; + declares an array of float numbers and an array of pointers to float numbers. -
+
EXAMPLE 2 Note the distinction between the declarations
extern int *x;
- extern int y[];
+ extern int y[];
+
The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
(an incomplete type), the storage for which is defined elsewhere.
-+
EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
extern int n;
@@ -7010,13 +7207,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
p = a; // invalid: not compatible because 4 != 6
r = c; // compatible, but defined behavior only if
// n == 6 and m == n+1
- }
+ }
+
-
-+ +
EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or function prototype scope. Array objects declared with the _Thread_local, static, or extern storage-class specifier cannot have a variable length array (VLA) type. However, an object declared with @@ -7042,7 +7240,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. int (*s)[m]; // valid: auto pointer to VLA extern int (*r)[m]; // invalid: r has linkage and points to VLA static int (*q)[m] = &B; // valid: q is a static block pointer to VLA - } + } +
Forward references: function declarators (6.7.6.3), function definitions (6.9.1), initialization (6.7.9). @@ -7053,62 +7252,64 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
143) Thus, * can be used only in function declarations that are not definitions (see 6.7.6.3).
-6.7.6.3 Function declarators (including prototypes)
+
+
A function declarator shall not specify a return type that is a function type or an array type. -
+
The only storage-class specifier that shall occur in a parameter declaration is register. -
+
An identifier list in a function declarator that is not part of a definition of that function shall be empty. -
+
After adjustment, the parameters in a parameter type list in a function declarator that is part of a definition of that function shall not have incomplete type.
+
If, in the declaration ''T D1'', D1 has the form - +
- D( parameter-type-list )+ D( parameter-type-list ) + or
- D( identifier-listopt )+ D( identifier-listopt ) + and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list T '', then the type specified for ident is ''derived-declarator-type-list function returning T ''. -
+
A parameter type list specifies the types of, and may declare identifiers for, the parameters of the function. -
+
A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to type'', where the type qualifiers (if any) are those specified within the [ and ] of the array type derivation. If the keyword static also appears within the [ and ] of the array type derivation, then for each call to the function, the value of the corresponding actual argument shall provide access to the first element of an array with at least as many elements as specified by the size expression. -
+
A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to function returning type'', as in 6.3.2.1. -
+
If the list terminates with an ellipsis (, ...), no information about the number or types of the parameters after the comma is supplied.144) -
+
The special case of an unnamed parameter of type void as the only item in the list specifies that the function has no parameters. -
+
If, in a parameter declaration, an identifier can be treated either as a typedef name or as a parameter name, it shall be taken as a typedef name. -
+
If the function declarator is not part of a definition of that function, parameters may have incomplete type and may use the [*] notation in their sequences of declarator specifiers to specify variable length array types. -
+
The storage-class specifier in the declaration specifiers for a parameter declaration, if present, is ignored unless the declared parameter is one of the members of the parameter type list for a function definition. -
+
An identifier list declares only the identifiers of the parameters of the function. An empty list in a function declarator that is part of a definition of that function specifies that the function has no parameters. The empty list in a function declarator that is not part of a @@ -7117,8 +7318,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
For two function types to be compatible, both shall specify compatible return types.146) Moreover, the parameter type lists, if both are present, shall agree in the number of parameters and in use of the ellipsis terminator; corresponding parameters shall have @@ -7134,10 +7335,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compatibility and of a composite type, each parameter declared with function or array type is taken as having the adjusted type and each parameter declared with qualified type is taken as having the unqualified version of its declared type.) -
+
EXAMPLE 1 The declaration
- int f(void), *fip(), (*pfi)();+ int f(void), *fip(), (*pfi)(); + declares a function f with no parameters returning an int, a function fip with no parameter specification returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the @@ -7145,33 +7347,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function designator, which is then used to call the function; it returns an int. -
+
If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either internal or external linkage (depending on what file scope declarations for these identifiers are visible), and the identifier of the pointer pfi has block scope and no linkage. -
+
EXAMPLE 2 The declaration
- int (*apfi[3])(int *x, int *y);+ int (*apfi[3])(int *x, int *y); + declares an array apfi of three pointers to functions returning int. Each of these functions has two parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and go out of scope at the end of the declaration of apfi. -
+
EXAMPLE 3 The declaration
- int (*fpfi(int (*)(long), int))(int, ...);+ int (*fpfi(int (*)(long), int))(int, ...); + declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two parameters: a pointer to a function returning an int (with one parameter of type long int), and an int. The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more - + additional arguments of any type. -
+
EXAMPLE 4 The following prototype has a variably modified parameter.
void addscalar(int n, int m,
@@ -7189,26 +7393,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
for (int j = 0, k = n*m+300; j < k; j++)
// a is a pointer to a VLA with n*m+300 elements
a[i][j] += x;
- }
+ }
+
-+
EXAMPLE 5 The following are all compatible function prototype declarators.
double maximum(int n, int m, double a[n][m]);
double maximum(int n, int m, double a[*][*]);
double maximum(int n, int m, double a[ ][*]);
- double maximum(int n, int m, double a[ ][m]);
+ double maximum(int n, int m, double a[ ][m]);
+
as are:
void f(double (* restrict a)[5]);
void f(double a[restrict][5]);
void f(double a[restrict 3][5]);
- void f(double a[restrict static 3][5]);
+ void f(double a[restrict static 3][5]);
+
(Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
Forward references: function definitions (6.9.1), type names (6.7.7). - +
144) The macros defined in the <stdarg.h> header (7.16) may be used to access arguments that @@ -7219,31 +7426,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
146) If both function types are ''old style'', parameter types are not compared.
-6.7.7 Type names
+
+
type-name:
- specifier-qualifier-list abstract-declaratoropt
+ specifier-qualifier-list abstract-declaratoropt
abstract-declarator:
pointer
- pointeropt direct-abstract-declarator
+ pointeropt direct-abstract-declarator
direct-abstract-declarator:
( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
+ direct-abstract-declaratoropt [ type-qualifier-listopt
+ assignment-expressionopt ]
+ direct-abstract-declaratoropt [ static type-qualifier-listopt
assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
+ direct-abstract-declaratoropt [ type-qualifier-list static
assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
+ direct-abstract-declaratoropt [ * ]
+ direct-abstract-declaratoropt ( parameter-type-listopt )
+
+
In several contexts, it is necessary to specify a type. This is accomplished using a type name, which is syntactically a declaration for a function or an object of that type that omits the identifier.147) -
+
EXAMPLE The constructions
(a) int
@@ -7253,7 +7461,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(e) int (*)[*]
(f) int *()
(g) int (*)(void)
- (h) int (*const [])(unsigned int, ...)
+ (h) int (*const [])(unsigned int, ...)
+
name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
@@ -7264,24 +7473,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
147) As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
parameter specification'', rather than redundant parentheses around the omitted identifier.
-6.7.8 Type definitions
+
+
typedef-name:
- identifier
+ identifier
+
+
If a typedef name specifies a variably modified type then it shall have block scope.
+
In a declaration whose storage-class specifier is typedef, each declarator defines an identifier to be a typedef name that denotes the type specified for the identifier in the way described in 6.7.6. Any array size expressions associated with variable length array @@ -7290,36 +7500,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. synonym for the type so specified. That is, in the following declarations:
typedef T type_ident;
- type_ident D;
+ type_ident D;
+
type_ident is defined as a typedef name with the type specified by the declaration
specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
typedef name shares the same name space as other identifiers declared in ordinary
declarators.
-+
EXAMPLE 1 After
typedef int MILES, KLICKSP();
- typedef struct { double hi, lo; } range;
+ typedef struct { double hi, lo; } range;
+
the constructions
MILES distance;
extern KLICKSP *metricp;
range x;
- range z, *zp;
+ range z, *zp;
+
are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
such a structure. The object distance has a type compatible with any other int object.
-+
EXAMPLE 2 After the declarations
typedef struct s1 { int x; } t1, *tp1;
- typedef struct s2 { int x; } t2, *tp2;
+ typedef struct s2 { int x; } t2, *tp2;
+
type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
-
-+ +
EXAMPLE 3 The following obscure constructions
typedef signed int t;
@@ -7328,7 +7542,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
unsigned t:4;
const t:5;
plain r:5;
- };
+ };
+
declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
@@ -7339,12 +7554,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
in an inner scope by
t f(t (t));
- long t;
+ long t;
+
then a function f is declared with type ''function returning signed int with one unnamed parameter
with type pointer to function returning signed int with one unnamed parameter with type signed
int'', and an identifier t with type long int.
-+
EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the following declarations of the signal function specify exactly the same type, the first without making use of any typedef names. @@ -7352,12 +7568,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. typedef void fv(int), (*pfv)(int); void (*signal(int, void (*)(int)))(int); fv *signal(int, fv *); - pfv signal(int, pfv); + pfv signal(int, pfv); + -
+
EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the time the typedef name is defined, not each time it is used: - +
void copyt(int n)
{
@@ -7367,19 +7584,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int b[n]; // a and b are different sizes
for (int i = 1; i < n; i++)
a[i-1] = b[i];
- }
+ }
+
-+
initializer:
assignment-expression
{ initializer-list }
{ initializer-list , }
initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
+ designationopt initializer
+ initializer-list , designationopt initializer
designation:
designator-list =
designator-list:
@@ -7387,42 +7605,45 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
designator-list designator
designator:
[ constant-expression ]
- . identifier
+ . identifier
+
+
No initializer shall attempt to provide a value for an object not contained within the entity being initialized. -
+
The type of the entity to be initialized shall be an array of unknown size or a complete object type that is not a variable length array type. -
+
All the expressions in an initializer for an object that has static or thread storage duration shall be constant expressions or string literals. -
+
If the declaration of an identifier has block scope, and the identifier has external or internal linkage, the declaration shall have no initializer for the identifier. -
+
If a designator has the form
- [ constant-expression ]+ [ constant-expression ] + then the current object (defined below) shall have array type and the expression shall be an integer constant expression. If the array is of unknown size, any nonnegative value is valid. -
+
If a designator has the form
- . identifier+ . identifier + then the current object (defined below) shall have structure or union type and the identifier shall be the name of a member of that type. - +
+
An initializer specifies the initial value stored in an object. -
+
Except where explicitly stated otherwise, for the purposes of this subclause unnamed members of objects of structure and union type do not participate in initialization. Unnamed members of structure objects have indeterminate value even after initialization. -
+
If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then: @@ -7434,35 +7655,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
The initializer for a scalar shall be a single expression, optionally enclosed in braces. The initial value of the object is that of the expression (after conversion); the same type constraints and conversions as for simple assignment apply, taking the type of the scalar to be the unqualified version of its declared type. -
+
The rest of this subclause deals with initializers for objects that have aggregate or union type. -
+
The initializer for a structure or union object that has automatic storage duration shall be either an initializer list as described below, or a single expression that has compatible structure or union type. In the latter case, the initial value of the object, including unnamed members, is that of the expression. -
+
An array of character type may be initialized by a character string literal or UTF-8 string literal, optionally enclosed in braces. Successive bytes of the string literal (including the terminating null character if there is room or if the array is of unknown size) initialize the elements of the array. -
+
An array with element type compatible with a qualified or unqualified version of wchar_t may be initialized by a wide string literal, optionally enclosed in braces. Successive wide characters of the wide string literal (including the terminating null wide character if there is room or if the array is of unknown size) initialize the elements of the array. -
+
Otherwise, the initializer for an object that has aggregate or union type shall be a brace- enclosed list of initializers for the elements or named members. - -
+ +
Each brace-enclosed initializer list has an associated current object. When no designations are present, subobjects of the current object are initialized in order according to the type of the current object: array elements in increasing subscript order, structure @@ -7470,18 +7691,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. designation causes the following initializer to begin initialization of the subobject described by the designator. Initialization then continues forward in order, beginning with the next subobject after that described by the designator.149) -
+
Each designator list begins its description with the current object associated with the closest surrounding brace pair. Each item in the designator list (in order) specifies a particular member of its current object and changes the current object for the next designator (if any) to be that member.150) The current object that results at the end of the designator list is the subobject to be initialized by the following initializer. -
+
The initialization shall occur in initializer list order, each initializer provided for a particular subobject overriding any previously listed initializer for the same subobject;151) all subobjects that are not initialized explicitly shall be initialized implicitly the same as objects that have static storage duration. -
+
If the aggregate or union contains elements or members that are aggregates or unions, these rules apply recursively to the subaggregates or contained unions. If the initializer of a subaggregate or contained union begins with a left brace, the initializers enclosed by @@ -7490,7 +7711,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. taken to account for the elements or members of the subaggregate or the first member of the contained union; any remaining initializers are left to initialize the next element or member of the aggregate of which the current subaggregate or contained union is a part. -
+
If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be @@ -7498,37 +7719,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
If an array of unknown size is initialized, its size is determined by the largest indexed element with an explicit initializer. The array type is completed at the end of its initializer list. -
+
The evaluations of the initialization list expressions are indeterminately sequenced with respect to one another and thus the order in which any side effects occur is unspecified.152) -
+
EXAMPLE 1 Provided that <complex.h> has been #included, the declarations
int i = 3.5;
- double complex c = 5 + 3 * I;
+ double complex c = 5 + 3 * I;
+
define and initialize i with the value 3 and c with the value 5.0 + i3.0.
-+
EXAMPLE 2 The declaration
- int x[] = { 1, 3, 5 };
+ int x[] = { 1, 3, 5 };
+
defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
and there are three initializers.
-+
EXAMPLE 3 The declaration
int y[4][3] = {
{ 1, 3, 5 },
{ 2, 4, 6 },
{ 3, 5, 7 },
- };
+ };
+
is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
@@ -7536,37 +7760,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int y[4][3] = {
1, 3, 5, 2, 4, 6, 3, 5, 7
- };
+ };
+
The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
next three are taken successively for y[1] and y[2].
-+
EXAMPLE 4 The declaration
int z[4][3] = {
{ 1 }, { 2 }, { 3 }, { 4 }
- };
+ };
+
initializes the first column of z as specified and initializes the rest with zeros.
-+
EXAMPLE 5 The declaration
- struct { int a[3], b; } w[] = { { 1 }, 2 };
+ struct { int a[3], b; } w[] = { { 1 }, 2 };
+
is a definition with an inconsistently bracketed initialization. It defines an array with two element
-
+
structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
-+
EXAMPLE 6 The declaration
short q[4][3][2] = {
{ 1 },
{ 2, 3 },
{ 4, 5, 6 }
- };
+ };
+
contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
object: q[0][0][0] is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize
q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
@@ -7580,7 +7808,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
1, 0, 0, 0, 0, 0,
2, 3, 0, 0, 0, 0,
4, 5, 6
- };
+ };
+
or by:
short q[4][3][2] = {
@@ -7594,42 +7823,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{ 4, 5 },
{ 6 },
}
- };
+ };
+
in a fully bracketed form.
-+
Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to cause confusion. -
+
EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the declaration
- typedef int A[]; // OK - declared with block scope+ typedef int A[]; // OK - declared with block scope + the declaration
- A a = { 1, 2 }, b = { 3, 4, 5 };
+ A a = { 1, 2 }, b = { 3, 4, 5 };
+
is identical to
- int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
+ int a[] = { 1, 2 }, b[] = { 3, 4, 5 };
+
due to the rules for incomplete types.
-
-+ +
EXAMPLE 8 The declaration
- char s[] = "abc", t[3] = "abc";+ char s[] = "abc", t[3] = "abc"; + defines ''plain'' char array objects s and t whose elements are initialized with character string literals. This declaration is identical to
char s[] = { 'a', 'b', 'c', '\0' },
- t[] = { 'a', 'b', 'c' };
+ t[] = { 'a', 'b', 'c' };
+
The contents of the arrays are modifiable. On the other hand, the declaration
- char *p = "abc";+ char *p = "abc"; + defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char'' with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to modify the contents of the array, the behavior is undefined. -
+
EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using designators:
@@ -7637,37 +7873,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
const char *nm[] = {
[member_two] = "member two",
[member_one] = "member one",
- };
+ };
+
-+
EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
- div_t answer = { .quot = 2, .rem = -1 };
+ div_t answer = { .quot = 2, .rem = -1 };
+
-+
EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists might be misunderstood:
struct { int a[3], b; } w[] =
- { [0].a = {1}, [1].a[0] = 2 };
+ { [0].a = {1}, [1].a[0] = 2 };
+
-+
EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator: -
int a[MAX] = {
1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
- };
+ };
+
+In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less than ten, some of the values provided by the first five initializers will be overridden by the second five. -
+
EXAMPLE 13 Any member of a union can be initialized:
- union { /* ... */ } u = { .any_member = 42 };
+ union { /* ... */ } u = { .any_member = 42 };
+
Forward references: common definitions <stddef.h> (7.19). - +
148) If the initializer list for a subaggregate or contained union does not begin with a left brace, its @@ -7686,28 +7927,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
152) In particular, the evaluation order need not be the same as the order of subobject initialization.
-6.7.10 Static assertions
+
+
static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
+ _Static_assert ( constant-expression , string-literal ) ;
+
+
The constant expression shall compare unequal to 0.
+
The constant expression shall be an integer constant expression. If the value of the constant expression compares unequal to 0, the declaration has no effect. Otherwise, the constraint is violated and the implementation shall produce a diagnostic message that includes the text of the string literal, except that characters not in the basic source character set are not required to appear in the message.
Forward references: diagnostics (7.2).
-
+
-6.8 Statements and blocks
+
+
statement:
labeled-statement
@@ -7715,19 +7957,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expression-statement
selection-statement
iteration-statement
- jump-statement
+ jump-statement
+
+
A statement specifies an action to be performed. Except as indicated, statements are executed in sequence. -
+
A block allows a set of declarations and statements to be grouped into one syntactic unit. The initializers of objects that have automatic storage duration, and the variable length array declarators of ordinary identifiers with block scope, are evaluated and the values are stored in the objects (including storing an indeterminate value in objects without an initializer) each time the declaration is reached in the order of execution, as if it were a statement, and within each declaration in the order that declarators appear. -
+
A full expression is an expression that is not part of another expression or of a declarator. Each of the following is a full expression: an initializer that is not part of a compound literal; the expression in an expression statement; the controlling expression of a selection @@ -7738,78 +7981,83 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: expression and null statements (6.8.3), selection statements
(6.8.4), iteration statements (6.8.5), the return statement (6.8.6.4).
-6.8.1 Labeled statements
+
+
labeled-statement:
identifier : statement
case constant-expression : statement
- default : statement
+ default : statement
+
+
A case or default label shall appear only in a switch statement. Further constraints on such labels are discussed under the switch statement. - -
+ +
Label names shall be unique within a function.
+
Any statement may be preceded by a prefix that declares an identifier as a label name. Labels in themselves do not alter the flow of control, which continues unimpeded across them.
Forward references: the goto statement (6.8.6.1), the switch statement (6.8.4.2).
-6.8.2 Compound statement
+
+
compound-statement:
- { block-item-listopt }
+ { block-item-listopt }
block-item-list:
block-item
block-item-list block-item
block-item:
declaration
- statement
+ statement
+
+
A compound statement is a block.
-6.8.3 Expression and null statements
+
+
expression-statement:
- expressionopt ;
+ expressionopt ;
+
+
The expression in an expression statement is evaluated as a void expression for its side effects.153) -
+
A null statement (consisting of just a semicolon) performs no operations. -
+
EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the discarding of its value may be made explicit by converting the expression to a void expression by means of a cast:
int p(int);
/* ... */
- (void)p(0);
+ (void)p(0);
+
-
-+ +
EXAMPLE 2 In the program fragment
char *s;
/* ... */
while (*s++ != '\0')
- ;
+ ;
+
a null statement is used to supply an empty loop body to the iteration statement.
-+
EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound statement.
@@ -7823,7 +8071,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
}
/* ... */
end_loop1: ;
- }
+ }
+
Forward references: iteration statements (6.8.5). @@ -7831,47 +8080,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
153) Such as assignments, and function calls which have side effects.
-6.8.4 Selection statements
+
+
selection-statement:
if ( expression ) statement
if ( expression ) statement else statement
- switch ( expression ) statement
+ switch ( expression ) statement
+
+
A selection statement selects among a set of statements depending on the value of a controlling expression. -
+
A selection statement is a block whose scope is a strict subset of the scope of its
enclosing block. Each associated substatement is also a block whose scope is a strict
subset of the scope of the selection statement.
-6.8.4.1 The if statement
+
+
The controlling expression of an if statement shall have scalar type.
+
In both forms, the first substatement is executed if the expression compares unequal to 0. In the else form, the second substatement is executed if the expression compares equal - + to 0. If the first substatement is reached via a label, the second substatement is not executed. -
+
An else is associated with the lexically nearest preceding if that is allowed by the
syntax.
-6.8.4.2 The switch statement
+
+
The controlling expression of a switch statement shall have integer type. -
+
If a switch statement has an associated case or default label within the scope of an identifier with a variably modified type, the entire switch statement shall be within the scope of that identifier.154) -
+
The expression of each case label shall be an integer constant expression and no two of the case constant expressions in the same switch statement shall have the same value after conversion. There may be at most one default label in a switch statement. @@ -7879,12 +8129,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. expressions with values that duplicate case constant expressions in the enclosing switch statement.)
+
A switch statement causes control to jump to, into, or past the statement that is the switch body, depending on the value of a controlling expression, and on the presence of a default label and the values of any case labels on or in the switch body. A case or default label is accessible only within the closest enclosing switch statement. -
+
The integer promotions are performed on the controlling expression. The constant expression in each case label is converted to the promoted type of the controlling expression. If a converted value matches that of the promoted controlling expression, @@ -7892,16 +8142,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. a default label, control jumps to the labeled statement. If no converted case constant expression matches and there is no default label, no part of the switch body is executed. - Implementation limits -
+
As discussed in 5.2.4.1, the implementation may limit the number of case values in a switch statement. - -
+ +
EXAMPLE In the artificial program fragment
switch (expr)
@@ -7913,7 +8163,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* falls through into default code */
default:
printf("%d\n", i);
- }
+ }
+
the object whose identifier is i exists with automatic storage duration (within the block) but is never
initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
access an indeterminate value. Similarly, the call to the function f cannot be reached.
@@ -7924,36 +8175,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
default label associated with the switch that is in the block containing the declaration.
-+
iteration-statement:
while ( expression ) statement
do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
+ for ( expressionopt ; expressionopt ; expressionopt ) statement
+ for ( declaration expressionopt ; expressionopt ) statement
+
+
The controlling expression of an iteration statement shall have scalar type. -
+
The declaration part of a for statement shall only declare identifiers for objects having storage class auto or register.
+
An iteration statement causes a statement called the loop body to be executed repeatedly until the controlling expression compares equal to 0. The repetition occurs regardless of whether the loop body is entered from the iteration statement or by a jump.155) -
+
An iteration statement is a block whose scope is a strict subset of the scope of its enclosing block. The loop body is also a block whose scope is a strict subset of the scope of the iteration statement. -
+
An iteration statement whose controlling expression is not a constant expression,156) that
performs no input/output operations, does not access volatile objects, and performs no
synchronization or atomic operations in its body, controlling expression, or (in the case of
-
+
a for statement) its expression-3, may be assumed by the implementation to
terminate.157)
@@ -7967,21 +8219,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
termination cannot be proven.
-6.8.5.1 The while statement
-
+
The evaluation of the controlling expression takes place before each execution of the loop
body.
-6.8.5.2 The do statement
-
+
The evaluation of the controlling expression takes place after each execution of the loop
body.
-6.8.5.3 The for statement
-
+
The statement
- for ( clause-1 ; expression-2 ; expression-3 ) statement+ for ( clause-1 ; expression-2 ; expression-3 ) statement + behaves as follows: The expression expression-2 is the controlling expression that is evaluated before each execution of the loop body. The expression expression-3 is evaluated as a void expression after each execution of the loop body. If clause-1 is a @@ -7989,7 +8242,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the entire loop, including the other two expressions; it is reached in the order of execution before the first evaluation of the controlling expression. If clause-1 is an expression, it is evaluated as a void expression before the first evaluation of the controlling expression.158) -
+
Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
nonzero constant.
@@ -8000,35 +8253,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
specifies an operation (such as incrementing) that is performed after each iteration.
-6.8.6 Jump statements
+
+
jump-statement:
goto identifier ;
continue ;
break ;
- return expressionopt ;
+ return expressionopt ;
+
-
+
+
A jump statement causes an unconditional jump to another place.
-6.8.6.1 The goto statement
+
+
The identifier in a goto statement shall name a label located somewhere in the enclosing function. A goto statement shall not jump from outside the scope of an identifier having a variably modified type to inside the scope of that identifier.
+
A goto statement causes an unconditional jump to the statement prefixed by the named label in the enclosing function. -
+
EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The following outline presents one possible approach to a problem based on these three assumptions:
+
/* ... */
goto first_time;
@@ -8055,7 +8307,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
}
// handle other operations
/* ... */
- }
+ }
+
+EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably modified types. A jump within the scope, however, is permitted.
@@ -8070,15 +8325,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
lab4:
a[j] = 6.6;
}
- goto lab4; // invalid: going INTO scope of VLA.
+ goto lab4; // invalid: going INTO scope of VLA.
+
-+
A continue statement shall appear only in or as a loop body.
+
A continue statement causes a jump to the loop-continuation portion of the smallest enclosing iteration statement; that is, to the end of the loop body. More precisely, in each of the statements @@ -8086,7 +8342,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* ... */ /* ... */ /* ... */
continue; continue; continue;
- /* ... */ /* ... */ /* ... */
+ /* ... */ /* ... */ /* ... */
+
contin: ; contin: ; contin: ;
} } while (/* ... */); }
unless the continue statement shown is in an enclosed iteration statement (in which
@@ -8096,35 +8353,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
159) Following the contin: label is a null statement.
-6.8.6.3 The break statement
+
+
A break statement shall appear only in or as a switch body or loop body.
+
A break statement terminates execution of the smallest enclosing switch or iteration
statement.
-
+
-6.8.6.4 The return statement
+
+
A return statement with an expression shall not appear in a function whose return type is void. A return statement without an expression shall only appear in a function whose return type is void.
+
A return statement terminates execution of the current function and returns control to its caller. A function may have any number of return statements. -
+
If a return statement with an expression is executed, the value of the expression is returned to the caller as the value of the function call expression. If the expression has a type different from the return type of the function in which it appears, the value is converted as if by assignment to an object having the return type of the function.160) -
+
EXAMPLE In:
struct s { double i; } f(void);
@@ -8143,14 +8400,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
return g.u1.f2;
}
/* ... */
- g.u2.f3 = f();
+ g.u2.f3 = f();
+
there is no undefined behavior, although there would be if the assignment were done directly (without using
a function call to fetch the value).
-
+
160) The return statement is not an assignment. The overlap restriction of subclause 6.5.16.1 does not
@@ -8158,34 +8416,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
or precision than implied by the type; a cast may be used to remove this extra range and precision.
-6.9 External definitions
+
+
translation-unit:
external-declaration
translation-unit external-declaration
external-declaration:
function-definition
- declaration
+ declaration
+
+
The storage-class specifiers auto and register shall not appear in the declaration specifiers in an external declaration. -
+
There shall be no more than one external definition for each identifier declared with internal linkage in a translation unit. Moreover, if an identifier declared with internal linkage is used in an expression (other than as a part of the operand of a sizeof operator whose result is an integer constant), there shall be exactly one external definition for the identifier in the translation unit.
+
As discussed in 5.1.1.1, the unit of program text after preprocessing is a translation unit, which consists of a sequence of external declarations. These are described as ''external'' because they appear outside any function (and hence have file scope). As discussed in 6.7, a declaration that also causes storage to be reserved for an object or a function named by the identifier is a definition. -
+
An external definition is an external declaration that is also a definition of a function (other than an inline definition) or an object. If an identifier declared with external linkage is used in an expression (other than as part of the operand of a sizeof operator @@ -8196,38 +8455,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
161) Thus, if an identifier declared with external linkage is not used in an expression, there need be no
external definition for it.
-6.9.1 Function definitions
+
+
function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
+ declaration-specifiers declarator declaration-listopt compound-statement
declaration-list:
declaration
- declaration-list declaration
+ declaration-list declaration
+
+
The identifier declared in a function definition (which is the name of the function) shall have a function type, as specified by the declarator portion of the function definition.162) -
+
The return type of a function shall be void or a complete object type other than array type. -
+
The storage-class specifier, if any, in the declaration specifiers shall be either extern or static. -
+
If the declarator includes a parameter type list, the declaration of each parameter shall include an identifier, except for the special case of a parameter list consisting of a single parameter of type void, in which case there shall not be an identifier. No declaration list shall follow. -
+
If the declarator includes an identifier list, each declaration in the declaration list shall have at least one declarator, those declarators shall declare only identifiers from the identifier list, and every identifier in the identifier list shall be declared. An identifier @@ -8237,9 +8497,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The declarator in a function definition specifies the name of the function being defined and the identifiers of its parameters. If the declarator includes a parameter type list, the list also specifies the types of all the parameters; such a declarator also serves as a @@ -8248,71 +8508,77 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. following declaration list. In either case, the type of each parameter is adjusted as described in 6.7.6.3 for a parameter type list; the resulting type shall be a complete object type. -
+
If a function that accepts a variable number of arguments is defined without a parameter type list that ends with the ellipsis notation, the behavior is undefined. -
+
Each parameter has automatic storage duration; its identifier is an lvalue.164) The layout of the storage for parameters is unspecified. -
+
On entry to the function, the size expressions of each variably modified parameter are evaluated and the value of each argument expression is converted to the type of the corresponding parameter as if by assignment. (Array expressions and function designators as arguments were converted to pointers before the call.) -
+
After all parameters have been assigned, the compound statement that constitutes the body of the function definition is executed. -
+
If the } that terminates a function is reached, and the value of the function call is used by the caller, the behavior is undefined. -
+
EXAMPLE 1 In the following:
extern int max(int a, int b)
{
return a > b ? a : b;
- }
+ }
+
extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
function declarator; and
- { return a > b ? a : b; }
+ { return a > b ? a : b; }
+
is the function body. The following similar definition uses the identifier-list form for the parameter
declarations:
-
+
extern int max(a, b)
int a, b;
{
return a > b ? a : b;
- }
+ }
+
Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
to the function, whereas the second form does not.
-+
EXAMPLE 2 To pass one function to another, one might say
int f(void);
/* ... */
- g(f);
+ g(f);
+
Then the definition of g might read
void g(int (*funcp)(void))
{
/* ... */
(*funcp)(); /* or funcp(); ... */
- }
+ }
+
or, equivalently,
void g(int func(void))
{
/* ... */
func(); /* or (*func)(); ... */
- }
+ }
+
163) See ''future language directions'' (6.11.7).
164) A parameter identifier cannot be redeclared in the function body except in an enclosed block.
-6.9.2 External object definitions
+
+
If the declaration of an identifier for an object has file scope and an initializer, the declaration is an external definition for the identifier. -
+
A declaration of an identifier for an object that has file scope without an initializer, and without a storage-class specifier or with the storage-class specifier static, constitutes a tentative definition. If a translation unit contains one or more tentative definitions for an @@ -8349,11 +8616,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the behavior is exactly as if the translation unit contains a file scope declaration of that identifier, with the composite type as of the end of the translation unit, with an initializer equal to 0. -
+
If the declaration of an identifier for an object is a tentative definition and has internal linkage, the declared type shall not be an incomplete type. - -
+ +
EXAMPLE 1
int i1 = 1; // definition, external linkage
@@ -8370,23 +8637,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
extern int i2; // refers to previous, whose linkage is internal
extern int i3; // refers to previous, whose linkage is external
extern int i4; // refers to previous, whose linkage is external
- extern int i5; // refers to previous, whose linkage is internal
+ extern int i5; // refers to previous, whose linkage is internal
+
-+
EXAMPLE 2 If at the end of the translation unit containing
- int i[];+ int i[]; + the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to zero on program startup. - + -
- +
+
preprocessing-file:
- groupopt
+ groupopt
group:
group-part
group group-part
@@ -8396,48 +8665,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
text-line
# non-directive
if-section:
- if-group elif-groupsopt else-groupopt endif-line
+ if-group elif-groupsopt else-groupopt endif-line
if-group:
- # if constant-expression new-line groupopt
- # ifdef identifier new-line groupopt
- # ifndef identifier new-line groupopt
+ # if constant-expression new-line groupopt
+ # ifdef identifier new-line groupopt
+ # ifndef identifier new-line groupopt
elif-groups:
elif-group
elif-groups elif-group
elif-group:
- # elif constant-expression new-line groupopt
+ # elif constant-expression new-line groupopt
else-group:
- # else new-line groupopt
+ # else new-line groupopt
endif-line:
# endif new-line
control-line:
# include pp-tokens new-line
# define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
+ # define identifier lparen identifier-listopt )
replacement-list new-line
# define identifier lparen ... ) replacement-list new-line
# define identifier lparen identifier-list , ... )
replacement-list new-line
# undef identifier new-line
# line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
+ # error pp-tokensopt new-line
+ # pragma pp-tokensopt new-line
# new-line
text-line:
- pp-tokensopt new-line
+ pp-tokensopt new-line
non-directive:
pp-tokens new-line
lparen:
a ( character not immediately preceded by white-space
replacement-list:
- pp-tokensopt
+ pp-tokensopt
pp-tokens:
preprocessing-token
pp-tokens preprocessing-token
new-line:
- the new-line character
+ the new-line character
+
+
A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the following constraints: The first token in the sequence is a # preprocessing token that (at the start of translation phase 4) is either the first character in the source file (optionally @@ -8446,35 +8716,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. line character that follows the first token in the sequence.165) A new-line character ends the preprocessing directive even if it occurs within what would otherwise be an - + invocation of a function-like macro. -
+
A text line shall not begin with a # preprocessing token. A non-directive shall not begin with any of the directive names appearing in the syntax. -
+
When in a group that is skipped (6.10.1), the directive syntax is relaxed to allow any sequence of preprocessing tokens to occur between the directive name and the following new-line character.
+
The only white-space characters that shall appear between preprocessing tokens within a preprocessing directive (from just after the introducing # preprocessing token through just before the terminating new-line character) are space and horizontal-tab (including spaces that have replaced comments or possibly other white-space characters in translation phase 3).
+
The implementation can process and skip sections of source files conditionally, include other source files, and replace macros. These capabilities are called preprocessing, because conceptually they occur before translation of the resulting translation unit. -
+
The preprocessing tokens within a preprocessing directive are not subject to macro expansion unless otherwise stated. -
+
EXAMPLE In:
#define EMPTY
- EMPTY # include <file.h>
+ EMPTY # include <file.h>
+
the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
replaced.
@@ -8486,35 +8757,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
# character string literal creation operator in 6.10.3.2, for example).
-+
The expression that controls conditional inclusion shall be an integer constant expression except that: identifiers (including those lexically identical to keywords) are interpreted as * described below;166) and it may contain unary operator expressions of the form
- defined identifier+ defined identifier + or
- defined ( identifier )+ defined ( identifier ) + which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is - + predefined or if it has been the subject of a #define preprocessing directive without an intervening #undef directive with the same subject identifier), 0 if it is not. -
+
Each preprocessing token that remains (in the list of preprocessing tokens that will become the controlling expression) after all macro replacements have occurred shall be in the lexical form of a token (6.4).
+
Preprocessing directives of the forms
- # if constant-expression new-line groupopt - # elif constant-expression new-line groupopt+ # if constant-expression new-line groupopt + # elif constant-expression new-line groupopt + check whether the controlling constant expression evaluates to nonzero. -
+
Prior to evaluation, macro invocations in the list of preprocessing tokens that will become the controlling constant expression are replaced (except for those macro names modified by the defined unary operator), just as in normal text. If the token defined is @@ -8537,16 +8811,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
Preprocessing directives of the forms
- # ifdef identifier new-line groupopt - # ifndef identifier new-line groupopt+ # ifdef identifier new-line groupopt + # ifndef identifier new-line groupopt + check whether the identifier is or is not currently defined as a macro name. Their conditions are equivalent to #if defined identifier and #if !defined identifier respectively. -
+
Each directive's condition is checked in order. If it evaluates to false (zero), the group
that it controls is skipped: directives are processed only through the name that determines
the directive in order to keep track of the level of nested conditionals; the rest of the
@@ -8576,39 +8851,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
including within a preprocessing directive.
-6.10.2 Source file inclusion
+
+
A #include directive shall identify a header or source file that can be processed by the implementation.
+
A preprocessing directive of the form
- # include <h-char-sequence> new-line+ # include <h-char-sequence> new-line + searches a sequence of implementation-defined places for a header identified uniquely by the specified sequence between the < and > delimiters, and causes the replacement of that directive by the entire contents of the header. How the places are specified or the header identified is implementation-defined. -
+
A preprocessing directive of the form
- # include "q-char-sequence" new-line+ # include "q-char-sequence" new-line + causes the replacement of that directive by the entire contents of the source file identified by the specified sequence between the " delimiters. The named source file is searched - + for in an implementation-defined manner. If this search is not supported, or if the search fails, the directive is reprocessed as if it read
- # include <h-char-sequence> new-line+ # include <h-char-sequence> new-line + with the identical contained sequence (including > characters, if any) from the original directive. -
+
A preprocessing directive of the form
- # include pp-tokens new-line+ # include pp-tokens new-line + (that does not match one of the two previous forms) is permitted. The preprocessing tokens after include in the directive are processed just as in normal text. (Each identifier currently defined as a macro name is replaced by its replacement list of @@ -8616,27 +8895,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the two previous forms.170) The method by which a sequence of preprocessing tokens between a < and a > preprocessing token pair or a pair of " characters is combined into a single header name preprocessing token is implementation-defined. -
+
The implementation shall provide unique mappings for sequences consisting of one or more nondigits or digits (6.4.2.1) followed by a period (.) and a single nondigit. The first character shall not be a digit. The implementation may ignore distinctions of alphabetical case and restrict the mapping to eight significant characters before the period. -
+
A #include preprocessing directive may appear in a source file that has been read because of a #include directive in another file, up to an implementation-defined nesting limit (see 5.2.4.1). -
+
EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
#include <stdio.h>
- #include "myprog.h"
+ #include "myprog.h"
+
-
-+ +
EXAMPLE 2 This illustrates macro-replaced #include directives:
#if VERSION == 1
@@ -8646,7 +8926,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#else
#define INCFILE "versN.h"
#endif
- #include INCFILE
+ #include INCFILE
+
Forward references: macro replacement (6.10.3).
@@ -8655,13 +8936,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
phases in 5.1.1.2); thus, an expansion that results in two string literals is an invalid directive.
-6.10.3 Macro replacement
+
+
Two replacement lists are identical if and only if the preprocessing tokens in both have the same number, ordering, spelling, and white-space separation, where all white-space separations are considered identical. -
+
An identifier currently defined as an object-like macro shall not be redefined by another #define preprocessing directive unless the second definition is an object-like macro definition and the two replacement lists are identical. Likewise, an identifier currently @@ -8669,46 +8950,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. preprocessing directive unless the second definition is a function-like macro definition that has the same number and spelling of parameters, and the two replacement lists are identical. -
+
There shall be white-space between the identifier and the replacement list in the definition of an object-like macro. -
+
If the identifier-list in the macro definition does not end with an ellipsis, the number of arguments (including those arguments consisting of no preprocessing tokens) in an invocation of a function-like macro shall equal the number of parameters in the macro definition. Otherwise, there shall be more arguments in the invocation than there are parameters in the macro definition (excluding the ...). There shall exist a ) preprocessing token that terminates the invocation. -
+
The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like macro that uses the ellipsis notation in the parameters. -
+
A parameter identifier in a function-like macro shall be uniquely declared within its scope.
+
The identifier immediately following the define is called the macro name. There is one name space for macro names. Any white-space characters preceding or following the replacement list of preprocessing tokens are not considered part of the replacement list - + for either form of macro. -
+
If a # preprocessing token, followed by an identifier, occurs lexically at the point at which a preprocessing directive could begin, the identifier is not subject to macro replacement. -
+
A preprocessing directive of the form
- # define identifier replacement-list new-line+ # define identifier replacement-list new-line + defines an object-like macro that causes each subsequent instance of the macro name171) to be replaced by the replacement list of preprocessing tokens that constitute the remainder of the directive. The replacement list is then rescanned for more macro names as specified below. -
+
A preprocessing directive of the form
- # define identifier lparen identifier-listopt ) replacement-list new-line
+ # define identifier lparen identifier-listopt ) replacement-list new-line
# define identifier lparen ... ) replacement-list new-line
- # define identifier lparen identifier-list , ... ) replacement-list new-line
+ # define identifier lparen identifier-list , ... ) replacement-list new-line
+
defines a function-like macro with parameters, whose use is similar syntactically to a
function call. The parameters are specified by the optional list of identifiers, whose scope
extends from their declaration in the identifier list until the new-line character that
@@ -8720,19 +9003,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
tokens making up an invocation of a function-like macro, new-line is considered a normal
white-space character.
-+
The sequence of preprocessing tokens bounded by the outside-most matching parentheses forms the list of arguments for the function-like macro. The individual arguments within the list are separated by comma preprocessing tokens, but comma preprocessing tokens between matching inner parentheses do not separate arguments. If there are sequences of preprocessing tokens within the list of arguments that would otherwise act as preprocessing directives,172) the behavior is undefined. -
+
If there is a ... in the identifier-list in the macro definition, then the trailing arguments, including any separating comma preprocessing tokens, are merged to form a single item: - + the variable arguments. The number of arguments so combined is such that, following merger, the number of arguments is one more than the number of parameters in the macro definition (excluding the ...). @@ -8745,8 +9028,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
172) Despite the name, a non-directive is a preprocessing directive.
-6.10.3.1 Argument substitution
-
+
After the arguments for the invocation of a function-like macro have been identified, argument substitution takes place. A parameter in the replacement list, unless preceded by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is @@ -8754,18 +9037,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. expanded. Before being substituted, each argument's preprocessing tokens are completely macro replaced as if they formed the rest of the preprocessing file; no other preprocessing tokens are available. -
+
An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
were a parameter, and the variable arguments shall form the preprocessing tokens used to
replace it.
-6.10.3.2 The # operator
+
+
Each # preprocessing token in the replacement list for a function-like macro shall be followed by a parameter as the next preprocessing token in the replacement list.
+
If, in the replacement list, a parameter is immediately preceded by a # preprocessing
token, both are replaced by a single character string literal preprocessing token that
contains the spelling of the preprocessing token sequence for the corresponding
@@ -8781,21 +9064,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
results is not a valid character string literal, the behavior is undefined. The character
string literal corresponding to an empty argument is "". The order of evaluation of # and
## operators is unspecified.
-
+
-6.10.3.3 The ## operator
+
+
A ## preprocessing token shall not occur at the beginning or at the end of a replacement list for either form of macro definition.
+
If, in the replacement list of a function-like macro, a parameter is immediately preceded or followed by a ## preprocessing token, the parameter is replaced by the corresponding argument's preprocessing token sequence; however, if an argument consists of no preprocessing tokens, the parameter is replaced by a placemarker preprocessing token instead.173) -
+
For both object-like and function-like macro invocations, before the replacement list is reexamined for more macro names to replace, each instance of a ## preprocessing token in the replacement list (not from an argument) is deleted and the preceding preprocessing @@ -8806,7 +9089,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. If the result is not a valid preprocessing token, the behavior is undefined. The resulting token is available for further macro replacement. The order of evaluation of ## operators is unspecified. -
+
EXAMPLE In the following fragment:
#define hash_hash # ## #
@@ -8814,71 +9097,76 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#define in_between(a) mkstr(a)
#define join(c, d) in_between(c hash_hash d)
char p[] = join(x, y); // equivalent to
- // char p[] = "x ## y";
+ // char p[] = "x ## y";
+
The expansion produces, at various stages:
join(x, y)
in_between(x hash_hash y)
in_between(x ## y)
mkstr(x ## y)
- "x ## y"
+ "x ## y"
+
In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
this new token is not the ## operator.
-
+
173) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
exist only within translation phase 4.
-6.10.3.4 Rescanning and further replacement
-
+
After all parameters in the replacement list have been substituted and # and ## processing has taken place, all placemarker preprocessing tokens are removed. The resulting preprocessing token sequence is then rescanned, along with all subsequent preprocessing tokens of the source file, for more macro names to replace. -
+
If the name of the macro being replaced is found during this scan of the replacement list (not including the rest of the source file's preprocessing tokens), it is not replaced. Furthermore, if any nested replacements encounter the name of the macro being replaced, it is not replaced. These nonreplaced macro name preprocessing tokens are no longer available for further replacement even if they are later (re)examined in contexts in which that macro name preprocessing token would otherwise have been replaced. -
+
The resulting completely macro-replaced preprocessing token sequence is not processed
as a preprocessing directive even if it resembles one, but all pragma unary operator
expressions within it are then processed as specified in 6.10.9 below.
-6.10.3.5 Scope of macro definitions
-
+
A macro definition lasts (independent of block structure) until a corresponding #undef directive is encountered or (if none is encountered) until the end of the preprocessing translation unit. Macro definitions have no significance after translation phase 4. -
+
A preprocessing directive of the form
- # undef identifier new-line+ # undef identifier new-line + causes the specified identifier no longer to be defined as a macro name. It is ignored if the specified identifier is not currently defined as a macro name. -
+
EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
#define TABSIZE 100
- int table[TABSIZE];
+ int table[TABSIZE];
+
-+
EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments. It has the advantages of working for any compatible types of the arguments and of generating in-line code without the overhead of function calling. It has the disadvantages of evaluating one or the other of its arguments a second time (including side effects) and generating more code than a function if invoked several times. It also cannot have its address taken, as it has none.
- #define max(a, b) ((a) > (b) ? (a) : (b))+ #define max(a, b) ((a) > (b) ? (a) : (b)) + The parentheses ensure that the arguments and the resulting expression are bound properly. - -
+ +
EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
#define x 3
@@ -8899,15 +9187,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
g(x+(3,4)-w) | h 5) & m
(f)^m(m);
p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
- char c[2][6] = { str(hello), str() };
+ char c[2][6] = { str(hello), str() };
+
results in
f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
int i[] = { 1, 23, 4, 5, };
- char c[2][6] = { "hello", "" };
+ char c[2][6] = { "hello", "" };
+
-+
EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the sequence
@@ -8925,9 +9215,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
== 0) str(: @\n), s);
#include xstr(INCFILE(2).h)
glue(HIGH, LOW);
- xglue(HIGH, LOW)
+ xglue(HIGH, LOW)
+
results in
-
+
printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
fputs(
@@ -8935,7 +9226,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
s);
#include "vers2.h" (after macro replacement, before file access)
"hello";
- "hello" ", world"
+ "hello" ", world"
+
or, after concatenation of the character string literals,
printf("x1= %d, x2= %s", x1, x2);
@@ -8944,21 +9236,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
s);
#include "vers2.h" (after macro replacement, before file access)
"hello";
- "hello, world"
+ "hello, world"
+
Space around the # and ## tokens in the macro definition is optional.
-+
EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
#define t(x,y,z) x ## y ## z
int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
- t(10,,), t(,11,), t(,,12), t(,,) };
+ t(10,,), t(,11,), t(,,12), t(,,) };
+
results in
int j[] = { 123, 45, 67, 89,
- 10, 11, 12, };
+ 10, 11, 12, };
+
-+
EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
#define OBJ_LIKE (1-1)
@@ -8966,17 +9261,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#define FUNC_LIKE(a) ( a )
#define FUNC_LIKE( a )( /* note the white space */ \
a /* other stuff on this line
- */ )
+ */ )
+
But the following redefinitions are invalid:
#define OBJ_LIKE (0) // different token sequence
#define OBJ_LIKE (1 - 1) // different white space
#define FUNC_LIKE(b) ( a ) // different parameter usage
- #define FUNC_LIKE(b) ( b ) // different parameter spelling
+ #define FUNC_LIKE(b) ( b ) // different parameter spelling
+
-+
EXAMPLE 7 Finally, to show the variable argument list macro facilities: - +
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define showlist(...) puts(#__VA_ARGS__)
@@ -8985,71 +9282,78 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
debug("Flag");
debug("X = %d\n", x);
showlist(The first, second, and third items.);
- report(x>y, "x is %d but y is %d", x, y);
+ report(x>y, "x is %d but y is %d", x, y);
+
results in
fprintf(stderr, "Flag" );
fprintf(stderr, "X = %d\n", x );
puts( "The first, second, and third items." );
((x>y)?puts("x>y"):
- printf("x is %d but y is %d", x, y));
+ printf("x is %d but y is %d", x, y));
+
-+
The string literal of a #line directive, if present, shall be a character string literal.
+
The line number of the current source line is one greater than the number of new-line characters read or introduced in translation phase 1 (5.1.1.2) while processing the source file to the current token. -
+
A preprocessing directive of the form
- # line digit-sequence new-line+ # line digit-sequence new-line + causes the implementation to behave as if the following sequence of source lines begins with a source line that has a line number as specified by the digit sequence (interpreted as a decimal integer). The digit sequence shall not specify zero, nor a number greater than 2147483647. -
+
A preprocessing directive of the form
- # line digit-sequence "s-char-sequenceopt" new-line+ # line digit-sequence "s-char-sequenceopt" new-line + sets the presumed line number similarly and changes the presumed name of the source file to be the contents of the character string literal. -
+
A preprocessing directive of the form
- # line pp-tokens new-line+ # line pp-tokens new-line + (that does not match one of the two previous forms) is permitted. The preprocessing tokens after line on the directive are processed just as in normal text (each identifier currently defined as a macro name is replaced by its replacement list of preprocessing tokens). The directive resulting after all replacements shall match one of the two previous forms and is then processed as appropriate. - + -
+
A preprocessing directive of the form
- # error pp-tokensopt new-line+ # error pp-tokensopt new-line + causes the implementation to produce a diagnostic message that includes the specified sequence of preprocessing tokens. -
+
A preprocessing directive of the form
- # pragma pp-tokensopt new-line+ # pragma pp-tokensopt new-line + where the preprocessing token STDC does not immediately follow pragma in the directive (prior to any macro replacement)174) causes the implementation to behave in an implementation-defined manner. The behavior might cause translation to fail or cause the translator or the resulting program to behave in a non-conforming manner. Any such pragma that is not recognized by the implementation is ignored. -
+
If the preprocessing token STDC does immediately follow pragma in the directive (prior to any macro replacement), then no macro replacement is performed on the directive, and the directive shall have one of the following forms175) whose meanings are described @@ -9059,14 +9363,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #pragma STDC FENV_ACCESS on-off-switch #pragma STDC CX_LIMITED_RANGE on-off-switch on-off-switch: one of - ON OFF DEFAULT + ON OFF DEFAULT +
Forward references: the FP_CONTRACT pragma (7.12.2), the FENV_ACCESS pragma (7.6.1), the CX_LIMITED_RANGE pragma (7.3.4). - +
174) An implementation is not required to perform macro replacement in pragmas, but it is permitted @@ -9078,24 +9383,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
175) See ''future language directions'' (6.11.8).
-6.10.7 Null directive
+
+
A preprocessing directive of the form
- # new-line+ # new-line + has no effect. -
+
The values of the predefined macros listed in the following subclauses176) (except for __FILE__ and __LINE__) remain constant throughout the translation unit. -
+
None of these macro names, nor the identifier defined, shall be the subject of a #define or a #undef preprocessing directive. Any other predefined macro names shall begin with a leading underscore followed by an uppercase letter or a second underscore. -
+
The implementation shall not predefine the macro __cplusplus, nor shall it define it in any standard header.
Forward references: standard headers (7.1.2). @@ -9104,8 +9410,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
176) See ''future language directions'' (6.11.9).
-6.10.8.1 Mandatory macros
-
+
The following macro names shall be defined by the implementation: __DATE__ The date of translation of the preprocessing translation unit: a character
@@ -9113,26 +9419,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
months are the same as those generated by the asctime function, and the
first character of dd is a space character if the value is less than 10. If the
date of translation is not available, an implementation-defined valid date
- shall be supplied.
+ shall be supplied.
+
__FILE__ The presumed name of the current source file (a character string literal).177)
__LINE__ The presumed line number (within the current source file) of the current
- source line (an integer constant).177)+ source line (an integer constant).177) + __STDC__ The integer constant 1, intended to indicate a conforming implementation. __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
- implementation or the integer constant 0 if it is not.+ implementation or the integer constant 0 if it is not. + - + __STDC_VERSION__ The integer constant 201ymmL.178) __TIME__ The time of translation of the preprocessing translation unit: a character
string literal of the form "hh:mm:ss" as in the time generated by the
asctime function. If the time of translation is not available, an
- implementation-defined valid time shall be supplied.
+ implementation-defined valid time shall be supplied.
+
Forward references: the asctime function (7.26.3.1).
+
The following macro names are conditionally defined by the implementation: __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
@@ -9155,59 +9465,70 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
consists of all the characters that are defined by ISO/IEC 10646, along with
all amendments and technical corrigenda, as of the specified year and
month. If some other encoding is used, the macro shall not be defined and
- the actual encoding used is implementation-defined.
+ the actual encoding used is implementation-defined.
+
__STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
the encoding for wchar_t, a member of the basic character set need not
have a code value equal to its value when used as the lone character in an
- integer character constant.
+ integer character constant.
+
__STDC_UTF_16__ The integer constant 1, intended to indicate that values of type
char16_t are UTF-16 encoded. If some other encoding is used, the
macro shall not be defined and the actual encoding used is implementation-
- defined.
+ defined.
+
__STDC_UTF_32__ The integer constant 1, intended to indicate that values of type
char32_t are UTF-32 encoded. If some other encoding is used, the
macro shall not be defined and the actual encoding used is implementation-
- defined.
+ defined.
+
Forward references: common definitions (7.19), unicode utilities (7.27).
-
+
-6.10.8.3 Conditional feature macros
-
+
The following macro names are conditionally defined by the implementation: __STDC_ANALYZABLE__ The integer constant 1, intended to indicate conformance to
- the specifications in annex L (Analyzability).+ the specifications in annex L (Analyzability). + __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
- specifications in annex F (IEC 60559 floating-point arithmetic).+ specifications in annex F (IEC 60559 floating-point arithmetic). + __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
adherence to the specifications in annex G (IEC 60559 compatible complex
- arithmetic).
+ arithmetic).
+
__STDC_LIB_EXT1__ The integer constant 201ymmL, intended to indicate support
- for the extensions defined in annex K (Bounds-checking interfaces).179)+ for the extensions defined in annex K (Bounds-checking interfaces).179) + __STDC_NO_COMPLEX__ The integer constant 1, intended to indicate that the
implementation does not support complex types or the <complex.h>
- header.
+ header.
+
__STDC_NO_THREADS__ The integer constant 1, intended to indicate that the
implementation does not support atomic types (including the _Atomic
type qualifier and the <stdatomic.h> header) or the <threads.h>
- header.
+ header.
+
__STDC_NO_VLA__ The integer constant 1, intended to indicate that the
-
implementation does not support variable length arrays or variably
- modified types.
+ modified types.
+
+
An implementation that defines __STDC_NO_COMPLEX__ shall not define
__STDC_IEC_559_COMPLEX__.
@@ -9216,12 +9537,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
each revision of this International Standard.
-6.10.9 Pragma operator
+
+
A unary operator expression of the form:
- _Pragma ( string-literal )+ _Pragma ( string-literal ) + is processed as follows: The string literal is destringized by deleting the L prefix, if present, deleting the leading and trailing double-quotes, replacing each escape sequence \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The @@ -9229,97 +9551,100 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. preprocessing tokens that are executed as if they were the pp-tokens in a pragma - + directive. The original four preprocessing tokens in the unary operator expression are removed. -
+
EXAMPLE A directive of the form:
- #pragma listing on "..\listing.dir"+ #pragma listing on "..\listing.dir" + can also be expressed as:
- _Pragma ( "listing on \"..\\listing.dir\"" )+ _Pragma ( "listing on \"..\\listing.dir\"" ) + The latter form is processed in the same way whether it appears literally as shown, or results from macro replacement, as in: - +
#define LISTING(x) PRAGMA(listing on #x)
#define PRAGMA(x) _Pragma(#x)
- LISTING ( ..\listing.dir )
+ LISTING ( ..\listing.dir )
+
-+
Future standardization may include additional floating-point types, including those with
greater range, precision, or both than long double.
-6.11.2 Linkages of identifiers
-
+
Declaring an identifier with internal linkage at file scope without the static storage-
class specifier is an obsolescent feature.
-6.11.3 External names
-
+
Restriction of the significance of an external name to fewer than 255 characters
(considering each universal character name or extended source character as a single
character) is an obsolescent feature that is a concession to existing implementations.
-6.11.4 Character escape sequences
-
+
Lowercase letters as escape sequences are reserved for future standardization. Other
characters may be used in extensions.
-6.11.5 Storage-class specifiers
-
+
The placement of a storage-class specifier other than at the beginning of the declaration
specifiers in a declaration is an obsolescent feature.
-6.11.6 Function declarators
-
+
The use of function declarators with empty parentheses (not prototype-format parameter
type declarators) is an obsolescent feature.
-6.11.7 Function definitions
-
+
The use of function definitions with separate parameter identifier and declaration lists
(not prototype-format parameter type and identifier declarators) is an obsolescent feature.
-6.11.8 Pragma directives
-
+
Pragmas whose first preprocessing token is STDC are reserved for future standardization.
-6.11.9 Predefined macro names
-
+
Macro names beginning with __STDC_ are reserved for future standardization.
-
+
-7. Library
+
+
A string is a contiguous sequence of characters terminated by and including the first null character. The term multibyte string is sometimes used instead to emphasize special processing given to multibyte characters contained in the string or to avoid confusion with a wide string. A pointer to a string is a pointer to its initial (lowest addressed) character. The length of a string is the number of bytes preceding the null character and the value of a string is the sequence of the values of the contained characters, in order. -
+
The decimal-point character is the character used by functions that convert floating-point numbers to or from character sequences to denote the beginning of the fractional part of such character sequences.180) It is represented in the text and examples by a period, but may be changed by the setlocale function. -
+
A null wide character is a wide character with code value zero. -
+
A wide string is a contiguous sequence of wide characters terminated by and including the first null wide character. A pointer to a wide string is a pointer to its initial (lowest addressed) wide character. The length of a wide string is the number of wide characters preceding the null wide character and the value of a wide string is the sequence of code values of the contained wide characters, in order. -
+
A shift sequence is a contiguous sequence of bytes within a multibyte string that (potentially) causes a change in shift state (see 5.2.1.2). A shift sequence shall not have a corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte @@ -9329,7 +9654,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
180) The functions that make use of the decimal-point character are the numeric conversion functions
@@ -9341,16 +9666,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
implementation's choice.
-7.1.2 Standard headers
-
+
Each library function is declared, with a type that includes a prototype, in a header,182) whose contents are made available by the #include preprocessing directive. The header declares a set of related functions, plus any necessary types and additional macros needed to facilitate their use. Declarations of types described in this clause shall not include type qualifiers, unless explicitly stated otherwise. -
+
The standard headers are183) -
<assert.h> <iso646.h> <stdarg.h> <string.h>
<complex.h> <limits.h> <stdatomic.h> <tgmath.h>
@@ -9358,11 +9682,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
<errno.h> <math.h> <stddef.h> <time.h>
<fenv.h> <setjmp.h> <stdint.h> <uchar.h>
<float.h> <signal.h> <stdio.h> <wchar.h>
- <inttypes.h> <stdalign.h> <stdlib.h> <wctype.h>
+ <inttypes.h> <stdalign.h> <stdlib.h> <wctype.h>
+
+If a file with the same name as one of the above < and > delimited sequences, not provided as part of the implementation, is placed in any of the standard places that are searched for included source files, the behavior is undefined. -
+
Standard headers may be included in any order; each may be included more than once in a given scope, with no effect different from being included only once, except that the effect of including <assert.h> depends on the definition of NDEBUG (see 7.2). If @@ -9373,18 +9699,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. included after the initial reference to the identifier. The program shall not have any macros with names lexically identical to keywords currently defined prior to the inclusion. -
+
Any definition of an object-like macro described in this clause shall expand to code that is fully protected by parentheses where necessary, so that it groups in an arbitrary expression as if it were a single identifier. -
+
Any declaration of a library function shall have external linkage. - -
+ +
A summary of the contents of the standard headers is given in annex B.
Forward references: diagnostics (7.2).
@@ -9396,8 +9722,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
implementations need not support; see 6.10.8.3.
-7.1.3 Reserved identifiers
-
+
Each header declares or defines all identifiers listed in its associated subclause, and optionally declares or defines identifiers listed in its associated future library directions subclause and identifiers which are always reserved either for any use or for use as file @@ -9417,26 +9743,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. future library directions) is reserved for use as a macro name and as an identifier with file scope in the same name space if any of its associated headers is included. -
+
No other identifiers are reserved. If the program declares or defines an identifier in a context in which it is reserved (other than as allowed by 7.1.4), or defines a reserved identifier as a macro name, the behavior is undefined. -
+
If the program removes (with #undef) any macro definition of an identifier in the first group listed above, the behavior is undefined. - +
184) The list of reserved identifiers with external linkage includes math_errhandling, setjmp,
va_copy, and va_end.
-7.1.4 Use of library functions
-
+
Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, @@ -9462,19 +9788,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compatible return type could be called.187) All object-like macros listed as expanding to - + integer constant expressions shall additionally be suitable for use in #if preprocessing directives. -
+
Provided that a library function can be declared without reference to any type defined in a header, it is also permissible to declare the function and use it without including its associated header. -
+
There is a sequence point immediately before a library function returns. -
+
The functions in the standard library are not guaranteed to be reentrant and may modify objects with static or thread storage duration.188) -
+
Unless explicitly stated otherwise in the detailed descriptions that follow, library functions shall prevent data races as follows: A library function shall not directly or indirectly access objects accessible by threads other than the current thread unless the @@ -9483,10 +9809,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the current thread unless the objects are accessed directly or indirectly via the function's non-const arguments.189) Implementations may share their own internal objects between threads if the objects are not visible to users and are protected against data races. -
+
Unless otherwise specified, library functions shall perform all operations solely within the current thread if those operations have effects that are visible to users.190) -
+
EXAMPLE The function atoi may be used in any of several ways:
#include <stdlib.h>
#undef atoi
const char *str;
/* ... */
- i = atoi(str);
+ i = atoi(str);
+
or
#include <stdlib.h>
const char *str;
/* ... */
- i = (atoi)(str);
+ i = (atoi)(str);
+
extern int atoi(const char *);
const char *str;
/* ... */
- i = atoi(str);
+ i = atoi(str);
+
- #define abs(x) _BUILTIN_abs(x)+ #define abs(x) _BUILTIN_abs(x) + for a compiler whose code generator will accept it. In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine function may write
- #undef abs+ #undef abs + whether the implementation's header provides a macro implementation of abs or a built-in implementation. The prototype for the function, which precedes and is hidden by any macro definition, is thereby revealed also. @@ -9554,39 +9886,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
190) This allows implementations to parallelize operations if there are no visible side effects.
-7.2 Diagnostics
-
+
The header <assert.h> defines the assert and static_assert macros and refers to another macro,
- NDEBUG+ NDEBUG + which is not defined by <assert.h>. If NDEBUG is defined as a macro name at the point in the source file where <assert.h> is included, the assert macro is defined simply as
- #define assert(ignore) ((void)0)+ #define assert(ignore) ((void)0) + The assert macro is redefined according to the current state of NDEBUG each time that <assert.h> is included. -
+
The assert macro shall be implemented as a macro, not as an actual function. If the macro definition is suppressed in order to access an actual function, the behavior is undefined. -
+
The macro
- static_assert+ static_assert + expands to _Static_assert. -
+
#include <assert.h>
- void assert(scalar expression);
+ void assert(scalar expression);
+
+
The assert macro puts diagnostic tests into programs; it expands to a void expression. When it is executed, if expression (which shall have a scalar type) is false (that is, compares equal to 0), the assert macro writes information about the particular call that @@ -9598,62 +9934,67 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The assert macro returns no value.
Forward references: the abort function (7.22.4.1). - +
191) The message written might be of the form:
Assertion failed: expression, function abc, file xyz, line nnn.
-7.3 Complex arithmetic
+
+
The header <complex.h> defines macros and declares functions that support complex arithmetic.192) -
+
Implementations that define the macro __STDC_NO_COMPLEX__ need not provide this header nor support any of its facilities. -
+
Each synopsis specifies a family of functions consisting of a principal function with one or more double complex parameters and a double complex or double return value; and other functions with the same name but with f and l suffixes which are corresponding functions with float and long double parameters and return values. -
+
The macro
- complex+ complex + expands to _Complex; the macro
- _Complex_I+ _Complex_I + expands to a constant expression of type const float _Complex, with the value of the imaginary unit.193) -
+
The macros
- imaginary+ imaginary + and
- _Imaginary_I+ _Imaginary_I + are defined if and only if the implementation supports imaginary types;194) if defined, they expand to _Imaginary and a constant expression of type const float _Imaginary with the value of the imaginary unit. -
+
The macro
- I+ I + expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not defined, I shall expand to _Complex_I. -
+
Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then redefine the macros complex, imaginary, and I. - +
Forward references: IEC 60559-compatible complex arithmetic (annex G).
194) A specification for imaginary types is in informative annex G.
-7.3.2 Conventions
-
+
Values are interpreted as radians, not degrees. An implementation may set errno but is
not required to.
-7.3.3 Branch cuts
-
+
Some of the functions below have branch cuts, across which the function is discontinuous. For implementations with a signed zero (including all IEC 60559 implementations) that follow the specifications of annex G, the sign of zero distinguishes @@ -9679,7 +10020,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. function, which has a branch cut along the negative real axis, the top of the cut, with imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with imaginary part -0, maps to the negative imaginary axis. -
+
Implementations that do not support a signed zero (see annex F) cannot distinguish the
sides of branch cuts. These implementations shall map a cut so the function is continuous
as the cut is approached coming around the finite endpoint of the cut in a counter
@@ -9688,14 +10029,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the finite endpoint of the cut along the negative real axis approaches the cut from above,
so the cut maps to the positive imaginary axis.
-7.3.4 The CX_LIMITED_RANGE pragma
+
+
#include <complex.h>
- #pragma STDC CX_LIMITED_RANGE on-off-switch
+ #pragma STDC CX_LIMITED_RANGE on-off-switch
+
+
The usual mathematical formulas for complex multiply, divide, and absolute value are
problematic because of their treatment of infinities and because of undue overflow and
underflow. The CX_LIMITED_RANGE pragma can be used to inform the
@@ -9708,7 +10050,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
another CX_LIMITED_RANGE pragma is encountered (including within a nested
compound statement), or until the end of the compound statement; at the end of a
compound statement the state for the pragma is restored to its condition just before the
-
+
compound statement. If this pragma is used in any other context, the behavior is
undefined. The default state for the pragma is ''off''.
@@ -9719,365 +10061,386 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
(x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
| x + iy | = (sqrt) x 2 + y 2
- -----
+ -----
+
where the programmer can determine they are safe.
-7.3.5 Trigonometric functions
+
+
#include <complex.h>
double complex cacos(double complex z);
float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
+ long double complex cacosl(long double complex z);
+
+
The cacos functions compute the complex arc cosine of z, with branch cuts outside the interval [-1, +1] along the real axis.
+
The cacos functions return the complex arc cosine value, in the range of a strip
mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
real axis.
-7.3.5.2 The casin functions
+
+
#include <complex.h>
double complex casin(double complex z);
float complex casinf(float complex z);
- long double complex casinl(long double complex z);
+ long double complex casinl(long double complex z);
+
+
The casin functions compute the complex arc sine of z, with branch cuts outside the interval [-1, +1] along the real axis.
+
The casin functions return the complex arc sine value, in the range of a strip
mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
-
+
along the real axis.
-7.3.5.3 The catan functions
+
+
#include <complex.h>
double complex catan(double complex z);
float complex catanf(float complex z);
- long double complex catanl(long double complex z);
+ long double complex catanl(long double complex z);
+
+
The catan functions compute the complex arc tangent of z, with branch cuts outside the interval [-i, +i] along the imaginary axis.
+
The catan functions return the complex arc tangent value, in the range of a strip
mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
along the real axis.
-7.3.5.4 The ccos functions
+
+
#include <complex.h>
double complex ccos(double complex z);
float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
+ long double complex ccosl(long double complex z);
+
+
The ccos functions compute the complex cosine of z.
+
The ccos functions return the complex cosine value.
-7.3.5.5 The csin functions
+
+
#include <complex.h>
double complex csin(double complex z);
float complex csinf(float complex z);
- long double complex csinl(long double complex z);
+ long double complex csinl(long double complex z);
+
+
The csin functions compute the complex sine of z. - +
+
The csin functions return the complex sine value.
-7.3.5.6 The ctan functions
+
+
#include <complex.h>
double complex ctan(double complex z);
float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
+ long double complex ctanl(long double complex z);
+
+
The ctan functions compute the complex tangent of z.
+
The ctan functions return the complex tangent value.
-7.3.6 Hyperbolic functions
+
+
#include <complex.h>
double complex cacosh(double complex z);
float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
+ long double complex cacoshl(long double complex z);
+
+
The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch cut at values less than 1 along the real axis.
+
The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
half-strip of nonnegative values along the real axis and in the interval [-ipi , +ipi ] along the
imaginary axis.
-7.3.6.2 The casinh functions
+
- +
+
#include <complex.h>
double complex casinh(double complex z);
float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
+ long double complex casinhl(long double complex z);
+
+
The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts outside the interval [-i, +i] along the imaginary axis.
+
The casinh functions return the complex arc hyperbolic sine value, in the range of a
strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
along the imaginary axis.
-7.3.6.3 The catanh functions
+
+
#include <complex.h>
double complex catanh(double complex z);
float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
+ long double complex catanhl(long double complex z);
+
+
The catanh functions compute the complex arc hyperbolic tangent of z, with branch cuts outside the interval [-1, +1] along the real axis.
+
The catanh functions return the complex arc hyperbolic tangent value, in the range of a
strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
along the imaginary axis.
-7.3.6.4 The ccosh functions
+
+
#include <complex.h>
double complex ccosh(double complex z);
float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
+ long double complex ccoshl(long double complex z);
+
+
The ccosh functions compute the complex hyperbolic cosine of z.
+
The ccosh functions return the complex hyperbolic cosine value.
-
+
-7.3.6.5 The csinh functions
+
+
#include <complex.h>
double complex csinh(double complex z);
float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
+ long double complex csinhl(long double complex z);
+
+
The csinh functions compute the complex hyperbolic sine of z.
+
The csinh functions return the complex hyperbolic sine value.
-7.3.6.6 The ctanh functions
+
+
#include <complex.h>
double complex ctanh(double complex z);
float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
+ long double complex ctanhl(long double complex z);
+
+
The ctanh functions compute the complex hyperbolic tangent of z.
+
The ctanh functions return the complex hyperbolic tangent value.
-7.3.7 Exponential and logarithmic functions
+
+
#include <complex.h>
double complex cexp(double complex z);
float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
+ long double complex cexpl(long double complex z);
+
+
The cexp functions compute the complex base-e exponential of z.
+
The cexp functions return the complex base-e exponential value.
-
+
-7.3.7.2 The clog functions
+
+
#include <complex.h>
double complex clog(double complex z);
float complex clogf(float complex z);
- long double complex clogl(long double complex z);
+ long double complex clogl(long double complex z);
+
+
The clog functions compute the complex natural (base-e) logarithm of z, with a branch cut along the negative real axis.
+
The clog functions return the complex natural logarithm value, in the range of a strip
mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
imaginary axis.
-7.3.8 Power and absolute-value functions
+
+
#include <complex.h>
double cabs(double complex z);
float cabsf(float complex z);
- long double cabsl(long double complex z);
+ long double cabsl(long double complex z);
+
+
The cabs functions compute the complex absolute value (also called norm, modulus, or magnitude) of z.
+
The cabs functions return the complex absolute value.
-7.3.8.2 The cpow functions
+
- +
+
#include <complex.h>
double complex cpow(double complex x, double complex y);
float complex cpowf(float complex x, float complex y);
long double complex cpowl(long double complex x,
- long double complex y);
+ long double complex y);
+
+
The cpow functions compute the complex power function xy , with a branch cut for the first parameter along the negative real axis.
+
The cpow functions return the complex power function value.
-7.3.8.3 The csqrt functions
+
+
#include <complex.h>
double complex csqrt(double complex z);
float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
+ long double complex csqrtl(long double complex z);
+
+
The csqrt functions compute the complex square root of z, with a branch cut along the negative real axis.
+
The csqrt functions return the complex square root value, in the range of the right half-
plane (including the imaginary axis).
-7.3.9 Manipulation functions
+
+
#include <complex.h>
double carg(double complex z);
float cargf(float complex z);
- long double cargl(long double complex z);
+ long double cargl(long double complex z);
+
+
The carg functions compute the argument (also called phase angle) of z, with a branch cut along the negative real axis.
+
The carg functions return the value of the argument in the interval [-pi , +pi ].
-
+
-7.3.9.2 The cimag functions
+
+
#include <complex.h>
double cimag(double complex z);
float cimagf(float complex z);
- long double cimagl(long double complex z);
+ long double cimagl(long double complex z);
+
+
The cimag functions compute the imaginary part of z.196)
+
The cimag functions return the imaginary part value (as a real).
196) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-7.3.9.3 The CMPLX macros
+
+
#include <complex.h>
double complex CMPLX(double x, double y);
float complex CMPLXF(float x, float y);
- long double complex CMPLXL(long double x, long double y);
+ long double complex CMPLXL(long double x, long double y);
+
+
The CMPLX macros expand to an expression of the specified complex type, with the real part having the (converted) value of x and the imaginary part having the (converted) value of y. - Recommended practice -
+
The resulting expression should be suitable for use as an initializer for an object with static or thread storage duration, provided both arguments are likewise suitable.
+
The CMPLX macros return the complex value x + i y. -
+
NOTE These macros act as if the implementation supported imaginary types and the definitions were:
#define CMPLX(x, y) ((double complex)((double)(x) + \
@@ -10085,84 +10448,89 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#define CMPLXF(x, y) ((float complex)((float)(x) + \
_Imaginary_I * (float)(y)))
#define CMPLXL(x, y) ((long double complex)((long double)(x) + \
- _Imaginary_I * (long double)(y)))
+ _Imaginary_I * (long double)(y)))
+
-
+
-+
#include <complex.h>
double complex conj(double complex z);
float complex conjf(float complex z);
- long double complex conjl(long double complex z);
+ long double complex conjl(long double complex z);
+
+
The conj functions compute the complex conjugate of z, by reversing the sign of its imaginary part.
+
The conj functions return the complex conjugate value.
-7.3.9.5 The cproj functions
+
+
#include <complex.h>
double complex cproj(double complex z);
float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
+ long double complex cprojl(long double complex z);
+
+
The cproj functions compute a projection of z onto the Riemann sphere: z projects to z except that all complex infinities (even those with one infinite part and one NaN part) project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is equivalent to
- INFINITY + I * copysign(0.0, cimag(z))+ INFINITY + I * copysign(0.0, cimag(z)) +
+
The cproj functions return the value of the projection onto the Riemann sphere.
-7.3.9.6 The creal functions
+
+
#include <complex.h>
double creal(double complex z);
float crealf(float complex z);
- long double creall(long double complex z);
+ long double creall(long double complex z);
+
+
The creal functions compute the real part of z.197) - +
+
The creal functions return the real part value. - +
197) For a variable z of complex type, z == creal(z) + cimag(z)*I.
-7.4 Character handling
-
+
The header <ctype.h> declares several functions useful for classifying and mapping characters.198) In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF. If the argument has any other value, the behavior is undefined. -
+
The behavior of these functions is affected by the current locale. Those functions that have locale-specific aspects only when not in the "C" locale are noted below. -
+
The term printing character refers to a member of a locale-specific set of characters, each
of which occupies one printing position on a display device; the term control character
refers to a member of a locale-specific set of characters that are not printing
@@ -10177,35 +10545,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
-7.4.1 Character classification functions
-
+
The functions in this subclause return nonzero (true) if and only if the value of the
argument c conforms to that in the description of the function.
-7.4.1.1 The isalnum function
+
+
#include <ctype.h>
- int isalnum(int c);
+ int isalnum(int c);
+
+
The isalnum function tests for any character for which isalpha or isdigit is true.
-7.4.1.2 The isalpha function
+
+
#include <ctype.h>
- int isalpha(int c);
+ int isalpha(int c);
+
+
The isalpha function tests for any character for which isupper or islower is true,
or any character that is one of a locale-specific set of alphabetic characters for which
-
+
none of iscntrl, isdigit, ispunct, or isspace is true.200) In the "C" locale,
isalpha returns true only for the characters for which isupper or islower is true.
@@ -10214,197 +10584,211 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
characters; all four combinations are possible.
-7.4.1.3 The isblank function
+
+
#include <ctype.h>
- int isblank(int c);
+ int isblank(int c);
+
+
The isblank function tests for any character that is a standard blank character or is one
of a locale-specific set of characters for which isspace is true and that is used to
separate words within a line of text. The standard blank characters are the following:
space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
for the standard blank characters.
-7.4.1.4 The iscntrl function
+
+
#include <ctype.h>
- int iscntrl(int c);
+ int iscntrl(int c);
+
+
The iscntrl function tests for any control character.
-7.4.1.5 The isdigit function
+
+
#include <ctype.h>
- int isdigit(int c);
+ int isdigit(int c);
+
+
The isdigit function tests for any decimal-digit character (as defined in 5.2.1).
-7.4.1.6 The isgraph function
+
+
#include <ctype.h>
- int isgraph(int c);
+ int isgraph(int c);
+
-
+
+
The isgraph function tests for any printing character except space (' ').
-7.4.1.7 The islower function
+
+
#include <ctype.h>
- int islower(int c);
+ int islower(int c);
+
+
The islower function tests for any character that is a lowercase letter or is one of a
locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
isspace is true. In the "C" locale, islower returns true only for the lowercase
letters (as defined in 5.2.1).
-7.4.1.8 The isprint function
+
+
#include <ctype.h>
- int isprint(int c);
+ int isprint(int c);
+
+
The isprint function tests for any printing character including space (' ').
-7.4.1.9 The ispunct function
+
+
#include <ctype.h>
- int ispunct(int c);
+ int ispunct(int c);
+
+
The ispunct function tests for any printing character that is one of a locale-specific set
of punctuation characters for which neither isspace nor isalnum is true. In the "C"
locale, ispunct returns true for every printing character for which neither isspace
nor isalnum is true.
-7.4.1.10 The isspace function
+
+
#include <ctype.h>
- int isspace(int c);
+ int isspace(int c);
+
+
The isspace function tests for any character that is a standard white-space character or
is one of a locale-specific set of characters for which isalnum is false. The standard
-
+
white-space characters are the following: space (' '), form feed ('\f'), new-line
('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
"C" locale, isspace returns true only for the standard white-space characters.
-7.4.1.11 The isupper function
+
+
#include <ctype.h>
- int isupper(int c);
+ int isupper(int c);
+
+
The isupper function tests for any character that is an uppercase letter or is one of a
locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
isspace is true. In the "C" locale, isupper returns true only for the uppercase
letters (as defined in 5.2.1).
-7.4.1.12 The isxdigit function
+
+
#include <ctype.h>
- int isxdigit(int c);
+ int isxdigit(int c);
+
+
The isxdigit function tests for any hexadecimal-digit character (as defined in 6.4.4.1).
-7.4.2 Character case mapping functions
+
+
#include <ctype.h>
- int tolower(int c);
+ int tolower(int c);
+
+
The tolower function converts an uppercase letter to a corresponding lowercase letter.
+
If the argument is a character for which isupper is true and there are one or more
corresponding characters, as specified by the current locale, for which islower is true,
the tolower function returns one of the corresponding characters (always the same one
for any given locale); otherwise, the argument is returned unchanged.
-
+
-7.4.2.2 The toupper function
+
+
#include <ctype.h>
- int toupper(int c);
+ int toupper(int c);
+
+
The toupper function converts a lowercase letter to a corresponding uppercase letter.
+
If the argument is a character for which islower is true and there are one or more
corresponding characters, as specified by the current locale, for which isupper is true,
the toupper function returns one of the corresponding characters (always the same one
for any given locale); otherwise, the argument is returned unchanged.
-
+
-7.5 Errors
-
+
The header <errno.h> defines several macros, all relating to the reporting of error conditions. -
+
The macros are
EDOM
EILSEQ
- ERANGE
+ ERANGE
+
which expand to integer constant expressions with type int, distinct positive values, and
which are suitable for use in #if preprocessing directives; and
- errno+ errno + which expands to a modifiable lvalue201) that has type int and thread local storage duration, the value of which is set to a positive error number by several library functions. If a macro definition is suppressed in order to access an actual object, or a program defines an identifier with the name errno, the behavior is undefined. -
+
The value of errno in the initial thread is zero at program startup (the initial value of errno in other threads is an indeterminate value), but is never set to zero by any library function.202) The value of errno may be set to nonzero by a library function call whether or not there is an error, provided the use of errno is not documented in the description of the function in this International Standard. -
+
Additional macro definitions, beginning with E and a digit or E and an uppercase letter,203) may also be specified by the implementation. - +
201) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue @@ -10418,8 +10802,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
203) See ''future library directions'' (7.30.3).
-7.6 Floating-point environment
-
+
The header <fenv.h> defines several macros, and declares types and functions that provide access to the floating-point environment. The floating-point environment refers collectively to any floating-point status flags and control modes supported by the @@ -10428,11 +10812,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. of exceptional floating-point arithmetic to provide auxiliary information.205) A floating- point control mode is a system variable whose value may be set by the user to affect the subsequent behavior of floating-point arithmetic. -
+
The floating-point environment has thread storage duration. The initial state for a thread's floating-point environment is the current state of the floating-point environment of the thread that creates it at the time of creation. -
+
Certain programming conventions support the intended model of use for the floating- point environment:206)
+
The type
- fenv_t+ fenv_t + represents the entire floating-point environment. -
+
The type
- fexcept_t+ fexcept_t + represents the floating-point status flags collectively, including any status the implementation associates with the flags. - -
+ +
Each of the macros
FE_DIVBYZERO
FE_INEXACT
FE_INVALID
FE_OVERFLOW
- FE_UNDERFLOW
+ FE_UNDERFLOW
+
is defined if and only if the implementation supports the floating-point exception by
means of the functions in 7.6.2.207) Additional implementation-defined floating-point
exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
@@ -10473,39 +10860,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expressions with values such that bitwise ORs of all combinations of the macros result in
distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
zero.208)
-+
The macro
- FE_ALL_EXCEPT+ FE_ALL_EXCEPT + is simply the bitwise OR of all floating-point exception macros defined by the implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0. -
+
Each of the macros
FE_DOWNWARD
FE_TONEAREST
FE_TOWARDZERO
- FE_UPWARD
+ FE_UPWARD
+
is defined if and only if the implementation supports getting and setting the represented
rounding direction by means of the fegetround and fesetround functions.
Additional implementation-defined rounding directions, with macro definitions beginning
with FE_ and an uppercase letter, may also be specified by the implementation. The
defined macros expand to integer constant expressions whose values are distinct
nonnegative values.209)
-+
The macro - +
- FE_DFL_ENV+ FE_DFL_ENV + represents the default floating-point environment -- the one installed at program startup
+
Additional implementation-defined environments, with macro definitions beginning with
FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
also be specified by the implementation.
@@ -10531,14 +10921,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
FLT_ROUNDS, they are not required to do so.
-7.6.1 The FENV_ACCESS pragma
+
+
#include <fenv.h>
- #pragma STDC FENV_ACCESS on-off-switch
+ #pragma STDC FENV_ACCESS on-off-switch
+
+
The FENV_ACCESS pragma provides a means to inform the implementation when a program might access the floating-point environment to test floating-point status flags or run under non-default floating-point control modes.210) The pragma shall occur either @@ -10561,10 +10952,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
EXAMPLE -
#include <fenv.h>
void f(double x)
@@ -10576,7 +10966,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
g(x + 1);
h(x + 1);
/* ... */
- }
+ }
+
+
If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.211)
@@ -10593,8 +10985,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
''off'', just one evaluation of x + 1 would suffice.
-7.6.2 Floating-point exceptions
-
+
The following functions provide access to the floating-point status flags.212) The int
input argument for the functions represents a subset of floating-point exceptions, and can
be zero or the bitwise OR of one or more floating-point exception macros, for example
@@ -10609,63 +11001,66 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
content of flags.
-7.6.2.1 The feclearexcept function
+
+
#include <fenv.h>
- int feclearexcept(int excepts);
+ int feclearexcept(int excepts);
+
+
The feclearexcept function attempts to clear the supported floating-point exceptions represented by its argument.
+
The feclearexcept function returns zero if the excepts argument is zero or if all
the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
-
+
-7.6.2.2 The fegetexceptflag function
+
+
#include <fenv.h>
int fegetexceptflag(fexcept_t *flagp,
- int excepts);
+ int excepts);
+
+
The fegetexceptflag function attempts to store an implementation-defined representation of the states of the floating-point status flags indicated by the argument excepts in the object pointed to by the argument flagp.
+
The fegetexceptflag function returns zero if the representation was successfully
stored. Otherwise, it returns a nonzero value.
-7.6.2.3 The feraiseexcept function
+
+
#include <fenv.h>
- int feraiseexcept(int excepts);
+ int feraiseexcept(int excepts);
+
+
The feraiseexcept function attempts to raise the supported floating-point exceptions represented by its argument.213) The order in which these floating-point exceptions are raised is unspecified, except as stated in F.8.6. Whether the feraiseexcept function additionally raises the ''inexact'' floating-point exception whenever it raises the ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
+
The feraiseexcept function returns zero if the excepts argument is zero or if all the specified exceptions were successfully raised. Otherwise, it returns a nonzero value. - +
213) The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
@@ -10673,15 +11068,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
in F.8.6 is in the same spirit.
-7.6.2.4 The fesetexceptflag function
+
+
#include <fenv.h>
int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
+ int excepts);
+
+
The fesetexceptflag function attempts to set the floating-point status flags indicated by the argument excepts to the states stored in the object pointed to by flagp. The value of *flagp shall have been set by a previous call to @@ -10689,34 +11085,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. exceptions represented by the argument excepts. This function does not raise floating- point exceptions, but only sets the state of the flags.
+
The fesetexceptflag function returns zero if the excepts argument is zero or if
all the specified flags were successfully set to the appropriate state. Otherwise, it returns
a nonzero value.
-7.6.2.5 The fetestexcept function
+
+
#include <fenv.h>
- int fetestexcept(int excepts);
+ int fetestexcept(int excepts);
+
+
The fetestexcept function determines which of a specified subset of the floating- point exception flags are currently set. The excepts argument specifies the floating- point status flags to be queried.214)
+
The fetestexcept function returns the value of the bitwise OR of the floating-point exception macros corresponding to the currently set floating-point exceptions included in excepts. -
+
EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set: - +
#include <fenv.h>
/* ... */
@@ -10729,50 +11126,53 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
if (set_excepts & FE_INVALID) f();
if (set_excepts & FE_OVERFLOW) g();
/* ... */
- }
+ }
+
214) This mechanism allows testing several floating-point exceptions with just one function call.
-7.6.3 Rounding
-
+
The fegetround and fesetround functions provide control of rounding direction
modes.
-7.6.3.1 The fegetround function
+
+
#include <fenv.h>
- int fegetround(void);
+ int fegetround(void);
+
+
The fegetround function gets the current rounding direction.
+
The fegetround function returns the value of the rounding direction macro
representing the current rounding direction or a negative value if there is no such
rounding direction macro or the current rounding direction is not determinable.
-7.6.3.2 The fesetround function
+
+
#include <fenv.h>
- int fesetround(int round);
+ int fesetround(int round);
+
+
The fesetround function establishes the rounding direction represented by its argument round. If the argument is not equal to the value of a rounding direction macro, the rounding direction is not changed.
+
The fesetround function returns zero if and only if the requested rounding direction was established. - -
+ +
EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the rounding direction fails.
@@ -10789,44 +11189,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* ... */
fesetround(save_round);
/* ... */
- }
+ }
+
-+
The functions in this section manage the floating-point environment -- status flags and
control modes -- as one entity.
-7.6.4.1 The fegetenv function
+
+
#include <fenv.h>
- int fegetenv(fenv_t *envp);
+ int fegetenv(fenv_t *envp);
+
+
The fegetenv function attempts to store the current floating-point environment in the object pointed to by envp.
+
The fegetenv function returns zero if the environment was successfully stored.
Otherwise, it returns a nonzero value.
-7.6.4.2 The feholdexcept function
+
+
#include <fenv.h>
- int feholdexcept(fenv_t *envp);
+ int feholdexcept(fenv_t *envp);
+
+
The feholdexcept function saves the current floating-point environment in the object pointed to by envp, clears the floating-point status flags, and then installs a non-stop (continue on floating-point exceptions) mode, if available, for all floating-point exceptions.215) - +
+
The feholdexcept function returns zero if and only if non-stop floating-point
exception handling was successfully installed.
@@ -10837,49 +11240,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
function to write routines that hide spurious floating-point exceptions from their callers.
-7.6.4.3 The fesetenv function
+
+
#include <fenv.h>
- int fesetenv(const fenv_t *envp);
+ int fesetenv(const fenv_t *envp);
+
+
The fesetenv function attempts to establish the floating-point environment represented by the object pointed to by envp. The argument envp shall point to an object set by a call to fegetenv or feholdexcept, or equal a floating-point environment macro. Note that fesetenv merely installs the state of the floating-point status flags represented through its argument, and does not raise these floating-point exceptions.
+
The fesetenv function returns zero if the environment was successfully established.
Otherwise, it returns a nonzero value.
-7.6.4.4 The feupdateenv function
+
+
#include <fenv.h>
- int feupdateenv(const fenv_t *envp);
+ int feupdateenv(const fenv_t *envp);
+
+
The feupdateenv function attempts to save the currently raised floating-point exceptions in its automatic storage, install the floating-point environment represented by the object pointed to by envp, and then raise the saved floating-point exceptions. The argument envp shall point to an object set by a call to feholdexcept or fegetenv, or equal a floating-point environment macro.
+
The feupdateenv function returns zero if all the actions were successfully carried out. Otherwise, it returns a nonzero value. - -
+ +
EXAMPLE Hide spurious underflow floating-point exceptions: - +
#include <fenv.h>
double f(double x)
@@ -10896,26 +11301,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
if (feupdateenv(&save_env))
return /* indication of an environmental problem */;
return result;
- }
+ }
+
-+
The header <float.h> defines several macros that expand to various limits and parameters of the standard floating-point types. -
+
The macros, their meanings, and the constraints (or restrictions) on their values are listed
in 5.2.4.2.2.
-
+
-7.8 Format conversion of integer types
-
+
The header <inttypes.h> includes the header <stdint.h> and extends it with additional facilities provided by hosted implementations. -
+
It declares functions for manipulating greatest-width integers and converting numeric character strings to greatest-width integers, and it declares the type
- imaxdiv_t+ imaxdiv_t + which is a structure type that is the type of the value returned by the imaxdiv function. For each type declared in <stdint.h>, it defines corresponding macros for conversion specifiers for use with the formatted input/output functions.216) @@ -10926,8 +11333,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
216) See ''future library directions'' (7.30.4).
-7.8.1 Macros for format specifiers
-
+
Each of the following object-like macros expands to a character string literal containing a * conversion specifier, possibly modified by a length modifier, suitable for use within the format argument of a formatted input/output function when converting the corresponding @@ -10937,39 +11344,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. name corresponding to a similar type name in 7.20.1. In these names, N represents the width of the type as described in 7.20.1. For example, PRIdFAST32 can be used in a format string to print the value of an integer of type int_fast32_t. -
+
The fprintf macros for signed integers are: -
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
+ PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
+
+The fprintf macros for unsigned integers are: -
PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
- PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
+ PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
+
+The fscanf macros for signed integers are: - -
+
SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
- SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
+ SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
+
+The fscanf macros for unsigned integers are: -
SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
- SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
+ SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
+
+For each type that the implementation provides in <stdint.h>, the corresponding fprintf macros shall be defined and the corresponding fscanf macros shall be defined unless the implementation does not have a suitable fscanf length modifier for the type. -
+
EXAMPLE
#include <inttypes.h>
@@ -10980,7 +11391,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
wprintf(L"The largest integer value is %020"
PRIxMAX "\n", i);
return 0;
- }
+ }
+
+
#include <inttypes.h>
- intmax_t imaxabs(intmax_t j);
+ intmax_t imaxabs(intmax_t j);
+
+
The imaxabs function computes the absolute value of an integer j. If the result cannot be represented, the behavior is undefined.218)
+
The imaxabs function returns the absolute value. - +
218) The absolute value of the most negative number cannot be represented in two's complement.
-7.8.2.2 The imaxdiv function
+
+
#include <inttypes.h>
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
+ imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
+
+
The imaxdiv function computes numer / denom and numer % denom in a single operation.
+
The imaxdiv function returns a structure of type imaxdiv_t comprising both the
quotient and the remainder. The structure shall contain (in either order) the members
quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
either part of the result cannot be represented, the behavior is undefined.
-7.8.2.3 The strtoimax and strtoumax functions
+
+
#include <inttypes.h>
intmax_t strtoimax(const char * restrict nptr,
char ** restrict endptr, int base);
uintmax_t strtoumax(const char * restrict nptr,
- char ** restrict endptr, int base);
+ char ** restrict endptr, int base);
+
+
The strtoimax and strtoumax functions are equivalent to the strtol, strtoll, strtoul, and strtoull functions, except that the initial portion of the string is converted to intmax_t and uintmax_t representation, respectively.
+
The strtoimax and strtoumax functions return the converted value, if any. If no conversion could be performed, zero is returned. If the correct value is outside the range of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned @@ -11054,25 +11469,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ERANGE is stored in errno.
Forward references: the strtol, strtoll, strtoul, and strtoull functions
(7.22.1.4).
-
+
-7.8.2.4 The wcstoimax and wcstoumax functions
+
+
#include <stddef.h> // for wchar_t
#include <inttypes.h>
intmax_t wcstoimax(const wchar_t * restrict nptr,
wchar_t ** restrict endptr, int base);
uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
+ wchar_t ** restrict endptr, int base);
+
+
The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll, wcstoul, and wcstoull functions except that the initial portion of the wide string is converted to intmax_t and uintmax_t representation, respectively.
+
The wcstoimax function returns the converted value, if any. If no conversion could be performed, zero is returned. If the correct value is outside the range of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the @@ -11080,13 +11496,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. errno.
Forward references: the wcstol, wcstoll, wcstoul, and wcstoull functions
(7.28.4.1.2).
-
+
-7.9 Alternative spellings
-
+
The header <iso646.h> defines the following eleven macros (on the left) that expand to the corresponding tokens (on the right): - +
and &&
and_eq &=
@@ -11098,30 +11514,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
or ||
or_eq |=
xor ^
- xor_eq ^=
+ xor_eq ^=
+
-+
The header <limits.h> defines several macros that expand to various limits and parameters of the standard integer types. -
+
The macros, their meanings, and the constraints (or restrictions) on their values are listed
in 5.2.4.2.1.
-
+
-7.11 Localization
-
+
The header <locale.h> declares two functions, one type, and defines several macros. -
+
The type is
- struct lconv+ struct lconv + which contains members related to the formatting of numeric values. The structure shall contain at least the following members, in any order. The semantics of the members and their normal ranges are explained in 7.11.2.1. In the "C" locale, the members shall have the values specified in the comments. - -
+
char *decimal_point; // "."
char *thousands_sep; // ""
@@ -11146,7 +11563,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
char int_p_sep_by_space; // CHAR_MAX
char int_n_sep_by_space; // CHAR_MAX
char int_p_sign_posn; // CHAR_MAX
- char int_n_sign_posn; // CHAR_MAX
+ char int_n_sign_posn; // CHAR_MAX
+
+The macros defined are NULL (described in 7.19); and
LC_ALL
@@ -11154,7 +11573,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
LC_CTYPE
LC_MONETARY
LC_NUMERIC
- LC_TIME
+ LC_TIME
+
which expand to integer constant expressions with distinct values, suitable for use as the
first argument to the setlocale function.219) Additional macro definitions, beginning
with the characters LC_ and an uppercase letter,220) may also be specified by the
@@ -11166,16 +11586,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
220) See ''future library directions'' (7.30.5).
-7.11.1 Locale control
+
+
#include <locale.h>
- char *setlocale(int category, const char *locale);
+ char *setlocale(int category, const char *locale);
+
+
The setlocale function selects the appropriate portion of the program's locale as specified by the category and locale arguments. The setlocale function may be used to change or query the program's entire current locale or portions thereof. The value @@ -11188,32 +11609,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. formatted input/output functions and the string conversion functions, as well as the nonmonetary formatting information returned by the localeconv function. LC_TIME affects the behavior of the strftime and wcsftime functions. -
+
A value of "C" for locale specifies the minimal environment for C translation; a value of "" for locale specifies the locale-specific native environment. Other implementation-defined strings may be passed as the second argument to setlocale. - -
+ +
At program startup, the equivalent of
- setlocale(LC_ALL, "C");+ setlocale(LC_ALL, "C"); + is executed. -
+
A call to the setlocale function may introduce a data race with other calls to the setlocale function or with calls to functions that are affected by the current locale. The implementation shall behave as if no library function calls the setlocale function.
+
If a pointer to a string is given for locale and the selection can be honored, the setlocale function returns a pointer to the string associated with the specified category for the new locale. If the selection cannot be honored, the setlocale function returns a null pointer and the program's locale is not changed. -
+
A null pointer for locale causes the setlocale function to return a pointer to the string associated with the category for the program's current locale; the program's locale is not changed.222) -
+
The pointer to string returned by the setlocale function is such that a subsequent call
with that string value and its associated category will restore that part of the program's
locale. The string pointed to shall not be modified by the program, but may be
@@ -11231,24 +11653,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
locale when category has the value LC_ALL.
-7.11.2 Numeric formatting convention inquiry
+
+
#include <locale.h>
- struct lconv *localeconv(void);
+ struct lconv *localeconv(void);
+
+
The localeconv function sets the components of an object with type struct lconv with values appropriate for the formatting of numeric quantities (monetary and otherwise) according to the rules of the current locale. - -
+ +
The members of the structure with type char * are pointers to strings, any of which (except decimal_point) can point to "", to indicate that the value is not available in the current locale or is of zero length. Apart from grouping and mon_grouping, the @@ -11257,131 +11680,159 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. available in the current locale. The members include the following: char *decimal_point
- The decimal-point character used to format nonmonetary quantities.+ The decimal-point character used to format nonmonetary quantities. + char *thousands_sep
The character used to separate groups of digits before the decimal-point
- character in formatted nonmonetary quantities.
+ character in formatted nonmonetary quantities.
+
char *grouping
A string whose elements indicate the size of each group of digits in
- formatted nonmonetary quantities.
+ formatted nonmonetary quantities.
+
char *mon_decimal_point
- The decimal-point used to format monetary quantities.+ The decimal-point used to format monetary quantities. + char *mon_thousands_sep
The separator for groups of digits before the decimal-point in formatted
- monetary quantities.
+ monetary quantities.
+
char *mon_grouping
A string whose elements indicate the size of each group of digits in
- formatted monetary quantities.
+ formatted monetary quantities.
+
char *positive_sign
The string used to indicate a nonnegative-valued formatted monetary
- quantity.
+ quantity.
+
char *negative_sign
- The string used to indicate a negative-valued formatted monetary quantity.+ The string used to indicate a negative-valued formatted monetary quantity. + char *currency_symbol
- The local currency symbol applicable to the current locale.+ The local currency symbol applicable to the current locale. + char frac_digits
The number of fractional digits (those after the decimal-point) to be
- displayed in a locally formatted monetary quantity.
+ displayed in a locally formatted monetary quantity.
+
char p_cs_precedes
-
+
Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a nonnegative locally formatted monetary quantity.
+ succeeds the value for a nonnegative locally formatted monetary quantity.
+
char n_cs_precedes
Set to 1 or 0 if the currency_symbol respectively precedes or
- succeeds the value for a negative locally formatted monetary quantity.
+ succeeds the value for a negative locally formatted monetary quantity.
+
char p_sep_by_space
Set to a value indicating the separation of the currency_symbol, the
sign string, and the value for a nonnegative locally formatted monetary
- quantity.
+ quantity.
+
char n_sep_by_space
Set to a value indicating the separation of the currency_symbol, the
sign string, and the value for a negative locally formatted monetary
- quantity.
+ quantity.
+
char p_sign_posn
Set to a value indicating the positioning of the positive_sign for a
- nonnegative locally formatted monetary quantity.
+ nonnegative locally formatted monetary quantity.
+
char n_sign_posn
Set to a value indicating the positioning of the negative_sign for a
- negative locally formatted monetary quantity.
+ negative locally formatted monetary quantity.
+
char *int_curr_symbol
The international currency symbol applicable to the current locale. The
first three characters contain the alphabetic international currency symbol
in accordance with those specified in ISO 4217. The fourth character
(immediately preceding the null character) is the character used to separate
- the international currency symbol from the monetary quantity.
+ the international currency symbol from the monetary quantity.
+
char int_frac_digits
The number of fractional digits (those after the decimal-point) to be
- displayed in an internationally formatted monetary quantity.
+ displayed in an internationally formatted monetary quantity.
+
char int_p_cs_precedes
Set to 1 or 0 if the int_curr_symbol respectively precedes or
succeeds the value for a nonnegative internationally formatted monetary
- quantity.
+ quantity.
+
char int_n_cs_precedes
Set to 1 or 0 if the int_curr_symbol respectively precedes or
succeeds the value for a negative internationally formatted monetary
- quantity.
+ quantity.
+
char int_p_sep_by_space
-
+
Set to a value indicating the separation of the int_curr_symbol, the
sign string, and the value for a nonnegative internationally formatted
- monetary quantity.
+ monetary quantity.
+
char int_n_sep_by_space
Set to a value indicating the separation of the int_curr_symbol, the
sign string, and the value for a negative internationally formatted monetary
- quantity.
+ quantity.
+
char int_p_sign_posn
Set to a value indicating the positioning of the positive_sign for a
- nonnegative internationally formatted monetary quantity.
+ nonnegative internationally formatted monetary quantity.
+
char int_n_sign_posn
-
Set to a value indicating the positioning of the negative_sign for a
- negative internationally formatted monetary quantity.
+ negative internationally formatted monetary quantity.
+
+The elements of grouping and mon_grouping are interpreted according to the following: CHAR_MAX No further grouping is to be performed. 0 The previous element is to be repeatedly used for the remainder of the
- digits.+ digits. + other The integer value is the number of digits that compose the current group. -
The next element is examined to determine the size of the next group of
- digits before the current group.
+ digits before the current group.
+
+The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space, and int_n_sep_by_space are interpreted according to the following: 0 No space separates the currency symbol and value. 1 If the currency symbol and sign string are adjacent, a space separates them from the
- value; otherwise, a space separates the currency symbol from the value.+ value; otherwise, a space separates the currency symbol from the value. + 2 If the currency symbol and sign string are adjacent, a space separates them;
- otherwise, a space separates the sign string from the value.+ otherwise, a space separates the sign string from the value. + For int_p_sep_by_space and int_n_sep_by_space, the fourth character of int_curr_symbol is used instead of a space. -
+
The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and int_n_sign_posn are interpreted according to the following: 0 Parentheses surround the quantity and currency symbol. @@ -11389,22 +11840,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 2 The sign string succeeds the quantity and currency symbol. 3 The sign string immediately precedes the currency symbol. 4 The sign string immediately succeeds the currency symbol. - -
+ +
The implementation shall behave as if no library function calls the localeconv function.
+
The localeconv function returns a pointer to the filled-in object. The structure pointed to by the return value shall not be modified by the program, but may be overwritten by a subsequent call to the localeconv function. In addition, calls to the setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may overwrite the contents of the structure. -
+
EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format monetary quantities.
- Local format International format+ Local format International format + Country Positive Negative Positive Negative @@ -11412,11 +11864,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C -
+
For these four countries, the respective values for the monetary members of the structure returned by localeconv could be:
- Country1 Country2 Country3 Country4+ Country1 Country2 Country3 Country4 + mon_decimal_point "," "" "," "." mon_thousands_sep "." "." "." "," @@ -11439,12 +11892,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. int_n_sep_by_space 2 1 2 1 int_p_sign_posn 1 1 1 1 int_n_sign_posn 4 1 4 2 - -
+ +
EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members affect the formatted value.
- p_sep_by_space+ p_sep_by_space + p_cs_precedes p_sign_posn 0 1 2 @@ -11453,105 +11907,118 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 1 +1.25$ +1.25 $ + 1.25$ 2 1.25$+ 1.25 $+ 1.25$ + 3 1.25+$ 1.25 +$ 1.25+ $ - 4 1.25$+ 1.25 $+ 1.25$ + + 4 1.25$+ 1.25 $+ 1.25$ + + - +
1 0 ($1.25) ($ 1.25) ($1.25)
1 +$1.25 +$ 1.25 + $1.25
2 $1.25+ $ 1.25+ $1.25 +
3 +$1.25 +$ 1.25 + $1.25
- 4 $+1.25 $+ 1.25 $ +1.25
+ 4 $+1.25 $+ 1.25 $ +1.25
+
-+
The header <math.h> declares two types and many mathematical functions and defines several macros. Most synopses specify a family of functions consisting of a principal function with one or more double parameters, a double return value, or both; and other functions with the same name but with f and l suffixes, which are corresponding functions with float and long double parameters, return values, or both.223) Integer arithmetic functions and conversion functions are discussed later. -
+
The types
float_t
- double_t
+ double_t
+
are floating types at least as wide as float and double, respectively, and such that
double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
float_t and double_t are float and double, respectively; if
FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
otherwise implementation-defined.224)
-+
The macro
- HUGE_VAL+ HUGE_VAL + expands to a positive double constant expression, not necessarily representable as a float. The macros
HUGE_VALF
- HUGE_VALL
+ HUGE_VALL
+
are respectively float and long double analogs of HUGE_VAL.225)
-+
The macro
- INFINITY+ INFINITY + expands to a constant expression of type float representing positive or unsigned infinity, if available; else to a positive constant of type float that overflows at - + translation time.226) -
+
The macro
- NAN+ NAN + is defined if and only if the implementation supports quiet NaNs for the float type. It expands to a constant expression of type float representing a quiet NaN. -
+
The number classification macros
FP_INFINITE
FP_NAN
FP_NORMAL
FP_SUBNORMAL
- FP_ZERO
+ FP_ZERO
+
represent the mutually exclusive kinds of floating-point values. They expand to integer
constant expressions with distinct values. Additional implementation-defined floating-
point classifications, with macro definitions beginning with FP_ and an uppercase letter,
may also be specified by the implementation.
-+
The macro
- FP_FAST_FMA+ FP_FAST_FMA + is optionally defined. If defined, it indicates that the fma function generally executes about as fast as, or faster than, a multiply and an add of double operands.227) The macros
FP_FAST_FMAF
- FP_FAST_FMAL
+ FP_FAST_FMAL
+
are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
these macros expand to the integer constant 1.
-+
The macros
FP_ILOGB0
- FP_ILOGBNAN
+ FP_ILOGBNAN
+
expand to integer constant expressions whose values are returned by ilogb(x) if x is
zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
-INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
-
-+ +
The macros
MATH_ERRNO
- MATH_ERREXCEPT
+ MATH_ERREXCEPT
+
expand to the integer constants 1 and 2, respectively; the macro
- math_errhandling+ math_errhandling + expands to an expression that has type int and the value MATH_ERRNO, MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is constant for the duration of the program. It is unspecified whether @@ -11580,14 +12047,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. substantially slower. -
+
The behavior of each of the functions in <math.h> is specified for all representable values of its input arguments, except where stated otherwise. Each function shall execute as if it were a single operation without raising SIGFPE and without generating any of the floating-point exceptions ''invalid'', ''divide-by-zero'', or ''overflow'' except to reflect the result of the function. -
+
For all functions, a domain error occurs if an input argument is outside the domain over which the mathematical function is defined. The description of each function lists any required domain errors; an implementation may define additional domain errors, provided @@ -11596,7 +12063,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. expression math_errhandling & MATH_ERRNO is nonzero, the integer expression errno acquires the value EDOM; if the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised. -
+
Similarly, a pole error (also known as a singularity or infinitary) occurs if the mathematical function has an exact infinite result as the finite input argument(s) are approached in the limit (for example, log(0.0)). The description of each function lists @@ -11605,14 +12072,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. error, the function returns an implementation-defined value; if the integer expression - + math_errhandling & MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the ''divide-by-zero'' floating-point exception is raised. -
+
Likewise, a range error occurs if the mathematical result of the function cannot be represented in an object of the specified type, due to extreme magnitude. -
+
A floating result overflows if the magnitude of the mathematical result is finite but so large that the mathematical result cannot be represented without extraordinary roundoff error in an object of the specified type. If a floating result overflows and default rounding @@ -11622,7 +12089,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the integer expression errno acquires the value ERANGE; if the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the ''overflow'' floating- point exception is raised. -
+
The result underflows if the magnitude of the mathematical result is so small that the mathematical result cannot be represented, without extraordinary roundoff error, in an object of the specified type.229) If the result underflows, the function returns an @@ -11632,7 +12099,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. value ERANGE is implementation-defined; if the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow'' floating-point exception is raised is implementation-defined. -
+
If a domain, pole, or range error occurs and the integer expression math_errhandling & MATH_ERRNO is zero,230) then errno shall either be set to the value corresponding to the error or left unmodified. If no such error occurs, errno @@ -11641,7 +12108,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
228) In an implementation that supports infinities, this allows an infinity as an argument to be a domain @@ -11653,14 +12120,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
230) Math errors are being indicated by the floating-point exception flags rather than by errno.
-7.12.2 The FP_CONTRACT pragma
+
+
#include <math.h>
- #pragma STDC FP_CONTRACT on-off-switch
+ #pragma STDC FP_CONTRACT on-off-switch
+
+
The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
state is ''off'') the implementation to contract expressions (6.5). Each pragma can occur
either outside external declarations or preceding all explicit declarations and statements
@@ -11674,30 +12142,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
implementation-defined.
-7.12.3 Classification macros
-
+
In the synopses in this subclause, real-floating indicates that the argument shall be an
expression of real floating type.
-7.12.3.1 The fpclassify macro
+
+
#include <math.h>
- int fpclassify(real-floating x);
+ int fpclassify(real-floating x);
+
+
The fpclassify macro classifies its argument value as NaN, infinite, normal, subnormal, zero, or into another implementation-defined category. First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then classification is based on the type of the argument.231)
+
The fpclassify macro returns the value of the number classification macro appropriate to the value of its argument. * - +
231) Since an expression can be evaluated with more range and precision than its type has, it is important to
@@ -11705,55 +12174,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
become subnormal when converted to double, and zero when converted to float.
-7.12.3.2 The isfinite macro
+
+
#include <math.h>
- int isfinite(real-floating x);
+ int isfinite(real-floating x);
+
+
The isfinite macro determines whether its argument has a finite value (zero, subnormal, or normal, and not infinite or NaN). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.
+
The isfinite macro returns a nonzero value if and only if its argument has a finite
value.
-7.12.3.3 The isinf macro
+
+
#include <math.h>
- int isinf(real-floating x);
+ int isinf(real-floating x);
+
+
The isinf macro determines whether its argument value is an infinity (positive or negative). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.
+
The isinf macro returns a nonzero value if and only if its argument has an infinite
value.
-7.12.3.4 The isnan macro
+
+
#include <math.h>
- int isnan(real-floating x);
+ int isnan(real-floating x);
+
+
The isnan macro determines whether its argument value is a NaN. First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.232) - +
+
The isnan macro returns a nonzero value if and only if its argument has a NaN value.
+
#include <math.h>
- int isnormal(real-floating x);
+ int isnormal(real-floating x);
+
+
The isnormal macro determines whether its argument value is normal (neither zero, subnormal, infinite, nor NaN). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.
+
The isnormal macro returns a nonzero value if and only if its argument has a normal
value.
-7.12.3.6 The signbit macro
+
+
#include <math.h>
- int signbit(real-floating x);
+ int signbit(real-floating x);
+
+
The signbit macro determines whether the sign of its argument value is negative.233)
+
The signbit macro returns a nonzero value if and only if the sign of its argument value is negative. - +
233) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
unsigned, it is treated as positive.
-7.12.4 Trigonometric functions
+
+
#include <math.h>
double acos(double x);
float acosf(float x);
- long double acosl(long double x);
+ long double acosl(long double x);
+
+
The acos functions compute the principal value of the arc cosine of x. A domain error occurs for arguments not in the interval [-1, +1].
+
The acos functions return arccos x in the interval [0, pi ] radians.
-7.12.4.2 The asin functions
+
+
#include <math.h>
double asin(double x);
float asinf(float x);
- long double asinl(long double x);
+ long double asinl(long double x);
+
+
The asin functions compute the principal value of the arc sine of x. A domain error occurs for arguments not in the interval [-1, +1].
+
The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
-7.12.4.3 The atan functions
+
+
#include <math.h>
double atan(double x);
float atanf(float x);
- long double atanl(long double x);
+ long double atanl(long double x);
+
+
The atan functions compute the principal value of the arc tangent of x. - +
+
The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
-7.12.4.4 The atan2 functions
+
+
#include <math.h>
double atan2(double y, double x);
float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
+ long double atan2l(long double y, long double x);
+
+
The atan2 functions compute the value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the return value. A domain error may occur if both arguments are zero.
+
The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
-7.12.4.5 The cos functions
+
+
#include <math.h>
double cos(double x);
float cosf(float x);
- long double cosl(long double x);
+ long double cosl(long double x);
+
+
The cos functions compute the cosine of x (measured in radians).
+
The cos functions return cos x.
-7.12.4.6 The sin functions
+
+
#include <math.h>
double sin(double x);
float sinf(float x);
- long double sinl(long double x);
+ long double sinl(long double x);
+
+
The sin functions compute the sine of x (measured in radians). - +
+
The sin functions return sin x.
-7.12.4.7 The tan functions
+
+
#include <math.h>
double tan(double x);
float tanf(float x);
- long double tanl(long double x);
+ long double tanl(long double x);
+
+
The tan functions return the tangent of x (measured in radians).
+
The tan functions return tan x.
-7.12.5 Hyperbolic functions
+
+
#include <math.h>
double acosh(double x);
float acoshf(float x);
- long double acoshl(long double x);
+ long double acoshl(long double x);
+
+
The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain error occurs for arguments less than 1.
+
The acosh functions return arcosh x in the interval [0, +(inf)].
-7.12.5.2 The asinh functions
+
+
#include <math.h>
double asinh(double x);
float asinhf(float x);
- long double asinhl(long double x);
+ long double asinhl(long double x);
+
+
The asinh functions compute the arc hyperbolic sine of x. - +
+
The asinh functions return arsinh x.
-7.12.5.3 The atanh functions
+
+
#include <math.h>
double atanh(double x);
float atanhf(float x);
- long double atanhl(long double x);
+ long double atanhl(long double x);
+
+
The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs for arguments not in the interval [-1, +1]. A pole error may occur if the argument equals -1 or +1.
+
The atanh functions return artanh x.
-7.12.5.4 The cosh functions
+
+
#include <math.h>
double cosh(double x);
float coshf(float x);
- long double coshl(long double x);
+ long double coshl(long double x);
+
+
The cosh functions compute the hyperbolic cosine of x. A range error occurs if the magnitude of x is too large.
+
The cosh functions return cosh x.
-7.12.5.5 The sinh functions
+
+
#include <math.h>
double sinh(double x);
float sinhf(float x);
- long double sinhl(long double x);
+ long double sinhl(long double x);
+
+
The sinh functions compute the hyperbolic sine of x. A range error occurs if the magnitude of x is too large. - +
+
The sinh functions return sinh x.
-7.12.5.6 The tanh functions
+
+
#include <math.h>
double tanh(double x);
float tanhf(float x);
- long double tanhl(long double x);
+ long double tanhl(long double x);
+
+
The tanh functions compute the hyperbolic tangent of x.
+
The tanh functions return tanh x.
-7.12.6 Exponential and logarithmic functions
+
+
#include <math.h>
double exp(double x);
float expf(float x);
- long double expl(long double x);
+ long double expl(long double x);
+
+
The exp functions compute the base-e exponential of x. A range error occurs if the magnitude of x is too large.
+
The exp functions return ex .
-7.12.6.2 The exp2 functions
+
+
#include <math.h>
double exp2(double x);
float exp2f(float x);
- long double exp2l(long double x);
+ long double exp2l(long double x);
+
+
The exp2 functions compute the base-2 exponential of x. A range error occurs if the magnitude of x is too large. - +
+
The exp2 functions return 2x .
-7.12.6.3 The expm1 functions
+
+
#include <math.h>
double expm1(double x);
float expm1f(float x);
- long double expm1l(long double x);
+ long double expm1l(long double x);
+
+
The expm1 functions compute the base-e exponential of the argument, minus 1. A range error occurs if x is too large.234)
+
The expm1 functions return ex - 1.
234) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
-7.12.6.4 The frexp functions
+
+
#include <math.h>
double frexp(double value, int *exp);
float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
+ long double frexpl(long double value, int *exp);
+
+
The frexp functions break a floating-point number into a normalized fraction and an integral power of 2. They store the integer in the int object pointed to by exp.
+
If value is not a floating-point number or if the integral power of 2 is outside the range
of int, the results are unspecified. Otherwise, the frexp functions return the value x,
such that x has a magnitude in the interval [1/2, 1) or zero, and value equals x x 2*exp .
@@ -12091,18 +12582,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-7.12.6.5 The ilogb functions
+
+
#include <math.h>
int ilogb(double x);
int ilogbf(float x);
- int ilogbl(long double x);
+ int ilogbl(long double x);
+
+
The ilogb functions extract the exponent of x as a signed int value. If x is zero they compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling @@ -12110,142 +12602,150 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside the range of the return type, the numeric result is unspecified.
+
The ilogb functions return the exponent of x as a signed int value.
Forward references: the logb functions (7.12.6.11).
-7.12.6.6 The ldexp functions
+
+
#include <math.h>
double ldexp(double x, int exp);
float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
+ long double ldexpl(long double x, int exp);
+
+
The ldexp functions multiply a floating-point number by an integral power of 2. A range error may occur.
+
The ldexp functions return x x 2exp .
-7.12.6.7 The log functions
+
- +
+
#include <math.h>
double log(double x);
float logf(float x);
- long double logl(long double x);
+ long double logl(long double x);
+
+
The log functions compute the base-e (natural) logarithm of x. A domain error occurs if the argument is negative. A pole error may occur if the argument is zero.
+
The log functions return loge x.
-7.12.6.8 The log10 functions
+
+
#include <math.h>
double log10(double x);
float log10f(float x);
- long double log10l(long double x);
+ long double log10l(long double x);
+
+
The log10 functions compute the base-10 (common) logarithm of x. A domain error occurs if the argument is negative. A pole error may occur if the argument is zero.
+
The log10 functions return log10 x.
-7.12.6.9 The log1p functions
+
+
#include <math.h>
double log1p(double x);
float log1pf(float x);
- long double log1pl(long double x);
+ long double log1pl(long double x);
+
+
The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.235) A domain error occurs if the argument is less than -1. A pole error may occur if the argument equals -1.
+
The log1p functions return loge (1 + x). - +
235) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
-7.12.6.10 The log2 functions
+
+
#include <math.h>
double log2(double x);
float log2f(float x);
- long double log2l(long double x);
+ long double log2l(long double x);
+
+
The log2 functions compute the base-2 logarithm of x. A domain error occurs if the argument is less than zero. A pole error may occur if the argument is zero.
+
The log2 functions return log2 x.
-7.12.6.11 The logb functions
+
+
#include <math.h>
double logb(double x);
float logbf(float x);
- long double logbl(long double x);
+ long double logbl(long double x);
+
+
The logb functions extract the exponent of x, as a signed integer value in floating-point format. If x is subnormal it is treated as though it were normalized; thus, for positive finite x,
- 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX+ 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX + A domain error or pole error may occur if the argument is zero.
+
The logb functions return the signed exponent of x.
-7.12.6.12 The modf functions
+
+
#include <math.h>
double modf(double value, double *iptr);
float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
+ long double modfl(long double value, long double *iptr);
+
+
The modf functions break the argument value into integral and fractional parts, each of which has the same type and sign as the argument. They store the integral part (in - + floating-point format) in the object pointed to by iptr.
+
The modf functions return the signed fractional part of value.
-7.12.6.13 The scalbn and scalbln functions
+
+
#include <math.h>
double scalbn(double x, int n);
@@ -12253,263 +12753,283 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
long double scalbnl(long double x, int n);
double scalbln(double x, long int n);
float scalblnf(float x, long int n);
- long double scalblnl(long double x, long int n);
+ long double scalblnl(long double x, long int n);
+
+
The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not normally by computing FLT_RADIXn explicitly. A range error may occur.
+
The scalbn and scalbln functions return x x FLT_RADIXn .
-7.12.7 Power and absolute-value functions
+
+
#include <math.h>
double cbrt(double x);
float cbrtf(float x);
- long double cbrtl(long double x);
+ long double cbrtl(long double x);
+
+
The cbrt functions compute the real cube root of x.
+
The cbrt functions return x1/3 .
-
+
-7.12.7.2 The fabs functions
+
+
#include <math.h>
double fabs(double x);
float fabsf(float x);
- long double fabsl(long double x);
+ long double fabsl(long double x);
+
+
The fabs functions compute the absolute value of a floating-point number x.
+
The fabs functions return | x |.
-7.12.7.3 The hypot functions
+
+
#include <math.h>
double hypot(double x, double y);
float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
+ long double hypotl(long double x, long double y);
+
+
The hypot functions compute the square root of the sum of the squares of x and y, without undue overflow or underflow. A range error may occur. -
+
+
The hypot functions return (sqrt)x2 + y2 .
-
- -----
+ -----
+
-+
#include <math.h>
double pow(double x, double y);
float powf(float x, float y);
- long double powl(long double x, long double y);
+ long double powl(long double x, long double y);
+
+
The pow functions compute x raised to the power y. A domain error occurs if x is finite and negative and y is finite and not an integer value. A range error may occur. A domain error may occur if x is zero and y is zero. A domain error or pole error may occur if x is zero and y is less than zero. - +
+
The pow functions return xy .
-7.12.7.5 The sqrt functions
+
+
#include <math.h>
double sqrt(double x);
float sqrtf(float x);
- long double sqrtl(long double x);
+ long double sqrtl(long double x);
+
+
The sqrt functions compute the nonnegative square root of x. A domain error occurs if the argument is less than zero.
+
The sqrt functions return (sqrt)x.
-
- -
+ -
+
-+
#include <math.h>
double erf(double x);
float erff(float x);
- long double erfl(long double x);
+ long double erfl(long double x);
+
+
The erf functions compute the error function of x.
+
2 x
(integral) e-t dt.
- 2
+ 2
+
The erf functions return erf x =
(sqrt)pi
-
- - 0
+ - 0
+
-+
#include <math.h>
double erfc(double x);
float erfcf(float x);
- long double erfcl(long double x);
+ long double erfcl(long double x);
+
+
The erfc functions compute the complementary error function of x. A range error occurs if x is too large. - +
+
2 (inf)
(integral) e-t dt.
- 2
+ 2
+
The erfc functions return erfc x = 1 - erf x =
(sqrt)pi
-
- - x
+ - x
+
-+
#include <math.h>
double lgamma(double x);
float lgammaf(float x);
- long double lgammal(long double x);
+ long double lgammal(long double x);
+
+
The lgamma functions compute the natural logarithm of the absolute value of gamma of x. A range error occurs if x is too large. A pole error may occur if x is a negative integer or zero.
+
The lgamma functions return loge | (Gamma)(x) |.
-7.12.8.4 The tgamma functions
+
+
#include <math.h>
double tgamma(double x);
float tgammaf(float x);
- long double tgammal(long double x);
+ long double tgammal(long double x);
+
+
The tgamma functions compute the gamma function of x. A domain error or pole error may occur if x is a negative integer or zero. A range error occurs if the magnitude of x is too large and may occur if the magnitude of x is too small.
+
The tgamma functions return (Gamma)(x).
-
+
-7.12.9 Nearest integer functions
+
+
#include <math.h>
double ceil(double x);
float ceilf(float x);
- long double ceill(long double x);
+ long double ceill(long double x);
+
+
The ceil functions compute the smallest integer value not less than x.
+
The ceil functions return [^x^], expressed as a floating-point number.
-7.12.9.2 The floor functions
+
+
#include <math.h>
double floor(double x);
float floorf(float x);
- long double floorl(long double x);
+ long double floorl(long double x);
+
+
The floor functions compute the largest integer value not greater than x.
+
The floor functions return [_x_], expressed as a floating-point number.
-7.12.9.3 The nearbyint functions
+
+
#include <math.h>
double nearbyint(double x);
float nearbyintf(float x);
- long double nearbyintl(long double x);
+ long double nearbyintl(long double x);
+
+
The nearbyint functions round their argument to an integer value in floating-point format, using the current rounding direction and without raising the ''inexact'' floating- point exception. - +
+
The nearbyint functions return the rounded integer value.
-7.12.9.4 The rint functions
+
+
#include <math.h>
double rint(double x);
float rintf(float x);
- long double rintl(long double x);
+ long double rintl(long double x);
+
+
The rint functions differ from the nearbyint functions (7.12.9.3) only in that the rint functions may raise the ''inexact'' floating-point exception if the result differs in value from the argument.
+
The rint functions return the rounded integer value.
-7.12.9.5 The lrint and llrint functions
+
+
#include <math.h>
long int lrint(double x);
@@ -12517,38 +13037,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
long int lrintl(long double x);
long long int llrint(double x);
long long int llrintf(float x);
- long long int llrintl(long double x);
+ long long int llrintl(long double x);
+
+
The lrint and llrint functions round their argument to the nearest integer value, rounding according to the current rounding direction. If the rounded value is outside the range of the return type, the numeric result is unspecified and a domain error or range error may occur.
+
The lrint and llrint functions return the rounded integer value.
-
+
-7.12.9.6 The round functions
+
+
#include <math.h>
double round(double x);
float roundf(float x);
- long double roundl(long double x);
+ long double roundl(long double x);
+
+
The round functions round their argument to the nearest integer value in floating-point format, rounding halfway cases away from zero, regardless of the current rounding direction.
+
The round functions return the rounded integer value.
-7.12.9.7 The lround and llround functions
+
+
#include <math.h>
long int lround(double x);
@@ -12556,72 +13078,76 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
long int lroundl(long double x);
long long int llround(double x);
long long int llroundf(float x);
- long long int llroundl(long double x);
+ long long int llroundl(long double x);
+
+
The lround and llround functions round their argument to the nearest integer value, rounding halfway cases away from zero, regardless of the current rounding direction. If the rounded value is outside the range of the return type, the numeric result is unspecified and a domain error or range error may occur.
+
The lround and llround functions return the rounded integer value.
-7.12.9.8 The trunc functions
+
- +
+
#include <math.h>
double trunc(double x);
float truncf(float x);
- long double truncl(long double x);
+ long double truncl(long double x);
+
+
The trunc functions round their argument to the integer value, in floating format, nearest to but no larger in magnitude than the argument.
+
The trunc functions return the truncated integer value.
-7.12.10 Remainder functions
+
+
#include <math.h>
double fmod(double x, double y);
float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
+ long double fmodl(long double x, long double y);
+
+
The fmod functions compute the floating-point remainder of x/y.
+
The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
whether a domain error occurs or the fmod functions return zero is implementation-
defined.
-7.12.10.2 The remainder functions
+
+
#include <math.h>
double remainder(double x, double y);
float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
+ long double remainderl(long double x, long double y);
+
+
The remainder functions compute the remainder x REM y required by IEC 60559.236) - +
+
The remainder functions return x REM y. If y is zero, whether a domain error occurs
or the functions return zero is implementation defined.
@@ -12632,58 +13158,61 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
all implementations.
-7.12.10.3 The remquo functions
+
+
#include <math.h>
double remquo(double x, double y, int *quo);
float remquof(float x, float y, int *quo);
long double remquol(long double x, long double y,
- int *quo);
+ int *quo);
+
+
The remquo functions compute the same remainder as the remainder functions. In the object pointed to by quo they store a value whose sign is the sign of x/y and whose magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where n is an implementation-defined integer greater than or equal to 3.
+
The remquo functions return x REM y. If y is zero, the value stored in the object
pointed to by quo is unspecified and whether a domain error occurs or the functions
return zero is implementation defined.
-7.12.11 Manipulation functions
+
+
#include <math.h>
double copysign(double x, double y);
float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
+ long double copysignl(long double x, long double y);
+
+
The copysign functions produce a value with the magnitude of x and the sign of y. They produce a NaN (with the sign of y) if x is a NaN. On implementations that represent a signed zero but do not treat negative zero consistently in arithmetic operations, the copysign functions regard the sign of zero as positive.
+
The copysign functions return a value with the magnitude of x and the sign of y.
-
+
-7.12.11.2 The nan functions
+
+
#include <math.h>
double nan(const char *tagp);
float nanf(const char *tagp);
- long double nanl(const char *tagp);
+ long double nanl(const char *tagp);
+
+
The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char- sequence)", (char**) NULL); the call nan("") is equivalent to strtod("NAN()", (char**) NULL). If tagp does not point to an n-char @@ -12691,49 +13220,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof and strtold.
+
The nan functions return a quiet NaN, if available, with content indicated through tagp. If the implementation does not support quiet NaNs, the functions return zero.
Forward references: the strtod, strtof, and strtold functions (7.22.1.3).
-7.12.11.3 The nextafter functions
+
+
#include <math.h>
double nextafter(double x, double y);
float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
+ long double nextafterl(long double x, long double y);
+
+
The nextafter functions determine the next representable value, in the type of the function, after x in the direction of y, where x and y are first converted to the type of the function.237) The nextafter functions return y if x equals y. A range error may occur if the magnitude of x is the largest finite value representable in the type and the result is infinite or not representable in the type.
+
The nextafter functions return the next representable value in the specified format after x in the direction of y. - +
237) The argument values are converted to the type of the function, even by a macro implementation of the
function.
-7.12.11.4 The nexttoward functions
+
+
#include <math.h>
double nexttoward(double x, long double y);
float nexttowardf(float x, long double y);
- long double nexttowardl(long double x, long double y);
+ long double nexttowardl(long double x, long double y);
+
+
The nexttoward functions are equivalent to the nextafter functions except that the
second parameter has type long double and the functions return y converted to the
type of the function if x equals y.238)
@@ -12743,45 +13274,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
range or precision in a floating second argument.
-7.12.12 Maximum, minimum, and positive difference functions
+
+
#include <math.h>
double fdim(double x, double y);
float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
+ long double fdiml(long double x, long double y);
+
+
The fdim functions determine the positive difference between their arguments:
{x - y if x > y
{
- {+0 if x <= y
+ {+0 if x <= y
+
A range error may occur.
+
The fdim functions return the positive difference value.
-7.12.12.2 The fmax functions
+
+
#include <math.h>
double fmax(double x, double y);
float fmaxf(float x, float y);
- long double fmaxl(long double x, long double y);
+ long double fmaxl(long double x, long double y);
+
-
+
+
The fmax functions determine the maximum numeric value of their arguments.239)
+
The fmax functions return the maximum numeric value of their arguments.
+
#include <math.h>
double fmin(double x, double y);
float fminf(float x, float y);
- long double fminl(long double x, long double y);
+ long double fminl(long double x, long double y);
+
+
The fmin functions determine the minimum numeric value of their arguments.240)
+
The fmin functions return the minimum numeric value of their arguments.
240) The fmin functions are analogous to the fmax functions in their treatment of NaNs.
-7.12.13 Floating multiply-add
+
+
#include <math.h>
double fma(double x, double y, double z);
float fmaf(float x, float y, float z);
long double fmal(long double x, long double y,
- long double z);
+ long double z);
+
+
The fma functions compute (x x y) + z, rounded as one ternary operation: they compute the value (as if) to infinite precision and round once to the result format, according to the current rounding mode. A range error may occur.
+
The fma functions return (x x y) + z, rounded as one ternary operation.
-
+
-7.12.14 Comparison macros
-
+
The relational and equality operators support the usual mathematical relationships
between numeric values. For any ordered pair of numeric values exactly one of the
relationships -- less, greater, and equal -- is true. Relational operators may raise the
@@ -12858,122 +13394,129 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
type is unspecified.
-7.12.14.1 The isgreater macro
+
+
#include <math.h>
- int isgreater(real-floating x, real-floating y);
+ int isgreater(real-floating x, real-floating y);
+
+
The isgreater macro determines whether its first argument is greater than its second argument. The value of isgreater(x, y) is always equal to (x) > (y); however, unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point exception when x and y are unordered.
+
The isgreater macro returns the value of (x) > (y).
-7.12.14.2 The isgreaterequal macro
+
+
#include <math.h>
- int isgreaterequal(real-floating x, real-floating y);
+ int isgreaterequal(real-floating x, real-floating y);
+
-
+
+
The isgreaterequal macro determines whether its first argument is greater than or equal to its second argument. The value of isgreaterequal(x, y) is always equal to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does not raise the ''invalid'' floating-point exception when x and y are unordered.
+
The isgreaterequal macro returns the value of (x) >= (y).
-7.12.14.3 The isless macro
+
+
#include <math.h>
- int isless(real-floating x, real-floating y);
+ int isless(real-floating x, real-floating y);
+
+
The isless macro determines whether its first argument is less than its second argument. The value of isless(x, y) is always equal to (x) < (y); however, unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point exception when x and y are unordered.
+
The isless macro returns the value of (x) < (y).
-7.12.14.4 The islessequal macro
+
+
#include <math.h>
- int islessequal(real-floating x, real-floating y);
+ int islessequal(real-floating x, real-floating y);
+
+
The islessequal macro determines whether its first argument is less than or equal to its second argument. The value of islessequal(x, y) is always equal to (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise the ''invalid'' floating-point exception when x and y are unordered.
+
The islessequal macro returns the value of (x) <= (y).
-
+
-7.12.14.5 The islessgreater macro
+
+
#include <math.h>
- int islessgreater(real-floating x, real-floating y);
+ int islessgreater(real-floating x, real-floating y);
+
+
The islessgreater macro determines whether its first argument is less than or greater than its second argument. The islessgreater(x, y) macro is similar to (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x and y twice).
+
The islessgreater macro returns the value of (x) < (y) || (x) > (y).
-7.12.14.6 The isunordered macro
+
+
#include <math.h>
- int isunordered(real-floating x, real-floating y);
+ int isunordered(real-floating x, real-floating y);
+
+
The isunordered macro determines whether its arguments are unordered.
+
The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
-
+
-7.13 Nonlocal jumps
-
+
The header <setjmp.h> defines the macro setjmp, and declares one function and one type, for bypassing the normal function call and return discipline.244) -
+
The type declared is
- jmp_buf+ jmp_buf + which is an array type suitable for holding the information needed to restore a calling environment. The environment of a call to the setjmp macro consists of information sufficient for a call to the longjmp function to return execution to the correct block and invocation of that block, were it called recursively. It does not include the state of the floating-point status flags, of open files, or of any other component of the abstract machine. -
+
It is unspecified whether setjmp is a macro or an identifier declared with external
linkage. If a macro definition is suppressed in order to access an actual function, or a
program defines an external identifier with the name setjmp, the behavior is undefined.
@@ -12983,25 +13526,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
a program.
-7.13.1 Save calling environment
+
+
#include <setjmp.h>
- int setjmp(jmp_buf env);
+ int setjmp(jmp_buf env);
+
+
The setjmp macro saves its calling environment in its jmp_buf argument for later use by the longjmp function.
+
If the return is from a direct invocation, the setjmp macro returns the value zero. If the return is from a call to the longjmp function, the setjmp macro returns a nonzero value. - Environmental limits -
+
An invocation of the setjmp macro shall appear only in one of the following contexts:
+
If the invocation appears in any other context, the behavior is undefined.
-7.13.2 Restore calling environment
+
+
#include <setjmp.h>
- _Noreturn void longjmp(jmp_buf env, int val);
+ _Noreturn void longjmp(jmp_buf env, int val);
+
+
The longjmp function restores the environment saved by the most recent invocation of the setjmp macro in the same invocation of the program with the corresponding jmp_buf argument. If there has been no such invocation, or if the function containing the invocation of the setjmp macro has terminated execution245) in the interim, or if the invocation of the setjmp macro was within the scope of an identifier with variably modified type and execution has left that scope in the interim, the behavior is undefined. -
+
All accessible objects have values, and all other components of the abstract machine246) have state, as of the time the longjmp function was called, except that the values of objects of automatic storage duration that are local to the function containing the @@ -13042,20 +13587,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and have been changed between the setjmp invocation and longjmp call are indeterminate.
+
After longjmp is completed, program execution continues as if the corresponding invocation of the setjmp macro had just returned the value specified by val. The longjmp function cannot cause the setjmp macro to return the value 0; if val is 0, the setjmp macro returns the value 1. -
+
EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation might cause memory associated with a variable length array object to be squandered. - - + +
#include <setjmp.h>
jmp_buf buf;
@@ -13077,7 +13622,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{
int b[n]; // b may remain allocated
longjmp(buf, 2); // might cause memory loss
- }
+ }
+
245) For example, by executing a return statement or because another longjmp call has caused a @@ -13086,28 +13632,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
246) This includes, but is not limited to, the floating-point status flags and the state of open files.
-7.14 Signal handling
-
+
The header <signal.h> declares a type and two functions and defines several macros, for handling various signals (conditions that may be reported during program execution). -
+
The type defined is
- sig_atomic_t+ sig_atomic_t + which is the (possibly volatile-qualified) integer type of an object that can be accessed as an atomic entity, even in the presence of asynchronous interrupts. -
+
The macros defined are
SIG_DFL
SIG_ERR
- SIG_IGN
+ SIG_IGN
+
which expand to constant expressions with distinct values that have type compatible with
the second argument to, and the return value of, the signal function, and whose values
compare unequal to the address of any declarable function; and the following, which
expand to positive integer constant expressions with type int and distinct values that are
the signal numbers, each corresponding to the specified condition:
-
SIGABRT abnormal termination, such as is initiated by the abort function
SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
@@ -13115,7 +13662,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
SIGILL detection of an invalid function image, such as an invalid instruction
SIGINT receipt of an interactive attention signal
SIGSEGV an invalid access to storage
- SIGTERM a termination request sent to the program
+ SIGTERM a termination request sent to the program
+
+An implementation need not generate any of these signals, except as a result of explicit calls to the raise function. Additional signals and pointers to undeclarable functions, with macro definitions beginning, respectively, with the letters SIG and an uppercase @@ -13126,7 +13675,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
247) See ''future library directions'' (7.30.6). The names of the signal numbers reflect the following terms
@@ -13134,16 +13683,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
and termination.
-7.14.1 Specify signal handling
+
+
#include <signal.h>
- void (*signal(int sig, void (*func)(int)))(int);
+ void (*signal(int sig, void (*func)(int)))(int);
+
+
The signal function chooses one of three ways in which receipt of the signal number sig is to be subsequently handled. If the value of func is SIG_DFL, default handling for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored. @@ -13151,7 +13701,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. invocation of such a function because of a signal, or (recursively) of any further functions called by that invocation (other than functions in the standard library),248) is called a signal handler. -
+
When a signal occurs and func points to a function, it is implementation-defined whether the equivalent of signal(sig, SIG_DFL); is executed or the implementation prevents some implementation-defined set of signals (at least including @@ -13161,10 +13711,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined value corresponding to a computational exception, the behavior is undefined; otherwise the program will resume execution at the point it was interrupted. -
+
If the signal occurs as the result of calling the abort or raise function, the signal handler shall not call the raise function. -
+
If the signal occurs other than as the result of calling the abort or raise function, the behavior is undefined if the signal handler refers to any object with static or thread storage duration that is not a lock-free atomic object other than by assigning a value to an @@ -13176,20 +13726,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. value of errno is indeterminate.249) - -
+ +
At program startup, the equivalent of
- signal(sig, SIG_IGN);+ signal(sig, SIG_IGN); + may be executed for some signals selected in an implementation-defined manner; the equivalent of
- signal(sig, SIG_DFL);+ signal(sig, SIG_DFL); + is executed for all other signals defined by the implementation. -
+
The implementation shall behave as if no library function calls the signal function.
+
If the request can be honored, the signal function returns the value of func for the most recent successful call to signal for the specified signal sig. Otherwise, a value of SIG_ERR is returned and a positive value is stored in errno. @@ -13203,53 +13755,57 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
249) If any signal is generated by an asynchronous signal handler, the behavior is undefined.
-7.14.2 Send signal
+
+
#include <signal.h>
- int raise(int sig);
+ int raise(int sig);
+
+
The raise function carries out the actions described in 7.14.1.1 for the signal sig. If a signal handler is called, the raise function shall not return until after the signal handler does.
+
The raise function returns zero if successful, nonzero if unsuccessful.
-
+
-7.15 Alignment
-
+
The header <stdalign.h> defines two macros. -
+
The macro
- alignas+ alignas + expands to _Alignas. -
+
The remaining macro is suitable for use in #if preprocessing directives. It is
- __alignas_is_defined+ __alignas_is_defined + which expands to the integer constant 1. - + -
+
The header <stdarg.h> declares a type and defines four macros, for advancing through a list of arguments whose number and types are not known to the called function when it is translated. -
+
A function may be called with a variable number of arguments of varying types. As described in 6.9.1, its parameter list contains one or more parameters. The rightmost parameter plays a special role in the access mechanism, and will be designated parmN in this description. -
+
The type declared is
- va_list+ va_list + which is a complete object type suitable for holding information needed by the macros va_start, va_arg, va_end, and va_copy. If access to the varying arguments is desired, the called function shall declare an object (generally referred to as ap in this @@ -13263,8 +13819,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. case the original function may make further use of the original list after the other function returns. -
+
The va_start and va_arg macros described in this subclause shall be implemented
as macros, not functions. It is unspecified whether va_copy and va_end are macros or
identifiers declared with external linkage. If a macro definition is suppressed in order to
@@ -13273,19 +13829,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
shall be matched by a corresponding invocation of the va_end macro in the same
function.
-7.16.1.1 The va_arg macro
+
+
#include <stdarg.h>
- type va_arg(va_list ap, type);
+ type va_arg(va_list ap, type);
+
+
The va_arg macro expands to an expression that has the specified type and the value of the next argument in the call. The parameter ap shall have been initialized by the va_start or va_copy macro (without an intervening invocation of the va_end - + macro for the same ap). Each invocation of the va_arg macro modifies ap so that the values of successive arguments are returned in turn. The parameter type shall be a type name specified such that the type of a pointer to an object that has the specified type can @@ -13299,75 +13856,78 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
The first invocation of the va_arg macro after that of the va_start macro returns the
value of the argument after that specified by parmN . Successive invocations return the
values of the remaining arguments in succession.
-7.16.1.2 The va_copy macro
+
+
#include <stdarg.h>
- void va_copy(va_list dest, va_list src);
+ void va_copy(va_list dest, va_list src);
+
+
The va_copy macro initializes dest as a copy of src, as if the va_start macro had been applied to dest followed by the same sequence of uses of the va_arg macro as had previously been used to reach the present state of src. Neither the va_copy nor va_start macro shall be invoked to reinitialize dest without an intervening invocation of the va_end macro for the same dest.
+
The va_copy macro returns no value.
-7.16.1.3 The va_end macro
+
+
#include <stdarg.h>
- void va_end(va_list ap);
+ void va_end(va_list ap);
+
+
The va_end macro facilitates a normal return from the function whose variable argument list was referred to by the expansion of the va_start macro, or the function containing the expansion of the va_copy macro, that initialized the va_list ap. The va_end macro may modify ap so that it is no longer usable (without being reinitialized - + by the va_start or va_copy macro). If there is no corresponding invocation of the va_start or va_copy macro, or if the va_end macro is not invoked before the return, the behavior is undefined.
+
The va_end macro returns no value.
-7.16.1.4 The va_start macro
+
+
#include <stdarg.h>
- void va_start(va_list ap, parmN);
+ void va_start(va_list ap, parmN);
+
+
The va_start macro shall be invoked before any access to the unnamed arguments. -
+
The va_start macro initializes ap for subsequent use by the va_arg and va_end macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap without an intervening invocation of the va_end macro for the same ap. -
+
The parameter parmN is the identifier of the rightmost parameter in the variable parameter list in the function definition (the one just before the , ...). If the parameter parmN is declared with the register storage class, with a function or array type, or with a type that is not compatible with the type that results after application of the default argument promotions, the behavior is undefined.
+
The va_start macro returns no value. -
+
EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of pointers is specified by the first argument to f1. - +
#include <stdarg.h>
#define MAXARGS 31
@@ -13383,16 +13943,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
array[ptr_no++] = va_arg(ap, char *);
va_end(ap);
f2(n_ptrs, array);
- }
+ }
+
Each call to f1 is required to have visible the definition of the function or a declaration such as
- void f1(int, ...);+ void f1(int, ...); + -
+
EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list is gathered again and passed to function f4. - +
#include <stdarg.h>
#define MAXARGS 31
@@ -13418,18 +13980,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
array[ptr_no++] = va_arg(ap_save, char *);
va_end(ap_save);
f4(n_ptrs, array);
- }
+ }
+
-+
The header <stdatomic.h> defines several macros and declares several types and functions for performing atomic operations on data shared between threads. -
+
Implementations that define the macro __STDC_NO_THREADS__ need not provide this header nor support any of its facilities. -
+
The macros defined are the atomic lock-free macros
ATOMIC_CHAR_LOCK_FREE
@@ -13440,32 +14003,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
ATOMIC_INT_LOCK_FREE
ATOMIC_LONG_LOCK_FREE
ATOMIC_LLONG_LOCK_FREE
- ATOMIC_ADDRESS_LOCK_FREE
+ ATOMIC_ADDRESS_LOCK_FREE
+
which indicate the lock-free property of the corresponding atomic types (both signed and
unsigned); and
- ATOMIC_FLAG_INIT+ ATOMIC_FLAG_INIT + which expands to an initializer for an object of type atomic_flag. -
+
The types include
- memory_order+ memory_order + which is an enumerated type whose enumerators identify memory ordering constraints;
- atomic_flag+ atomic_flag + which is a structure type representing a lock-free, primitive atomic flag;
- atomic_bool+ atomic_bool + which is a structure type representing the atomic analog of the type _Bool;
- atomic_address+ atomic_address + which is a structure type representing the atomic analog of a pointer type; and several atomic analogs of integer types. -
+
In the following operation definitions:
+
NOTE Many operations are volatile-qualified. The ''volatile as device register'' semantics have not
changed in the standard. This qualification means that volatility is preserved when applying these
operations to volatile objects.
-7.17.2 Initialization
+
+
#include <stdatomic.h>
- #define ATOMIC_VAR_INIT(C value)
+ #define ATOMIC_VAR_INIT(C value)
+
+
The ATOMIC_VAR_INIT macro expands to a token sequence suitable for initializing an atomic object of a type that is initialization-compatible with value. An atomic object with automatic storage duration that is not explicitly initialized using ATOMIC_VAR_INIT is initially in an indeterminate state; however, the default (zero) initialization for objects with static or thread-local storage duration is guaranteed to produce a valid state. -
+
Concurrent access to the variable being initialized, even via an atomic operation, constitutes a data race. -
+
EXAMPLE
- atomic_int guide = ATOMIC_VAR_INIT(42);+ atomic_int guide = ATOMIC_VAR_INIT(42); + -
+
#include <stdatomic.h>
- void atomic_init(volatile A *obj, C value);
+ void atomic_init(volatile A *obj, C value);
+
+
The atomic_init generic function initializes the atomic object pointed to by obj to the value value, while also initializing any additional state that the implementation might need to carry for the atomic object. - -
+ +
Although this function initializes an atomic object, it does not avoid data races; concurrent access to the variable being initialized, even via an atomic operation, constitutes a data race.
+
The atomic_init generic function returns no value. -
+
EXAMPLE
atomic_int guide;
- atomic_init(&guide, 42);
+ atomic_init(&guide, 42);
+
-+
The enumerated type memory_order specifies the detailed regular (non-atomic) memory synchronization operations as defined in 5.1.2.4 and may provide for operation ordering. Its enumeration constants are as follows: -
memory_order_relaxed
memory_order_consume
memory_order_acquire
memory_order_release
memory_order_acq_rel
- memory_order_seq_cst
+ memory_order_seq_cst
+
+For memory_order_relaxed, no operation orders memory. -
+
For memory_order_release, memory_order_acq_rel, and memory_order_seq_cst, a store operation performs a release operation on the affected memory location. -
+
For memory_order_acquire, memory_order_acq_rel, and memory_order_seq_cst, a load operation performs an acquire operation on the affected memory location. -
+
For memory_order_consume, a load operation performs a consume operation on the affected memory location. -
+
For memory_order_seq_cst, there shall be a single total order S on all operations, consistent with the ''happens before'' order and modification orders for all affected locations, such that each memory_order_seq_cst operation that loads a value observes either the last preceding modification according to this order S, or the result of an operation that is not memory_order_seq_cst. -
+
NOTE 1 Although it is not explicitly required that S include lock operations, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the ''happens before'' ordering. -
+
NOTE 2 Atomic operations specifying memory_order_relaxed are relaxed only with respect to memory ordering. Implementations must still guarantee that any given atomic access to a particular atomic - + object be indivisible with respect to all other atomic accesses to that object. -
+
For an atomic operation B that reads the value of an atomic object M, if there is a memory_order_seq_cst fence X sequenced before B, then B observes either the last memory_order_seq_cst modification of M preceding X in the total order S or a later modification of M in its modification order. -
+
For atomic operations A and B on an atomic object M, where A modifies M and B takes its value, if there is a memory_order_seq_cst fence X such that A is sequenced before X and B follows X in S, then B observes either the effects of A or a later modification of M in its modification order. -
+
For atomic operations A and B on an atomic object M, where A modifies M and B takes its value, if there are memory_order_seq_cst fences X and Y such that A is sequenced before X, Y is sequenced before B, and X precedes Y in S, then B observes either the effects of A or a later modification of M in its modification order. -
+
Atomic read-modify-write operations shall always read the last value (in the modification order) stored before the write associated with the read-modify-write operation. -
+
An atomic store shall only store a value that has been computed from constants and program input values by a finite sequence of program evaluations, such that each evaluation observes the values of variables as computed by the last prior assignment in @@ -13602,61 +14176,68 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
NOTE 3 The second requirement disallows ''out-of-thin-air'', or ''speculative'' stores of atomics when relaxed atomics are used. Since unordered operations are involved, evaluations may appear in this sequence out of thread order. For example, with x and y initially zero,
// Thread 1:
r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
+ atomic_store_explicit(&x, r1, memory_order_relaxed);
+
// Thread 2:
r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, 42, memory_order_relaxed);
+ atomic_store_explicit(&y, 42, memory_order_relaxed);
+
is allowed to produce r1 == 42 && r2 == 42. The sequence of evaluations justifying this consists of:
-
+
atomic_store_explicit(&y, 42, memory_order_relaxed);
r1 = atomic_load_explicit(&y, memory_order_relaxed);
atomic_store_explicit(&x, r1, memory_order_relaxed);
- r2 = atomic_load_explicit(&x, memory_order_relaxed);
+ r2 = atomic_load_explicit(&x, memory_order_relaxed);
+
On the other hand,
// Thread 1:
r1 = atomic_load_explicit(&y, memory_order_relaxed);
- atomic_store_explicit(&x, r1, memory_order_relaxed);
+ atomic_store_explicit(&x, r1, memory_order_relaxed);
+
// Thread 2:
r2 = atomic_load_explicit(&x, memory_order_relaxed);
- atomic_store_explicit(&y, r2, memory_order_relaxed);
+ atomic_store_explicit(&y, r2, memory_order_relaxed);
+
is not allowed to produce r1 == 42 && r2 = 42, since there is no sequence of evaluations that results
in the computation of 42. In the absence of ''relaxed'' operations and read-modify-write operations with
weaker than memory_order_acq_rel ordering, the second requirement has no impact.
- Recommended practice
-+
The requirements do not forbid r1 == 42 && r2 == 42 in the following example, with x and y initially zero:
// Thread 1:
r1 = atomic_load_explicit(&x, memory_order_relaxed);
if (r1 == 42)
- atomic_store_explicit(&y, r1, memory_order_relaxed);
+ atomic_store_explicit(&y, r1, memory_order_relaxed);
+
// Thread 2:
r2 = atomic_load_explicit(&y, memory_order_relaxed);
if (r2 == 42)
- atomic_store_explicit(&x, 42, memory_order_relaxed);
+ atomic_store_explicit(&x, 42, memory_order_relaxed);
+
However, this is not useful behavior, and implementations should not allow it.
-+
Implementations should make atomic stores visible to atomic loads within a reasonable amount of time. @@ -13664,52 +14245,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
251) Among other implications, atomic variables shall not decay.
-7.17.3.1 The kill_dependency macro
+
+
#include <stdatomic.h>
- type kill_dependency(type y);
+ type kill_dependency(type y);
+
+
The kill_dependency macro terminates a dependency chain; the argument does not carry a dependency to the return value. - +
+
The kill_dependency macro returns the value of y.
-7.17.4 Fences
-
+
This subclause introduces synchronization primitives called fences. Fences can have acquire semantics, release semantics, or both. A fence with acquire semantics is called an acquire fence; a fence with release semantics is called a release fence. -
+
A release fence A synchronizes with an acquire fence B if there exist atomic operations X and Y , both operating on some atomic object M, such that A is sequenced before X, X modifies M, Y is sequenced before B, and Y reads the value written by X or a value written by any side effect in the hypothetical release sequence X would head if it were a release operation. -
+
A release fence A synchronizes with an atomic operation B that performs an acquire operation on an atomic object M if there exists an atomic operation X such that A is sequenced before X, X modifies M, and B reads the value written by X or a value written by any side effect in the hypothetical release sequence X would head if it were a release operation. -
+
An atomic operation A that is a release operation on an atomic object M synchronizes
with an acquire fence B if there exists some atomic operation X on M such that X is
sequenced before B and reads the value written by A or a value written by any side effect
in the release sequence headed by A.
-7.17.4.1 The atomic_thread_fence function
+
+
#include <stdatomic.h>
- void atomic_thread_fence(memory_order order);
+ void atomic_thread_fence(memory_order order);
+
+
Depending on the value of order, this operation:
+
The atomic_thread_fence function returns no value.
-7.17.4.2 The atomic_signal_fence function
+
+
#include <stdatomic.h>
- void atomic_signal_fence(memory_order order);
+ void atomic_signal_fence(memory_order order);
+
+
Equivalent to atomic_thread_fence(order), except that ''synchronizes with'' relationships are established only between a thread and a signal handler executed in the same thread. -
+
NOTE 1 The atomic_signal_fence function can be used to specify the order in which actions performed by the thread become visible to the signal handler. -
+
NOTE 2 Compiler optimizations and reorderings of loads and stores are inhibited in the same way as with atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would have inserted are not emitted.
+
The atomic_signal_fence function returns no value.
-7.17.5 Lock-free property
-
+
The atomic lock-free macros indicate the lock-free property of integer and address atomic types. A value of 0 indicates that the type is never lock-free; a value of 1 indicates that the type is sometimes lock-free; a value of 2 indicates that the type is always lock-free. -
+
NOTE Operations that are lock-free should also be address-free. That is, atomic operations on the same
memory location via two different addresses will communicate atomically. The implementation should not
depend on any per-process state. This restriction enables communication via memory mapped into a
process more than once and memory shared between two processes.
-7.17.5.1 The atomic_is_lock_free generic function
+
+
#include <stdatomic.h>
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
+ _Bool atomic_is_lock_free(atomic_type const volatile *obj);
+
+
The atomic_is_lock_free generic function indicates whether or not the object pointed to by obj is lock-free. atomic_type can be any atomic type.
+
The atomic_is_lock_free generic function returns nonzero (true) if and only if the
object's operations are lock-free. The result of a lock-free query on one object cannot be
-
+
inferred from the result of a lock-free query on another object.
-7.17.6 Atomic integer and address types
-
+
For each line in the following table, the atomic type name is declared as the corresponding direct type. - -
+
Atomic type name Direct type
atomic_char _Atomic char
@@ -13822,79 +14406,84 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atomic_size_t _Atomic size_t
atomic_ptrdiff_t _Atomic ptrdiff_t
atomic_intmax_t _Atomic intmax_t
- atomic_uintmax_t _Atomic uintmax_t
+ atomic_uintmax_t _Atomic uintmax_t
+
+The semantics of the operations on these types are defined in 7.17.7. -
+
The atomic_bool type provides an atomic boolean. - -
+ +
The atomic_address type provides atomic void * operations. The unit of addition/subtraction shall be one byte. -
+
NOTE The representation of atomic integer and address types need not have the same size as their
corresponding regular types. They should have the same size whenever possible, as it eases effort required
to port existing code.
-7.17.7 Operations on atomic types
-
+
There are only a few kinds of operations on atomic types, though there are many
instances of those kinds. This subclause specifies each general kind.
-7.17.7.1 The atomic_store generic functions
+
+
#include <stdatomic.h>
void atomic_store(volatile A *object, C desired);
void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
+ C desired, memory_order order);
+
+
The order argument shall not be memory_order_acquire, memory_order_consume, nor memory_order_acq_rel. Atomically replace the value pointed to by object with the value of desired. Memory is affected according to the value of order.
+
The atomic_store generic functions return no value.
-7.17.7.2 The atomic_load generic functions
+
+
#include <stdatomic.h>
C atomic_load(volatile A *object);
C atomic_load_explicit(volatile A *object,
- memory_order order);
+ memory_order order);
+
+
The order argument shall not be memory_order_release nor memory_order_acq_rel. Memory is affected according to the value of order.
+
#include <stdatomic.h>
C atomic_exchange(volatile A *object, C desired);
C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
+ C desired, memory_order order);
+
+
Atomically replace the value pointed to by object with desired. Memory is affected according to the value of order. These operations are read-modify-write operations (5.1.2.4).
+
Atomically returns the value pointed to by object immediately before the effects.
-7.17.7.4 The atomic_compare_exchange generic functions
+
+
#include <stdatomic.h>
_Bool atomic_compare_exchange_strong(volatile A *object,
@@ -13906,9 +14495,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
C *expected, C desired);
_Bool atomic_compare_exchange_weak_explicit(
volatile A *object, C *expected, C desired,
- memory_order success, memory_order failure);
+ memory_order success, memory_order failure);
+
+
The failure argument shall not be memory_order_release nor memory_order_acq_rel. The failure argument shall be no stronger than the success argument. Atomically, compares the value pointed to by object for equality @@ -13917,40 +14507,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. object. Further, if the comparison is true, memory is affected according to the value of success, and if the comparison is false, memory is affected according to the value of failure. These operations are atomic read-modify-write operations (5.1.2.4). -
+
NOTE 1 The effect of the compare-and-exchange operations is - +
if (*object == *expected)
*object = desired;
else
- *expected = *object;
+ *expected = *object;
+
-+
The weak compare-and-exchange operations may fail spuriously, that is, return zero while leaving the value pointed to by expected unchanged. -
+
NOTE 2 This spurious failure enables implementation of compare-and-exchange on a broader class of machines, e.g. load-locked store-conditional machines. -
+
EXAMPLE A consequence of spurious failure is that nearly all uses of weak compare-and-exchange will be in a loop.
exp = atomic_load(&cur);
do {
des = function(exp);
- } while (!atomic_compare_exchange_weak(&cur, &exp, des));
+ } while (!atomic_compare_exchange_weak(&cur, &exp, des));
+
When a compare-and-exchange is in a loop, the weak version will yield better performance on some
platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the
strong one is preferable.
+
The result of the comparison.
-7.17.7.5 The atomic_fetch and modify generic functions
-
+
The following operations perform arithmetic and bitwise computations. All of these operations are applicable to an object of any atomic integer type. Only addition and subtraction are applicable to atomic_address. None of these operations is applicable @@ -13962,26 +14554,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. xor ^ bitwise exclusive or and & bitwise and
+
#include <stdatomic.h>
C atomic_fetch_key(volatile A *object, M operand);
C atomic_fetch_key_explicit(volatile A *object,
- M operand, memory_order order);
+ M operand, memory_order order);
+
+
Atomically replaces the value pointed to by object with the result of the computation applied to the value pointed to by object and the given operand. Memory is affected according to the value of order. These operations are atomic read-modify-write - + operations (5.1.2.4). For signed integer types, arithmetic is defined to use two's complement representation with silent wrap-around on overflow; there are no undefined results. For address types, the result may be an undefined address, but the operations otherwise have no undefined behavior.
+
Atomically, the value pointed to by object immediately before the effects. -
+
NOTE The operation of the atomic_fetch and modify generic functions are nearly equivalent to the
operation of the corresponding op= compound assignment operators. The only differences are that the
compound assignment operators are not guaranteed to operate atomically, and the value yielded by a
@@ -13989,152 +14582,166 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atomic_fetch and modify generic functions is the previous value of the atomic object.
-7.17.8 Atomic flag type and operations
-
+
The atomic_flag type provides the classic test-and-set functionality. It has two states, set and clear. -
+
Operations on an object of type atomic_flag shall be lock free. -
+
NOTE Hence the operations should also be address-free. No other type requires lock-free operations, so the atomic_flag type is the minimum hardware-implemented type needed to conform to this International standard. The remaining types can be emulated with atomic_flag, though with less than ideal properties. -
+
The macro ATOMIC_FLAG_INIT may be used to initialize an atomic_flag to the clear state. An atomic_flag that is not explicitly initialized with ATOMIC_FLAG_INIT is initially in an indeterminate state. -
+
EXAMPLE
- atomic_flag guard = ATOMIC_FLAG_INIT;+ atomic_flag guard = ATOMIC_FLAG_INIT; + -
+
#include <stdatomic.h>
bool atomic_flag_test_and_set(
volatile atomic_flag *object);
bool atomic_flag_test_and_set_explicit(
- volatile atomic_flag *object, memory_order order);
+ volatile atomic_flag *object, memory_order order);
+
+
Atomically sets the value pointed to by object to true. Memory is affected according to the value of order. These operations are atomic read-modify-write operations (5.1.2.4). - +
+
Atomically, the value of the object immediately before the effects.
-7.17.8.2 The atomic_flag_clear functions
+
+
#include <stdatomic.h>
void atomic_flag_clear(volatile atomic_flag *object);
void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
+ volatile atomic_flag *object, memory_order order);
+
+
The order argument shall not be memory_order_acquire nor memory_order_acq_rel. Atomically sets the value pointed to by object to false. Memory is affected according to the value of order.
+
The atomic_flag_clear functions return no value.
-
+
-7.18 Boolean type and values
-
+
The header <stdbool.h> defines four macros. -
+
The macro
- bool+ bool + expands to _Bool. -
+
The remaining three macros are suitable for use in #if preprocessing directives. They are
- true+ true + which expands to the integer constant 1,
- false+ false + which expands to the integer constant 0, and
- __bool_true_false_are_defined+ __bool_true_false_are_defined + which expands to the integer constant 1. -
+
Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then redefine the macros bool, true, and false.252) - +
252) See ''future library directions'' (7.30.7).
-7.19 Common definitions
-
+
The header <stddef.h> defines the following macros and declares the following types. Some are also defined in other headers, as noted in their respective subclauses. -
+
The types are
- ptrdiff_t+ ptrdiff_t + which is the signed integer type of the result of subtracting two pointers;
- size_t+ size_t + which is the unsigned integer type of the result of the sizeof operator;
- max_align_t+ max_align_t + which is an object type whose alignment is as great as is supported by the implementation in all contexts; and
- wchar_t+ wchar_t + which is an integer type whose range of values can represent distinct codes for all members of the largest extended character set specified among the supported locales; the null character shall have the code value zero. Each member of the basic character set shall have a code value equal to its value when used as the lone character in an integer character constant if an implementation does not define __STDC_MB_MIGHT_NEQ_WC__. -
+
The macros are
- NULL+ NULL + which expands to an implementation-defined null pointer constant; and
- offsetof(type, member-designator)+ offsetof(type, member-designator) + which expands to an integer constant expression that has type size_t, the value of which is the offset in bytes, to the structure member (designated by member-designator), from the beginning of its structure (designated by type). The type and member designator shall be such that given
- static type t;+ static type t; + then the expression &(t.member-designator) evaluates to an address constant. (If the specified member is a bit-field, the behavior is undefined.) - Recommended practice -
+
The types used for size_t and ptrdiff_t should not have an integer conversion rank greater than that of signed long int unless the implementation supports objects large enough to make this necessary. - +
Forward references: localization (7.11).
-
+
-7.20 Integer types
-
+
The header <stdint.h> declares sets of integer types having specified widths, and defines corresponding sets of macros.253) It also defines macros that specify limits of integer types corresponding to types defined in other standard headers. -
+
Types are defined in the following categories:
+
Corresponding macros specify limits of the declared types and construct suitable constants. -
+
For each type described herein that the implementation provides,254) <stdint.h> shall declare that typedef name and define the associated macros. Conversely, for each type described herein that the implementation does not provide, <stdint.h> shall not @@ -14161,58 +14768,59 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
254) Some of these types may denote implementation-defined extended integer types.
-7.20.1 Integer types
-
+
When typedef names differing only in the absence or presence of the initial u are defined, they shall denote corresponding signed and unsigned types as described in 6.2.5; an implementation providing one of these corresponding types shall also provide the other. -
+
In the following descriptions, the symbol N represents an unsigned decimal integer with
no leading zeros (e.g., 8 or 24, but not 04 or 048).
-
+
-7.20.1.1 Exact-width integer types
-
+
The typedef name intN_t designates a signed integer type with width N , no padding bits, and a two's complement representation. Thus, int8_t denotes such a signed integer type with a width of exactly 8 bits. -
+
The typedef name uintN_t designates an unsigned integer type with width N and no padding bits. Thus, uint24_t denotes such an unsigned integer type with a width of exactly 24 bits. -
+
These types are optional. However, if an implementation provides integer types with
widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
two's complement representation, it shall define the corresponding typedef names.
-7.20.1.2 Minimum-width integer types
-
+
The typedef name int_leastN_t designates a signed integer type with a width of at least N , such that no signed integer type with lesser size has at least the specified width. Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits. -
+
The typedef name uint_leastN_t designates an unsigned integer type with a width of at least N , such that no unsigned integer type with lesser size has at least the specified width. Thus, uint_least16_t denotes an unsigned integer type with a width of at least 16 bits. -
+
The following types are required:
int_least8_t uint_least8_t
int_least16_t uint_least16_t
int_least32_t uint_least32_t
- int_least64_t uint_least64_t
+ int_least64_t uint_least64_t
+
All other types of this form are optional.
-+
Each of the following types designates an integer type that is usually fastest255) to operate with among all integer types that have at least the specified width. -
+
The typedef name int_fastN_t designates the fastest signed integer type with a width of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer type with a width of at least N . @@ -14220,14 +14828,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
The following types are required:
int_fast8_t uint_fast8_t
int_fast16_t uint_fast16_t
int_fast32_t uint_fast32_t
- int_fast64_t uint_fast64_t
+ int_fast64_t uint_fast64_t
+
All other types of this form are optional.
+
The following type designates a signed integer type with the property that any valid pointer to void can be converted to this type, then converted back to pointer to void, and the result will compare equal to the original pointer:
- intptr_t+ intptr_t + The following type designates an unsigned integer type with the property that any valid pointer to void can be converted to this type, then converted back to pointer to void, and the result will compare equal to the original pointer:
- uintptr_t+ uintptr_t + These types are optional. -
+
The following type designates a signed integer type capable of representing any value of any signed integer type:
- intmax_t+ intmax_t + The following type designates an unsigned integer type capable of representing any value of any unsigned integer type:
- uintmax_t+ uintmax_t + These types are required. -
+
The following object-like macros specify the minimum and maximum limits of the types * declared in <stdint.h>. Each macro name corresponds to a similar type name in 7.20.1. -
+
Each instance of any defined macro shall be replaced by a constant expression suitable
for use in #if preprocessing directives, and this expression shall have the same type as
would an expression that is an object of the corresponding type converted according to
the integer promotions. Its implementation-defined value shall be equal to or greater in
magnitude (absolute value) than the corresponding value given below, with the same sign,
except where stated to be exactly the given value.
-
+
-7.20.2.1 Limits of exact-width integer types
-
+
- INTN_MIN exactly -(2 N -1 )+ INTN_MIN exactly -(2 N -1 ) +
- INTN_MAX exactly 2 N -1 - 1+ INTN_MAX exactly 2 N -1 - 1 +
+
- INT_LEASTN_MIN -(2 N -1 - 1)+ INT_LEASTN_MIN -(2 N -1 - 1) +
- INT_LEASTN_MAX 2 N -1 - 1+ INT_LEASTN_MAX 2 N -1 - 1 +
+
- INT_FASTN_MIN -(2 N -1 - 1)+ INT_FASTN_MIN -(2 N -1 - 1) +
+
- INTPTR_MIN -(215 - 1)+ INTPTR_MIN -(215 - 1) +
+
+
The following object-like macros specify the minimum and maximum limits of integer * types corresponding to types defined in other standard headers. -
+
Each instance of these macros shall be replaced by a constant expression suitable for use in #if preprocessing directives, and this expression shall have the same type as would an expression that is an object of the corresponding type converted according to the integer @@ -14367,22 +14986,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - + WINT_MIN see below WINT_MAX see below -
+
If sig_atomic_t (see 7.14) is defined as a signed integer type, the value of SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of SIG_ATOMIC_MAX shall be no less than 255. -
+
If wchar_t (see 7.19) is defined as a signed integer type, the value of WCHAR_MIN shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127; otherwise, wchar_t is defined as an unsigned integer type, and the value of WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.257) -
+
If wint_t (see 7.28) is defined as a signed integer type, the value of WINT_MIN shall
be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
@@ -14395,22 +15014,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character set.
-7.20.4 Macros for integer constants
-
+
The following function-like macros expand to integer constants suitable for initializing * objects that have integer types corresponding to types defined in <stdint.h>. Each macro name corresponds to a similar type name in 7.20.1.2 or 7.20.1.5. -
+
The argument in any instance of these macros shall be an unsuffixed integer constant (as defined in 6.4.4.1) with a value that does not exceed the limits for the corresponding type. -
+
Each invocation of one of these macros shall expand to an integer constant expression
suitable for use in #if preprocessing directives. The type of the expression shall have
the same type as would an expression of the corresponding type converted according to
the integer promotions. The value of the expression shall be that of the argument.
-7.20.4.1 Macros for minimum-width integer constants
-
+
The macro INTN_C(value) shall expand to an integer constant expression
corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
to an integer constant expression corresponding to the type uint_leastN_t. For
@@ -14420,94 +15039,107 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-7.20.4.2 Macros for greatest-width integer constants
-
+
The following macro expands to an integer constant expression having the value specified by its argument and the type intmax_t:
- INTMAX_C(value)+ INTMAX_C(value) + The following macro expands to an integer constant expression having the value specified by its argument and the type uintmax_t: - +
- UINTMAX_C(value)+ UINTMAX_C(value) + -
+
The header <stdio.h> defines several macros, and declares three types and many functions for performing input and output. -
+
The types declared are size_t (described in 7.19);
- FILE+ FILE + which is an object type capable of recording all the information needed to control a stream, including its file position indicator, a pointer to its associated buffer (if any), an error indicator that records whether a read/write error has occurred, and an end-of-file indicator that records whether the end of the file has been reached; and
- fpos_t+ fpos_t + which is a complete object type other than an array type capable of recording all the information needed to specify uniquely every position within a file. -
+
The macros are NULL (described in 7.19);
_IOFBF
_IOLBF
- _IONBF
+ _IONBF
+
which expand to integer constant expressions with distinct values, suitable for use as the
third argument to the setvbuf function;
- BUFSIZ+ BUFSIZ + which expands to an integer constant expression that is the size of the buffer used by the setbuf function;
- EOF+ EOF + which expands to an integer constant expression, with type int and a negative value, that is returned by several functions to indicate end-of-file, that is, no more input from a stream;
- FOPEN_MAX+ FOPEN_MAX + which expands to an integer constant expression that is the minimum number of files that the implementation guarantees can be open simultaneously;
- FILENAME_MAX+ FILENAME_MAX + which expands to an integer constant expression that is the size needed for an array of char large enough to hold the longest file name string that the implementation - + guarantees can be opened;258)
- L_tmpnam+ L_tmpnam + which expands to an integer constant expression that is the size needed for an array of char large enough to hold a temporary file name string generated by the tmpnam function;
SEEK_CUR
SEEK_END
- SEEK_SET
+ SEEK_SET
+
which expand to integer constant expressions with distinct values, suitable for use as the
third argument to the fseek function;
- TMP_MAX+ TMP_MAX + which expands to an integer constant expression that is the minimum number of unique file names that can be generated by the tmpnam function;
stderr
stdin
- stdout
+ stdout
+
which are expressions of type ''pointer to FILE'' that point to the FILE objects
associated, respectively, with the standard error, input, and output streams.
-+
The header <wchar.h> declares a number of functions useful for wide character input and output. The wide character input/output functions described in that subclause provide operations analogous to most of those described here, except that the fundamental units internal to the program are wide characters. The external representation (in the file) is a sequence of ''generalized'' multibyte characters, as described further in 7.21.3. -
+
The input/output functions are given the following collective terms:
+
Input and output, whether to or from physical devices such as terminals and tape drives, or whether to or from files supported on structured storage devices, are mapped into logical data streams, whose properties are more uniform than their various inputs and outputs. Two forms of mapping are supported, for text streams and for binary streams.259) -
+
A text stream is an ordered sequence of characters composed into lines, each line consisting of zero or more characters plus a terminating new-line character. Whether the last line requires a terminating new-line character is implementation-defined. Characters @@ -14556,24 +15188,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. immediately preceded by space characters; and the last character is a new-line character. Whether space characters that are written out immediately before a new-line character appear when read in is implementation-defined. -
+
A binary stream is an ordered sequence of characters that can transparently record internal data. Data read in from a binary stream shall compare equal to the data that were earlier written out to that stream, under the same implementation. Such a stream may, however, have an implementation-defined number of null characters appended to the end of the stream. -
+
Each stream has an orientation. After a stream is associated with an external file, but before any operations are performed on it, the stream is without orientation. Once a wide character input/output function has been applied to a stream without orientation, the - + stream becomes a wide-oriented stream. Similarly, once a byte input/output function has been applied to a stream without orientation, the stream becomes a byte-oriented stream. Only a call to the freopen function or the fwide function can otherwise alter the orientation of a stream. (A successful call to freopen removes any orientation.)260) -
+
Byte input/output functions shall not be applied to a wide-oriented stream and wide character input/output functions shall not be applied to a byte-oriented stream. The remaining stream operations do not affect, and are not affected by, a stream's orientation, @@ -14586,14 +15218,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. function can overwrite a partial multibyte character; any file contents beyond the byte(s) written are henceforth indeterminate.
+
Each wide-oriented stream has an associated mbstate_t object that stores the current parse state of the stream. A successful call to fgetpos stores a representation of the value of this mbstate_t object as part of the value of the fpos_t object. A later successful call to fsetpos using the same stored fpos_t value restores the value of the associated mbstate_t object as well as the position within the controlled stream. - Environmental limits -
+
An implementation shall support text files with lines containing at least 254 characters, including the terminating new-line character. The value of the macro BUFSIZ shall be at least 256. @@ -14604,7 +15236,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
259) An implementation need not distinguish between text streams and binary streams. In such an @@ -14614,8 +15246,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
260) The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
-7.21.3 Files
-
+
A stream is associated with an external file (which may be a physical device) by opening a file, which may involve creating a new file. Creating an existing file causes its former contents to be discarded, if necessary. If a file can support positioning requests (such as a @@ -14625,11 +15257,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. position indicator is initially positioned at the beginning or the end of the file. The file position indicator is maintained by subsequent reads, writes, and positioning requests, to facilitate an orderly progression through the file. -
+
Binary files are not truncated, except as defined in 7.21.5.3. Whether a write on a text stream causes the associated file to be truncated beyond that point is implementation- defined. -
+
When a stream is unbuffered, characters are intended to appear from the source or at the destination as soon as possible. Otherwise characters may be accumulated and transmitted to or from the host environment as a block. When a stream is fully buffered, @@ -14641,25 +15273,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. when input is requested on a line buffered stream that requires the transmission of characters from the host environment. Support for these characteristics is implementation-defined, and may be affected via the setbuf and setvbuf functions. -
+
A file may be disassociated from a controlling stream by closing the file. Output streams are flushed (any unwritten buffer contents are transmitted to the host environment) before the stream is disassociated from the file. The value of a pointer to a FILE object is indeterminate after the associated file is closed (including the standard text streams). Whether a file of zero length (on which no characters have been written by an output stream) actually exists is implementation-defined. -
+
The file may be subsequently reopened, by the same or another program execution, and its contents reclaimed or modified (if it can be repositioned at its start). If the main function returns to its original caller, or if the exit function is called, all open files are closed (hence all output streams are flushed) before program termination. Other paths to program termination, such as calling the abort function, need not close all files properly. -
+
The address of the FILE object used to control a stream may be significant; a copy of a FILE object need not serve in place of the original. - -
+ +
At program startup, three text streams are predefined and need not be opened explicitly
+
Functions that open additional (nontemporary) files require a file name, which is a string. The rules for composing valid file names are implementation-defined. Whether the same file can be simultaneously open multiple times is also implementation-defined. -
+
Although both text and binary wide-oriented streams are conceptually sequences of wide characters, the external file associated with a wide-oriented stream is a sequence of multibyte characters, generalized as follows: @@ -14681,37 +15313,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. encodings valid for use internal to the program).
+
Moreover, the encodings used for multibyte characters may differ among files. Both the nature and choice of such encodings are implementation-defined. -
+
The wide character input functions read multibyte characters from the stream and convert them to wide characters as if they were read by successive calls to the fgetwc function. Each conversion occurs as if by a call to the mbrtowc function, with the conversion state described by the stream's own mbstate_t object. The byte input functions read characters from the stream as if by successive calls to the fgetc function. -
+
The wide character output functions convert wide characters to multibyte characters and write them to the stream as if they were written by successive calls to the fputwc function. Each conversion occurs as if by a call to the wcrtomb function, with the conversion state described by the stream's own mbstate_t object. The byte output functions write characters to the stream as if by successive calls to the fputc function. -
+
In some cases, some of the byte input/output functions also perform conversions between multibyte characters and wide characters. These conversions also occur as if by calls to the mbrtowc and wcrtomb functions. -
+
An encoding error occurs if the character sequence presented to the underlying mbrtowc function does not form a valid (generalized) multibyte character, or if the code value passed to the underlying wcrtomb does not correspond to a valid (generalized) - + multibyte character. The wide character input/output functions and the byte input/output functions store the value of the macro EILSEQ in errno if and only if an encoding error occurs. - Environmental limits -
+
The value of FOPEN_MAX shall be at least eight, including the three standard text streams.
Forward references: the exit function (7.22.4.4), the fgetc function (7.21.7.1), the
@@ -14726,39 +15358,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
with state-dependent encoding that does not assuredly end in the initial shift state.
-7.21.4 Operations on files
+
+
#include <stdio.h>
- int remove(const char *filename);
+ int remove(const char *filename);
+
+
The remove function causes the file whose name is the string pointed to by filename to be no longer accessible by that name. A subsequent attempt to open that file using that name will fail, unless it is created anew. If the file is open, the behavior of the remove function is implementation-defined.
+
The remove function returns zero if the operation succeeds, nonzero if it fails.
-7.21.4.2 The rename function
+
+
#include <stdio.h>
- int rename(const char *old, const char *new);
+ int rename(const char *old, const char *new);
+
+
The rename function causes the file whose name is the string pointed to by old to be henceforth known by the name given by the string pointed to by new. The file named old is no longer accessible by that name. If a file named by the string pointed to by new exists prior to the call to the rename function, the behavior is implementation-defined. - +
+
The rename function returns zero if the operation succeeds, nonzero if it fails,262) in
which case if the file existed previously it is still known by its original name.
@@ -14767,61 +15401,63 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
or that it is necessary to copy its contents to effectuate its renaming.
-7.21.4.3 The tmpfile function
+
+
#include <stdio.h>
- FILE *tmpfile(void);
+ FILE *tmpfile(void);
+
+
The tmpfile function creates a temporary binary file that is different from any other existing file and that will automatically be removed when it is closed or at program termination. If the program terminates abnormally, whether an open temporary file is removed is implementation-defined. The file is opened for update with "wb+" mode. - Recommended practice -
+
It should be possible to open at least TMP_MAX temporary files during the lifetime of the program (this limit may be shared with tmpnam) and there should be no limit on the number simultaneously open other than this limit and any limit on the number of open files (FOPEN_MAX).
+
The tmpfile function returns a pointer to the stream of the file that it created. If the file cannot be created, the tmpfile function returns a null pointer.
Forward references: the fopen function (7.21.5.3).
-7.21.4.4 The tmpnam function
+
+
#include <stdio.h>
- char *tmpnam(char *s);
+ char *tmpnam(char *s);
+
+
The tmpnam function generates a string that is a valid file name and that is not the same as the name of an existing file.263) The function is potentially capable of generating at - + least TMP_MAX different strings, but any or all of them may already be in use by existing files and thus not be suitable return values. -
+
The tmpnam function generates a different string each time it is called. -
+
Calls to the tmpnam function with a null pointer argument may introduce data races with each other. The implementation shall behave as if no library function calls the tmpnam function.
+
If no suitable string can be generated, the tmpnam function returns a null pointer. Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an internal static object and returns a pointer to that object (subsequent calls to the tmpnam function may modify the same object). If the argument is not a null pointer, it is assumed to point to an array of at least L_tmpnam chars; the tmpnam function writes its result in that array and returns the argument as its value. - Environmental limits -
+
The value of the macro TMP_MAX shall be at least 25.
+
#include <stdio.h>
- int fclose(FILE *stream);
+ int fclose(FILE *stream);
+
+
A successful call to the fclose function causes the stream pointed to by stream to be flushed and the associated file to be closed. Any unwritten buffered data for the stream are delivered to the host environment to be written to the file; any unread buffered data @@ -14848,44 +15485,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and any buffer set by the setbuf or setvbuf function is disassociated from the stream (and deallocated if it was automatically allocated).
+
The fclose function returns zero if the stream was successfully closed, or EOF if any
errors were detected.
-
+
-7.21.5.2 The fflush function
+
+
#include <stdio.h>
- int fflush(FILE *stream);
+ int fflush(FILE *stream);
+
+
If stream points to an output stream or an update stream in which the most recent operation was not input, the fflush function causes any unwritten data for that stream to be delivered to the host environment to be written to the file; otherwise, the behavior is undefined. -
+
If stream is a null pointer, the fflush function performs this flushing action on all streams for which the behavior is defined above.
+
The fflush function sets the error indicator for the stream and returns EOF if a write error occurs, otherwise it returns zero.
Forward references: the fopen function (7.21.5.3).
-7.21.5.3 The fopen function
+
+
#include <stdio.h>
FILE *fopen(const char * restrict filename,
- const char * restrict mode);
+ const char * restrict mode);
+
+
The fopen function opens the file whose name is the string pointed to by filename, and associates a stream with it. -
+
The argument mode points to a string. If the string is one of the following, the file is open in the indicated mode. Otherwise, the behavior is undefined.264) r open text file for reading @@ -14896,7 +15535,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wb truncate to zero length or create binary file for writing - + wbx create binary file for writing ab append; open or create binary file for writing at end-of-file r+ open text file for update (reading and writing) @@ -14907,22 +15546,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. w+b or wb+ truncate to zero length or create binary file for update w+bx or wb+x create binary file for update a+b or ab+ append; open or create binary file for update, writing at end-of-file -
+
Opening a file with read mode ('r' as the first character in the mode argument) fails if the file does not exist or cannot be read. -
+
Opening a file with exclusive mode ('x' as the last character in the mode argument) fails if the file already exists or cannot be created. Otherwise, the file is created with exclusive (also known as non-shared) access to the extent that the underlying system supports exclusive access. -
+
Opening a file with append mode ('a' as the first character in the mode argument) causes all subsequent writes to the file to be forced to the then current end-of-file, regardless of intervening calls to the fseek function. In some implementations, opening a binary file with append mode ('b' as the second or third character in the above list of mode argument values) may initially position the file position indicator for the stream beyond the last data written, because of null character padding. -
+
When a file is opened with update mode ('+' as the second or third character in the above list of mode argument values), both input and output may be performed on the associated stream. However, output shall not be directly followed by input without an @@ -14931,15 +15570,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. intervening call to a file positioning function, unless the input operation encounters end- of-file. Opening (or creating) a text file with update mode may instead open (or create) a binary stream in some implementations. -
+
When opened, a stream is fully buffered if and only if it can be determined not to refer to an interactive device. The error and end-of-file indicators for the stream are cleared.
+
The fopen function returns a pointer to the object controlling the stream. If the open operation fails, fopen returns a null pointer.
Forward references: file positioning functions (7.21.9). - +
264) If the string begins with one of the above sequences, the implementation might choose to ignore the
@@ -14947,30 +15586,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
conform to the properties in 7.21.2).
-7.21.5.4 The freopen function
+
+
#include <stdio.h>
FILE *freopen(const char * restrict filename,
const char * restrict mode,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The freopen function opens the file whose name is the string pointed to by filename and associates the stream pointed to by stream with it. The mode argument is used just as in the fopen function.265) -
+
If filename is a null pointer, the freopen function attempts to change the mode of the stream to that specified by mode, as if the name of the file currently associated with the stream had been used. It is implementation-defined which changes of mode are permitted (if any), and under what circumstances. -
+
The freopen function first attempts to close any file that is associated with the specified stream. Failure to close the file is ignored. The error and end-of-file indicators for the stream are cleared.
+
The freopen function returns a null pointer if the open operation fails. Otherwise,
freopen returns the value of stream.
@@ -14980,15 +15620,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
returned by the fopen function may be assigned.
-7.21.5.5 The setbuf function
+
+
#include <stdio.h>
void setbuf(FILE * restrict stream,
- char * restrict buf);
+ char * restrict buf);
+
+
Except that it returns no value, the setbuf function is equivalent to the setvbuf function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf is a null pointer), with the value _IONBF for mode. @@ -14996,22 +15637,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The setbuf function returns no value.
Forward references: the setvbuf function (7.21.5.6).
-7.21.5.6 The setvbuf function
+
+
#include <stdio.h>
int setvbuf(FILE * restrict stream,
char * restrict buf,
- int mode, size_t size);
+ int mode, size_t size);
+
+
The setvbuf function may be used only after the stream pointed to by stream has been associated with an open file and before any other operation (other than an unsuccessful call to setvbuf) is performed on the stream. The argument mode @@ -15023,22 +15665,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. allocated by the setvbuf function. The contents of the array at any time are indeterminate.
+
The setvbuf function returns zero on success, or nonzero if an invalid value is given for mode or if the request cannot be honored. - +
266) The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
before a buffer that has automatic storage duration is deallocated upon block exit.
-7.21.6 Formatted input/output functions
-
+
The formatted input/output functions shall behave as if there is a sequence point after the actions associated with each specifier.267) @@ -15046,29 +15688,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
267) The fprintf functions perform writes to memory for the %n specifier.
-7.21.6.1 The fprintf function
+
+
#include <stdio.h>
int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
+
The fprintf function writes output to the stream pointed to by stream, under control of the string pointed to by format that specifies how subsequent arguments are converted for output. If there are insufficient arguments for the format, the behavior is undefined. If the format is exhausted while arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored. The fprintf function returns when the end of the format string is encountered. -
+
The format shall be a multibyte character sequence, beginning and ending in its initial shift state. The format is composed of zero or more directives: ordinary multibyte characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments, converting them, if applicable, according to the corresponding conversion specifier, and then writing the result to the output stream. -
+
Each conversion specification is introduced by the character %. After the %, the following appear in sequence:
+
As noted above, a field width, or precision, or both, may be indicated by an asterisk. In this case, an int argument supplies the field width or precision. The arguments specifying field width, or precision, or both, shall appear (in that order) before the argument (if any) to be converted. A negative field width argument is taken as a - flag followed by a positive field width. A negative precision argument is taken as if the precision were omitted. -
+
The flag characters and their meanings are: - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)+ this flag is not specified.) + + The result of a signed conversion always begins with a plus or minus sign. (It
begins with a sign only when a negative value is converted if this flag is not
- specified.)269)
+ specified.)269)
+
space If the first character of a signed conversion is not a sign, or if a signed conversion
results in no characters, a space is prefixed to the result. If the space and + flags
- both appear, the space flag is ignored.
+ both appear, the space flag is ignored.
+
# The result is converted to an ''alternative form''. For o conversion, it increases
the precision, if and only if necessary, to force the first digit of the result to be a
@@ -15121,19 +15767,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
contains a decimal-point character, even if no digits follow it. (Normally, a
decimal-point character appears in the result of these conversions only if a digit
follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
+ result. For other conversions, the behavior is undefined.
+
0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
(following any indication of sign or base) are used to pad to the field width rather
than performing space padding, except when converting an infinity or NaN. If the
- 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
+ 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
+
-
-+
conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
+ conversions, the behavior is undefined.
+
+The length modifiers and their meanings are: hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
@@ -15141,14 +15790,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
been promoted according to the integer promotions, but its value shall be
converted to signed char or unsigned char before printing); or that
a following n conversion specifier applies to a pointer to a signed char
- argument.
+ argument.
+
h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
short int or unsigned short int argument (the argument will
have been promoted according to the integer promotions, but its value shall
be converted to short int or unsigned short int before printing);
or that a following n conversion specifier applies to a pointer to a short
- int argument.
+ int argument.
+
l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
long int or unsigned long int argument; that a following n
@@ -15156,40 +15807,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
following c conversion specifier applies to a wint_t argument; that a
following s conversion specifier applies to a pointer to a wchar_t
argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
+ specifier.
+
ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
long long int or unsigned long long int argument; or that a
following n conversion specifier applies to a pointer to a long long int
- argument.
+ argument.
+
j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
+ specifier applies to a pointer to an intmax_t argument.
+
z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
size_t or the corresponding signed integer type argument; or that a
following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
+ corresponding to size_t argument.
+
t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
-
+
ptrdiff_t or the corresponding unsigned integer type argument; or that a
following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
+ argument.
+
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.+ applies to a long double argument. + If a length modifier appears with any conversion specifier other than as specified above, the behavior is undefined. -
+
The conversion specifiers and their meanings are: d,i The int argument is converted to signed decimal in the style [-]dddd. The
precision specifies the minimum number of digits to appear; if the value
being converted can be represented in fewer digits, it is expanded with
leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no characters.
+ value with a precision of zero is no characters.
+
o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
@@ -15197,7 +15855,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
conversion. The precision specifies the minimum number of digits to appear;
if the value being converted can be represented in fewer digits, it is expanded
with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no characters.
+ zero value with a precision of zero is no characters.
+
f,F A double argument representing a floating-point number is converted to
decimal notation in the style [-]ddd.ddd, where the number of digits after
@@ -15212,15 +15871,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
[-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
any n-char-sequence, is implementation-defined. The F conversion specifier
produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
- respectively.270)
+ respectively.270)
+
e,E A double argument representing a floating-point number is converted in the
style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
argument is nonzero) before the decimal-point character and the number of
- digits after it is equal to the precision; if the precision is missing, it is taken as
+ digits after it is equal to the precision; if the precision is missing, it is taken as
+
-
+
6; if the precision is zero and the # flag is not specified, no decimal-point
character appears. The value is rounded to the appropriate number of digits.
@@ -15229,7 +15890,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
and only as many more digits as necessary to represent the exponent. If the
value is zero, the exponent is zero.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
g,G A double argument representing a floating-point number is converted in
style f or e (or in style F or E in the case of a G conversion specifier),
@@ -15243,7 +15905,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
fractional portion of the result and the decimal-point character is removed if
there is no fractional portion remaining.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
a,A A double argument representing a floating-point number is converted in the
style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
@@ -15252,12 +15915,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
of hexadecimal digits after it is equal to the precision; if the precision is
missing and FLT_RADIX is a power of 2, then the precision is sufficient for
an exact representation of the value; if the precision is missing and
- FLT_RADIX is not a power of 2, then the precision is sufficient to
+ FLT_RADIX is not a power of 2, then the precision is sufficient to
+
-
+
distinguish272) values of type double, except that trailing zeros may be
omitted; if the precision is zero and the # flag is not specified, no decimal-
@@ -15267,7 +15931,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
least one digit, and only as many more digits as necessary to represent the
decimal exponent of 2. If the value is zero, the exponent is zero.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
c If no l length modifier is present, the int argument is converted to an
unsigned char, and the resulting character is written.
@@ -15275,7 +15940,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
an ls conversion specification with no precision and an argument that points
to the initial element of a two-element array of wchar_t, the first element
containing the wint_t argument to the lc conversion specification and the
- second a null wide character.
+ second a null wide character.
+
s If no l length modifier is present, the argument shall be a pointer to the initial
element of an array of character type.273) Characters from the array are
@@ -15293,43 +15959,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(byte). If no precision is specified, the array shall contain a null wide
character. If a precision is specified, no more than that many bytes are
written (including shift sequences, if any), and the array shall contain a null
- wide character if, to equal the multibyte character sequence length given by
+ wide character if, to equal the multibyte character sequence length given by
+
-
+
the precision, the function would need to access a wide character one past the
- end of the array. In no case is a partial multibyte character written.274)
+ end of the array. In no case is a partial multibyte character written.274)
+
p The argument shall be a pointer to void. The value of the pointer is
converted to a sequence of printing characters, in an implementation-defined
- manner.
+ manner.
+
n The argument shall be a pointer to signed integer into which is written the
number of characters written to the output stream so far by this call to
fprintf. No argument is converted, but one is consumed. If the conversion
specification includes any flags, a field width, or a precision, the behavior is
- undefined.
+ undefined.
+
% A % character is written. No argument is converted. The complete
-
- conversion specification shall be %%.+ conversion specification shall be %%. + +
If a conversion specification is invalid, the behavior is undefined.275) If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined. -
+
In no case does a nonexistent or small field width cause truncation of a field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result. -
+
For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded to a hexadecimal floating number with the given precision. - Recommended practice -
+
For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly representable in the given precision, the result should be one of the two adjacent numbers in hexadecimal floating style with the given precision, with the extra stipulation that the error should have a correct sign for the current rounding direction. -
+
For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most DECIMAL_DIG, then the result should be correctly rounded.276) If the number of significant decimal digits is more than DECIMAL_DIG but the source value is exactly @@ -15338,18 +16009,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value - + of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that the error should have a correct sign for the current rounding direction.
+
The fprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. - Environmental limits -
+
The number of characters that can be produced by any single conversion shall be at least 4095. -
+
EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal places:
@@ -15360,16 +16031,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int day, hour, min;
fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
weekday, month, day, hour, min);
- fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
+ fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));
+
-+
EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the members of the extended character set that consist of more than one byte each consist of exactly two bytes, the first of which is denoted here by a and the second by an uppercase letter. -
+
Given the following wide string with length seven,
- static wchar_t wstr[] = L" X Yabc Z W";+ static wchar_t wstr[] = L" X Yabc Z W"; + the seven calls
fprintf(stdout, "|1234567890123|\n");
@@ -15378,7 +16051,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
fprintf(stdout, "|%13.10ls|\n", wstr);
fprintf(stdout, "|%13.11ls|\n", wstr);
fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
- fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
+ fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);
+
will print the following seven lines:
|1234567890123|
@@ -15387,10 +16061,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
| X Yabc Z|
| X Yabc Z W|
| abc Z W|
- | Z|
+ | Z|
+
Forward references: conversion state (7.28.6), the wcrtomb function (7.28.6.3.3). - +
268) Note that 0 is taken as a flag, not as the beginning of a field width.
@@ -15420,22 +16095,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the case of fixed-point conversion by the source value as well.
-7.21.6.2 The fscanf function
+
+
#include <stdio.h>
int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
+
The fscanf function reads input from the stream pointed to by stream, under control of the string pointed to by format that specifies the admissible input sequences and how they are to be converted for assignment, using subsequent arguments as pointers to the objects to receive the converted input. If there are insufficient arguments for the format, the behavior is undefined. If the format is exhausted while arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored. -
+
The format shall be a multibyte character sequence, beginning and ending in its initial shift state. The format is composed of zero or more directives: one or more white-space characters, an ordinary multibyte character (neither % nor a white-space character), or a @@ -15448,30 +16124,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
The fscanf function executes each directive of the format in turn. When all directives have been executed, or if a directive fails (as detailed below), the function returns. Failures are described as input failures (due to the occurrence of an encoding error or the unavailability of input characters), or matching failures (due to inappropriate input). -
+
A directive composed of white-space character(s) is executed by reading input up to the first non-white-space character (which remains unread), or until no more characters can be read. -
+
A directive that is an ordinary multibyte character is executed by reading the next characters of the stream. If any of those characters differ from the ones composing the directive, the directive fails and the differing and subsequent characters remain unread. Similarly, if end-of-file, an encoding error, or a read error prevents a character from being read, the directive fails. -
+
A directive that is a conversion specification defines a set of matching input sequences, as described below for each specifier. A conversion specification is executed in the - + following steps: -
+
Input white-space characters (as specified by the isspace function) are skipped, unless the specification includes a [, c, or n specifier.277) -
+
An input item is read from the stream, unless the specification includes an n specifier. An input item is defined as the longest sequence of input characters which does not exceed any specified field width and which is, or is a prefix of, a matching input sequence.278) @@ -15479,7 +16155,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. item is zero, the execution of the directive fails; this condition is a matching failure unless end-of-file, an encoding error, or a read error prevented input from the stream, in which case it is an input failure. -
+
Except in the case of a % specifier, the input item (or, in the case of a %n directive, the count of input characters) is converted to a type appropriate to the conversion specifier. If the input item is not a matching sequence, the execution of the directive fails: this @@ -15488,77 +16164,91 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the format argument that has not already received a conversion result. If this object does not have an appropriate type, or if the result of the conversion cannot be represented in the object, the behavior is undefined. -
+
The length modifiers and their meanings are: hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.+ to an argument with type pointer to signed char or unsigned char. + h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to short int or unsigned short
- int.
+ int.
+
l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to long int or unsigned long
int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
+ conversion specifier applies to an argument with type pointer to wchar_t.
+
ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to long long int or unsigned
- long long int.
+ long long int.
+
-
+
j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.+ to an argument with type pointer to intmax_t or uintmax_t. + z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to size_t or the corresponding signed
- integer type.
+ integer type.
+
t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
+ unsigned integer type.
+
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.+ applies to an argument with type pointer to long double. + If a length modifier appears with any conversion specifier other than as specified above, the behavior is undefined. -
+
The conversion specifiers and their meanings are: d Matches an optionally signed decimal integer, whose format is the same as
expected for the subject sequence of the strtol function with the value 10
for the base argument. The corresponding argument shall be a pointer to
- signed integer.
+ signed integer.
+
i Matches an optionally signed integer, whose format is the same as expected
for the subject sequence of the strtol function with the value 0 for the
base argument. The corresponding argument shall be a pointer to signed
- integer.
+ integer.
+
o Matches an optionally signed octal integer, whose format is the same as
expected for the subject sequence of the strtoul function with the value 8
for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
u Matches an optionally signed decimal integer, whose format is the same as
expected for the subject sequence of the strtoul function with the value 10
for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
x Matches an optionally signed hexadecimal integer, whose format is the same
as expected for the subject sequence of the strtoul function with the value
16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
-
+
format is the same as expected for the subject sequence of the strtod
- function. The corresponding argument shall be a pointer to floating.
+ function. The corresponding argument shall be a pointer to floating.
+
c Matches a sequence of characters of exactly the number specified by the field
width (1 if no field width is present in the directive).279)
@@ -15572,8 +16262,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
initialized to zero before the first multibyte character is converted. The
corresponding argument shall be a pointer to the initial element of an array of
wchar_t large enough to accept the resulting sequence of wide characters.
- No null wide character is added.
- s Matches a sequence of non-white-space characters.279)
+ No null wide character is added.
+
+ s Matches a sequence of non-white-space characters.279)
If no l length modifier is present, the corresponding argument shall be a
pointer to the initial element of a character array large enough to accept the
@@ -15585,19 +16276,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
before the first multibyte character is converted. The corresponding argument
shall be a pointer to the initial element of an array of wchar_t large enough
to accept the sequence and the terminating null wide character, which will be
- added automatically.
+ added automatically.
+
[ Matches a nonempty sequence of characters from a set of expected characters
- (the scanset).279) + (the scanset).279) If no l length modifier is present, the corresponding argument shall be a pointer to the initial element of a character array large enough to accept the sequence and a terminating null character, which will be added automatically. If an l length modifier is present, the input shall be a sequence of multibyte characters that begins in the initial shift state. Each multibyte character is converted to a wide character as if by a call to the mbrtowc function, with - the conversion state described by an mbstate_t object initialized to zero+ the conversion state described by an mbstate_t object initialized to zero + - +
before the first multibyte character is converted. The corresponding argument
shall be a pointer to the initial element of an array of wchar_t large enough
@@ -15614,7 +16307,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the first following right bracket character is the one that ends the
specification. If a - character is in the scanlist and is not the first, nor the
second where the first character is a ^, nor the last character, the behavior is
- implementation-defined.
+ implementation-defined.
+
p Matches an implementation-defined set of sequences, which should be the
same as the set of sequences that may be produced by the %p conversion of
@@ -15622,7 +16316,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pointer to void. The input item is converted to a pointer value in an
implementation-defined manner. If the input item is a value converted earlier
during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
+ equal to that value; otherwise the behavior of the %p conversion is undefined.
+
n No input is consumed. The corresponding argument shall be a pointer to
signed integer into which is to be written the number of characters read from
@@ -15630,58 +16325,63 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
%n directive does not increment the assignment count returned at the
completion of execution of the fscanf function. No argument is converted,
but one is consumed. If the conversion specification includes an assignment-
- suppressing character or a field width, the behavior is undefined.
+ suppressing character or a field width, the behavior is undefined.
+
% Matches a single % character; no conversion or assignment occurs. The
-
- complete conversion specification shall be %%.+ complete conversion specification shall be %%. + +
If a conversion specification is invalid, the behavior is undefined.280) -
+
The conversion specifiers A, E, F, G, and X are also valid and behave the same as, respectively, a, e, f, g, and x. - -
+ +
Trailing white space (including new-line characters) is left unread unless matched by a directive. The success of literal matches and suppressed assignments is not directly determinable other than via the %n directive.
+
The fscanf function returns the value of the macro EOF if an input failure occurs before the first conversion (if any) has completed. Otherwise, the function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure. -
+
EXAMPLE 1 The call:
#include <stdio.h>
/* ... */
int n, i; float x; char name[50];
- n = fscanf(stdin, "%d%f%s", &i, &x, name);
+ n = fscanf(stdin, "%d%f%s", &i, &x, name);
+
with the input line:
- 25 54.32E-1 thompson+ 25 54.32E-1 thompson + will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0. -
+
EXAMPLE 2 The call:
#include <stdio.h>
/* ... */
int i; float x; char name[50];
- fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
+ fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);
+
with input:
- 56789 0123 56a72+ 56789 0123 56a72 + will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the sequence 56\0. The next character read from the input stream will be a. -
+
EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name: -
#include <stdio.h>
/* ... */
@@ -15689,16 +16389,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
do {
count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
fscanf(stdin,"%*[^\n]");
- } while (!feof(stdin) && !ferror(stdin));
+ } while (!feof(stdin) && !ferror(stdin));
+
+If the stdin stream contains the following lines: - +
2 quarts of oil
-12.8degrees Celsius
lots of luck
10.0LBS of
dirt
- 100ergs of energy
+ 100ergs of energy
+
the execution of the above example will be analogous to the following assignments:
quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
@@ -15709,58 +16412,64 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
count = 3;
count = 0; // "100e" fails to match "%f"
- count = EOF;
+ count = EOF;
+
-+
EXAMPLE 4 In:
#include <stdio.h>
/* ... */
int d1, d2, n1, n2, i;
- i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
+ i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);
+
the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
-+
EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the members of the extended character set that consist of more than one byte each consist of exactly two bytes, the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes entry into the alternate shift state. -
+
After the call:
#include <stdio.h>
/* ... */
char str[50];
- fscanf(stdin, "a%s", str);
+ fscanf(stdin, "a%s", str);
+
with the input line:
- a(uparrow) X Y(downarrow) bc+ a(uparrow) X Y(downarrow) bc + str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte characters, in the more general case) appears to be a single-byte white-space character. -
+
In contrast, after the call:
#include <stdio.h>
#include <stddef.h>
/* ... */
wchar_t wstr[50];
- fscanf(stdin, "a%ls", wstr);
+ fscanf(stdin, "a%ls", wstr);
+
with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
terminating null wide character.
-+
However, the call: - +
#include <stdio.h>
#include <stddef.h>
/* ... */
wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
+ fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);
+
with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
string.
-+
Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte character Y, after the call:
@@ -15768,7 +16477,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#include <stddef.h>
/* ... */
wchar_t wstr[50];
- fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
+ fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);
+
with the same input line, zero will again be returned, but stdin will be left with a partially consumed
multibyte character.
@@ -15789,48 +16499,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
280) See ''future library directions'' (7.30.9).
-7.21.6.3 The printf function
+
+
#include <stdio.h>
- int printf(const char * restrict format, ...);
+ int printf(const char * restrict format, ...);
+
+
The printf function is equivalent to fprintf with the argument stdout interposed before the arguments to printf.
+
The printf function returns the number of characters transmitted, or a negative value if
an output or encoding error occurred.
-7.21.6.4 The scanf function
+
+
#include <stdio.h>
- int scanf(const char * restrict format, ...);
+ int scanf(const char * restrict format, ...);
+
+
The scanf function is equivalent to fscanf with the argument stdin interposed before the arguments to scanf. - +
+
The scanf function returns the value of the macro EOF if an input failure occurs before
the first conversion (if any) has completed. Otherwise, the scanf function returns the
number of input items assigned, which can be fewer than provided for, or even zero, in
the event of an early matching failure.
-7.21.6.5 The snprintf function
+
+
#include <stdio.h>
int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
+
The snprintf function is equivalent to fprintf, except that the output is written into an array (specified by argument s) rather than to a stream. If n is zero, nothing is written, and s may be a null pointer. Otherwise, output characters beyond the n-1st are @@ -15838,77 +16551,80 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. of the characters actually written into the array. If copying takes place between objects that overlap, the behavior is undefined.
+
The snprintf function returns the number of characters that would have been written
had n been sufficiently large, not counting the terminating null character, or a negative
value if an encoding error occurred. Thus, the null-terminated output has been
completely written if and only if the returned value is nonnegative and less than n.
-7.21.6.6 The sprintf function
+
+
#include <stdio.h>
int sprintf(char * restrict s,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
+
The sprintf function is equivalent to fprintf, except that the output is written into an array (specified by the argument s) rather than to a stream. A null character is written at the end of the characters written; it is not counted as part of the returned value. If copying takes place between objects that overlap, the behavior is undefined.
+
The sprintf function returns the number of characters written in the array, not
counting the terminating null character, or a negative value if an encoding error occurred.
-
+
-7.21.6.7 The sscanf function
+
+
#include <stdio.h>
int sscanf(const char * restrict s,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
+
The sscanf function is equivalent to fscanf, except that input is obtained from a string (specified by the argument s) rather than from a stream. Reaching the end of the string is equivalent to encountering end-of-file for the fscanf function. If copying takes place between objects that overlap, the behavior is undefined.
+
The sscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the sscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.21.6.8 The vfprintf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vfprintf(FILE * restrict stream,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vfprintf function is equivalent to fprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfprintf function does not invoke the va_end macro.281)
+
The vfprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. -
+
EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine. - +
#include <stdarg.h>
#include <stdio.h>
@@ -15921,7 +16637,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
// print out remainder of message
vfprintf(stderr, format, args);
va_end(args);
- }
+ }
+
+
#include <stdarg.h>
#include <stdio.h>
int vfscanf(FILE * restrict stream,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vfscanf function is equivalent to fscanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfscanf function does not invoke the - va_end macro.281) + va_end macro.281)
+
The vfscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vfscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.21.6.10 The vprintf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vprintf(const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vprintf function is equivalent to printf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and - + possibly subsequent va_arg calls). The vprintf function does not invoke the - va_end macro.281) + va_end macro.281)
+
The vprintf function returns the number of characters transmitted, or a negative value
if an output or encoding error occurred.
-7.21.6.11 The vscanf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vscanf(const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vscanf function is equivalent to scanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vscanf function does not invoke the va_end - macro.281) + macro.281)
+
The vscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.21.6.12 The vsnprintf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vsnprintf(char * restrict s, size_t n,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vsnprintf function is equivalent to snprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vsnprintf function does not invoke the - va_end macro.281) If copying takes place between objects that overlap, the behavior is + va_end macro.281) If copying takes place between objects that overlap, the behavior is undefined. - +
+
The vsnprintf function returns the number of characters that would have been written
had n been sufficiently large, not counting the terminating null character, or a negative
value if an encoding error occurred. Thus, the null-terminated output has been
completely written if and only if the returned value is nonnegative and less than n.
-7.21.6.13 The vsprintf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vsprintf(char * restrict s,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vsprintf function is equivalent to sprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vsprintf function does not invoke the - va_end macro.281) If copying takes place between objects that overlap, the behavior is + va_end macro.281) If copying takes place between objects that overlap, the behavior is undefined.
+
The vsprintf function returns the number of characters written in the array, not
counting the terminating null character, or a negative value if an encoding error occurred.
-7.21.6.14 The vsscanf function
+
+
#include <stdarg.h>
#include <stdio.h>
int vsscanf(const char * restrict s,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vsscanf function is equivalent to sscanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vsscanf function does not invoke the - va_end macro.281) + va_end macro.281)
+
The vsscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vsscanf function
-
+
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.21.7 Character input/output functions
+
+
#include <stdio.h>
- int fgetc(FILE *stream);
+ int fgetc(FILE *stream);
+
+
If the end-of-file indicator for the input stream pointed to by stream is not set and a next character is present, the fgetc function obtains that character as an unsigned char converted to an int and advances the associated file position indicator for the stream (if defined).
+
If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end- of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the fgetc function returns the next character from the input stream pointed to by stream. @@ -16086,177 +16810,186 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
282) An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
-7.21.7.2 The fgets function
+
+
#include <stdio.h>
char *fgets(char * restrict s, int n,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The fgets function reads at most one less than the number of characters specified by n from the stream pointed to by stream into the array pointed to by s. No additional characters are read after a new-line character (which is retained) or after end-of-file. A null character is written immediately after the last character read into the array.
+
The fgets function returns s if successful. If end-of-file is encountered and no
characters have been read into the array, the contents of the array remain unchanged and a
null pointer is returned. If a read error occurs during the operation, the array contents are
indeterminate and a null pointer is returned.
-
+
-7.21.7.3 The fputc function
+
+
#include <stdio.h>
- int fputc(int c, FILE *stream);
+ int fputc(int c, FILE *stream);
+
+
The fputc function writes the character specified by c (converted to an unsigned char) to the output stream pointed to by stream, at the position indicated by the associated file position indicator for the stream (if defined), and advances the indicator appropriately. If the file cannot support positioning requests, or if the stream was opened with append mode, the character is appended to the output stream.
+
The fputc function returns the character written. If a write error occurs, the error
indicator for the stream is set and fputc returns EOF.
-7.21.7.4 The fputs function
+
+
#include <stdio.h>
int fputs(const char * restrict s,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The fputs function writes the string pointed to by s to the stream pointed to by stream. The terminating null character is not written.
+
The fputs function returns EOF if a write error occurs; otherwise it returns a
nonnegative value.
-7.21.7.5 The getc function
+
+
#include <stdio.h>
- int getc(FILE *stream);
+ int getc(FILE *stream);
+
+
The getc function is equivalent to fgetc, except that if it is implemented as a macro, it may evaluate stream more than once, so the argument should never be an expression with side effects. - +
+
The getc function returns the next character from the input stream pointed to by
stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
getc returns EOF. If a read error occurs, the error indicator for the stream is set and
getc returns EOF.
-7.21.7.6 The getchar function
+
+
#include <stdio.h>
- int getchar(void);
+ int getchar(void);
+
+
The getchar function is equivalent to getc with the argument stdin.
+
The getchar function returns the next character from the input stream pointed to by
stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
getchar returns EOF. *
-7.21.7.7 The putc function
+
+
#include <stdio.h>
- int putc(int c, FILE *stream);
+ int putc(int c, FILE *stream);
+
+
The putc function is equivalent to fputc, except that if it is implemented as a macro, it may evaluate stream more than once, so that argument should never be an expression with side effects.
+
The putc function returns the character written. If a write error occurs, the error
indicator for the stream is set and putc returns EOF.
-7.21.7.8 The putchar function
+
+
#include <stdio.h>
- int putchar(int c);
+ int putchar(int c);
+
+
The putchar function is equivalent to putc with the second argument stdout. - +
+
The putchar function returns the character written. If a write error occurs, the error
indicator for the stream is set and putchar returns EOF.
-7.21.7.9 The puts function
+
+
#include <stdio.h>
- int puts(const char *s);
+ int puts(const char *s);
+
+
The puts function writes the string pointed to by s to the stream pointed to by stdout, and appends a new-line character to the output. The terminating null character is not written.
+
The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
value.
-7.21.7.10 The ungetc function
+
+
#include <stdio.h>
- int ungetc(int c, FILE *stream);
+ int ungetc(int c, FILE *stream);
+
+
The ungetc function pushes the character specified by c (converted to an unsigned char) back onto the input stream pointed to by stream. Pushed-back characters will be returned by subsequent reads on that stream in the reverse order of their pushing. A successful intervening call (with the stream pointed to by stream) to a file positioning function (fseek, fsetpos, or rewind) discards any pushed-back characters for the stream. The external storage corresponding to the stream is unchanged. -
+
One character of pushback is guaranteed. If the ungetc function is called too many times on the same stream without an intervening read or file positioning operation on that stream, the operation may fail. -
+
If the value of c equals that of the macro EOF, the operation fails and the input stream is unchanged. -
+
A successful call to the ungetc function clears the end-of-file indicator for the stream. The value of the file position indicator for the stream after reading or discarding all pushed-back characters shall be the same as it was before the characters were pushed back. For a text stream, the value of its file position indicator after a successful call to the ungetc function is unspecified until all pushed-back characters are read or discarded. - + For a binary stream, its file position indicator is decremented by each successful call to the ungetc function; if its value was zero before a call, it is indeterminate after the call.283)
+
The ungetc function returns the character pushed back after conversion, or EOF if the operation fails.
Forward references: file positioning functions (7.21.9). @@ -16265,18 +16998,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
283) See ''future library directions'' (7.30.9).
-7.21.8 Direct input/output functions
+
+
#include <stdio.h>
size_t fread(void * restrict ptr,
size_t size, size_t nmemb,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The fread function reads, into the array pointed to by ptr, up to nmemb elements whose size is specified by size, from the stream pointed to by stream. For each object, size calls are made to the fgetc function and the results stored, in the order @@ -16285,7 +17019,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. read. If an error occurs, the resulting value of the file position indicator for the stream is indeterminate. If a partial element is read, its value is indeterminate.
+
The fread function returns the number of elements successfully read, which may be
less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
fread returns zero and the contents of the array and the state of the stream remain
@@ -16294,18 +17028,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-7.21.8.2 The fwrite function
+
+
#include <stdio.h>
size_t fwrite(const void * restrict ptr,
size_t size, size_t nmemb,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The fwrite function writes, from the array pointed to by ptr, up to nmemb elements whose size is specified by size, to the stream pointed to by stream. For each object, size calls are made to the fputc function, taking the values (in order) from an array of @@ -16314,95 +17049,99 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. error occurs, the resulting value of the file position indicator for the stream is indeterminate.
+
The fwrite function returns the number of elements successfully written, which will be
less than nmemb only if a write error is encountered. If size or nmemb is zero,
fwrite returns zero and the state of the stream remains unchanged.
-7.21.9 File positioning functions
+
+
#include <stdio.h>
int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
+ fpos_t * restrict pos);
+
+
The fgetpos function stores the current values of the parse state (if any) and file position indicator for the stream pointed to by stream in the object pointed to by pos. The values stored contain unspecified information usable by the fsetpos function for repositioning the stream to its position at the time of the call to the fgetpos function.
+
If successful, the fgetpos function returns zero; on failure, the fgetpos function returns nonzero and stores an implementation-defined positive value in errno.
Forward references: the fsetpos function (7.21.9.3).
-
+
-7.21.9.2 The fseek function
+
+
#include <stdio.h>
- int fseek(FILE *stream, long int offset, int whence);
+ int fseek(FILE *stream, long int offset, int whence);
+
+
The fseek function sets the file position indicator for the stream pointed to by stream. If a read or write error occurs, the error indicator for the stream is set and fseek fails. -
+
For a binary stream, the new position, measured in characters from the beginning of the file, is obtained by adding offset to the position specified by whence. The specified position is the beginning of the file if whence is SEEK_SET, the current value of the file position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not meaningfully support fseek calls with a whence value of SEEK_END. -
+
For a text stream, either offset shall be zero, or offset shall be a value returned by an earlier successful call to the ftell function on a stream associated with the same file and whence shall be SEEK_SET. -
+
After determining the new position, a successful call to the fseek function undoes any effects of the ungetc function on the stream, clears the end-of-file indicator for the stream, and then establishes the new position. After a successful fseek call, the next operation on an update stream may be either input or output.
+
The fseek function returns nonzero only for a request that cannot be satisfied.
Forward references: the ftell function (7.21.9.4).
-7.21.9.3 The fsetpos function
+
+
#include <stdio.h>
- int fsetpos(FILE *stream, const fpos_t *pos);
+ int fsetpos(FILE *stream, const fpos_t *pos);
+
+
The fsetpos function sets the mbstate_t object (if any) and file position indicator for the stream pointed to by stream according to the value of the object pointed to by pos, which shall be a value obtained from an earlier successful call to the fgetpos function on a stream associated with the same file. If a read or write error occurs, the error indicator for the stream is set and fsetpos fails. -
+
A successful call to the fsetpos function undoes any effects of the ungetc function on the stream, clears the end-of-file indicator for the stream, and then establishes the new parse state and position. After a successful fsetpos call, the next operation on an - + update stream may be either input or output.
+
If successful, the fsetpos function returns zero; on failure, the fsetpos function
returns nonzero and stores an implementation-defined positive value in errno.
-7.21.9.4 The ftell function
+
+
#include <stdio.h>
- long int ftell(FILE *stream);
+ long int ftell(FILE *stream);
+
+
The ftell function obtains the current value of the file position indicator for the stream pointed to by stream. For a binary stream, the value is the number of characters from the beginning of the file. For a text stream, its file position indicator contains unspecified @@ -16411,82 +17150,88 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. return values is not necessarily a meaningful measure of the number of characters written or read.
+
If successful, the ftell function returns the current value of the file position indicator
for the stream. On failure, the ftell function returns -1L and stores an
implementation-defined positive value in errno.
-7.21.9.5 The rewind function
+
+
#include <stdio.h>
- void rewind(FILE *stream);
+ void rewind(FILE *stream);
+
+
The rewind function sets the file position indicator for the stream pointed to by stream to the beginning of the file. It is equivalent to
- (void)fseek(stream, 0L, SEEK_SET)+ (void)fseek(stream, 0L, SEEK_SET) + except that the error indicator for the stream is also cleared.
+
The rewind function returns no value.
-
+
-7.21.10 Error-handling functions
+
+
#include <stdio.h>
- void clearerr(FILE *stream);
+ void clearerr(FILE *stream);
+
+
The clearerr function clears the end-of-file and error indicators for the stream pointed to by stream.
+
The clearerr function returns no value.
-7.21.10.2 The feof function
+
+
#include <stdio.h>
- int feof(FILE *stream);
+ int feof(FILE *stream);
+
+
The feof function tests the end-of-file indicator for the stream pointed to by stream.
+
The feof function returns nonzero if and only if the end-of-file indicator is set for
stream.
-7.21.10.3 The ferror function
+
+
#include <stdio.h>
- int ferror(FILE *stream);
+ int ferror(FILE *stream);
+
+
The ferror function tests the error indicator for the stream pointed to by stream.
+
The ferror function returns nonzero if and only if the error indicator is set for
stream.
-
+
-7.21.10.4 The perror function
+
+
#include <stdio.h>
- void perror(const char *s);
+ void perror(const char *s);
+
+
The perror function maps the error number in the integer expression errno to an error message. It writes a sequence of characters to the standard error stream thus: first (if s is not a null pointer and the character pointed to by s is not the null character), the @@ -16494,42 +17239,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. message string followed by a new-line character. The contents of the error message strings are the same as those returned by the strerror function with argument errno.
+
The perror function returns no value.
Forward references: the strerror function (7.23.6.2).
-
+
-7.22 General utilities
-
+
The header <stdlib.h> declares five types and several functions of general utility, and defines several macros.284) -
+
The types declared are size_t and wchar_t (both described in 7.19),
- div_t+ div_t + which is a structure type that is the type of the value returned by the div function,
- ldiv_t+ ldiv_t + which is a structure type that is the type of the value returned by the ldiv function, and
- lldiv_t+ lldiv_t + which is a structure type that is the type of the value returned by the lldiv function. -
+
The macros defined are NULL (described in 7.19);
- EXIT_FAILURE+ EXIT_FAILURE + and
- EXIT_SUCCESS+ EXIT_SUCCESS + which expand to integer constant expressions that can be used as the argument to the exit function to return unsuccessful or successful termination status, respectively, to the host environment;
- RAND_MAX+ RAND_MAX + which expands to an integer constant expression that is the maximum value returned by the rand function; and
- MB_CUR_MAX+ MB_CUR_MAX + which expands to a positive integer expression with type size_t that is the maximum number of bytes in a multibyte character for the extended character set specified by the current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX. @@ -16537,62 +17289,66 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
284) See ''future library directions'' (7.30.10).
-7.22.1 Numeric conversion functions
-
+
The functions atof, atoi, atol, and atoll need not affect the value of the integer
expression errno on an error. If the value of the result cannot be represented, the
behavior is undefined.
-7.22.1.1 The atof function
+
+
#include <stdlib.h>
- double atof(const char *nptr);
+ double atof(const char *nptr);
+
+
The atof function converts the initial portion of the string pointed to by nptr to double representation. Except for the behavior on error, it is equivalent to
- strtod(nptr, (char **)NULL)+ strtod(nptr, (char **)NULL) +
+
The atof function returns the converted value.
Forward references: the strtod, strtof, and strtold functions (7.22.1.3).
-7.22.1.2 The atoi, atol, and atoll functions
+
+
#include <stdlib.h>
int atoi(const char *nptr);
long int atol(const char *nptr);
- long long int atoll(const char *nptr);
+ long long int atoll(const char *nptr);
+
+
The atoi, atol, and atoll functions convert the initial portion of the string pointed to by nptr to int, long int, and long long int representation, respectively. Except for the behavior on error, they are equivalent to
atoi: (int)strtol(nptr, (char **)NULL, 10)
atol: strtol(nptr, (char **)NULL, 10)
- atoll: strtoll(nptr, (char **)NULL, 10)
+ atoll: strtoll(nptr, (char **)NULL, 10)
+
+
The atoi, atol, and atoll functions return the converted value.
Forward references: the strtol, strtoll, strtoul, and strtoull functions
(7.22.1.4).
-
+
-7.22.1.3 The strtod, strtof, and strtold functions
+
+
#include <stdlib.h>
double strtod(const char * restrict nptr,
@@ -16600,9 +17356,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
float strtof(const char * restrict nptr,
char ** restrict endptr);
long double strtold(const char * restrict nptr,
- char ** restrict endptr);
+ char ** restrict endptr);
+
+
The strtod, strtof, and strtold functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation, respectively. First, they decompose the input string into three parts: an initial, possibly @@ -16611,7 +17368,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and a final string of one or more unrecognized characters, including the terminating null character of the input string. Then, they attempt to convert the subject sequence to a floating-point number, and return the result. -
+
The expected form of the subject sequence is an optional plus or minus sign, then one of the following:
n-char-sequence:
digit
nondigit
n-char-sequence digit
- n-char-sequence nondigit
+ n-char-sequence nondigit
+
+
If the subject sequence has the expected form for a floating-point number, the sequence of characters starting with the first digit or the decimal-point character (whichever occurs first) is interpreted as a floating constant according to the rules of 6.4.4.2, except that the - + decimal-point character is used in place of a period, and that if neither an exponent part nor a decimal-point character appears in a decimal floating point number, or if a binary exponent part does not appear in a hexadecimal floating point number, an exponent part @@ -16643,29 +17401,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the subject sequence begins with a minus sign, the sequence is interpreted as negated.285) A character sequence INF or INFINITY is interpreted as an infinity, if representable in the return type, else like a floating constant that is too large for the range of the return - type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet + type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet NaN, if supported in the return type, else like a subject sequence part that does not have the expected form; the meaning of the n-char sequences is implementation-defined.286) A pointer to the final string is stored in the object pointed to by endptr, provided that endptr is not a null pointer. -
+
If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the value resulting from the conversion is correctly rounded. -
+
In other than the "C" locale, additional locale-specific subject sequence forms may be accepted. -
+
If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer. - Recommended practice -
+
If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and the result is not exactly representable, the result should be one of the two numbers in the appropriate internal format that are adjacent to the hexadecimal floating source value, with the extra stipulation that the error should have a correct sign for the current rounding direction. -
+
If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in <float.h>) significant digits, the result should be correctly rounded. If the subject sequence D has the decimal form and more than DECIMAL_DIG significant digits, @@ -16674,11 +17432,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. The result should be one of the (equal or adjacent) values that would be obtained by correctly rounding L and U according to the current rounding direction, with the extra - + stipulation that the error with respect to D should have a correct sign for the current rounding direction.287)
+
The functions return the converted value, if any. If no conversion could be performed,
zero is returned. If the correct value overflows and default rounding is in effect (7.12.1),
plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the
@@ -16700,9 +17458,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
to the same internal floating value, but if not will round to adjacent values.
-7.22.1.4 The strtol, strtoll, strtoul, and strtoull functions
+
+
#include <stdlib.h>
long int strtol(
@@ -16720,9 +17478,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
unsigned long long int strtoull(
const char * restrict nptr,
char ** restrict endptr,
- int base);
+ int base);
+
+
The strtol, strtoll, strtoul, and strtoull functions convert the initial portion of the string pointed to by nptr to long int, long long int, unsigned long int, and unsigned long long int representation, respectively. First, @@ -16730,12 +17489,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. white-space characters (as specified by the isspace function), a subject sequence - + resembling an integer represented in some radix determined by the value of base, and a final string of one or more unrecognized characters, including the terminating null character of the input string. Then, they attempt to convert the subject sequence to an integer, and return the result. -
+
If the value of base is zero, the expected form of the subject sequence is that of an integer constant as described in 6.4.4.1, optionally preceded by a plus or minus sign, but not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the @@ -16745,13 +17504,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ascribed the values 10 through 35; only letters and digits whose ascribed values are less than that of base are permitted. If the value of base is 16, the characters 0x or 0X may optionally precede the sequence of letters and digits, following the sign if present. -
+
The subject sequence is defined as the longest initial subsequence of the input string, starting with the first non-white-space character, that is of the expected form. The subject sequence contains no characters if the input string is empty or consists entirely of white space, or if the first non-white-space character is other than a sign or a permissible letter or digit. -
+
If the subject sequence has the expected form and the value of base is zero, the sequence of characters starting with the first digit is interpreted as an integer constant according to the rules of 6.4.4.1. If the subject sequence has the expected form and the value of base @@ -16759,42 +17518,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. as given above. If the subject sequence begins with a minus sign, the value resulting from the conversion is negated (in the return type). A pointer to the final string is stored in the object pointed to by endptr, provided that endptr is not a null pointer. -
+
In other than the "C" locale, additional locale-specific subject sequence forms may be accepted. -
+
If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
+
The strtol, strtoll, strtoul, and strtoull functions return the converted
value, if any. If no conversion could be performed, zero is returned. If the correct value
is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
-
+
-7.22.2 Pseudo-random sequence generation functions
+
+
#include <stdlib.h>
- int rand(void);
+ int rand(void);
+
+
The rand function computes a sequence of pseudo-random integers in the range 0 to RAND_MAX.288) -
+
The rand function is not required to avoid data races. The implementation shall behave as if no library function calls the rand function.
+
The rand function returns a pseudo-random integer. - Environmental limits -
+
The value of the RAND_MAX macro shall be at least 32767.
+
#include <stdlib.h>
- void srand(unsigned int seed);
+ void srand(unsigned int seed);
+
+
The srand function uses the argument as a seed for a new sequence of pseudo-random numbers to be returned by subsequent calls to rand. If srand is then called with the same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is called before any calls to srand have been made, the same sequence shall be generated as when srand is first called with a seed value of 1. -
+
The implementation shall behave as if no library function calls the srand function.
+
The srand function returns no value. - -
+ +
EXAMPLE The following functions define a portable implementation of rand and srand.
static unsigned long int next = 1;
@@ -16838,11 +17599,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
void srand(unsigned int seed)
{
next = seed;
- }
+ }
+
-+
The order and contiguity of storage allocated by successive calls to the
aligned_alloc, calloc, malloc, and realloc functions is unspecified. The
pointer returned if the allocation succeeds is suitably aligned so that it may be assigned to
@@ -16856,36 +17618,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
is returned, or the behavior is as if the size were some nonzero value, except that the
returned pointer shall not be used to access an object.
-7.22.3.1 The aligned_alloc function
+
+
#include <stdlib.h>
- void *aligned_alloc(size_t alignment, size_t size);
+ void *aligned_alloc(size_t alignment, size_t size);
+
+
The aligned_alloc function allocates space for an object whose alignment is specified by alignment, whose size is specified by size, and whose value is indeterminate. The value of alignment shall be a valid alignment supported by the implementation and the value of size shall be an integral multiple of alignment.
+
The aligned_alloc function returns either a null pointer or a pointer to the allocated
space.
-
+
-7.22.3.2 The calloc function
+
+
#include <stdlib.h>
- void *calloc(size_t nmemb, size_t size);
+ void *calloc(size_t nmemb, size_t size);
+
+
The calloc function allocates space for an array of nmemb objects, each of whose size is size. The space is initialized to all bits zero.289)
+
The calloc function returns either a null pointer or a pointer to the allocated space.
+
#include <stdlib.h>
- void free(void *ptr);
+ void free(void *ptr);
+
+
The free function causes the space pointed to by ptr to be deallocated, that is, made available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if the argument does not match a pointer earlier returned by a memory management function, or if the space has been deallocated by a call to free or realloc, the behavior is undefined.
+
The free function returns no value.
-7.22.3.4 The malloc function
+
+
#include <stdlib.h>
- void *malloc(size_t size);
+ void *malloc(size_t size);
+
+
The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate. - +
+
The malloc function returns either a null pointer or a pointer to the allocated space.
-7.22.3.5 The realloc function
+
+
#include <stdlib.h>
- void *realloc(void *ptr, size_t size);
+ void *realloc(void *ptr, size_t size);
+
+
The realloc function deallocates the old object pointed to by ptr and returns a pointer to a new object that has the size specified by size. The contents of the new object shall be the same as that of the old object prior to deallocation, up to the lesser of the new and old sizes. Any bytes in the new object beyond the size of the old object have indeterminate values. -
+
If ptr is a null pointer, the realloc function behaves like the malloc function for the specified size. Otherwise, if ptr does not match a pointer earlier returned by a memory management function, or if the space has been deallocated by a call to the free or realloc function, the behavior is undefined. If memory for the new object cannot be allocated, the old object is not deallocated and its value is unchanged.
+
The realloc function returns a pointer to the new object (which may have the same
value as a pointer to the old object), or a null pointer if the new object could not be
allocated.
-7.22.4 Communication with the environment
+
+
#include <stdlib.h>
- _Noreturn void abort(void);
+ _Noreturn void abort(void);
+
+
The abort function causes abnormal program termination to occur, unless the signal SIGABRT is being caught and the signal handler does not return. Whether open streams with unwritten buffered data are flushed, open streams are closed, or temporary files are removed is implementation-defined. An implementation-defined form of the status unsuccessful termination is returned to the host environment by means of the function call raise(SIGABRT). - +
+
The abort function does not return to its caller.
-7.22.4.2 The atexit function
+
+
#include <stdlib.h>
- int atexit(void (*func)(void));
+ int atexit(void (*func)(void));
+
+
The atexit function registers the function pointed to by func, to be called without arguments at normal program termination.290) - Environmental limits -
+
The implementation shall support the registration of at least 32 functions.
+
The atexit function returns zero if the registration succeeds, nonzero if it fails.
Forward references: the at_quick_exit function (7.22.4.3), the exit function
(7.22.4.4).
@@ -16999,62 +17768,64 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
applications may need to call both registration functions with the same argument.
-7.22.4.3 The at_quick_exit function
+
+
#include <stdlib.h>
- int at_quick_exit(void (*func)(void));
+ int at_quick_exit(void (*func)(void));
+
+
The at_quick_exit function registers the function pointed to by func, to be called without arguments should quick_exit be called.291) - Environmental limits -
+
The implementation shall support the registration of at least 32 functions.
+
The at_quick_exit function returns zero if the registration succeeds, nonzero if it fails.
Forward references: the quick_exit function (7.22.4.7). - +
291) The at_quick_exit function registrations are distinct from the atexit registrations, so
applications may need to call both registration functions with the same argument.
-7.22.4.4 The exit function
+
+
#include <stdlib.h>
- _Noreturn void exit(int status);
+ _Noreturn void exit(int status);
+
+
The exit function causes normal program termination to occur. No functions registered by the at_quick_exit function are called. If a program calls the exit function more than once, or calls the quick_exit function in addition to the exit function, the behavior is undefined. -
+
First, all functions registered by the atexit function are called, in the reverse order of their registration,292) except that a function is called after any previously registered functions that had already been called at the time it was registered. If, during the call to any such function, a call to the longjmp function is made that would terminate the call to the registered function, the behavior is undefined. -
+
Next, all open streams with unwritten buffered data are flushed, all open streams are closed, and all files created by the tmpfile function are removed. -
+
Finally, control is returned to the host environment. If the value of status is zero or EXIT_SUCCESS, an implementation-defined form of the status successful termination is returned. If the value of status is EXIT_FAILURE, an implementation-defined form of the status unsuccessful termination is returned. Otherwise the status returned is implementation-defined.
+
The exit function cannot return to its caller.
+
#include <stdlib.h>
- _Noreturn void _Exit(int status);
+ _Noreturn void _Exit(int status);
+
+
The _Exit function causes normal program termination to occur and control to be returned to the host environment. No functions registered by the atexit function, the at_quick_exit function, or signal handlers registered by the signal function are called. The status returned to the host environment is determined in the same way as for - + the exit function (7.22.4.4). Whether open streams with unwritten buffered data are flushed, open streams are closed, or temporary files are removed is implementation- defined.
+
The _Exit function cannot return to its caller.
-7.22.4.6 The getenv function
+
+
#include <stdlib.h>
- char *getenv(const char *name);
+ char *getenv(const char *name);
+
+
The getenv function searches an environment list, provided by the host environment, for a string that matches the string pointed to by name. The set of environment names and the method for altering the environment list are implementation-defined. The getenv function need not avoid data races with other threads of execution that modify the environment list.293) -
+
The implementation shall behave as if no library function calls the getenv function.
+
The getenv function returns a pointer to a string associated with the matched list member. The string pointed to shall not be modified by the program, but may be overwritten by a subsequent call to the getenv function. If the specified name cannot @@ -17110,32 +17883,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
293) Many implementations provide non-standard functions that modify the environment list.
-7.22.4.7 The quick_exit function
+
+
#include <stdlib.h>
- _Noreturn void quick_exit(int status);
+ _Noreturn void quick_exit(int status);
+
+
The quick_exit function causes normal program termination to occur. No functions registered by the atexit function or signal handlers registered by the signal function are called. If a program calls the quick_exit function more than once, or calls the exit function in addition to the quick_exit function, the behavior is undefined. -
+
The quick_exit function first calls all functions registered by the at_quick_exit function, in the reverse order of their registration,294) except that a function is called after - + any previously registered functions that had already been called at the time it was registered. If, during the call to any such function, a call to the longjmp function is made that would terminate the call to the registered function, the behavior is undefined. -
+
Then control is returned to the host environment by means of the function call _Exit(status).
+
The quick_exit function cannot return to its caller.
+
#include <stdlib.h>
- int system(const char *string);
+ int system(const char *string);
+
+
If string is a null pointer, the system function determines whether the host environment has a command processor. If string is not a null pointer, the system function passes the string pointed to by string to that command processor to be executed in a manner which the implementation shall document; this might then cause the program calling system to behave in a non-conforming manner or to terminate.
+
If the argument is a null pointer, the system function returns nonzero only if a
command processor is available. If the argument is not a null pointer, and the system
function does return, it returns an implementation-defined value.
-7.22.5 Searching and sorting utilities
-
+
These utilities make use of a comparison function to search or sort arrays of unspecified type. Where an argument declared as size_t nmemb specifies the length of the array for a function, nmemb can have the value zero on a call to that function; the comparison function is not called, a search finds no matching element, and sorting performs no rearrangement. Pointer arguments on such a call shall still have valid values, as described in 7.1.4. -
+
The implementation shall ensure that the second argument of the comparison function (when called from bsearch), or both arguments (when called from qsort), are pointers to elements of the array.295) The first argument when called from bsearch @@ -17178,18 +17953,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
The comparison function shall not alter the contents of the array. The implementation may reorder elements of the array between calls to the comparison function, but shall not alter the contents of any individual element. -
+
When the same objects (consisting of size bytes, irrespective of their current positions in the array) are passed more than once to the comparison function, the results shall be consistent with one another. That is, for qsort they shall define a total ordering on the array, and for bsearch the same object shall always compare the same way with the key. -
+
A sequence point occurs immediately before and immediately after each call to the comparison function, and also between any call to the comparison function and any movement of the objects passed as arguments to that call. @@ -17200,24 +17975,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
((char *)p - (char *)base) % size == 0
(char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
+ (char *)p < (char *)base + nmemb * size
+
-+
#include <stdlib.h>
void *bsearch(const void *key, const void *base,
size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
+ int (*compar)(const void *, const void *));
+
+
The bsearch function searches an array of nmemb objects, the initial element of which is pointed to by base, for an element that matches the object pointed to by key. The size of each element of the array is specified by size. -
+
The comparison function pointed to by compar is called with two arguments that point to the key object and to an array element, in that order. The function shall return an integer less than, equal to, or greater than zero if the key object is considered, @@ -17225,90 +18002,93 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. shall consist of: all the elements that compare less than, all the elements that compare equal to, and all the elements that compare greater than the key object, in that order.296)
+
The bsearch function returns a pointer to a matching element of the array, or a null pointer if no match is found. If two elements compare as equal, which element is - + matched is unspecified.
296) In practice, the entire array is sorted according to the comparison function.
-7.22.5.2 The qsort function
+
+
#include <stdlib.h>
void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
+ int (*compar)(const void *, const void *));
+
+
The qsort function sorts an array of nmemb objects, the initial element of which is pointed to by base. The size of each object is specified by size. -
+
The contents of the array are sorted into ascending order according to a comparison function pointed to by compar, which is called with two arguments that point to the objects being compared. The function shall return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. -
+
If two elements compare as equal, their order in the resulting sorted array is unspecified.
+
The qsort function returns no value.
-7.22.6 Integer arithmetic functions
+
+
#include <stdlib.h>
int abs(int j);
long int labs(long int j);
- long long int llabs(long long int j);
+ long long int llabs(long long int j);
+
+
The abs, labs, and llabs functions compute the absolute value of an integer j. If the result cannot be represented, the behavior is undefined.297)
+
The abs, labs, and llabs, functions return the absolute value. - +
297) The absolute value of the most negative number cannot be represented in two's complement.
-7.22.6.2 The div, ldiv, and lldiv functions
+
+
#include <stdlib.h>
div_t div(int numer, int denom);
ldiv_t ldiv(long int numer, long int denom);
- lldiv_t lldiv(long long int numer, long long int denom);
+ lldiv_t lldiv(long long int numer, long long int denom);
+
+
The div, ldiv, and lldiv, functions compute numer / denom and numer % denom in a single operation.
+
The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
lldiv_t, respectively, comprising both the quotient and the remainder. The structures
shall contain (in either order) the members quot (the quotient) and rem (the remainder),
each of which has the same type as the arguments numer and denom. If either part of
the result cannot be represented, the behavior is undefined.
-7.22.7 Multibyte/wide character conversion functions
-
+
The behavior of the multibyte character functions is affected by the LC_CTYPE category
of the current locale. For a state-dependent encoding, each function is placed into its
initial conversion state at program startup and can be returned to that state by a call for
@@ -17323,28 +18103,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character codes, but are grouped with an adjacent multibyte character.
-7.22.7.1 The mblen function
+
+
#include <stdlib.h>
- int mblen(const char *s, size_t n);
+ int mblen(const char *s, size_t n);
+
+
If s is not a null pointer, the mblen function determines the number of bytes contained in the multibyte character pointed to by s. Except that the conversion state of the mbtowc function is not affected, it is equivalent to - -
+
mbtowc((wchar_t *)0, (const char *)0, 0);
- mbtowc((wchar_t *)0, s, n);
+ mbtowc((wchar_t *)0, s, n);
+
+The implementation shall behave as if no library function calls the mblen function.
+
If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte character encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the mblen function either returns 0 (if s points to the null character), @@ -17353,16 +18135,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. multibyte character).
Forward references: the mbtowc function (7.22.7.2).
-7.22.7.2 The mbtowc function
+
+
#include <stdlib.h>
int mbtowc(wchar_t * restrict pwc,
const char * restrict s,
- size_t n);
+ size_t n);
+
+
If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with the byte pointed to by s to determine the number of bytes needed to complete the next multibyte character (including any shift sequences). If the function determines that the @@ -17370,29 +18153,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. corresponding wide character and then, if pwc is not a null pointer, stores that value in the object pointed to by pwc. If the corresponding wide character is the null wide character, the function is left in the initial conversion state. -
+
The implementation shall behave as if no library function calls the mbtowc function.
+
If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte character encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the mbtowc function either returns 0 (if s points to the null character), or returns the number of bytes that are contained in the converted multibyte character (if the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid multibyte character). -
+
In no case will the value returned be greater than n or the value of the MB_CUR_MAX
macro.
-
+
-7.22.7.3 The wctomb function
+
+
#include <stdlib.h>
- int wctomb(char *s, wchar_t wc);
+ int wctomb(char *s, wchar_t wc);
+
+
The wctomb function determines the number of bytes needed to represent the multibyte character corresponding to the wide character given by wc (including any shift sequences), and stores the multibyte character representation in the array whose first @@ -17400,46 +18184,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. are stored. If wc is a null wide character, a null byte is stored, preceded by any shift sequence needed to restore the initial shift state, and the function is left in the initial conversion state. -
+
The implementation shall behave as if no library function calls the wctomb function.
+
If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte character encodings, respectively, do or do not have state-dependent encodings. If s is not a null pointer, the wctomb function returns -1 if the value of wc does not correspond to a valid multibyte character, or returns the number of bytes that are contained in the multibyte character corresponding to the value of wc. -
+
In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
-7.22.8 Multibyte/wide string conversion functions
-
+
The behavior of the multibyte string functions is affected by the LC_CTYPE category of
the current locale.
-7.22.8.1 The mbstowcs function
+
+
#include <stdlib.h>
size_t mbstowcs(wchar_t * restrict pwcs,
const char * restrict s,
- size_t n);
+ size_t n);
+
+
The mbstowcs function converts a sequence of multibyte characters that begins in the initial shift state from the array pointed to by s into a sequence of corresponding wide characters and stores not more than n wide characters into the array pointed to by pwcs. No multibyte characters that follow a null character (which is converted into a null wide character) will be examined or converted. Each multibyte character is converted as if by a call to the mbtowc function, except that the conversion state of the mbtowc function is - + not affected. -
+
No more than n elements will be modified in the array pointed to by pwcs. If copying takes place between objects that overlap, the behavior is undefined.
+
If an invalid multibyte character is encountered, the mbstowcs function returns (size_t)(-1). Otherwise, the mbstowcs function returns the number of array elements modified, not including a terminating null wide character, if any.299) @@ -17448,48 +18233,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
299) The array will not be null-terminated if the value returned is n.
-7.22.8.2 The wcstombs function
+
+
#include <stdlib.h>
size_t wcstombs(char * restrict s,
const wchar_t * restrict pwcs,
- size_t n);
+ size_t n);
+
+
The wcstombs function converts a sequence of wide characters from the array pointed to by pwcs into a sequence of corresponding multibyte characters that begins in the initial shift state, and stores these multibyte characters into the array pointed to by s, stopping if a multibyte character would exceed the limit of n total bytes or if a null character is stored. Each wide character is converted as if by a call to the wctomb function, except that the conversion state of the wctomb function is not affected. -
+
No more than n bytes will be modified in the array pointed to by s. If copying takes place between objects that overlap, the behavior is undefined.
+
If a wide character is encountered that does not correspond to a valid multibyte character,
the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
returns the number of bytes modified, not including a terminating null character, if
- any.299)
+ any.299)
-
+
-7.23 String handling
+
+
The header <string.h> declares one type and several functions, and defines one macro useful for manipulating arrays of character type and other objects treated as arrays of character type.300) The type is size_t and the macro is NULL (both described in 7.19). Various methods are used for determining the lengths of the arrays, but in all cases a char * or void * argument points to the initial (lowest addressed) character of the array. If an array is accessed beyond the end of an object, the behavior is undefined. -
+
Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments @@ -17497,7 +18283,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. function that locates a character finds no occurrence, a function that compares two character sequences returns zero, and a function that copies characters copies zero characters. -
+
For all functions in this subclause, each character shall be interpreted as if it had the type unsigned char (and therefore every possible object representation is valid and has a different value). @@ -17506,83 +18292,87 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
300) See ''future library directions'' (7.30.11).
-7.23.2 Copying functions
+
+
#include <string.h>
void *memcpy(void * restrict s1,
const void * restrict s2,
- size_t n);
+ size_t n);
+
+
The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. If copying takes place between objects that overlap, the behavior is undefined.
+
The memcpy function returns the value of s1.
-
+
-7.23.2.2 The memmove function
+
+
#include <string.h>
- void *memmove(void *s1, const void *s2, size_t n);
+ void *memmove(void *s1, const void *s2, size_t n);
+
+
The memmove function copies n characters from the object pointed to by s2 into the object pointed to by s1. Copying takes place as if the n characters from the object pointed to by s2 are first copied into a temporary array of n characters that does not overlap the objects pointed to by s1 and s2, and then the n characters from the temporary array are copied into the object pointed to by s1.
+
The memmove function returns the value of s1.
-7.23.2.3 The strcpy function
+
+
#include <string.h>
char *strcpy(char * restrict s1,
- const char * restrict s2);
+ const char * restrict s2);
+
+
The strcpy function copies the string pointed to by s2 (including the terminating null character) into the array pointed to by s1. If copying takes place between objects that overlap, the behavior is undefined.
+
The strcpy function returns the value of s1.
-7.23.2.4 The strncpy function
+
+
#include <string.h>
char *strncpy(char * restrict s1,
const char * restrict s2,
- size_t n);
+ size_t n);
+
+
The strncpy function copies not more than n characters (characters that follow a null character are not copied) from the array pointed to by s2 to the array pointed to by - + s1.301) If copying takes place between objects that overlap, the behavior is undefined. -
+
If the array pointed to by s2 is a string that is shorter than n characters, null characters are appended to the copy in the array pointed to by s1, until n characters in all have been written.
+
The strncpy function returns the value of s1.
+
#include <string.h>
char *strcat(char * restrict s1,
- const char * restrict s2);
+ const char * restrict s2);
+
+
The strcat function appends a copy of the string pointed to by s2 (including the terminating null character) to the end of the string pointed to by s1. The initial character of s2 overwrites the null character at the end of s1. If copying takes place between objects that overlap, the behavior is undefined.
+
The strcat function returns the value of s1.
-7.23.3.2 The strncat function
+
+
#include <string.h>
char *strncat(char * restrict s1,
const char * restrict s2,
- size_t n);
+ size_t n);
+
+
The strncat function appends not more than n characters (a null character and characters that follow it are not appended) from the array pointed to by s2 to the end of the string pointed to by s1. The initial character of s2 overwrites the null character at the end of s1. A terminating null character is always appended to the result.302) If copying - + takes place between objects that overlap, the behavior is undefined.
+
The strncat function returns the value of s1.
Forward references: the strlen function (7.23.6.3).
@@ -17636,25 +18428,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
strlen(s1)+n+1.
-7.23.4 Comparison functions
-
+
The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
and strncmp is determined by the sign of the difference between the values of the first
pair of characters (both interpreted as unsigned char) that differ in the objects being
compared.
-7.23.4.1 The memcmp function
+
+
#include <string.h>
- int memcmp(const void *s1, const void *s2, size_t n);
+ int memcmp(const void *s1, const void *s2, size_t n);
+
+
The memcmp function compares the first n characters of the object pointed to by s1 to the first n characters of the object pointed to by s2.303)
+
The memcmp function returns an integer greater than, equal to, or less than zero,
accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
pointed to by s2.
@@ -17665,239 +18458,252 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
comparison.
-7.23.4.2 The strcmp function
+
+
#include <string.h>
- int strcmp(const char *s1, const char *s2);
+ int strcmp(const char *s1, const char *s2);
+
+
The strcmp function compares the string pointed to by s1 to the string pointed to by s2.
+
The strcmp function returns an integer greater than, equal to, or less than zero,
accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
-
+
pointed to by s2.
-7.23.4.3 The strcoll function
+
+
#include <string.h>
- int strcoll(const char *s1, const char *s2);
+ int strcoll(const char *s1, const char *s2);
+
+
The strcoll function compares the string pointed to by s1 to the string pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
+
The strcoll function returns an integer greater than, equal to, or less than zero,
accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
pointed to by s2 when both are interpreted as appropriate to the current locale.
-7.23.4.4 The strncmp function
+
+
#include <string.h>
- int strncmp(const char *s1, const char *s2, size_t n);
+ int strncmp(const char *s1, const char *s2, size_t n);
+
+
The strncmp function compares not more than n characters (characters that follow a null character are not compared) from the array pointed to by s1 to the array pointed to by s2.
+
The strncmp function returns an integer greater than, equal to, or less than zero,
accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
to, or less than the possibly null-terminated array pointed to by s2.
-7.23.4.5 The strxfrm function
+
+
#include <string.h>
size_t strxfrm(char * restrict s1,
const char * restrict s2,
- size_t n);
+ size_t n);
+
+
The strxfrm function transforms the string pointed to by s2 and places the resulting string into the array pointed to by s1. The transformation is such that if the strcmp function is applied to two transformed strings, it returns a value greater than, equal to, or - + less than zero, corresponding to the result of the strcoll function applied to the same two original strings. No more than n characters are placed into the resulting array pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to be a null pointer. If copying takes place between objects that overlap, the behavior is undefined.
+
The strxfrm function returns the length of the transformed string (not including the terminating null character). If the value returned is n or more, the contents of the array pointed to by s1 are indeterminate. -
+
EXAMPLE The value of the following expression is the size of the array needed to hold the transformation of the string pointed to by s.
- 1 + strxfrm(NULL, s, 0)+ 1 + strxfrm(NULL, s, 0) + -
+
#include <string.h>
- void *memchr(const void *s, int c, size_t n);
+ void *memchr(const void *s, int c, size_t n);
+
+
The memchr function locates the first occurrence of c (converted to an unsigned char) in the initial n characters (each interpreted as unsigned char) of the object pointed to by s. The implementation shall behave as if it reads the characters sequentially and stops as soon as a matching character is found.
+
The memchr function returns a pointer to the located character, or a null pointer if the
character does not occur in the object.
-7.23.5.2 The strchr function
+
+
#include <string.h>
- char *strchr(const char *s, int c);
+ char *strchr(const char *s, int c);
+
+
The strchr function locates the first occurrence of c (converted to a char) in the string pointed to by s. The terminating null character is considered to be part of the string. - +
+
The strchr function returns a pointer to the located character, or a null pointer if the
character does not occur in the string.
-7.23.5.3 The strcspn function
+
+
#include <string.h>
- size_t strcspn(const char *s1, const char *s2);
+ size_t strcspn(const char *s1, const char *s2);
+
+
The strcspn function computes the length of the maximum initial segment of the string pointed to by s1 which consists entirely of characters not from the string pointed to by s2.
+
The strcspn function returns the length of the segment.
-7.23.5.4 The strpbrk function
+
+
#include <string.h>
- char *strpbrk(const char *s1, const char *s2);
+ char *strpbrk(const char *s1, const char *s2);
+
+
The strpbrk function locates the first occurrence in the string pointed to by s1 of any character from the string pointed to by s2.
+
The strpbrk function returns a pointer to the character, or a null pointer if no character
from s2 occurs in s1.
-7.23.5.5 The strrchr function
+
+
#include <string.h>
- char *strrchr(const char *s, int c);
+ char *strrchr(const char *s, int c);
+
+
The strrchr function locates the last occurrence of c (converted to a char) in the string pointed to by s. The terminating null character is considered to be part of the string. - +
+
The strrchr function returns a pointer to the character, or a null pointer if c does not
occur in the string.
-7.23.5.6 The strspn function
+
+
#include <string.h>
- size_t strspn(const char *s1, const char *s2);
+ size_t strspn(const char *s1, const char *s2);
+
+
The strspn function computes the length of the maximum initial segment of the string pointed to by s1 which consists entirely of characters from the string pointed to by s2.
+
The strspn function returns the length of the segment.
-7.23.5.7 The strstr function
+
+
#include <string.h>
- char *strstr(const char *s1, const char *s2);
+ char *strstr(const char *s1, const char *s2);
+
+
The strstr function locates the first occurrence in the string pointed to by s1 of the sequence of characters (excluding the terminating null character) in the string pointed to by s2.
+
The strstr function returns a pointer to the located string, or a null pointer if the string
is not found. If s2 points to a string with zero length, the function returns s1.
-7.23.5.8 The strtok function
+
+
#include <string.h>
char *strtok(char * restrict s1,
- const char * restrict s2);
+ const char * restrict s2);
+
+
A sequence of calls to the strtok function breaks the string pointed to by s1 into a sequence of tokens, each of which is delimited by a character from the string pointed to by s2. The first call in the sequence has a non-null first argument; subsequent calls in the sequence have a null first argument. The separator string pointed to by s2 may be different from call to call. - -
+ +
The first call in the sequence searches the string pointed to by s1 for the first character that is not contained in the current separator string pointed to by s2. If no such character is found, then there are no tokens in the string pointed to by s1 and the strtok function returns a null pointer. If such a character is found, it is the start of the first token. -
+
The strtok function then searches from there for a character that is contained in the current separator string. If no such character is found, the current token extends to the end of the string pointed to by s1, and subsequent searches for a token will return a null pointer. If such a character is found, it is overwritten by a null character, which terminates the current token. The strtok function saves a pointer to the following character, from which the next search for a token will start. -
+
Each subsequent call, with a null pointer as the value of the first argument, starts searching from the saved pointer and behaves as described above. -
+
The strtok function is not required to avoid data races. The implementation shall behave as if no library function calls the strtok function.
+
The strtok function returns a pointer to the first character of a token, or a null pointer if there is no token. -
+
EXAMPLE
#include <string.h>
@@ -17906,66 +18712,70 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
t = strtok(str, "?"); // t points to the token "a"
t = strtok(NULL, ","); // t points to the token "??b"
t = strtok(NULL, "#,"); // t points to the token "c"
- t = strtok(NULL, "?"); // t is a null pointer
+ t = strtok(NULL, "?"); // t is a null pointer
+
-+
#include <string.h>
- void *memset(void *s, int c, size_t n);
+ void *memset(void *s, int c, size_t n);
+
+
The memset function copies the value of c (converted to an unsigned char) into each of the first n characters of the object pointed to by s.
+
The memset function returns the value of s.
-
+
-7.23.6.2 The strerror function
+
+
#include <string.h>
- char *strerror(int errnum);
+ char *strerror(int errnum);
+
+
The strerror function maps the number in errnum to a message string. Typically, the values for errnum come from errno, but strerror shall map any value of type int to a message. -
+
The strerror function is not required to avoid data races. The implementation shall behave as if no library function calls the strerror function.
+
The strerror function returns a pointer to the string, the contents of which are locale-
specific. The array pointed to shall not be modified by the program, but may be
overwritten by a subsequent call to the strerror function.
-7.23.6.3 The strlen function
+
+
#include <string.h>
- size_t strlen(const char *s);
+ size_t strlen(const char *s);
+
+
The strlen function computes the length of the string pointed to by s.
+
The strlen function returns the number of characters that precede the terminating null
character.
-
+
-7.24 Type-generic math
-
+
The header <tgmath.h> includes the headers <math.h> and <complex.h> and defines several type-generic macros. -
+
Of the <math.h> and <complex.h> functions without an f (float) or l (long double) suffix, several have one or more parameters whose corresponding real type is double. For each such function, except modf, there is a corresponding type-generic @@ -17973,7 +18783,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. synopsis are generic parameters. Use of the macro invokes a function whose corresponding real type and type domain are determined by the arguments for the generic parameters.305) -
+
Use of the macro invokes a function whose generic parameters have the corresponding real type determined as follows:
+
For each unsuffixed function in <math.h> for which there is a function in <complex.h> with the same name except for a c prefix, the corresponding type- generic macro (for both functions) has the same name as the function in <math.h>. The @@ -17992,7 +18802,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
<math.h> <complex.h> type-generic
function function macro
@@ -18012,10 +18822,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
log clog log
pow cpow pow
sqrt csqrt sqrt
- fabs cabs fabs
+ fabs cabs fabs
+
If at least one argument for a generic parameter is complex, then use of the macro invokes
a complex function; otherwise, use of the macro invokes a real function.
-+
For each unsuffixed function in <math.h> without a c-prefixed counterpart in <complex.h> (except modf), the corresponding type-generic macro has the same name as the function. These type-generic macros are: @@ -18029,19 +18840,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. exp2 ilogb lround tgamma expm1 ldexp nearbyint trunc fdim lgamma nextafter - floor llrint nexttoward + floor llrint nexttoward + If all arguments for generic parameters are real, then use of the macro invokes a real function; otherwise, use of the macro results in undefined behavior. - -
+ +
For each unsuffixed function in <complex.h> that is not a c-prefixed counterpart to a function in <math.h>, the corresponding type-generic macro has the same name as the function. These type-generic macros are:
carg conj creal
- cimag cproj
+ cimag cproj
+
Use of the macro with any real or complex argument invokes a complex function.
-+
EXAMPLE With the declarations
#include <tgmath.h>
@@ -18051,9 +18864,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
long double ld;
float complex fc;
double complex dc;
- long double complex ldc;
+ long double complex ldc;
+
functions invoked by use of type-generic macros are shown in the following table:
-
+
macro use invokes
exp(n) exp(n), the function
@@ -18076,7 +18890,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
cimag(ld) cimagl(ld)
fabs(fc) cabsf(fc)
carg(dc) carg(dc), the function
- cproj(ldc) cprojl(ldc)
+ cproj(ldc) cprojl(ldc)
+
304) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
@@ -18086,192 +18901,218 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the behavior is undefined.
-7.25 Threads
+
+
The header <threads.h> defines macros, and declares types, enumeration constants, and functions that support multiple threads of execution. -
+
Implementations that define the macro __STDC_NO_THREADS__ need not provide this header nor support any of its facilities. -
+
The macros are
- ONCE_FLAG_INIT+ ONCE_FLAG_INIT + which expands to a value that can be used to initialize an object of type once_flag; and
- TSS_DTOR_ITERATIONS+ TSS_DTOR_ITERATIONS + which expands to an integer constant expression representing the maximum number of times that destructors will be called when a thread terminates. -
+
The types are
- cnd_t+ cnd_t + which is a complete object type that holds an identifier for a condition variable;
- thrd_t+ thrd_t + which is a complete object type that holds an identifier for a thread;
- tss_t+ tss_t + which is a complete object type that holds an identifier for a thread-specific storage pointer;
- mtx_t+ mtx_t + which is a complete object type that holds an identifier for a mutex;
- tss_dtor_t+ tss_dtor_t + which is the function pointer type void (*)(void*), used for a destructor for a thread-specific storage pointer;
- thrd_start_t+ thrd_start_t + which is the function pointer type int (*)(void*) that is passed to thrd_create to create a new thread;
- once_flag+ once_flag + which is a complete object type that holds a flag for use by call_once; and - +
- xtime+ xtime + which is a structure type that holds a time specified in seconds and nanoseconds. The structure shall contain at least the following members, in any order. -
time_t sec;
- long nsec;
+ long nsec;
+
+The enumeration constants are
- mtx_plain+ mtx_plain + which is passed to mtx_init to create a mutex object that supports neither timeout nor test and return;
- mtx_recursive+ mtx_recursive + which is passed to mtx_init to create a mutex object that supports recursive locking;
- mtx_timed+ mtx_timed + which is passed to mtx_init to create a mutex object that supports timeout;
- mtx_try+ mtx_try + which is passed to mtx_init to create a mutex object that supports test and return;
- thrd_timeout+ thrd_timeout + which is returned by a timed wait function to indicate that the time specified in the call was reached without acquiring the requested resource;
- thrd_success+ thrd_success + which is returned by a function to indicate that the requested operation succeeded;
- thrd_busy+ thrd_busy + which is returned by a function to indicate that the requested operation failed because a resource requested by a test and return function is already in use;
- thrd_error+ thrd_error + which is returned by a function to indicate that the requested operation failed; and
- thrd_nomem+ thrd_nomem + which is returned by a function to indicate that the requested operation failed because it was unable to allocate memory. - + -
+
#include <threads.h>
- void call_once(once_flag *flag, void (*func)(void));
+ void call_once(once_flag *flag, void (*func)(void));
+
+
The call_once function uses the once_flag pointed to by flag to ensure that func is called exactly once, the first time the call_once function is called with that value of flag. Completion of an effective call to the call_once function synchronizes with all subsequent calls to the call_once function with the same value of flag.
+
The call_once function returns no value.
-7.25.3 Condition variable functions
+
+
#include <threads.h>
- int cnd_broadcast(cnd_t *cond);
+ int cnd_broadcast(cnd_t *cond);
+
+
The cnd_broadcast function unblocks all of the threads that are blocked on the condition variable pointed to by cond at the time of the call. If no threads are blocked on the condition variable pointed to by cond at the time of the call, the function does nothing.
+
The cnd_broadcast function returns thrd_success on success, or thrd_error
if the request could not be honored.
-7.25.3.2 The cnd_destroy function
+
+
#include <threads.h>
- void cnd_destroy(cnd_t *cond);
+ void cnd_destroy(cnd_t *cond);
+
+
The cnd_destroy function releases all resources used by the condition variable pointed to by cond. The cnd_destroy function requires that no threads be blocked waiting for the condition variable pointed to by cond. - +
+
The cnd_destroy function returns no value.
-7.25.3.3 The cnd_init function
+
+
#include <threads.h>
- int cnd_init(cnd_t *cond);
+ int cnd_init(cnd_t *cond);
+
+
The cnd_init function creates a condition variable. If it succeeds it sets the variable pointed to by cond to a value that uniquely identifies the newly created condition variable. A thread that calls cnd_wait on a newly created condition variable will block.
+
The cnd_init function returns thrd_success on success, or thrd_nomem if no
memory could be allocated for the newly created condition, or thrd_error if the
request could not be honored.
-7.25.3.4 The cnd_signal function
+
+
#include <threads.h>
- int cnd_signal(cnd_t *cond);
+ int cnd_signal(cnd_t *cond);
+
+
The cnd_signal function unblocks one of the threads that are blocked on the condition variable pointed to by cond at the time of the call. If no threads are blocked on the condition variable at the time of the call, the function does nothing and return success.
+
The cnd_signal function returns thrd_success on success or thrd_error if
the request could not be honored.
-7.25.3.5 The cnd_timedwait function
+
- +
+
#include <threads.h>
int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
+ const xtime *xt);
+
+
The cnd_timedwait function atomically unlocks the mutex pointed to by mtx and endeavors to block until the condition variable pointed to by cond is signaled by a call to cnd_signal or to cnd_broadcast, or until after the time specified by the xtime @@ -18279,19 +19120,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pointed to by mtx before it returns. The cnd_timedwait function requires that the mutex pointed to by mtx be locked by the calling thread.
+
The cnd_timedwait function returns thrd_success upon success, or
thrd_timeout if the time specified in the call was reached without acquiring the
requested resource, or thrd_error if the request could not be honored.
-7.25.3.6 The cnd_wait function
+
+
#include <threads.h>
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
+ int cnd_wait(cnd_t *cond, mtx_t *mtx);
+
+
The cnd_wait function atomically unlocks the mutex pointed to by mtx and endeavors to block until the condition variable pointed to by cond is signaled by a call to cnd_signal or to cnd_broadcast. When the calling thread becomes unblocked it @@ -18299,35 +19141,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. not locked by the calling thread, the cnd_wait function will act as if the abort function is called.
+
The cnd_wait function returns thrd_success on success or thrd_error if the
request could not be honored.
-7.25.4 Mutex functions
+
+
#include <threads.h>
- void mtx_destroy(mtx_t *mtx);
+ void mtx_destroy(mtx_t *mtx);
+
+
The mtx_destroy function releases any resources used by the mutex pointed to by mtx. No threads can be blocked waiting for the mutex pointed to by mtx. - +
+
The mtx_destroy function returns no value.
-7.25.4.2 The mtx_init function
+
+
#include <threads.h>
- int mtx_init(mtx_t *mtx, int type);
+ int mtx_init(mtx_t *mtx, int type);
+
+
The mtx_init function creates a mutex object with properties indicated by type, which must have one of the six values: mtx_plain for a simple non-recursive mutex, @@ -18336,96 +19180,101 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. mtx_plain | mtx_recursive for a simple recursive mutex, mtx_timed | mtx_recursive for a recursive mutex that supports timeout, or mtx_try | mtx_recursive for a recursive mutex that supports test and return. -
+
If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that uniquely identifies the newly created mutex.
+
The mtx_init function returns thrd_success on success, or thrd_error if the
request could not be honored.
-7.25.4.3 The mtx_lock function
+
+
#include <threads.h>
- int mtx_lock(mtx_t *mtx);
+ int mtx_lock(mtx_t *mtx);
+
+
The mtx_lock function blocks until it locks the mutex pointed to by mtx. If the mutex is non-recursive, it shall not be locked by the calling thread. Prior calls to mtx_unlock on the same mutex shall synchronize with this operation.
+
The mtx_lock function returns thrd_success on success, or thrd_busy if the
resource requested is already in use, or thrd_error if the request could not be
honored.
-
+
-7.25.4.4 The mtx_timedlock function
+
+
#include <threads.h>
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
+ int mtx_timedlock(mtx_t *mtx, const xtime *xt);
+
+
The mtx_timedlock function endeavors to block until it locks the mutex pointed to by mtx or until the time specified by the xtime object xt has passed. The specified mutex shall support timeout. If the operation succeeds, prior calls to mtx_unlock on the same mutex shall synchronize with this operation.
+
The mtx_timedlock function returns thrd_success on success, or thrd_busy
if the resource requested is already in use, or thrd_timeout if the time specified was
reached without acquiring the requested resource, or thrd_error if the request could
not be honored.
-7.25.4.5 The mtx_trylock function
+
+
#include <threads.h>
- int mtx_trylock(mtx_t *mtx);
+ int mtx_trylock(mtx_t *mtx);
+
+
The mtx_trylock function endeavors to lock the mutex pointed to by mtx. The specified mutex shall support either test and return or timeout. If the mutex is already locked, the function returns without blocking. If the operation succeeds, prior calls to mtx_unlock on the same mutex shall synchronize with this operation.
+
The mtx_trylock function returns thrd_success on success, or thrd_busy if
the resource requested is already in use, or thrd_error if the request could not be
honored.
-7.25.4.6 The mtx_unlock function
+
+
#include <threads.h>
- int mtx_unlock(mtx_t *mtx);
+ int mtx_unlock(mtx_t *mtx);
+
+
The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to by mtx shall be locked by the calling thread. - +
+
The mtx_unlock function returns thrd_success on success or thrd_error if
the request could not be honored.
-7.25.5 Thread functions
+
+
#include <threads.h>
int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
+ void *arg);
+
+
The thrd_create function creates a new thread executing func(arg). If the thrd_create function succeeds, it sets the object pointed to by thr to the identifier of the newly created thread. (A thread's identifier may be reused for a different thread once @@ -18433,237 +19282,253 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. completion of the thrd_create function synchronizes with the beginning of the execution of the new thread.
+
The thrd_create function returns thrd_success on success, or thrd_nomem if
no memory could be allocated for the thread requested, or thrd_error if the request
could not be honored.
-7.25.5.2 The thrd_current function
+
+
#include <threads.h>
- thrd_t thrd_current(void);
+ thrd_t thrd_current(void);
+
+
The thrd_current function identifies the thread that called it.
+
The thrd_current function returns the identifier of the thread that called it.
-7.25.5.3 The thrd_detach function
+
- +
+
#include <threads.h>
- int thrd_detach(thrd_t thr);
+ int thrd_detach(thrd_t thr);
+
+
The thrd_detach function tells the operating system to dispose of any resources allocated to the thread identified by thr when that thread terminates. The thread identified by thr shall not have been previously detached or joined with another thread.
+
The thrd_detach function returns thrd_success on success or thrd_error if
the request could not be honored.
-7.25.5.4 The thrd_equal function
+
+
#include <threads.h>
- int thrd_equal(thrd_t thr0, thrd_t thr1);
+ int thrd_equal(thrd_t thr0, thrd_t thr1);
+
+
The thrd_equal function will determine whether the thread identified by thr0 refers to the thread identified by thr1.
+
The thrd_equal function returns zero if the thread thr0 and the thread thr1 refer to
different threads. Otherwise the thrd_equal function returns a nonzero value.
-7.25.5.5 The thrd_exit function
+
+
#include <threads.h>
- void thrd_exit(int res);
+ void thrd_exit(int res);
+
+
The thrd_exit function terminates execution of the calling thread and sets its result code to res.
+
The thrd_exit function returns no value.
-7.25.5.6 The thrd_join function
+
+
#include <threads.h>
- int thrd_join(thrd_t thr, int *res);
+ int thrd_join(thrd_t thr, int *res);
+
+
The thrd_join function joins the thread identified by thr with the current thread by blocking until the other thread has terminated. If the parameter res is not a null pointer, - + it stores the thread's result code in the integer pointed to by res. The termination of the other thread synchronizes with the completion of the thrd_join function. The thread identified by thr shall not have been previously detached or joined with another thread.
+
The thrd_join function returns thrd_success on success or thrd_error if the
request could not be honored.
-7.25.5.7 The thrd_sleep function
+
+
#include <threads.h>
- void thrd_sleep(const xtime *xt);
+ void thrd_sleep(const xtime *xt);
+
+
The thrd_sleep function suspends execution of the calling thread until after the time specified by the xtime object pointed to by xt.
+
The thrd_sleep function returns no value.
-7.25.5.8 The thrd_yield function
+
+
#include <threads.h>
- void thrd_yield(void);
+ void thrd_yield(void);
+
+
The thrd_yield function endeavors to permit other threads to run, even if the current thread would ordinarily continue to run.
+
The thrd_yield function returns no value.
-7.25.6 Thread-specific storage functions
+
+
#include <threads.h>
- int tss_create(tss_t *key, tss_dtor_t dtor);
+ int tss_create(tss_t *key, tss_dtor_t dtor);
+
+
The tss_create function creates a thread-specific storage pointer with destructor dtor, which may be null. - +
+
If the tss_create function is successful, it sets the thread-specific storage pointed to
by key to a value that uniquely identifies the newly created pointer and returns
thrd_success; otherwise, thrd_error is returned and the thread-specific storage
pointed to by key is set to an undefined value.
-7.25.6.2 The tss_delete function
+
+
#include <threads.h>
- void tss_delete(tss_t key);
+ void tss_delete(tss_t key);
+
+
The tss_delete function releases any resources used by the thread-specific storage identified by key.
+
The tss_delete function returns no value.
-7.25.6.3 The tss_get function
+
+
#include <threads.h>
- void *tss_get(tss_t key);
+ void *tss_get(tss_t key);
+
+
The tss_get function returns the value for the current thread held in the thread-specific storage identified by key.
+
The tss_get function returns the value for the current thread if successful, or zero if
unsuccessful.
-7.25.6.4 The tss_set function
+
+
#include <threads.h>
- int tss_set(tss_t key, void *val);
+ int tss_set(tss_t key, void *val);
+
+
The tss_set function sets the value for the current thread held in the thread-specific storage identified by key to val. - +
+
The tss_set function returns thrd_success on success or thrd_error if the
request could not be honored.
-7.25.7 Time functions
+
+
#include <threads.h>
- int xtime_get(xtime *xt, int base);
+ int xtime_get(xtime *xt, int base);
+
+
The xtime_get function sets the xtime object pointed to by xt to hold the current time based on the time base base.
+
If the xtime_get function is successful it returns the nonzero value base, which must be TIME_UTC; otherwise, it returns zero.306) - +
306) Although an xtime object describes times with nanosecond resolution, the actual resolution in an
xtime object is system dependent.
-7.26 Date and time
+
+
The header <time.h> defines two macros, and declares several types and functions for manipulating time. Many functions deal with a calendar time that represents the current date (according to the Gregorian calendar) and time. Some functions deal with local time, which is the calendar time expressed for some specific time zone, and with Daylight Saving Time, which is a temporary change in the algorithm for determining local time. The local time zone and Daylight Saving Time are implementation-defined. -
+
The macros defined are NULL (described in 7.19); and
- CLOCKS_PER_SEC+ CLOCKS_PER_SEC + which expands to an expression with type clock_t (described below) that is the number per second of the value returned by the clock function. -
+
The types declared are size_t (described in 7.19);
- clock_t+ clock_t + and
- time_t+ time_t + which are arithmetic types capable of representing times; and
- struct tm+ struct tm + which holds the components of a calendar time, called the broken-down time. -
+
The range and precision of times representable in clock_t and time_t are implementation-defined. The tm structure shall contain at least the following members, in any order. The semantics of the members and their normal ranges are expressed in the @@ -18677,11 +19542,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. int tm_year; // years since 1900 int tm_wday; // days since Sunday -- [0, 6] int tm_yday; // days since January 1 -- [0, 365] - int tm_isdst; // Daylight Saving Time flag + int tm_isdst; // Daylight Saving Time flag + - + The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight Saving Time is not in effect, and negative if the information is not available. @@ -18689,19 +19555,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
307) The range [0, 60] for tm_sec allows for a positive leap second.
-7.26.2 Time manipulation functions
+
+
#include <time.h>
- clock_t clock(void);
+ clock_t clock(void);
+
+
The clock function determines the processor time used.
+
The clock function returns the implementation's best approximation to the processor
time used by the program since the beginning of an implementation-defined era related
only to the program invocation. To determine the time in seconds, the value returned by
@@ -18714,33 +19581,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the program and its return value subtracted from the value returned by subsequent calls.
-7.26.2.2 The difftime function
+
+
#include <time.h>
- double difftime(time_t time1, time_t time0);
+ double difftime(time_t time1, time_t time0);
+
+
The difftime function computes the difference between two calendar times: time1 - time0.
+
The difftime function returns the difference expressed in seconds as a double.
-
+
-7.26.2.3 The mktime function
+
+
#include <time.h>
- time_t mktime(struct tm *timeptr);
+ time_t mktime(struct tm *timeptr);
+
+
The mktime function converts the broken-down time, expressed as local time, in the structure pointed to by timeptr into a calendar time value with the same encoding as that of the values returned by the time function. The original values of the tm_wday @@ -18751,11 +19620,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. time, but with their values forced to the ranges indicated above; the final value of tm_mday is not set until tm_mon and tm_year are determined.
+
The mktime function returns the specified calendar time encoded as a value of type time_t. If the calendar time cannot be represented, the function returns the value (time_t)(-1). -
+
EXAMPLE What day of the week is July 4, 2001?
#include <stdio.h>
@@ -18765,12 +19634,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
"Thursday", "Friday", "Saturday", "-unknown-"
};
struct tm time_str;
- /* ... */
+ /* ... */
+
-
+
time_str.tm_year = 2001 - 1900;
time_str.tm_mon = 7 - 1;
@@ -18781,7 +19651,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
time_str.tm_isdst = -1;
if (mktime(&time_str) == (time_t)(-1))
time_str.tm_wday = 7;
- printf("%s\n", wday[time_str.tm_wday]);
+ printf("%s\n", wday[time_str.tm_wday]);
+
+
#include <time.h>
- time_t time(time_t *timer);
+ time_t time(time_t *timer);
+
+
The time function determines the current calendar time. The encoding of the value is unspecified.
+
The time function returns the implementation's best approximation to the current
calendar time. The value (time_t)(-1) is returned if the calendar time is not
available. If timer is not a null pointer, the return value is also assigned to the object it
points to.
-7.26.3 Time conversion functions
-
+
Except for the strftime function, these functions each return a pointer to one of two
types of static objects: a broken-down time structure or an array of char. Execution of
any of the functions that return a pointer to one of these object types may overwrite the
@@ -18816,19 +19688,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
previous call to any of them and the functions are not required to avoid data races. The
implementation shall behave as if no other library functions call these functions.
-7.26.3.1 The asctime function
+
+
#include <time.h>
- char *asctime(const struct tm *timeptr);
+ char *asctime(const struct tm *timeptr);
+
+
The asctime function converts the broken-down time in the structure pointed to by timeptr into a string in the form - +
- Sun Sep 16 01:03:52 1973\n\0+ Sun Sep 16 01:03:52 1973\n\0 + using the equivalent of the following algorithm. char *asctime(const struct tm *timeptr) { @@ -18847,85 +19721,91 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. timeptr->tm_mday, timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec, 1900 + timeptr->tm_year); - return result; + return result; + } -
+
If any of the fields of the broken-down time contain values that are outside their normal ranges,310) the behavior of the asctime function is undefined. Likewise, if the calculated year exceeds four digits or is less than the year 1000, the behavior is undefined.
+
The asctime function returns a pointer to the string.
310) See 7.26.1.
-7.26.3.2 The ctime function
+
+
#include <time.h>
- char *ctime(const time_t *timer);
+ char *ctime(const time_t *timer);
+
+
The ctime function converts the calendar time pointed to by timer to local time in the form of a string. It is equivalent to
- asctime(localtime(timer))+ asctime(localtime(timer)) + - +
+
The ctime function returns the pointer returned by the asctime function with that broken-down time as argument.
Forward references: the localtime function (7.26.3.4).
-7.26.3.3 The gmtime function
+
+
#include <time.h>
- struct tm *gmtime(const time_t *timer);
+ struct tm *gmtime(const time_t *timer);
+
+
The gmtime function converts the calendar time pointed to by timer into a broken- down time, expressed as UTC.
+
The gmtime function returns a pointer to the broken-down time, or a null pointer if the
specified time cannot be converted to UTC.
-7.26.3.4 The localtime function
+
+
#include <time.h>
- struct tm *localtime(const time_t *timer);
+ struct tm *localtime(const time_t *timer);
+
+
The localtime function converts the calendar time pointed to by timer into a broken-down time, expressed as local time.
+
The localtime function returns a pointer to the broken-down time, or a null pointer if
the specified time cannot be converted to local time.
-7.26.3.5 The strftime function
+
- +
+
#include <time.h>
size_t strftime(char * restrict s,
size_t maxsize,
const char * restrict format,
- const struct tm * restrict timeptr);
+ const struct tm * restrict timeptr);
+
+
The strftime function places characters into the array pointed to by s as controlled by the string pointed to by format. The format shall be a multibyte character sequence, beginning and ending in its initial shift state. The format string consists of zero or @@ -18935,7 +19815,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. All ordinary multibyte characters (including the terminating null character) are copied unchanged into the array. If copying takes place between objects that overlap, the behavior is undefined. No more than maxsize characters are placed into the array. -
+
Each conversion specifier is replaced by appropriate characters as described in the following list. The appropriate characters are determined using the LC_TIME category of the current locale and by the values of zero or more members of the broken-down time @@ -18947,24 +19827,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %B is replaced by the locale's full month name. [tm_mon] %c is replaced by the locale's appropriate date and time representation. [all specified
- in 7.26.1]+ in 7.26.1] + %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
- number (00-99). [tm_year]+ number (00-99). [tm_year] + %d is replaced by the day of the month as a decimal number (01-31). [tm_mday] %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year] %e is replaced by the day of the month as a decimal number (1-31); a single digit is
- preceded by a space. [tm_mday]+ preceded by a space. [tm_mday] + %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
- tm_mday]+ tm_mday] + %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
- number (00-99). [tm_year, tm_wday, tm_yday]+ number (00-99). [tm_year, tm_wday, tm_yday] + %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
- [tm_year, tm_wday, tm_yday]+ [tm_year, tm_wday, tm_yday] + %h is equivalent to ''%b''. [tm_mon] %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour] %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour] @@ -18972,94 +19858,115 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %m is replaced by the month as a decimal number (01-12). [tm_mon] %M is replaced by the minute as a decimal number (00-59). [tm_min] %n is replaced by a new-line character. - + %p is replaced by the locale's equivalent of the AM/PM designations associated with a
- 12-hour clock. [tm_hour]+ 12-hour clock. [tm_hour] + %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec] %R is equivalent to ''%H:%M''. [tm_hour, tm_min] %S is replaced by the second as a decimal number (00-60). [tm_sec] %t is replaced by a horizontal-tab character. %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
- tm_sec]+ tm_sec] + %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
- is 1. [tm_wday]+ is 1. [tm_wday] + %U is replaced by the week number of the year (the first Sunday as the first day of week
- 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]+ 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday] + %V is replaced by the ISO 8601 week number (see below) as a decimal number
- (01-53). [tm_year, tm_wday, tm_yday]+ (01-53). [tm_year, tm_wday, tm_yday] + %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
- [tm_wday]+ [tm_wday] + %W is replaced by the week number of the year (the first Monday as the first day of
- week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]+ week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday] + %x is replaced by the locale's appropriate date representation. [all specified in 7.26.1] %X is replaced by the locale's appropriate time representation. [all specified in 7.26.1] %y is replaced by the last 2 digits of the year as a decimal number (00-99).
- [tm_year]+ [tm_year] + %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year] %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
- zone is determinable. [tm_isdst]
+ zone is determinable. [tm_isdst]
+
%Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
- time zone is determinable. [tm_isdst]+ time zone is determinable. [tm_isdst] + %% is replaced by %. -
+
Some conversion specifiers can be modified by the inclusion of an E or O modifier character to indicate an alternative format or specification. If the alternative format or specification does not exist for the current locale, the modifier is ignored. %Ec is replaced by the locale's alternative date and time representation. %EC is replaced by the name of the base year (period) in the locale's alternative
- representation.+ representation. + %Ex is replaced by the locale's alternative date representation. %EX is replaced by the locale's alternative time representation. %Ey is replaced by the offset from %EC (year only) in the locale's alternative
- representation.+ representation. + %EY is replaced by the locale's full alternative year representation. - + %Od is replaced by the day of the month, using the locale's alternative numeric symbols
(filled as needed with leading zeros, or with leading spaces if there is no alternative
- symbol for zero).
+ symbol for zero).
+
%Oe is replaced by the day of the month, using the locale's alternative numeric symbols
- (filled as needed with leading spaces).+ (filled as needed with leading spaces). + %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
- symbols.+ symbols. + %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
- symbols.+ symbols. + %Om is replaced by the month, using the locale's alternative numeric symbols. %OM is replaced by the minutes, using the locale's alternative numeric symbols. %OS is replaced by the seconds, using the locale's alternative numeric symbols. %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
- representation, where Monday is 1.+ representation, where Monday is 1. + %OU is replaced by the week number, using the locale's alternative numeric symbols. %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
- symbols.+ symbols. + %Ow is replaced by the weekday as a number, using the locale's alternative numeric
- symbols.+ symbols. + %OW is replaced by the week number of the year, using the locale's alternative numeric
- symbols.+ symbols. + %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric -
- symbols.+ symbols. + +
%g, %G, and %V give values according to the ISO 8601 week-based year. In this system, weeks begin on a Monday and week 1 of the year is the week that includes January 4th, which is also the week that includes the first Thursday of the year, and is also the first @@ -19069,9 +19976,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and %V is replaced by 01. -
+
If a conversion specifier is not one of the above, the behavior is undefined. -
+
In the "C" locale, the E and O modifiers are ignored and the replacement strings for the following specifiers are: %a the first three characters of %A. @@ -19079,38 +19986,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %b the first three characters of %B. %B one of ''January'', ''February'', ... , ''December''. %c equivalent to ''%a %b %e %T %Y''. - + %p one of ''AM'' or ''PM''. %r equivalent to ''%I:%M:%S %p''. %x equivalent to ''%m/%d/%y''. %X equivalent to %T. %Z implementation-defined.
+
If the total number of resulting characters including the terminating null character is not
more than maxsize, the strftime function returns the number of characters placed
into the array pointed to by s not including the terminating null character. Otherwise,
zero is returned and the contents of the array are indeterminate.
-
+
-7.27 Unicode utilities
-
+
The header <uchar.h> declares types and functions for manipulating Unicode characters. -
+
The types declared are mbstate_t (described in 7.29.1) and size_t (described in 7.19);
- char16_t+ char16_t + which is an unsigned integer type used for 16-bit characters and is the same type as uint_least16_t (described in 7.20.1.2); and
- char32_t+ char32_t + which is an unsigned integer type used for 32-bit characters and is the same type as uint_least32_t (also described in 7.20.1.2). -
+
These functions have a parameter, ps, of type pointer to mbstate_t that points to an
object that can completely describe the current conversion state of the associated
multibyte character sequence, which the functions alter as necessary. If ps is a null
@@ -19119,105 +20028,116 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
to avoid data races in this case. The implementation behaves as if no library function
calls these functions with a null pointer for ps.
-7.27.1.1 The mbrtoc16 function
+
+
#include <uchar.h>
size_t mbrtoc16(char16_t * restrict pc16,
const char * restrict s, size_t n,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the mbrtoc16 function is equivalent to the call:
- mbrtoc16(NULL, "", 1, ps)+ mbrtoc16(NULL, "", 1, ps) + In this case, the values of the parameters pc16 and n are ignored. -
+
If s is not a null pointer, the mbrtoc16 function inspects at most n bytes beginning with the byte pointed to by s to determine the number of bytes needed to complete the next multibyte character (including any shift sequences). If the function determines that the next multibyte character is complete and valid, it determines the values of the corresponding wide characters and then, if pc16 is not a null pointer, stores the value of the first (or only) such character in the object pointed to by pc16. Subsequent calls will - + store successive wide characters without consuming any additional input until all the characters have been stored. If the corresponding wide character is the null wide character, the resulting state described is the initial conversion state.
+
The mbrtoc16 function returns the first of the following that applies (given the current conversion state): 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).+ corresponds to the null wide character (which is the value stored). + between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
+ of bytes that complete the multibyte character.
+
(size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).+ bytes from the input have been consumed by this call). + (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
multibyte character, and all n bytes have been processed (no value is
- stored).311)
+ stored).311)
+
(size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
do not contribute to a complete and valid multibyte character (no
value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
+ and the conversion state is unspecified.
+
311) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
sequence of redundant shift sequences (for implementations with state-dependent encodings).
-7.27.1.2 The c16rtomb function
+
+
#include <uchar.h>
size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the c16rtomb function is equivalent to the call
- c16rtomb(buf, L'\0', ps)+ c16rtomb(buf, L'\0', ps) + where buf is an internal buffer. -
+
If s is not a null pointer, the c16rtomb function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by c16 (including any shift sequences), and stores the multibyte character representation in the - + array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If c16 is a null wide character, a null byte is stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state described is the initial conversion state.
+
The c16rtomb function returns the number of bytes stored in the array object (including
any shift sequences). When c16 is not a valid wide character, an encoding error occurs:
the function stores the value of the macro EILSEQ in errno and returns
(size_t)(-1); the conversion state is unspecified.
-7.27.1.3 The mbrtoc32 function
+
+
#include <uchar.h>
size_t mbrtoc32(char32_t * restrict pc32,
const char * restrict s, size_t n,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the mbrtoc32 function is equivalent to the call:
- mbrtoc32(NULL, "", 1, ps)+ mbrtoc32(NULL, "", 1, ps) + In this case, the values of the parameters pc32 and n are ignored. -
+
If s is not a null pointer, the mbrtoc32 function inspects at most n bytes beginning with the byte pointed to by s to determine the number of bytes needed to complete the next multibyte character (including any shift sequences). If the function determines that the @@ -19228,49 +20148,56 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. characters have been stored. If the corresponding wide character is the null wide character, the resulting state described is the initial conversion state.
+
The mbrtoc32 function returns the first of the following that applies (given the current conversion state): 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).+ corresponds to the null wide character (which is the value stored). + between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte - +
character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
+ of bytes that complete the multibyte character.
+
(size_t)(-3) if the next character resulting from a previous call has been stored (no
- bytes from the input have been consumed by this call).+ bytes from the input have been consumed by this call). + (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
multibyte character, and all n bytes have been processed (no value is
- stored).312)
+ stored).312)
+
(size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
do not contribute to a complete and valid multibyte character (no
value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
+ and the conversion state is unspecified.
+
312) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
sequence of redundant shift sequences (for implementations with state-dependent encodings).
-7.27.1.4 The c32rtomb function
+
+
#include <uchar.h>
size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the c32rtomb function is equivalent to the call
- c32rtomb(buf, L'\0', ps)+ c32rtomb(buf, L'\0', ps) + where buf is an internal buffer. -
+
If s is not a null pointer, the c32rtomb function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by c32 (including any shift sequences), and stores the multibyte character representation in the @@ -19278,7 +20205,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. c32 is a null wide character, a null byte is stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state described is the initial conversion state.
+
The c32rtomb function returns the number of bytes stored in the array object (including
any shift sequences). When c32 is not a valid wide character, an encoding error occurs:
the function stores the value of the macro EILSEQ in errno and returns
@@ -19287,41 +20214,45 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-7.28 Extended multibyte and wide character utilities
+
+
The header <wchar.h> defines four macros, and declares four data types, one tag, and many functions.313) -
+
The types declared are wchar_t and size_t (both described in 7.19);
- mbstate_t+ mbstate_t + which is a complete object type other than an array type that can hold the conversion state information necessary to convert between sequences of multibyte characters and wide characters;
- wint_t+ wint_t + which is an integer type unchanged by default argument promotions that can hold any value corresponding to members of the extended character set, as well as at least one value that does not correspond to any member of the extended character set (see WEOF below);314) and
- struct tm+ struct tm + which is declared as an incomplete structure type (the contents are described in 7.26.1). -
+
The macros defined are NULL (described in 7.19); WCHAR_MIN and WCHAR_MAX (described in 7.20.3); and
- WEOF+ WEOF + which expands to a constant expression of type wint_t whose value does not correspond to any member of the extended character set.315) It is accepted (and returned) by several functions in this subclause to indicate end-of-file, that is, no more input from a stream. It is also used as a wide character value that does not correspond to any member of the extended character set. -
+
The functions declared are grouped as follows:
+
Unless explicitly stated otherwise, if the execution of a function described in this subclause causes copying to take place between objects that overlap, the behavior is undefined. @@ -19348,8 +20279,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
315) The value of the macro WEOF may differ from that of EOF and need not be negative.
-7.28.2 Formatted wide character input/output functions
-
+
The formatted wide character input/output functions shall behave as if there is a sequence point after the actions associated with each specifier.316) @@ -19357,29 +20288,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
316) The fwprintf functions perform writes to memory for the %n specifier.
-7.28.2.1 The fwprintf function
+
+
#include <stdio.h>
#include <wchar.h>
int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
+
The fwprintf function writes output to the stream pointed to by stream, under control of the wide string pointed to by format that specifies how subsequent arguments are converted for output. If there are insufficient arguments for the format, the behavior is undefined. If the format is exhausted while arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored. The fwprintf function returns when the end of the format string is encountered. -
+
The format is composed of zero or more directives: ordinary wide characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments, converting them, if applicable, according to the corresponding conversion specifier, and then writing the result to the output stream. -
+
Each conversion specification is introduced by the wide character %. After the %, the following appear in sequence:
+
As noted above, a field width, or precision, or both, may be indicated by an asterisk. In this case, an int argument supplies the field width or precision. The arguments specifying field width, or precision, or both, shall appear (in that order) before the argument (if any) to be converted. A negative field width argument is taken as a - flag followed by a positive field width. A negative precision argument is taken as if the precision were omitted. -
+
The flag wide characters and their meanings are: - The result of the conversion is left-justified within the field. (It is right-justified if
- this flag is not specified.)+ this flag is not specified.) + + The result of a signed conversion always begins with a plus or minus sign. (It
begins with a sign only when a negative value is converted if this flag is not
- specified.)318)
+ specified.)318)
+
space If the first wide character of a signed conversion is not a sign, or if a signed
conversion results in no wide characters, a space is prefixed to the result. If the
- space and + flags both appear, the space flag is ignored.
+ space and + flags both appear, the space flag is ignored.
+
# The result is converted to an ''alternative form''. For o conversion, it increases
the precision, if and only if necessary, to force the first digit of the result to be a
zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
- conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
+ conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
+
-
+
and G conversions, the result of converting a floating-point number always
contains a decimal-point wide character, even if no digits follow it. (Normally, a
decimal-point wide character appears in the result of these conversions only if a
digit follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
+ result. For other conversions, the behavior is undefined.
+
0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
-
(following any indication of sign or base) are used to pad to the field width rather
than performing space padding, except when converting an infinity or NaN. If the
0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
conversions, if a precision is specified, the 0 flag is ignored. For other
- conversions, the behavior is undefined.
+ conversions, the behavior is undefined.
+
+The length modifiers and their meanings are: hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
@@ -19454,14 +20392,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
been promoted according to the integer promotions, but its value shall be
converted to signed char or unsigned char before printing); or that
a following n conversion specifier applies to a pointer to a signed char
- argument.
+ argument.
+
h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
short int or unsigned short int argument (the argument will
have been promoted according to the integer promotions, but its value shall
be converted to short int or unsigned short int before printing);
or that a following n conversion specifier applies to a pointer to a short
- int argument.
+ int argument.
+
l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
long int or unsigned long int argument; that a following n
@@ -19469,40 +20409,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
following c conversion specifier applies to a wint_t argument; that a
following s conversion specifier applies to a pointer to a wchar_t
argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
- specifier.
+ specifier.
+
ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
long long int or unsigned long long int argument; or that a
following n conversion specifier applies to a pointer to a long long int
- argument.
+ argument.
+
j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
-
+
an intmax_t or uintmax_t argument; or that a following n conversion
- specifier applies to a pointer to an intmax_t argument.
+ specifier applies to a pointer to an intmax_t argument.
+
z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
size_t or the corresponding signed integer type argument; or that a
following n conversion specifier applies to a pointer to a signed integer type
- corresponding to size_t argument.
+ corresponding to size_t argument.
+
t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
ptrdiff_t or the corresponding unsigned integer type argument; or that a
following n conversion specifier applies to a pointer to a ptrdiff_t
- argument.
+ argument.
+
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to a long double argument.+ applies to a long double argument. + If a length modifier appears with any conversion specifier other than as specified above, the behavior is undefined. -
+
The conversion specifiers and their meanings are: d,i The int argument is converted to signed decimal in the style [-]dddd. The
precision specifies the minimum number of digits to appear; if the value
being converted can be represented in fewer digits, it is expanded with
leading zeros. The default precision is 1. The result of converting a zero
- value with a precision of zero is no wide characters.
+ value with a precision of zero is no wide characters.
+
o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
@@ -19510,9 +20457,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
conversion. The precision specifies the minimum number of digits to appear;
if the value being converted can be represented in fewer digits, it is expanded
with leading zeros. The default precision is 1. The result of converting a
- zero value with a precision of zero is no wide characters.
+ zero value with a precision of zero is no wide characters.
+
f,F A double argument representing a floating-point number is converted to
-
+
decimal notation in the style [-]ddd.ddd, where the number of digits after
the decimal-point wide character is equal to the precision specification. If the
@@ -19526,7 +20474,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
[-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
any n-wchar-sequence, is implementation-defined. The F conversion
specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
- nan, respectively.319)
+ nan, respectively.319)
+
e,E A double argument representing a floating-point number is converted in the
style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
@@ -19539,7 +20488,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
and only as many more digits as necessary to represent the exponent. If the
value is zero, the exponent is zero.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
g,G A double argument representing a floating-point number is converted in
style f or e (or in style F or E in the case of a G conversion specifier),
@@ -19553,17 +20503,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
fractional portion of the result and the decimal-point wide character is
removed if there is no fractional portion remaining.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
a,A A double argument representing a floating-point number is converted in the
style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
nonzero if the argument is a normalized floating-point number and is
otherwise unspecified) before the decimal-point wide character320) and the
number of hexadecimal digits after it is equal to the precision; if the precision
- is missing and FLT_RADIX is a power of 2, then the precision is sufficient
+ is missing and FLT_RADIX is a power of 2, then the precision is sufficient
+
-
+
for an exact representation of the value; if the precision is missing and
FLT_RADIX is not a power of 2, then the precision is sufficient to
@@ -19576,12 +20528,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
represent the decimal exponent of 2. If the value is zero, the exponent is
zero.
A double argument representing an infinity or NaN is converted in the style
- of an f or F conversion specifier.
+ of an f or F conversion specifier.
+
c If no l length modifier is present, the int argument is converted to a wide
character as if by calling btowc and the resulting wide character is written.
If an l length modifier is present, the wint_t argument is converted to
- wchar_t and written.
+ wchar_t and written.
+
s If no l length modifier is present, the argument shall be a pointer to the initial
element of a character array containing a multibyte character sequence
@@ -19598,41 +20552,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
written up to (but not including) a terminating null wide character. If the
precision is specified, no more than that many wide characters are written. If
the precision is not specified or is greater than the size of the array, the array
- shall contain a null wide character.
+ shall contain a null wide character.
+
p The argument shall be a pointer to void. The value of the pointer is
- converted to a sequence of printing wide characters, in an implementation-+ converted to a sequence of printing wide characters, in an implementation- + - +
- defined manner.+ defined manner. + n The argument shall be a pointer to signed integer into which is written the
number of wide characters written to the output stream so far by this call to
fwprintf. No argument is converted, but one is consumed. If the
conversion specification includes any flags, a field width, or a precision, the
- behavior is undefined.
+ behavior is undefined.
+
% A % wide character is written. No argument is converted. The complete
-
- conversion specification shall be %%.+ conversion specification shall be %%. + +
If a conversion specification is invalid, the behavior is undefined.322) If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined. -
+
In no case does a nonexistent or small field width cause truncation of a field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result. -
+
For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded to a hexadecimal floating number with the given precision. - Recommended practice -
+
For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly representable in the given precision, the result should be one of the two adjacent numbers in hexadecimal floating style with the given precision, with the extra stipulation that the error should have a correct sign for the current rounding direction. -
+
For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most DECIMAL_DIG, then the result should be correctly rounded.323) If the number of significant decimal digits is more than DECIMAL_DIG but the source value is exactly @@ -19642,16 +20601,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that the error should have a correct sign for the current rounding direction.
+
The fwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. - - Environmental limits -
+ +
The number of wide characters that can be produced by any single conversion shall be at least 4095. -
+
EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal places:
@@ -19663,7 +20622,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int day, hour, min;
fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
weekday, month, day, hour, min);
- fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
+ fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
+
Forward references: the btowc function (7.28.6.1.1), the mbrtowc function
(7.28.6.3.2).
@@ -19692,16 +20652,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the case of fixed-point conversion by the source value as well.
-7.28.2.2 The fwscanf function
+
+
#include <stdio.h>
#include <wchar.h>
int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
+
The fwscanf function reads input from the stream pointed to by stream, under control of the wide string pointed to by format that specifies the admissible input sequences and how they are to be converted for assignment, using subsequent arguments @@ -19709,7 +20670,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. arguments for the format, the behavior is undefined. If the format is exhausted while arguments remain, the excess arguments are evaluated (as always) but are otherwise ignored. -
+
The format is composed of zero or more directives: one or more white-space wide characters, an ordinary wide character (neither % nor a white-space wide character), or a conversion specification. Each conversion specification is introduced by the wide @@ -19718,34 +20679,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
The fwscanf function executes each directive of the format in turn. When all directives have been executed, or if a directive fails (as detailed below), the function returns. Failures are described as input failures (due to the occurrence of an encoding error or the unavailability of input characters), or matching failures (due to inappropriate input). -
+
A directive composed of white-space wide character(s) is executed by reading input up to the first non-white-space wide character (which remains unread), or until no more wide characters can be read. -
+
A directive that is an ordinary wide character is executed by reading the next wide character of the stream. If that wide character differs from the directive, the directive fails and the differing and subsequent wide characters remain unread. Similarly, if end- of-file, an encoding error, or a read error prevents a wide character from being read, the directive fails. -
+
A directive that is a conversion specification defines a set of matching input sequences, as described below for each specifier. A conversion specification is executed in the following steps: -
+
Input white-space wide characters (as specified by the iswspace function) are skipped, unless the specification includes a [, c, or n specifier.324) -
+
An input item is read from the stream, unless the specification includes an n specifier. An input item is defined as the longest sequence of input wide characters which does not exceed any specified field width and which is, or is a prefix of, a matching input @@ -19753,7 +20714,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. length of the input item is zero, the execution of the directive fails; this condition is a matching failure unless end-of-file, an encoding error, or a read error prevented input from the stream, in which case it is an input failure. -
+
Except in the case of a % specifier, the input item (or, in the case of a %n directive, the count of input wide characters) is converted to a type appropriate to the conversion specifier. If the input item is not a matching sequence, the execution of the directive fails: @@ -19762,76 +20723,90 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. following the format argument that has not already received a conversion result. If this - + object does not have an appropriate type, or if the result of the conversion cannot be represented in the object, the behavior is undefined. -
+
The length modifiers and their meanings are: hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to signed char or unsigned char.+ to an argument with type pointer to signed char or unsigned char. + h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to short int or unsigned short
- int.
+ int.
+
l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to long int or unsigned long
int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
an argument with type pointer to double; or that a following c, s, or [
- conversion specifier applies to an argument with type pointer to wchar_t.
+ conversion specifier applies to an argument with type pointer to wchar_t.
+
ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to long long int or unsigned
- long long int.
+ long long int.
+
j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
- to an argument with type pointer to intmax_t or uintmax_t.+ to an argument with type pointer to intmax_t or uintmax_t. + z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to size_t or the corresponding signed
- integer type.
+ integer type.
+
t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
to an argument with type pointer to ptrdiff_t or the corresponding
- unsigned integer type.
+ unsigned integer type.
+
L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
- applies to an argument with type pointer to long double.+ applies to an argument with type pointer to long double. + If a length modifier appears with any conversion specifier other than as specified above, the behavior is undefined. -
+
The conversion specifiers and their meanings are: d Matches an optionally signed decimal integer, whose format is the same as
expected for the subject sequence of the wcstol function with the value 10
for the base argument. The corresponding argument shall be a pointer to
- signed integer.
+ signed integer.
+
i Matches an optionally signed integer, whose format is the same as expected
-
+
for the subject sequence of the wcstol function with the value 0 for the
base argument. The corresponding argument shall be a pointer to signed
- integer.
+ integer.
+
o Matches an optionally signed octal integer, whose format is the same as
expected for the subject sequence of the wcstoul function with the value 8
for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
u Matches an optionally signed decimal integer, whose format is the same as
expected for the subject sequence of the wcstoul function with the value 10
for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
x Matches an optionally signed hexadecimal integer, whose format is the same
as expected for the subject sequence of the wcstoul function with the value
16 for the base argument. The corresponding argument shall be a pointer to
- unsigned integer.
+ unsigned integer.
+
a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
format is the same as expected for the subject sequence of the wcstod
- function. The corresponding argument shall be a pointer to floating.
+ function. The corresponding argument shall be a pointer to floating.
+
c Matches a sequence of wide characters of exactly the number specified by the
field width (1 if no field width is present in the directive).
@@ -19843,9 +20818,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
accept the sequence. No null character is added.
If an l length modifier is present, the corresponding argument shall be a
pointer to the initial element of an array of wchar_t large enough to accept
- the sequence. No null wide character is added.
+ the sequence. No null wide character is added.
+
s Matches a sequence of non-white-space wide characters.
-
+
If no l length modifier is present, characters from the input field are
converted as if by repeated calls to the wcrtomb function, with the
@@ -19857,7 +20833,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If an l length modifier is present, the corresponding argument shall be a
pointer to the initial element of an array of wchar_t large enough to accept
the sequence and the terminating null wide character, which will be added
- automatically.
+ automatically.
+
[ Matches a nonempty sequence of wide characters from a set of expected
characters (the scanset).
@@ -19883,7 +20860,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
the specification; otherwise the first following right bracket wide character is
the one that ends the specification. If a - wide character is in the scanlist and
is not the first, nor the second where the first wide character is a ^, nor the
- last character, the behavior is implementation-defined.
+ last character, the behavior is implementation-defined.
+
p Matches an implementation-defined set of sequences, which should be the
same as the set of sequences that may be produced by the %p conversion of
@@ -19891,9 +20869,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pointer to void. The input item is converted to a pointer value in an
implementation-defined manner. If the input item is a value converted earlier
during the same program execution, the pointer that results shall compare
- equal to that value; otherwise the behavior of the %p conversion is undefined.
+ equal to that value; otherwise the behavior of the %p conversion is undefined.
+
n No input is consumed. The corresponding argument shall be a pointer to
-
+
signed integer into which is to be written the number of wide characters read
from the input stream so far by this call to the fwscanf function. Execution
@@ -19901,55 +20880,61 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
completion of execution of the fwscanf function. No argument is
converted, but one is consumed. If the conversion specification includes an
assignment-suppressing wide character or a field width, the behavior is
- undefined.
+ undefined.
+
% Matches a single % wide character; no conversion or assignment occurs. The
-
- complete conversion specification shall be %%.+ complete conversion specification shall be %%. + +
If a conversion specification is invalid, the behavior is undefined.326) -
+
The conversion specifiers A, E, F, G, and X are also valid and behave the same as, respectively, a, e, f, g, and x. -
+
Trailing white space (including new-line wide characters) is left unread unless matched by a directive. The success of literal matches and suppressed assignments is not directly determinable other than via the %n directive.
+
The fwscanf function returns the value of the macro EOF if an input failure occurs before the first conversion (if any) has completed. Otherwise, the function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure. -
+
EXAMPLE 1 The call:
#include <stdio.h>
#include <wchar.h>
/* ... */
int n, i; float x; wchar_t name[50];
- n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
+ n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);
+
with the input line:
- 25 54.32E-1 thompson+ 25 54.32E-1 thompson + will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0. -
+
EXAMPLE 2 The call:
#include <stdio.h>
#include <wchar.h>
/* ... */
int i; float x; double y;
- fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
+ fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);
+
with input:
- 56789 0123 56a72+ 56789 0123 56a72 + will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value 56.0. The next wide character read from the input stream will be a. - +
Forward references: the wcstod, wcstof, and wcstold functions (7.28.4.1.1), the wcstol, wcstoll, wcstoul, and wcstoull functions (7.28.4.1.2), the wcrtomb function (7.28.6.3.3). @@ -19963,68 +20948,71 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
326) See ''future library directions'' (7.30.12).
-7.28.2.3 The swprintf function
+
+
#include <wchar.h>
int swprintf(wchar_t * restrict s,
size_t n,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
+
The swprintf function is equivalent to fwprintf, except that the argument s specifies an array of wide characters into which the generated output is to be written, rather than written to a stream. No more than n wide characters are written, including a terminating null wide character, which is always added (unless n is zero).
+
The swprintf function returns the number of wide characters written in the array, not
counting the terminating null wide character, or a negative value if an encoding error
occurred or if n or more wide characters were requested to be written.
-7.28.2.4 The swscanf function
+
+
#include <wchar.h>
int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
+
The swscanf function is equivalent to fwscanf, except that the argument s specifies a wide string from which the input is to be obtained, rather than from a stream. Reaching the end of the wide string is equivalent to encountering end-of-file for the fwscanf function.
+
The swscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the swscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-
+
-7.28.2.5 The vfwprintf function
+
+
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
int vfwprintf(FILE * restrict stream,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vfwprintf function is equivalent to fwprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfwprintf function does not invoke the va_end macro.327)
+
The vfwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. -
+
EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting routine.
@@ -20040,177 +21028,186 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
// print out remainder of message
vfwprintf(stderr, format, args);
va_end(args);
- }
+ }
+
-
+
327) As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
invoke the va_arg macro, the value of arg after the return is indeterminate.
-7.28.2.6 The vfwscanf function
+
+
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
int vfwscanf(FILE * restrict stream,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vfwscanf function is equivalent to fwscanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfwscanf function does not invoke the - va_end macro.327) + va_end macro.327)
+
The vfwscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vfwscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.28.2.7 The vswprintf function
+
+
#include <stdarg.h>
#include <wchar.h>
int vswprintf(wchar_t * restrict s,
size_t n,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vswprintf function is equivalent to swprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vswprintf function does not invoke the - va_end macro.327) + va_end macro.327)
+
The vswprintf function returns the number of wide characters written in the array, not
counting the terminating null wide character, or a negative value if an encoding error
occurred or if n or more wide characters were requested to be generated.
-
+
-7.28.2.8 The vswscanf function
+
+
#include <stdarg.h>
#include <wchar.h>
int vswscanf(const wchar_t * restrict s,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vswscanf function is equivalent to swscanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vswscanf function does not invoke the - va_end macro.327) + va_end macro.327)
+
The vswscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vswscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.28.2.9 The vwprintf function
+
+
#include <stdarg.h>
#include <wchar.h>
int vwprintf(const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vwprintf function is equivalent to wprintf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vwprintf function does not invoke the - va_end macro.327) + va_end macro.327)
+
The vwprintf function returns the number of wide characters transmitted, or a negative
value if an output or encoding error occurred.
-
+
-7.28.2.10 The vwscanf function
+
+
#include <stdarg.h>
#include <wchar.h>
int vwscanf(const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
+
The vwscanf function is equivalent to wscanf, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vwscanf function does not invoke the - va_end macro.327) + va_end macro.327)
+
The vwscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the vwscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.28.2.11 The wprintf function
+
+
#include <wchar.h>
- int wprintf(const wchar_t * restrict format, ...);
+ int wprintf(const wchar_t * restrict format, ...);
+
+
The wprintf function is equivalent to fwprintf with the argument stdout interposed before the arguments to wprintf.
+
The wprintf function returns the number of wide characters transmitted, or a negative
value if an output or encoding error occurred.
-7.28.2.12 The wscanf function
+
+
#include <wchar.h>
- int wscanf(const wchar_t * restrict format, ...);
+ int wscanf(const wchar_t * restrict format, ...);
+
+
The wscanf function is equivalent to fwscanf with the argument stdin interposed before the arguments to wscanf. - +
+
The wscanf function returns the value of the macro EOF if an input failure occurs
before the first conversion (if any) has completed. Otherwise, the wscanf function
returns the number of input items assigned, which can be fewer than provided for, or even
zero, in the event of an early matching failure.
-7.28.3 Wide character input/output functions
+
+
#include <stdio.h>
#include <wchar.h>
- wint_t fgetwc(FILE *stream);
+ wint_t fgetwc(FILE *stream);
+
+
If the end-of-file indicator for the input stream pointed to by stream is not set and a next wide character is present, the fgetwc function obtains that wide character as a wchar_t converted to a wint_t and advances the associated file position indicator for the stream (if defined).
+
If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
the fgetwc function returns the next wide character from the input stream pointed to by
@@ -20223,84 +21220,88 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
-7.28.3.2 The fgetws function
+
+
#include <stdio.h>
#include <wchar.h>
wchar_t *fgetws(wchar_t * restrict s,
- int n, FILE * restrict stream);
+ int n, FILE * restrict stream);
+
+
The fgetws function reads at most one less than the number of wide characters specified by n from the stream pointed to by stream into the array pointed to by s. No - + additional wide characters are read after a new-line wide character (which is retained) or after end-of-file. A null wide character is written immediately after the last wide character read into the array.
+
The fgetws function returns s if successful. If end-of-file is encountered and no
characters have been read into the array, the contents of the array remain unchanged and a
null pointer is returned. If a read or encoding error occurs during the operation, the array
contents are indeterminate and a null pointer is returned.
-7.28.3.3 The fputwc function
+
+
#include <stdio.h>
#include <wchar.h>
- wint_t fputwc(wchar_t c, FILE *stream);
+ wint_t fputwc(wchar_t c, FILE *stream);
+
+
The fputwc function writes the wide character specified by c to the output stream pointed to by stream, at the position indicated by the associated file position indicator for the stream (if defined), and advances the indicator appropriately. If the file cannot support positioning requests, or if the stream was opened with append mode, the character is appended to the output stream.
+
The fputwc function returns the wide character written. If a write error occurs, the
error indicator for the stream is set and fputwc returns WEOF. If an encoding error
occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
-7.28.3.4 The fputws function
+
+
#include <stdio.h>
#include <wchar.h>
int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
+ FILE * restrict stream);
+
+
The fputws function writes the wide string pointed to by s to the stream pointed to by stream. The terminating null wide character is not written.
+
The fputws function returns EOF if a write or encoding error occurs; otherwise, it
returns a nonnegative value.
-
+
-7.28.3.5 The fwide function
+
+
#include <stdio.h>
#include <wchar.h>
- int fwide(FILE *stream, int mode);
+ int fwide(FILE *stream, int mode);
+
+
The fwide function determines the orientation of the stream pointed to by stream. If mode is greater than zero, the function first attempts to make the stream wide oriented. If mode is less than zero, the function first attempts to make the stream byte oriented.329) Otherwise, mode is zero and the function does not alter the orientation of the stream.
+
The fwide function returns a value greater than zero if, after the call, the stream has wide orientation, a value less than zero if the stream has byte orientation, or zero if the stream has no orientation. @@ -20309,97 +21310,102 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
329) If the orientation of the stream has already been determined, fwide does not change it.
-7.28.3.6 The getwc function
+
+
#include <stdio.h>
#include <wchar.h>
- wint_t getwc(FILE *stream);
+ wint_t getwc(FILE *stream);
+
+
The getwc function is equivalent to fgetwc, except that if it is implemented as a macro, it may evaluate stream more than once, so the argument should never be an expression with side effects.
+
The getwc function returns the next wide character from the input stream pointed to by
stream, or WEOF.
-7.28.3.7 The getwchar function
+
+
#include <wchar.h>
- wint_t getwchar(void);
+ wint_t getwchar(void);
+
-
+
+
The getwchar function is equivalent to getwc with the argument stdin.
+
The getwchar function returns the next wide character from the input stream pointed to
by stdin, or WEOF.
-7.28.3.8 The putwc function
+
+
#include <stdio.h>
#include <wchar.h>
- wint_t putwc(wchar_t c, FILE *stream);
+ wint_t putwc(wchar_t c, FILE *stream);
+
+
The putwc function is equivalent to fputwc, except that if it is implemented as a macro, it may evaluate stream more than once, so that argument should never be an expression with side effects.
+
The putwc function returns the wide character written, or WEOF.
-7.28.3.9 The putwchar function
+
+
#include <wchar.h>
- wint_t putwchar(wchar_t c);
+ wint_t putwchar(wchar_t c);
+
+
The putwchar function is equivalent to putwc with the second argument stdout.
+
The putwchar function returns the character written, or WEOF.
-7.28.3.10 The ungetwc function
+
+
#include <stdio.h>
#include <wchar.h>
- wint_t ungetwc(wint_t c, FILE *stream);
+ wint_t ungetwc(wint_t c, FILE *stream);
+
+
The ungetwc function pushes the wide character specified by c back onto the input stream pointed to by stream. Pushed-back wide characters will be returned by subsequent reads on that stream in the reverse order of their pushing. A successful - + intervening call (with the stream pointed to by stream) to a file positioning function (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the stream. The external storage corresponding to the stream is unchanged. -
+
One wide character of pushback is guaranteed, even if the call to the ungetwc function follows just after a call to a formatted wide character input function fwscanf, vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times on the same stream without an intervening read or file positioning operation on that stream, the operation may fail. -
+
If the value of c equals that of the macro WEOF, the operation fails and the input stream is unchanged. -
+
A successful call to the ungetwc function clears the end-of-file indicator for the stream. The value of the file position indicator for the stream after reading or discarding all pushed-back wide characters is the same as it was before the wide characters were pushed @@ -20407,17 +21413,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. call to the ungetwc function is unspecified until all pushed-back wide characters are read or discarded.
+
The ungetwc function returns the wide character pushed back, or WEOF if the operation
fails.
-7.28.4 General wide string utilities
-
+
The header <wchar.h> declares a number of functions useful for wide string manipulation. Various methods are used for determining the lengths of the arrays, but in all cases a wchar_t * argument points to the initial (lowest addressed) element of the array. If an array is accessed beyond the end of an object, the behavior is undefined. -
+
Where an argument declared as size_t n determines the length of the array for a
function, n can have the value zero on a call to that function. Unless explicitly stated
otherwise in the description of a particular function in this subclause, pointer arguments
@@ -20425,13 +21431,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
function that locates a wide character finds no occurrence, a function that compares two
wide character sequences returns zero, and a function that copies wide characters copies
zero wide characters.
-
+
-7.28.4.1 Wide string numeric conversion functions
+
+
#include <wchar.h>
double wcstod(const wchar_t * restrict nptr,
@@ -20439,9 +21445,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
float wcstof(const wchar_t * restrict nptr,
wchar_t ** restrict endptr);
long double wcstold(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr);
+ wchar_t ** restrict endptr);
+
+
The wcstod, wcstof, and wcstold functions convert the initial portion of the wide string pointed to by nptr to double, float, and long double representation, respectively. First, they decompose the input string into three parts: an initial, possibly @@ -20450,7 +21457,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. infinity or NaN; and a final wide string of one or more unrecognized wide characters, including the terminating null wide character of the input wide string. Then, they attempt to convert the subject sequence to a floating-point number, and return the result. -
+
The expected form of the subject sequence is an optional plus or minus sign, then one of the following:
n-wchar-sequence:
digit
nondigit
n-wchar-sequence digit
- n-wchar-sequence nondigit
+ n-wchar-sequence nondigit
+
+
If the subject sequence has the expected form for a floating-point number, the sequence of wide characters starting with the first digit or the decimal-point wide character (whichever occurs first) is interpreted as a floating constant according to the rules of @@ -20487,23 +21495,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. sign, the sequence is interpreted as negated.330) A wide character sequence INF or INFINITY is interpreted as an infinity, if representable in the return type, else like a floating constant that is too large for the range of the return type. A wide character - sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported + sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported in the return type, else like a subject sequence part that does not have the expected form; the meaning of the n-wchar sequences is implementation-defined.331) A pointer to the final wide string is stored in the object pointed to by endptr, provided that endptr is not a null pointer. -
+
If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the value resulting from the conversion is correctly rounded. -
+
In other than the "C" locale, additional locale-specific subject sequence forms may be accepted. -
+
If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer. - Recommended practice -
+
If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and the result is not exactly representable, the result should be one of the two numbers in the appropriate internal format that are adjacent to the hexadecimal floating source value, @@ -20512,8 +21520,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in <float.h>) significant digits, the result should be correctly rounded. If the subject sequence D has the decimal form and more than DECIMAL_DIG significant digits, @@ -20524,7 +21532,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. stipulation that the error with respect to D should have a correct sign for the current rounding direction.332)
+
The functions return the converted value, if any. If no conversion could be performed, zero is returned. If the correct value overflows and default rounding is in effect (7.12.1), plus or minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the @@ -20536,7 +21544,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
330) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
@@ -20551,9 +21559,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
to the same internal floating value, but if not will round to adjacent values.
-7.28.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions
+
+
#include <wchar.h>
long int wcstol(
@@ -20571,9 +21579,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
unsigned long long int wcstoull(
const wchar_t * restrict nptr,
wchar_t ** restrict endptr,
- int base);
+ int base);
+
+
The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial portion of the wide string pointed to by nptr to long int, long long int, unsigned long int, and unsigned long long int representation, @@ -20583,7 +21592,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. by the value of base, and a final wide string of one or more unrecognized wide characters, including the terminating null wide character of the input wide string. Then, they attempt to convert the subject sequence to an integer, and return the result. -
+
If the value of base is zero, the expected form of the subject sequence is that of an integer constant as described for the corresponding single-byte characters in 6.4.4.1, optionally preceded by a plus or minus sign, but not including an integer suffix. If the @@ -20594,14 +21603,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. letters and digits whose ascribed values are less than that of base are permitted. If the value of base is 16, the wide characters 0x or 0X may optionally precede the sequence of letters and digits, following the sign if present. - -
+ +
The subject sequence is defined as the longest initial subsequence of the input wide string, starting with the first non-white-space wide character, that is of the expected form. The subject sequence contains no wide characters if the input wide string is empty or consists entirely of white space, or if the first non-white-space wide character is other than a sign or a permissible letter or digit. -
+
If the subject sequence has the expected form and the value of base is zero, the sequence of wide characters starting with the first digit is interpreted as an integer constant according to the rules of 6.4.4.1. If the subject sequence has the expected form and the @@ -20610,58 +21619,60 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. resulting from the conversion is negated (in the return type). A pointer to the final wide string is stored in the object pointed to by endptr, provided that endptr is not a null pointer. -
+
In other than the "C" locale, additional locale-specific subject sequence forms may be accepted. -
+
If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
+
The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
value, if any. If no conversion could be performed, zero is returned. If the correct value
is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
sign of the value, if any), and the value of the macro ERANGE is stored in errno.
-7.28.4.2 Wide string copying functions
+
+
#include <wchar.h>
wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
+ const wchar_t * restrict s2);
+
+
The wcscpy function copies the wide string pointed to by s2 (including the terminating null wide character) into the array pointed to by s1.
+
The wcscpy function returns the value of s1.
-
+
-7.28.4.2.2 The wcsncpy function
+
+
#include <wchar.h>
wchar_t *wcsncpy(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
+ size_t n);
+
+
The wcsncpy function copies not more than n wide characters (those that follow a null wide character are not copied) from the array pointed to by s2 to the array pointed to by s1.333) -
+
If the array pointed to by s2 is a wide string that is shorter than n wide characters, null wide characters are appended to the copy in the array pointed to by s1, until n wide characters in all have been written.
+
The wcsncpy function returns the value of s1.
+
#include <wchar.h>
wchar_t *wmemcpy(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
+ size_t n);
+
+
The wmemcpy function copies n wide characters from the object pointed to by s2 to the object pointed to by s1.
+
The wmemcpy function returns the value of s1.
-
+
-7.28.4.2.4 The wmemmove function
+
+
#include <wchar.h>
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
+ size_t n);
+
+
The wmemmove function copies n wide characters from the object pointed to by s2 to the object pointed to by s1. Copying takes place as if the n wide characters from the object pointed to by s2 are first copied into a temporary array of n wide characters that does not overlap the objects pointed to by s1 or s2, and then the n wide characters from the temporary array are copied into the object pointed to by s1.
+
The wmemmove function returns the value of s1.
-7.28.4.3 Wide string concatenation functions
+
+
#include <wchar.h>
wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
+ const wchar_t * restrict s2);
+
+
The wcscat function appends a copy of the wide string pointed to by s2 (including the terminating null wide character) to the end of the wide string pointed to by s1. The initial wide character of s2 overwrites the null wide character at the end of s1.
+
The wcscat function returns the value of s1.
-7.28.4.3.2 The wcsncat function
+
+
#include <wchar.h>
wchar_t *wcsncat(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
+ size_t n);
+
+
The wcsncat function appends not more than n wide characters (a null wide character and those that follow it are not appended) from the array pointed to by s2 to the end of - + the wide string pointed to by s1. The initial wide character of s2 overwrites the null wide character at the end of s1. A terminating null wide character is always appended to the result.334)
+
The wcsncat function returns the value of s1.
+
Unless explicitly stated otherwise, the functions described in this subclause order two
wide characters the same way as two integers of the underlying integer type designated
by wchar_t.
-7.28.4.4.1 The wcscmp function
+
+
#include <wchar.h>
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
+ int wcscmp(const wchar_t *s1, const wchar_t *s2);
+
+
The wcscmp function compares the wide string pointed to by s1 to the wide string pointed to by s2.
+
The wcscmp function returns an integer greater than, equal to, or less than zero,
accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
wide string pointed to by s2.
-7.28.4.4.2 The wcscoll function
+
+
#include <wchar.h>
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
+ int wcscoll(const wchar_t *s1, const wchar_t *s2);
+
+
The wcscoll function compares the wide string pointed to by s1 to the wide string pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
+
The wcscoll function returns an integer greater than, equal to, or less than zero,
accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
-
+
wide string pointed to by s2 when both are interpreted as appropriate to the current
locale.
-7.28.4.4.3 The wcsncmp function
+
+
#include <wchar.h>
int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
+ size_t n);
+
+
The wcsncmp function compares not more than n wide characters (those that follow a null wide character are not compared) from the array pointed to by s1 to the array pointed to by s2.
+
The wcsncmp function returns an integer greater than, equal to, or less than zero,
accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
to, or less than the possibly null-terminated array pointed to by s2.
-7.28.4.4.4 The wcsxfrm function
+
+
#include <wchar.h>
size_t wcsxfrm(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
+ size_t n);
+
+
The wcsxfrm function transforms the wide string pointed to by s2 and places the resulting wide string into the array pointed to by s1. The transformation is such that if the wcscmp function is applied to two transformed wide strings, it returns a value greater @@ -20830,175 +21849,184 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. into the resulting array pointed to by s1, including the terminating null wide character. If n is zero, s1 is permitted to be a null pointer.
+
The wcsxfrm function returns the length of the transformed wide string (not including the terminating null wide character). If the value returned is n or greater, the contents of the array pointed to by s1 are indeterminate. -
+
EXAMPLE The value of the following expression is the length of the array needed to hold the transformation of the wide string pointed to by s: - +
- 1 + wcsxfrm(NULL, s, 0)+ 1 + wcsxfrm(NULL, s, 0) + -
+
#include <wchar.h>
int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
+ size_t n);
+
+
The wmemcmp function compares the first n wide characters of the object pointed to by s1 to the first n wide characters of the object pointed to by s2.
+
The wmemcmp function returns an integer greater than, equal to, or less than zero,
accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
pointed to by s2.
-7.28.4.5 Wide string search functions
+
+
#include <wchar.h>
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
+ wchar_t *wcschr(const wchar_t *s, wchar_t c);
+
+
The wcschr function locates the first occurrence of c in the wide string pointed to by s. The terminating null wide character is considered to be part of the wide string.
+
The wcschr function returns a pointer to the located wide character, or a null pointer if
the wide character does not occur in the wide string.
-7.28.4.5.2 The wcscspn function
+
+
#include <wchar.h>
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
+ size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
+
+
The wcscspn function computes the length of the maximum initial segment of the wide string pointed to by s1 which consists entirely of wide characters not from the wide string pointed to by s2. - +
+
The wcscspn function returns the length of the segment.
-7.28.4.5.3 The wcspbrk function
+
+
#include <wchar.h>
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
+ wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
+
+
The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of any wide character from the wide string pointed to by s2.
+
The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
no wide character from s2 occurs in s1.
-7.28.4.5.4 The wcsrchr function
+
+
#include <wchar.h>
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
+ wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
+
+
The wcsrchr function locates the last occurrence of c in the wide string pointed to by s. The terminating null wide character is considered to be part of the wide string.
+
The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
not occur in the wide string.
-7.28.4.5.5 The wcsspn function
+
+
#include <wchar.h>
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
+ size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
+
+
The wcsspn function computes the length of the maximum initial segment of the wide string pointed to by s1 which consists entirely of wide characters from the wide string pointed to by s2.
+
The wcsspn function returns the length of the segment.
-
+
-7.28.4.5.6 The wcsstr function
+
+
#include <wchar.h>
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
+ wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
+
+
The wcsstr function locates the first occurrence in the wide string pointed to by s1 of the sequence of wide characters (excluding the terminating null wide character) in the wide string pointed to by s2.
+
The wcsstr function returns a pointer to the located wide string, or a null pointer if the
wide string is not found. If s2 points to a wide string with zero length, the function
returns s1.
-7.28.4.5.7 The wcstok function
+
+
#include <wchar.h>
wchar_t *wcstok(wchar_t * restrict s1,
const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
+ wchar_t ** restrict ptr);
+
+
A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into a sequence of tokens, each of which is delimited by a wide character from the wide string pointed to by s2. The third argument points to a caller-provided wchar_t pointer into which the wcstok function stores information necessary for it to continue scanning the same wide string. -
+
The first call in a sequence has a non-null first argument and stores an initial value in the object pointed to by ptr. Subsequent calls in the sequence have a null first argument and the object pointed to by ptr is required to have the value stored by the previous call in the sequence, which is then updated. The separator wide string pointed to by s2 may be different from call to call. -
+
The first call in the sequence searches the wide string pointed to by s1 for the first wide character that is not contained in the current separator wide string pointed to by s2. If no such wide character is found, then there are no tokens in the wide string pointed to by s1 and the wcstok function returns a null pointer. If such a wide character is found, it is the start of the first token. -
+
The wcstok function then searches from there for a wide character that is contained in the current separator wide string. If no such wide character is found, the current token - + extends to the end of the wide string pointed to by s1, and subsequent searches in the same wide string for a token return a null pointer. If such a wide character is found, it is overwritten by a null wide character, which terminates the current token. -
+
In all cases, the wcstok function stores sufficient information in the pointer pointed to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start searching just past the element overwritten by a null wide character (if any).
+
The wcstok function returns a pointer to the first wide character of a token, or a null pointer if there is no token. -
+
EXAMPLE
#include <wchar.h>
@@ -21009,99 +22037,104 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
- t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
+ t = wcstok(NULL, L"?", &ptr1); // t is a null pointer
+
-+
#include <wchar.h>
wchar_t *wmemchr(const wchar_t *s, wchar_t c,
- size_t n);
+ size_t n);
+
+
The wmemchr function locates the first occurrence of c in the initial n wide characters of the object pointed to by s.
+
The wmemchr function returns a pointer to the located wide character, or a null pointer if
the wide character does not occur in the object.
-
+
-7.28.4.6 Miscellaneous functions
+
+
#include <wchar.h>
- size_t wcslen(const wchar_t *s);
+ size_t wcslen(const wchar_t *s);
+
+
The wcslen function computes the length of the wide string pointed to by s.
+
The wcslen function returns the number of wide characters that precede the terminating
null wide character.
-7.28.4.6.2 The wmemset function
+
+
#include <wchar.h>
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
+ wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
+
+
The wmemset function copies the value of c into each of the first n wide characters of the object pointed to by s.
+
The wmemset function returns the value of s.
-7.28.5 Wide character time conversion functions
+
+
#include <time.h>
#include <wchar.h>
size_t wcsftime(wchar_t * restrict s,
size_t maxsize,
const wchar_t * restrict format,
- const struct tm * restrict timeptr);
+ const struct tm * restrict timeptr);
+
+
The wcsftime function is equivalent to the strftime function, except that:
+
If the total number of resulting wide characters including the terminating null wide
character is not more than maxsize, the wcsftime function returns the number of
wide characters placed into the array pointed to by s not including the terminating null
wide character. Otherwise, zero is returned and the contents of the array are
indeterminate.
-7.28.6 Extended multibyte/wide character conversion utilities
-
+
The header <wchar.h> declares an extended set of functions useful for conversion between multibyte characters and wide characters. -
+
Most of the following functions -- those that are listed as ''restartable'', 7.28.6.3 and 7.28.6.4 -- take as a last argument a pointer to an object of type mbstate_t that is used to describe the current conversion state from a particular multibyte character sequence to a wide character sequence (or the reverse) under the rules of a particular setting for the LC_CTYPE category of the current locale. -
+
The initial conversion state corresponds, for a conversion in either direction, to the beginning of a new multibyte character in the initial shift state. A zero-valued mbstate_t object is (at least) one way to describe an initial conversion state. A zero- @@ -21111,7 +22144,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. different multibyte character sequence, or in the other conversion direction, or with a different LC_CTYPE category setting than on earlier function calls, the behavior is undefined.335) -
+
On entry, each function takes the described conversion state (either internal or pointed to by an argument) as current. The conversion state described by the referenced object is altered as needed to track the shift state, and the position within a multibyte character, for @@ -21120,7 +22153,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
335) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
@@ -21128,61 +22161,64 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character string.
-7.28.6.1 Single-byte/wide character conversion functions
+
+
#include <wchar.h> *
- wint_t btowc(int c);
+ wint_t btowc(int c);
+
+
The btowc function determines whether c constitutes a valid single-byte character in the initial shift state.
+
The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
does not constitute a valid single-byte character in the initial shift state. Otherwise, it
returns the wide character representation of that character.
-7.28.6.1.2 The wctob function
+
+
#include <wchar.h> *
- int wctob(wint_t c);
+ int wctob(wint_t c);
+
+
The wctob function determines whether c corresponds to a member of the extended character set whose multibyte character representation is a single byte when in the initial shift state.
+
The wctob function returns EOF if c does not correspond to a multibyte character with
length one in the initial shift state. Otherwise, it returns the single-byte representation of
that character as an unsigned char converted to an int.
-7.28.6.2 Conversion state functions
+
+
#include <wchar.h>
- int mbsinit(const mbstate_t *ps);
+ int mbsinit(const mbstate_t *ps);
+
+
If ps is not a null pointer, the mbsinit function determines whether the referenced mbstate_t object describes an initial conversion state. - +
+
The mbsinit function returns nonzero if ps is a null pointer or if the referenced object
describes an initial conversion state; otherwise, it returns zero.
-7.28.6.3 Restartable multibyte/wide character conversion functions
-
+
These functions differ from the corresponding multibyte character functions of 7.22.7 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type pointer to mbstate_t that points to an object that can completely describe the current @@ -21191,48 +22227,52 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. program startup to the initial conversion state; the functions are not required to avoid data races in this case. The implementation behaves as if no library function calls these functions with a null pointer for ps. -
+
Also unlike their corresponding functions, the return value does not represent whether the
encoding is state-dependent.
-7.28.6.3.1 The mbrlen function
+
+
#include <wchar.h>
size_t mbrlen(const char * restrict s,
size_t n,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
The mbrlen function is equivalent to the call:
- mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)+ mbrtowc(NULL, s, n, ps != NULL ? ps : &internal) + where internal is the mbstate_t object for the mbrlen function, except that the expression designated by ps is evaluated only once.
+
The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2), or (size_t)(-1).
Forward references: the mbrtowc function (7.28.6.3.2).
-
+
-7.28.6.3.2 The mbrtowc function
+
+
#include <wchar.h>
size_t mbrtowc(wchar_t * restrict pwc,
const char * restrict s,
size_t n,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the mbrtowc function is equivalent to the call:
- mbrtowc(NULL, "", 1, ps)+ mbrtowc(NULL, "", 1, ps) + In this case, the values of the parameters pwc and n are ignored. -
+
If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with the byte pointed to by s to determine the number of bytes needed to complete the next multibyte character (including any shift sequences). If the function determines that the @@ -21241,48 +22281,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the object pointed to by pwc. If the corresponding wide character is the null wide character, the resulting state described is the initial conversion state.
+
The mbrtowc function returns the first of the following that applies (given the current conversion state): 0 if the next n or fewer bytes complete the multibyte character that
- corresponds to the null wide character (which is the value stored).+ corresponds to the null wide character (which is the value stored). + between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
character (which is the value stored); the value returned is the number
- of bytes that complete the multibyte character.
+ of bytes that complete the multibyte character.
+
(size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
multibyte character, and all n bytes have been processed (no value is
- stored).336)
+ stored).336)
+
(size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
do not contribute to a complete and valid multibyte character (no
value is stored); the value of the macro EILSEQ is stored in errno,
- and the conversion state is unspecified.
+ and the conversion state is unspecified.
+
-
+
336) When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
sequence of redundant shift sequences (for implementations with state-dependent encodings).
-7.28.6.3.3 The wcrtomb function
+
+
#include <wchar.h>
size_t wcrtomb(char * restrict s,
wchar_t wc,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
If s is a null pointer, the wcrtomb function is equivalent to the call
- wcrtomb(buf, L'\0', ps)+ wcrtomb(buf, L'\0', ps) + where buf is an internal buffer. -
+
If s is not a null pointer, the wcrtomb function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by wc (including any shift sequences), and stores the multibyte character representation in the @@ -21290,14 +22336,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wc is a null wide character, a null byte is stored, preceded by any shift sequence needed to restore the initial shift state; the resulting state described is the initial conversion state.
+
The wcrtomb function returns the number of bytes stored in the array object (including
any shift sequences). When wc is not a valid wide character, an encoding error occurs:
the function stores the value of the macro EILSEQ in errno and returns
(size_t)(-1); the conversion state is unspecified.
-7.28.6.4 Restartable multibyte/wide string conversion functions
-
+
These functions differ from the corresponding multibyte string functions of 7.22.8 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to mbstate_t that points to an object that can completely describe the current conversion @@ -21306,24 +22352,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. to the initial conversion state; the functions are not required to avoid data races in this case. The implementation behaves as if no library function calls these functions with a null pointer for ps. -
+
Also unlike their corresponding functions, the conversion source parameter, src, has a
pointer-to-pointer type. When the function is storing the results of conversions (that is,
when dst is not a null pointer), the pointer object pointed to by this parameter is updated
to reflect the amount of the source processed by that invocation.
-
+
-7.28.6.4.1 The mbsrtowcs function
+
+
#include <wchar.h>
size_t mbsrtowcs(wchar_t * restrict dst,
const char ** restrict src,
size_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
The mbsrtowcs function converts a sequence of multibyte characters that begins in the conversion state described by the object pointed to by ps, from the array indirectly pointed to by src into a sequence of corresponding wide characters. If dst is not a null @@ -21333,14 +22380,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. not form a valid multibyte character, or (if dst is not a null pointer) when len wide characters have been stored into the array pointed to by dst.337) Each conversion takes place as if by a call to the mbrtowc function. -
+
If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if conversion stopped due to reaching a terminating null character) or the address just past the last multibyte character converted (if any). If conversion stopped due to reaching a terminating null character and if dst is not a null pointer, the resulting state described is the initial conversion state.
+
If the input conversion encounters a sequence of bytes that do not form a valid multibyte character, an encoding error occurs: the mbsrtowcs function stores the value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion state is @@ -21350,23 +22397,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
337) Thus, the value of len is ignored if dst is a null pointer.
-7.28.6.4.2 The wcsrtombs function
+
+
#include <wchar.h>
size_t wcsrtombs(char * restrict dst,
const wchar_t ** restrict src,
size_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
+
The wcsrtombs function converts a sequence of wide characters from the array indirectly pointed to by src into a sequence of corresponding multibyte characters that begins in the conversion state described by the object pointed to by ps. If dst is not a @@ -21377,14 +22425,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. next multibyte character would exceed the limit of len total bytes to be stored into the array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb function.338) -
+
If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if conversion stopped due to reaching a terminating null wide character) or the address just past the last wide character converted (if any). If conversion stopped due to reaching a terminating null wide character, the resulting state described is the initial conversion state.
+
If conversion stops because a wide character is reached that does not correspond to a valid multibyte character, an encoding error occurs: the wcsrtombs function stores the value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion @@ -21394,35 +22442,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
338) If conversion stops because a terminating null wide character has been reached, the bytes stored
include those necessary to reach the initial shift state immediately before the null byte.
-7.29 Wide character classification and mapping utilities
+
+
The header <wctype.h> defines one macro, and declares three data types and many functions.339) -
+
The types declared are
- wint_t+ wint_t + described in 7.28.1;
- wctrans_t+ wctrans_t + which is a scalar type that can hold values which represent locale-specific character mappings; and
- wctype_t+ wctype_t + which is a scalar type that can hold values which represent locale-specific character classifications. -
+
The macro defined is WEOF (described in 7.28.1). -
+
The functions declared are grouped as follows:
+
For all functions described in this subclause that accept an argument of type wint_t, the value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If this argument has any other value, the behavior is undefined. -
+
The behavior of these functions is affected by the LC_CTYPE category of the current locale. - +
339) See ''future library directions'' (7.30.13).
-7.29.2 Wide character classification utilities
-
+
The header <wctype.h> declares several functions useful for classifying wide characters. -
+
The term printing wide character refers to a member of a locale-specific set of wide
characters, each of which occupies at least one printing position on a display device. The
term control wide character refers to a member of a locale-specific set of wide characters
that are not printing wide characters.
-7.29.2.1 Wide character classification functions
-
+
The functions in this subclause return nonzero (true) if and only if the value of the argument wc conforms to that in the description of the function. -
+
Each of the following functions returns true for each wide character that corresponds (as
if by a call to the wctob function) to a single-byte character for which the corresponding
character classification function from 7.4.1 returns true, except that the iswgraph and
@@ -21476,29 +22527,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
&& iswspace(wc) is true, but not both.
-7.29.2.1.1 The iswalnum function
+
+
#include <wctype.h>
- int iswalnum(wint_t wc);
+ int iswalnum(wint_t wc);
+
+
The iswalnum function tests for any wide character for which iswalpha or
iswdigit is true.
-7.29.2.1.2 The iswalpha function
+
+
#include <wctype.h>
- int iswalpha(wint_t wc);
+ int iswalpha(wint_t wc);
+
+
The iswalpha function tests for any wide character for which iswupper or
iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
-
+
wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
is true.341)
@@ -21507,54 +22560,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
wide characters; all four combinations are possible.
-7.29.2.1.3 The iswblank function
+
+
#include <wctype.h>
- int iswblank(wint_t wc);
+ int iswblank(wint_t wc);
+
+
The iswblank function tests for any wide character that is a standard blank wide
character or is one of a locale-specific set of wide characters for which iswspace is true
and that is used to separate words within a line of text. The standard blank wide
characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
locale, iswblank returns true only for the standard blank characters.
-7.29.2.1.4 The iswcntrl function
+
+
#include <wctype.h>
- int iswcntrl(wint_t wc);
+ int iswcntrl(wint_t wc);
+
+
The iswcntrl function tests for any control wide character.
-7.29.2.1.5 The iswdigit function
+
+
#include <wctype.h>
- int iswdigit(wint_t wc);
+ int iswdigit(wint_t wc);
+
+
The iswdigit function tests for any wide character that corresponds to a decimal-digit
character (as defined in 5.2.1).
-7.29.2.1.6 The iswgraph function
+
+
#include <wctype.h>
- int iswgraph(wint_t wc);
+ int iswgraph(wint_t wc);
+
-
+
+
The iswgraph function tests for any wide character for which iswprint is true and
iswspace is false.342)
@@ -21564,100 +22621,107 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
characters other than ' '.
-7.29.2.1.7 The iswlower function
+
+
#include <wctype.h>
- int iswlower(wint_t wc);
+ int iswlower(wint_t wc);
+
+
The iswlower function tests for any wide character that corresponds to a lowercase
letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
iswdigit, iswpunct, or iswspace is true.
-7.29.2.1.8 The iswprint function
+
+
#include <wctype.h>
- int iswprint(wint_t wc);
+ int iswprint(wint_t wc);
+
+
The iswprint function tests for any printing wide character.
-7.29.2.1.9 The iswpunct function
+
+
#include <wctype.h>
- int iswpunct(wint_t wc);
+ int iswpunct(wint_t wc);
+
+
The iswpunct function tests for any printing wide character that is one of a locale-
specific set of punctuation wide characters for which neither iswspace nor iswalnum
- is true.342)
+ is true.342)
-7.29.2.1.10 The iswspace function
+
+
#include <wctype.h>
- int iswspace(wint_t wc);
+ int iswspace(wint_t wc);
+
-
+
+
The iswspace function tests for any wide character that corresponds to a locale-specific
set of white-space wide characters for which none of iswalnum, iswgraph, or
iswpunct is true.
-7.29.2.1.11 The iswupper function
+
+
#include <wctype.h>
- int iswupper(wint_t wc);
+ int iswupper(wint_t wc);
+
+
The iswupper function tests for any wide character that corresponds to an uppercase
letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
iswdigit, iswpunct, or iswspace is true.
-7.29.2.1.12 The iswxdigit function
+
+
#include <wctype.h>
- int iswxdigit(wint_t wc);
+ int iswxdigit(wint_t wc);
+
+
The iswxdigit function tests for any wide character that corresponds to a
hexadecimal-digit character (as defined in 6.4.4.1).
-7.29.2.2 Extensible wide character classification functions
-
+
The functions wctype and iswctype provide extensible wide character classification
as well as testing equivalent to that performed by the functions described in the previous
subclause (7.29.2.1).
-7.29.2.2.1 The iswctype function
+
+
#include <wctype.h>
- int iswctype(wint_t wc, wctype_t desc);
+ int iswctype(wint_t wc, wctype_t desc);
+
+
The iswctype function determines whether the wide character wc has the property described by desc. The current setting of the LC_CTYPE category shall be the same as during the call to wctype that returned the value desc. -
+
Each of the following expressions has a truth-value equivalent to the call to the wide character classification function (7.29.2.1) in the comment that follows the expression: - +
iswctype(wc, wctype("alnum")) // iswalnum(wc)
iswctype(wc, wctype("alpha")) // iswalpha(wc)
@@ -21670,229 +22734,239 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
iswctype(wc, wctype("punct")) // iswpunct(wc)
iswctype(wc, wctype("space")) // iswspace(wc)
iswctype(wc, wctype("upper")) // iswupper(wc)
- iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
+ iswctype(wc, wctype("xdigit")) // iswxdigit(wc)
+
+
The iswctype function returns nonzero (true) if and only if the value of the wide character wc has the property described by desc. If desc is zero, the iswctype function returns zero (false).
Forward references: the wctype function (7.29.2.2.2).
-7.29.2.2.2 The wctype function
+
+
#include <wctype.h>
- wctype_t wctype(const char *property);
+ wctype_t wctype(const char *property);
+
+
The wctype function constructs a value with type wctype_t that describes a class of wide characters identified by the string argument property. -
+
The strings listed in the description of the iswctype function shall be valid in all locales as property arguments to the wctype function.
+
If property identifies a valid class of wide characters according to the LC_CTYPE
category of the current locale, the wctype function returns a nonzero value that is valid
as the second argument to the iswctype function; otherwise, it returns zero.
-
+
-7.29.3 Wide character case mapping utilities
-
+
The header <wctype.h> declares several functions useful for mapping wide characters.
-7.29.3.1 Wide character case mapping functions
+
+
#include <wctype.h>
- wint_t towlower(wint_t wc);
+ wint_t towlower(wint_t wc);
+
+
The towlower function converts an uppercase letter to a corresponding lowercase letter.
+
If the argument is a wide character for which iswupper is true and there are one or
more corresponding wide characters, as specified by the current locale, for which
iswlower is true, the towlower function returns one of the corresponding wide
characters (always the same one for any given locale); otherwise, the argument is
returned unchanged.
-7.29.3.1.2 The towupper function
+
+
#include <wctype.h>
- wint_t towupper(wint_t wc);
+ wint_t towupper(wint_t wc);
+
+
The towupper function converts a lowercase letter to a corresponding uppercase letter.
+
If the argument is a wide character for which iswlower is true and there are one or
more corresponding wide characters, as specified by the current locale, for which
iswupper is true, the towupper function returns one of the corresponding wide
characters (always the same one for any given locale); otherwise, the argument is
returned unchanged.
-7.29.3.2 Extensible wide character case mapping functions
-
+
The functions wctrans and towctrans provide extensible wide character mapping as
well as case mapping equivalent to that performed by the functions described in the
previous subclause (7.29.3.1).
-
+
-7.29.3.2.1 The towctrans function
+
+
#include <wctype.h>
- wint_t towctrans(wint_t wc, wctrans_t desc);
+ wint_t towctrans(wint_t wc, wctrans_t desc);
+
+
The towctrans function maps the wide character wc using the mapping described by desc. The current setting of the LC_CTYPE category shall be the same as during the call to wctrans that returned the value desc. -
+
Each of the following expressions behaves the same as the call to the wide character case mapping function (7.29.3.1) in the comment that follows the expression:
towctrans(wc, wctrans("tolower")) // towlower(wc)
- towctrans(wc, wctrans("toupper")) // towupper(wc)
+ towctrans(wc, wctrans("toupper")) // towupper(wc)
+
+
The towctrans function returns the mapped value of wc using the mapping described
by desc. If desc is zero, the towctrans function returns the value of wc.
-7.29.3.2.2 The wctrans function
+
+
#include <wctype.h>
- wctrans_t wctrans(const char *property);
+ wctrans_t wctrans(const char *property);
+
+
The wctrans function constructs a value with type wctrans_t that describes a mapping between wide characters identified by the string argument property. -
+
The strings listed in the description of the towctrans function shall be valid in all locales as property arguments to the wctrans function.
+
If property identifies a valid mapping of wide characters according to the LC_CTYPE
category of the current locale, the wctrans function returns a nonzero value that is valid
as the second argument to the towctrans function; otherwise, it returns zero.
-
+
-7.30 Future library directions
-
+
The following names are grouped under individual headers for convenience. All external
names described below are reserved no matter what headers are included by the program.
-7.30.1 Complex arithmetic
-
+
The function names
cerf cexpm1 clog2
cerfc clog10 clgamma
- cexp2 clog1p ctgamma
+ cexp2 clog1p ctgamma
+
and the same names suffixed with f or l may be added to the declarations in the
<complex.h> header.
-+
Function names that begin with either is or to, and a lowercase letter may be added to
the declarations in the <ctype.h> header.
-7.30.3 Errors
-
+
Macros that begin with E and a digit or E and an uppercase letter may be added to the
declarations in the <errno.h> header.
-7.30.4 Format conversion of integer types
-
+
Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
added to the macros defined in the <inttypes.h> header.
-7.30.5 Localization
-
+
Macros that begin with LC_ and an uppercase letter may be added to the definitions in
the <locale.h> header.
-7.30.6 Signal handling
-
+
Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
letter may be added to the definitions in the <signal.h> header.
-7.30.7 Boolean type and values
-
+
The ability to undefine and perhaps then redefine the macros bool, true, and false is
an obsolescent feature.
-7.30.8 Integer types
-
+
Typedef names beginning with int or uint and ending with _t may be added to the
types defined in the <stdint.h> header. Macro names beginning with INT or UINT
and ending with _MAX, _MIN, or _C may be added to the macros defined in the
<stdint.h> header.
-
+
-7.30.9 Input/output
-
+
Lowercase letters may be added to the conversion specifiers and length modifiers in fprintf and fscanf. Other characters may be used in extensions. -
+
The use of ungetc on a binary stream where the file position indicator is zero prior to *
the call is an obsolescent feature.
-7.30.10 General utilities
-
+
Function names that begin with str and a lowercase letter may be added to the
declarations in the <stdlib.h> header.
-7.30.11 String handling
-
+
Function names that begin with str, mem, or wcs and a lowercase letter may be added
to the declarations in the <string.h> header.
-7.30.12 Extended multibyte and wide character utilities
-
+
Function names that begin with wcs and a lowercase letter may be added to the declarations in the <wchar.h> header. -
+
Lowercase letters may be added to the conversion specifiers and length modifiers in
fwprintf and fwscanf. Other characters may be used in extensions.
-7.30.13 Wide character classification and mapping utilities
+
+
Function names that begin with is or to and a lowercase letter may be added to the
declarations in the <wctype.h> header.
-
+
-Annex A
-
+
(informative)
- Language syntax summary
+ Language syntax summary
+
+
NOTE The notation is described in 6.1.
-A.1 Lexical grammar
+
keyword
identifier
constant
string-literal
- punctuator
+ punctuator
+
(6.4) preprocessing-token:
-
+
header-name
identifier
@@ -21900,9 +22974,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character-constant
string-literal
punctuator
- each non-white-space character that cannot be one of the above
+ each non-white-space character that cannot be one of the above
+
-
alignof goto union
@@ -21919,202 +22994,245 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
enum static _Noreturn
extern struct _Static_assert
float switch _Thread_local
- for typedef
+ for typedef
+
-
identifier-nondigit
identifier identifier-nondigit
- identifier digit
+ identifier digit
+
(6.4.2.1) identifier-nondigit:
nondigit
universal-character-name
- other implementation-defined characters
+ other implementation-defined characters
+
(6.4.2.1) nondigit: one of
_ a b c d e f g h i j k l m
n o p q r s t u v w x y z
A B C D E F G H I J K L M
- N O P Q R S T U V W X Y Z
+ N O P Q R S T U V W X Y Z
+
(6.4.2.1) digit: one of
-
+
- 0 1 2 3 4 5 6 7 8 9+ 0 1 2 3 4 5 6 7 8 9 + -
\u hex-quad
- \U hex-quad hex-quad
+ \U hex-quad hex-quad
+
(6.4.3) hex-quad:
hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
+ hexadecimal-digit hexadecimal-digit
+
-
integer-constant
floating-constant
enumeration-constant
- character-constant
+ character-constant
+
(6.4.4.1) integer-constant:
- decimal-constant integer-suffixopt - octal-constant integer-suffixopt - hexadecimal-constant integer-suffixopt+ decimal-constant integer-suffixopt + octal-constant integer-suffixopt + hexadecimal-constant integer-suffixopt + (6.4.4.1) decimal-constant:
nonzero-digit
- decimal-constant digit
+ decimal-constant digit
+
(6.4.4.1) octal-constant:
0
- octal-constant octal-digit
+ octal-constant octal-digit
+
(6.4.4.1) hexadecimal-constant:
hexadecimal-prefix hexadecimal-digit
- hexadecimal-constant hexadecimal-digit
+ hexadecimal-constant hexadecimal-digit
+
(6.4.4.1) hexadecimal-prefix: one of
- 0x 0X+ 0x 0X + (6.4.4.1) nonzero-digit: one of
- 1 2 3 4 5 6 7 8 9+ 1 2 3 4 5 6 7 8 9 + (6.4.4.1) octal-digit: one of - +
- 0 1 2 3 4 5 6 7+ 0 1 2 3 4 5 6 7 + (6.4.4.1) hexadecimal-digit: one of
0 1 2 3 4 5 6 7 8 9
a b c d e f
- A B C D E F
+ A B C D E F
+
(6.4.4.1) integer-suffix:
- unsigned-suffix long-suffixopt
+ unsigned-suffix long-suffixopt
unsigned-suffix long-long-suffix
- long-suffix unsigned-suffixopt
- long-long-suffix unsigned-suffixopt
+ long-suffix unsigned-suffixopt
+ long-long-suffix unsigned-suffixopt
+
(6.4.4.1) unsigned-suffix: one of
- u U+ u U + (6.4.4.1) long-suffix: one of
- l L+ l L + (6.4.4.1) long-long-suffix: one of
- ll LL+ ll LL + (6.4.4.2) floating-constant:
decimal-floating-constant
- hexadecimal-floating-constant
+ hexadecimal-floating-constant
+
(6.4.4.2) decimal-floating-constant:
- fractional-constant exponent-partopt floating-suffixopt - digit-sequence exponent-part floating-suffixopt+ fractional-constant exponent-partopt floating-suffixopt + digit-sequence exponent-part floating-suffixopt + (6.4.4.2) hexadecimal-floating-constant:
hexadecimal-prefix hexadecimal-fractional-constant
- binary-exponent-part floating-suffixopt
+ binary-exponent-part floating-suffixopt
hexadecimal-prefix hexadecimal-digit-sequence
- binary-exponent-part floating-suffixopt
+ binary-exponent-part floating-suffixopt
+
(6.4.4.2) fractional-constant:
- digit-sequenceopt . digit-sequence - digit-sequence .+ digit-sequenceopt . digit-sequence + digit-sequence . + (6.4.4.2) exponent-part:
- e signopt digit-sequence - E signopt digit-sequence+ e signopt digit-sequence + E signopt digit-sequence + (6.4.4.2) sign: one of - +
- + -+ + - + (6.4.4.2) digit-sequence:
digit
- digit-sequence digit
+ digit-sequence digit
+
(6.4.4.2) hexadecimal-fractional-constant:
- hexadecimal-digit-sequenceopt .
+ hexadecimal-digit-sequenceopt .
hexadecimal-digit-sequence
- hexadecimal-digit-sequence .
+ hexadecimal-digit-sequence .
+
(6.4.4.2) binary-exponent-part:
- p signopt digit-sequence - P signopt digit-sequence+ p signopt digit-sequence + P signopt digit-sequence + (6.4.4.2) hexadecimal-digit-sequence:
hexadecimal-digit
- hexadecimal-digit-sequence hexadecimal-digit
+ hexadecimal-digit-sequence hexadecimal-digit
+
(6.4.4.2) floating-suffix: one of
- f l F L+ f l F L + (6.4.4.3) enumeration-constant:
- identifier+ identifier + (6.4.4.4) character-constant:
' c-char-sequence '
L' c-char-sequence '
u' c-char-sequence '
- U' c-char-sequence '
+ U' c-char-sequence '
+
(6.4.4.4) c-char-sequence:
c-char
- c-char-sequence c-char
+ c-char-sequence c-char
+
(6.4.4.4) c-char:
any member of the source character set except
the single-quote ', backslash \, or new-line character
- escape-sequence
+ escape-sequence
+
(6.4.4.4) escape-sequence:
-
+
simple-escape-sequence
octal-escape-sequence
hexadecimal-escape-sequence
- universal-character-name
+ universal-character-name
+
(6.4.4.4) simple-escape-sequence: one of
\' \" \? \\
- \a \b \f \n \r \t \v
+ \a \b \f \n \r \t \v
+
(6.4.4.4) octal-escape-sequence:
\ octal-digit
\ octal-digit octal-digit
- \ octal-digit octal-digit octal-digit
+ \ octal-digit octal-digit octal-digit
+
(6.4.4.4) hexadecimal-escape-sequence:
\x hexadecimal-digit
- hexadecimal-escape-sequence hexadecimal-digit
+ hexadecimal-escape-sequence hexadecimal-digit
+
-- encoding-prefixopt " s-char-sequenceopt "+ encoding-prefixopt " s-char-sequenceopt " + (6.4.5) encoding-prefix:
u8
u
U
- L
+ L
+
(6.4.5) s-char-sequence:
s-char
- s-char-sequence s-char
+ s-char-sequence s-char
+
(6.4.5) s-char:
any member of the source character set except
the double-quote ", backslash \, or new-line character
- escape-sequence
+ escape-sequence
+
-
[ ] ( ) { } . ->
++ -- & * + - ~ !
@@ -22122,33 +23240,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
? : ; ...
= *= /= %= += -= <<= >>= &= ^= |=
, # ##
- <: :> <% %> %: %:%:
+ <: :> <% %> %: %:%:
+
-
< h-char-sequence >
- " q-char-sequence "
+ " q-char-sequence "
+
(6.4.7) h-char-sequence:
h-char
- h-char-sequence h-char
+ h-char-sequence h-char
+
(6.4.7) h-char:
any member of the source character set except
- the new-line character and >
+ the new-line character and >
+
(6.4.7) q-char-sequence:
q-char
- q-char-sequence q-char
+ q-char-sequence q-char
+
(6.4.7) q-char:
any member of the source character set except
- the new-line character and "
+ the new-line character and "
+
-
digit
. digit
@@ -22158,46 +23282,53 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pp-number E sign
pp-number p sign
pp-number P sign
- pp-number .
+ pp-number .
+
-
identifier
constant
string-literal
( expression )
- generic-selection
+ generic-selection
+
(6.5.1.1) generic-selection:
- _Generic ( assignment-expression , generic-assoc-list )+ _Generic ( assignment-expression , generic-assoc-list ) + (6.5.1.1) generic-assoc-list:
generic-association
- generic-assoc-list , generic-association
+ generic-assoc-list , generic-association
+
(6.5.1.1) generic-association:
type-name : assignment-expression
- default : assignment-expression
+ default : assignment-expression
+
(6.5.2) postfix-expression:
primary-expression
postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
+ postfix-expression ( argument-expression-listopt )
postfix-expression . identifier
postfix-expression -> identifier
postfix-expression ++
postfix-expression --
( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
+ ( type-name ) { initializer-list , }
+
(6.5.2) argument-expression-list:
assignment-expression
- argument-expression-list , assignment-expression
+ argument-expression-list , assignment-expression
+
(6.5.3) unary-expression:
-
+
postfix-expression
++ unary-expression
@@ -22205,103 +23336,125 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
unary-operator cast-expression
sizeof unary-expression
sizeof ( type-name )
- alignof ( type-name )
+ alignof ( type-name )
+
(6.5.3) unary-operator: one of
- & * + - ~ !+ & * + - ~ ! + (6.5.4) cast-expression:
unary-expression
- ( type-name ) cast-expression
+ ( type-name ) cast-expression
+
(6.5.5) multiplicative-expression:
cast-expression
multiplicative-expression * cast-expression
multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
+ multiplicative-expression % cast-expression
+
(6.5.6) additive-expression:
multiplicative-expression
additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
+ additive-expression - multiplicative-expression
+
(6.5.7) shift-expression:
additive-expression
shift-expression << additive-expression
- shift-expression >> additive-expression
+ shift-expression >> additive-expression
+
(6.5.8) relational-expression:
shift-expression
relational-expression < shift-expression
relational-expression > shift-expression
relational-expression <= shift-expression
- relational-expression >= shift-expression
+ relational-expression >= shift-expression
+
(6.5.9) equality-expression:
relational-expression
equality-expression == relational-expression
- equality-expression != relational-expression
+ equality-expression != relational-expression
+
(6.5.10) AND-expression:
equality-expression
- AND-expression & equality-expression
+ AND-expression & equality-expression
+
(6.5.11) exclusive-OR-expression:
-
+
AND-expression
- exclusive-OR-expression ^ AND-expression
+ exclusive-OR-expression ^ AND-expression
+
(6.5.12) inclusive-OR-expression:
exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
+ inclusive-OR-expression | exclusive-OR-expression
+
(6.5.13) logical-AND-expression:
inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
+ logical-AND-expression && inclusive-OR-expression
+
(6.5.14) logical-OR-expression:
logical-AND-expression
- logical-OR-expression || logical-AND-expression
+ logical-OR-expression || logical-AND-expression
+
(6.5.15) conditional-expression:
logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
+ logical-OR-expression ? expression : conditional-expression
+
(6.5.16) assignment-expression:
conditional-expression
- unary-expression assignment-operator assignment-expression
+ unary-expression assignment-operator assignment-expression
+
(6.5.16) assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=+ = *= /= %= += -= <<= >>= &= ^= |= + (6.5.17) expression:
assignment-expression
- expression , assignment-expression
+ expression , assignment-expression
+
(6.6) constant-expression:
- conditional-expression+ conditional-expression + -
- declaration-specifiers init-declarator-listopt ; - static_assert-declaration+ declaration-specifiers init-declarator-listopt ; + static_assert-declaration + (6.7) declaration-specifiers:
- storage-class-specifier declaration-specifiersopt - type-specifier declaration-specifiersopt - type-qualifier declaration-specifiersopt - function-specifier declaration-specifiersopt - alignment-specifier declaration-specifiersopt+ storage-class-specifier declaration-specifiersopt + type-specifier declaration-specifiersopt + type-qualifier declaration-specifiersopt + function-specifier declaration-specifiersopt + alignment-specifier declaration-specifiersopt + (6.7) init-declarator-list: - +
init-declarator
- init-declarator-list , init-declarator
+ init-declarator-list , init-declarator
+
(6.7) init-declarator:
declarator
- declarator = initializer
+ declarator = initializer
+
(6.7.1) storage-class-specifier:
typedef
@@ -22309,7 +23462,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
static
_Thread_local
auto
- register
+ register
+
(6.7.2) type-specifier:
void
@@ -22326,152 +23480,185 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atomic-type-specifier
struct-or-union-specifier
enum-specifier
- typedef-name
+ typedef-name
+
(6.7.2.1) struct-or-union-specifier:
- struct-or-union identifieropt { struct-declaration-list }
- struct-or-union identifier
+ struct-or-union identifieropt { struct-declaration-list }
+ struct-or-union identifier
+
(6.7.2.1) struct-or-union:
struct
- union
+ union
+
(6.7.2.1) struct-declaration-list:
struct-declaration
- struct-declaration-list struct-declaration
+ struct-declaration-list struct-declaration
+
(6.7.2.1) struct-declaration:
-
+
- specifier-qualifier-list struct-declarator-listopt ; - static_assert-declaration+ specifier-qualifier-list struct-declarator-listopt ; + static_assert-declaration + (6.7.2.1) specifier-qualifier-list:
- type-specifier specifier-qualifier-listopt - type-qualifier specifier-qualifier-listopt+ type-specifier specifier-qualifier-listopt + type-qualifier specifier-qualifier-listopt + (6.7.2.1) struct-declarator-list:
struct-declarator
- struct-declarator-list , struct-declarator
+ struct-declarator-list , struct-declarator
+
(6.7.2.1) struct-declarator:
declarator
- declaratoropt : constant-expression
+ declaratoropt : constant-expression
+
(6.7.2.2) enum-specifier:
- enum identifieropt { enumerator-list }
- enum identifieropt { enumerator-list , }
- enum identifier
+ enum identifieropt { enumerator-list }
+ enum identifieropt { enumerator-list , }
+ enum identifier
+
(6.7.2.2) enumerator-list:
enumerator
- enumerator-list , enumerator
+ enumerator-list , enumerator
+
(6.7.2.2) enumerator:
enumeration-constant
- enumeration-constant = constant-expression
+ enumeration-constant = constant-expression
+
(6.7.2.4) atomic-type-specifier:
- _Atomic ( type-name )+ _Atomic ( type-name ) + (6.7.3) type-qualifier:
const
restrict
volatile
- _Atomic
+ _Atomic
+
(6.7.4) function-specifier:
inline
- _Noreturn
+ _Noreturn
+
(6.7.5) alignment-specifier:
_Alignas ( type-name )
- _Alignas ( constant-expression )
+ _Alignas ( constant-expression )
+
(6.7.6) declarator:
-
+
- pointeropt direct-declarator+ pointeropt direct-declarator + (6.7.6) direct-declarator:
identifier
( declarator )
- direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
- direct-declarator [ static type-qualifier-listopt assignment-expression ]
+ direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
+ direct-declarator [ static type-qualifier-listopt assignment-expression ]
direct-declarator [ type-qualifier-list static assignment-expression ]
- direct-declarator [ type-qualifier-listopt * ]
+ direct-declarator [ type-qualifier-listopt * ]
direct-declarator ( parameter-type-list )
- direct-declarator ( identifier-listopt )
+ direct-declarator ( identifier-listopt )
+
(6.7.6) pointer:
- * type-qualifier-listopt - * type-qualifier-listopt pointer+ * type-qualifier-listopt + * type-qualifier-listopt pointer + (6.7.6) type-qualifier-list:
type-qualifier
- type-qualifier-list type-qualifier
+ type-qualifier-list type-qualifier
+
(6.7.6) parameter-type-list:
parameter-list
- parameter-list , ...
+ parameter-list , ...
+
(6.7.6) parameter-list:
parameter-declaration
- parameter-list , parameter-declaration
+ parameter-list , parameter-declaration
+
(6.7.6) parameter-declaration:
declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
+ declaration-specifiers abstract-declaratoropt
+
(6.7.6) identifier-list:
identifier
- identifier-list , identifier
+ identifier-list , identifier
+
(6.7.7) type-name:
- specifier-qualifier-list abstract-declaratoropt+ specifier-qualifier-list abstract-declaratoropt + (6.7.7) abstract-declarator: - +
pointer
- pointeropt direct-abstract-declarator
+ pointeropt direct-abstract-declarator
+
(6.7.7) direct-abstract-declarator:
( abstract-declarator )
- direct-abstract-declaratoropt [ type-qualifier-listopt
- assignment-expressionopt ]
- direct-abstract-declaratoropt [ static type-qualifier-listopt
+ direct-abstract-declaratoropt [ type-qualifier-listopt
+ assignment-expressionopt ]
+ direct-abstract-declaratoropt [ static type-qualifier-listopt
assignment-expression ]
- direct-abstract-declaratoropt [ type-qualifier-list static
+ direct-abstract-declaratoropt [ type-qualifier-list static
assignment-expression ]
- direct-abstract-declaratoropt [ * ]
- direct-abstract-declaratoropt ( parameter-type-listopt )
+ direct-abstract-declaratoropt [ * ]
+ direct-abstract-declaratoropt ( parameter-type-listopt )
+
(6.7.8) typedef-name:
- identifier+ identifier + (6.7.9) initializer:
assignment-expression
{ initializer-list }
- { initializer-list , }
+ { initializer-list , }
+
(6.7.9) initializer-list:
- designationopt initializer - initializer-list , designationopt initializer+ designationopt initializer + initializer-list , designationopt initializer + (6.7.9) designation:
- designator-list =+ designator-list = + (6.7.9) designator-list:
designator
- designator-list designator
+ designator-list designator
+
(6.7.9) designator:
[ constant-expression ]
- . identifier
+ . identifier
+
(6.7.10) static_assert-declaration:
-
+
- _Static_assert ( constant-expression , string-literal ) ;+ _Static_assert ( constant-expression , string-literal ) ; + -
labeled-statement
@@ -22479,147 +23666,178 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expression-statement
selection-statement
iteration-statement
- jump-statement
+ jump-statement
+
(6.8.1) labeled-statement:
identifier : statement
case constant-expression : statement
- default : statement
+ default : statement
+
(6.8.2) compound-statement:
- { block-item-listopt }
+ { block-item-listopt }
+
(6.8.2) block-item-list:
block-item
- block-item-list block-item
+ block-item-list block-item
+
(6.8.2) block-item:
declaration
- statement
+ statement
+
(6.8.3) expression-statement:
- expressionopt ;+ expressionopt ; + (6.8.4) selection-statement:
if ( expression ) statement
if ( expression ) statement else statement
- switch ( expression ) statement
+ switch ( expression ) statement
+
(6.8.5) iteration-statement:
while ( expression ) statement
do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
+ for ( expressionopt ; expressionopt ; expressionopt ) statement
+ for ( declaration expressionopt ; expressionopt ) statement
+
(6.8.6) jump-statement:
-
+
goto identifier ;
continue ;
break ;
- return expressionopt ;
+ return expressionopt ;
+
-
external-declaration
- translation-unit external-declaration
+ translation-unit external-declaration
+
(6.9) external-declaration:
function-definition
- declaration
+ declaration
+
(6.9.1) function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement+ declaration-specifiers declarator declaration-listopt compound-statement + (6.9.1) declaration-list:
declaration
- declaration-list declaration
+ declaration-list declaration
+
-- groupopt+ groupopt + (6.10) group:
group-part
- group group-part
+ group group-part
+
(6.10) group-part:
if-section
control-line
text-line
- # non-directive
+ # non-directive
+
(6.10) if-section:
- if-group elif-groupsopt else-groupopt endif-line+ if-group elif-groupsopt else-groupopt endif-line + (6.10) if-group:
- # if constant-expression new-line groupopt - # ifdef identifier new-line groupopt - # ifndef identifier new-line groupopt+ # if constant-expression new-line groupopt + # ifdef identifier new-line groupopt + # ifndef identifier new-line groupopt + (6.10) elif-groups:
elif-group
- elif-groups elif-group
+ elif-groups elif-group
+
(6.10) elif-group:
-
+
- # elif constant-expression new-line groupopt+ # elif constant-expression new-line groupopt + (6.10) else-group:
- # else new-line groupopt+ # else new-line groupopt + (6.10) endif-line:
- # endif new-line+ # endif new-line + (6.10) control-line:
# include pp-tokens new-line
# define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
+ # define identifier lparen identifier-listopt )
replacement-list new-line
# define identifier lparen ... ) replacement-list new-line
# define identifier lparen identifier-list , ... )
replacement-list new-line
# undef identifier new-line
# line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
+ # error pp-tokensopt new-line
+ # pragma pp-tokensopt new-line
+ # new-line
+
(6.10) text-line:
- pp-tokensopt new-line+ pp-tokensopt new-line + (6.10) non-directive:
- pp-tokens new-line+ pp-tokens new-line + (6.10) lparen:
- a ( character not immediately preceded by white-space+ a ( character not immediately preceded by white-space + (6.10) replacement-list:
- pp-tokensopt+ pp-tokensopt + (6.10) pp-tokens:
preprocessing-token
- pp-tokens preprocessing-token
+ pp-tokens preprocessing-token
+
(6.10) new-line:
-
+
- the new-line character+ the new-line character + -
(informative)
- Library summary
+ Library summary
+
-
NDEBUG
static_assert
- void assert(scalar expression);
+ void assert(scalar expression);
+
-
__STDC_NO_COMPLEX__ imaginary
complex _Imaginary_I
@@ -22694,9 +23912,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
long double complex cprojl(long double complex z);
double creal(double complex z);
float crealf(float complex z);
- long double creall(long double complex z);
+ long double creall(long double complex z);
+
-
int isalnum(int c);
int isalpha(int c);
@@ -22711,16 +23930,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int isupper(int c);
int isxdigit(int c);
int tolower(int c);
- int toupper(int c);
+ int toupper(int c);
+
-
EDOM EILSEQ ERANGE errno
__STDC_WANT_LIB_EXT1__
- errno_t
+ errno_t
+
-
fenv_t FE_OVERFLOW FE_TOWARDZERO
fexcept_t FE_UNDERFLOW FE_UPWARD
@@ -22739,9 +23960,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int fegetenv(fenv_t *envp);
int feholdexcept(fenv_t *envp);
int fesetenv(const fenv_t *envp);
- int feupdateenv(const fenv_t *envp);
+ int feupdateenv(const fenv_t *envp);
+
-
FLT_ROUNDS DBL_DIG FLT_MAX
FLT_EVAL_METHOD LDBL_DIG DBL_MAX
@@ -22756,10 +23978,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
DBL_DECIMAL_DIG LDBL_MAX_EXP DBL_TRUE_MIN
LDBL_DECIMAL_DIG FLT_MAX_10_EXP LDBL_TRUE_MIN
DECIMAL_DIG DBL_MAX_10_EXP
- FLT_DIG LDBL_MAX_10_EXP
+ FLT_DIG LDBL_MAX_10_EXP
+
-
imaxdiv_t
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
@@ -22782,35 +24005,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
intmax_t wcstoimax(const wchar_t * restrict nptr,
wchar_t ** restrict endptr, int base);
uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
+ wchar_t ** restrict endptr, int base);
+
-
and bitor not_eq xor
and_eq compl or xor_eq
- bitand not or_eq
+ bitand not or_eq
+
-
CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
- CHAR_MIN USHRT_MAX LONG_MAX
+ CHAR_MIN USHRT_MAX LONG_MAX
+
-
struct lconv LC_ALL LC_CTYPE LC_NUMERIC
NULL LC_COLLATE LC_MONETARY LC_TIME
char *setlocale(int category, const char *locale);
- struct lconv *localeconv(void);
+ struct lconv *localeconv(void);
+
-
float_t FP_INFINITE FP_FAST_FMAL
double_t FP_NAN FP_ILOGB0
@@ -23004,39 +24231,44 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int isless(real-floating x, real-floating y);
int islessequal(real-floating x, real-floating y);
int islessgreater(real-floating x, real-floating y);
- int isunordered(real-floating x, real-floating y);
+ int isunordered(real-floating x, real-floating y);
+
-
jmp_buf
int setjmp(jmp_buf env);
- _Noreturn void longjmp(jmp_buf env, int val);
+ _Noreturn void longjmp(jmp_buf env, int val);
+
-
sig_atomic_t SIG_IGN SIGILL SIGTERM
SIG_DFL SIGABRT SIGINT
SIG_ERR SIGFPE SIGSEGV
void (*signal(int sig, void (*func)(int)))(int);
- int raise(int sig);
+ int raise(int sig);
+
-
alignas
- __alignas_is_defined
+ __alignas_is_defined
+
-
va_list
type va_arg(va_list ap, type);
void va_copy(va_list dest, va_list src);
void va_end(va_list ap);
- void va_start(va_list ap, parmN);
+ void va_start(va_list ap, parmN);
+
-
ATOMIC_CHAR_LOCK_FREE atomic_uint
ATOMIC_CHAR16_T_LOCK_FREE atomic_long
@@ -23100,25 +24332,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
volatile atomic_flag *object, memory_order order);
void atomic_flag_clear(volatile atomic_flag *object);
void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
+ volatile atomic_flag *object, memory_order order);
+
-
bool
true
false
- __bool_true_false_are_defined
+ __bool_true_false_are_defined
+
-
ptrdiff_t max_align_t NULL
size_t wchar_t
offsetof(type, member-designator)
__STDC_WANT_LIB_EXT1__
- rsize_t
+ rsize_t
+
-
intN_t INT_LEASTN_MIN PTRDIFF_MAX
uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
@@ -23134,12 +24369,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
INTN_MAX UINTMAX_MAX UINTMAX_C(value)
UINTN_MAX PTRDIFF_MIN
__STDC_WANT_LIB_EXT1__
- RSIZE_MAX
+ RSIZE_MAX
+
-
size_t _IOLBF FILENAME_MAX TMP_MAX
FILE _IONBF L_tmpnam stderr
@@ -23256,11 +24492,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int vsscanf_s(const char * restrict s,
const char * restrict format,
va_list arg);
- char *gets_s(char *s, rsize_t n);
+ char *gets_s(char *s, rsize_t n);
+
-
size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
wchar_t lldiv_t EXIT_SUCCESS
@@ -23355,11 +24592,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
const char * restrict src, rsize_t len);
errno_t wcstombs_s(size_t * restrict retval,
char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
+ const wchar_t * restrict src, rsize_t len);
+
-
size_t
NULL
@@ -23421,9 +24659,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
errno_t strerror_s(char *s, rsize_t maxsize,
errno_t errnum);
size_t strerrorlen_s(errno_t errnum);
- size_t strnlen_s(const char *s, size_t maxsize);
+ size_t strnlen_s(const char *s, size_t maxsize);
+
-
acos sqrt fmod nextafter
asin fabs frexp nexttoward
@@ -23439,10 +24678,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
tanh floor logb cimag
exp fma lrint conj
log fmax lround cproj
- pow fmin nearbyint creal
+ pow fmin nearbyint creal
+
-
ONCE_FLAG_INIT mtx_plain
TSS_DTOR_ITERATIONS mtx_recursive
@@ -23481,10 +24721,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
void tss_delete(tss_t key);
void *tss_get(tss_t key);
int tss_set(tss_t key, void *val);
- int xtime_get(xtime *xt, int base);
+ int xtime_get(xtime *xt, int base);
+
-
NULL size_t time_t
CLOCKS_PER_SEC clock_t struct tm
@@ -23510,9 +24751,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
struct tm *gmtime_s(const time_t * restrict timer,
struct tm * restrict result);
struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
+ struct tm * restrict result);
+
-
mbstate_t size_t char16_t char32_t
size_t mbrtoc16(char16_t * restrict pc16,
@@ -23524,14 +24766,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
const char * restrict s, size_t n,
mbstate_t * restrict ps);
size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
-
wchar_t wint_t WCHAR_MAX
size_t struct tm WCHAR_MIN
@@ -23707,10 +24950,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
errno_t wcsrtombs_s(size_t * restrict retval,
char * restrict dst, rsize_t dstmax,
const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
-
wint_t wctrans_t wctype_t WEOF
int iswalnum(wint_t wc);
@@ -23730,13 +24974,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
wint_t towlower(wint_t wc);
wint_t towupper(wint_t wc);
wint_t towctrans(wint_t wc, wctrans_t desc);
- wctrans_t wctrans(const char *property);
+ wctrans_t wctrans(const char *property);
+
-+
(informative)
- Sequence points
+ Sequence points
+
+The following are the sequence points described in 5.1.2.3:
+
(normative)
- Universal character names for identifiers
+ Universal character names for identifiers
+
+
This clause lists the hexadecimal code values that are valid in universal character names
in identifiers.
-D.1 Ranges of characters allowed
-
+
00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6, 00D8-00F6, 00F8-00FF -
+
0100-167F, 1681-180D, 180F-1FFF -
+
200B-200D, 202A-202E, 203F-2040, 2054, 2060-206F -
+
2070-218F, 2460-24FF, 2776-2793, 2C00-2DFF, 2E80-2FFF -
+
3004-3007, 3021-302F, 3031-303F -
+
3040-D7FF -
+
F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD -
+
10000-1FFFD, 20000-2FFFD, 30000-3FFFD, 40000-4FFFD, 50000-5FFFD,
60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD,
B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
-D.2 Ranges of characters disallowed initially
-
+
0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F
-
+
-Annex E
-
+
(informative)
- Implementation limits
+ Implementation limits
+
+The contents of the header <limits.h> are given below, in alphabetical order. The minimum magnitudes shown shall be replaced by implementation-defined magnitudes with the same sign. The values shall all be constant expressions suitable for use in #if preprocessing directives. The components are described further in 5.2.4.2.1. -
#define CHAR_BIT 8
#define CHAR_MAX UCHAR_MAX or SCHAR_MAX
@@ -23825,23 +25072,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#define USHRT_MAX 65535
#define UINT_MAX 65535
#define ULONG_MAX 4294967295
- #define ULLONG_MAX 18446744073709551615
+ #define ULLONG_MAX 18446744073709551615
+
+The contents of the header <float.h> are given below. All integer values, except FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing directives; all floating values shall be constant expressions. The components are described further in 5.2.4.2.2. -
+
The values given in the following list shall be replaced by implementation-defined expressions: -
#define FLT_EVAL_METHOD
- #define FLT_ROUNDS
+ #define FLT_ROUNDS
+
+The values given in the following list shall be replaced by implementation-defined constant expressions that are greater or equal in magnitude (absolute value) to those shown, with the same sign: - -
+
#define DLB_DECIMAL_DIG 10
#define DBL_DIG 10
@@ -23865,32 +25114,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#define LDBL_MAX_10_EXP +37
#define LDBL_MAX_EXP
#define LDBL_MIN_10_EXP -37
- #define LDBL_MIN_EXP
+ #define LDBL_MIN_EXP
+
+The values given in the following list shall be replaced by implementation-defined constant expressions with values that are greater than or equal to those shown: -
#define DBL_MAX 1E+37
#define FLT_MAX 1E+37
- #define LDBL_MAX 1E+37
+ #define LDBL_MAX 1E+37
+
+The values given in the following list shall be replaced by implementation-defined constant expressions with (positive) values that are less than or equal to those shown: - +
#define DBL_EPSILON 1E-9
#define DBL_MIN 1E-37
#define FLT_EPSILON 1E-5
#define FLT_MIN 1E-37
#define LDBL_EPSILON 1E-9
- #define LDBL_MIN 1E-37
+ #define LDBL_MIN 1E-37
+
-
(normative)
- IEC 60559 floating-point arithmetic
+ IEC 60559 floating-point arithmetic
+
-+
This annex specifies C language support for the IEC 60559 floating-point standard. The
IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
microprocessor systems, second edition (IEC 60559:1989), previously designated
@@ -23910,8 +25164,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
specifications.
-F.2 Types
-
+
The C floating types match the IEC 60559 formats as follows:
+ +
The long double type should match an IEC 60559 extended format.
+
This specification does not define the behavior of signaling NaNs.346) It generally uses
the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
functions in <math.h> provide designations for IEC 60559 NaNs and infinities.
@@ -23949,8 +25203,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
sufficient for closure of the arithmetic.
-F.3 Operators and functions
-
+
C operators and functions provide IEC 60559 required and recommended facilities as listed below.
+
If the integer type is _Bool, 6.3.1.2 applies and no floating-point exceptions are raised
(even for NaN). Otherwise, if the floating value is infinite or NaN or if the integral part
of the floating value exceeds the range of the integer type, then the ''invalid'' floating-
@@ -24049,11 +25303,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
<math.h>.
-F.5 Binary-decimal conversion
-
+
Conversion from the widest supported IEC 60559 format to decimal with DECIMAL_DIG digits and back is the identity function.348) -
+
Conversions involving IEC 60559 formats follow all pertinent recommended practice. In particular, conversion between any supported IEC 60559 format and decimal with DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current @@ -24062,8 +25316,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
Functions such as strtod that convert character sequences to floating types honor the
rounding direction. Hence, if the rounding direction might be upward or downward, the
implementation cannot convert a minus-signed sequence by negating the converted
@@ -24076,7 +25330,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
DBL_DIG are 18 and 15, respectively, for these formats.)
-F.6 The return statement
+
349) Assignment removes any extra range and precision.
-F.7 Contracted expressions
-
+
A contracted expression is correctly rounded (once) and treats infinities, NaNs, signed zeros, subnormals, and the rounding directions in a manner consistent with the basic arithmetic operations covered by IEC 60559. - Recommended practice -
+
A contracted expression should raise floating-point exceptions in a manner generally
consistent with the basic arithmetic operations. *
-F.8 Floating-point environment
-
+
The floating-point environment defined in <fenv.h> includes the IEC 60559 floating- point exception status flags and directed-rounding control modes. It includes also IEC 60559 dynamic rounding precision and trap enablement modes, if the @@ -24106,8 +25360,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
350) This specification does not require dynamic rounding precision nor trap enablement modes.
-F.8.1 Environment management
-
+
IEC 60559 requires that floating-point operations implicitly raise floating-point exception status flags, and that rounding control modes can be set explicitly to affect result values of floating-point operations. When the state for the FENV_ACCESS pragma (defined in @@ -24117,7 +25371,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
351) If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
@@ -24125,16 +25379,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
which allows certain optimizations (see F.9).
-F.8.2 Translation
-
+
During translation the IEC 60559 default modes are in effect:
+
The implementation should produce a diagnostic message for each translation-time
floating-point exception, other than ''inexact'';352) the implementation should then
proceed with the translation of the program.
@@ -24146,8 +25400,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
strtod, provide execution-time conversion of numeric strings.
-F.8.3 Execution
-
+
At program startup the floating-point environment is initialized as prescribed by IEC 60559:
+
An arithmetic constant expression of floating type, other than one in an initializer for an object that has static or thread storage duration, is evaluated (as if) during execution; thus, it is affected by any operative floating-point control modes and raises floating-point exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on'').353) -
+
EXAMPLE - -
+
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -24182,7 +25435,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
float y = 0.0/0.0; // raises an exception
double z = 0.0/0.0; // raises an exception
/* ... */
- }
+ }
+
+For the static initialization, the division is done at translation time, raising no (execution-time) floating- point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at execution time. @@ -24195,19 +25450,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. efficiency of translation-time evaluation through static initialization, such as
- const static double one_third = 1.0/3.0;+ const static double one_third = 1.0/3.0; + -
+
All computation for automatic initialization is done (as if) at execution time; thus, it is affected by any operative modes and raises floating-point exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation for initialization of objects that have static or thread storage duration is done (as if) at translation time. -
+
EXAMPLE -
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -24220,7 +25475,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
float y = 1.1e75f; // may raise exceptions
long double z = 1.1e75; // does not raise exceptions
/* ... */
- }
+ }
+
+The static initialization of v raises no (execution-time) floating-point exceptions because its computation is done at translation time. The automatic initialization of u and w require an execution-time conversion to float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations @@ -24231,7 +25488,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - + their internal representations occur at translation time in all cases. @@ -24240,35 +25497,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. For example, the automatic initialization
- double_t x = 1.1e75;+ double_t x = 1.1e75; + could be done at translation time, regardless of the expression evaluation method. -
+
Operations defined in 6.5 and functions and macros defined for the standard libraries change floating-point status flags and control modes just as indicated by their specifications (including conformance to IEC 60559). They do not change flags or modes (so as to be detectable by the user) in any other cases. -
+
If the argument to the feraiseexcept function in <fenv.h> represents IEC 60559
valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
before ''inexact''.
-F.9 Optimization
-
+
This section identifies code transformations that might subvert IEC 60559-specified
behavior, and others that do not.
-F.9.1 Global transformations
-
+
Floating-point arithmetic operations and external function calls may entail side effects which optimization shall honor, at least where the state of the FENV_ACCESS pragma is ''on''. The flags and modes in the floating-point environment may be regarded as global variables; floating-point operations (+, *, etc.) implicitly read the modes and write the flags. -
+
Concern about side effects may inhibit code motion and removal of seemingly useless code. For example, in
@@ -24279,60 +25537,72 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* ... */
for (i = 0; i < n; i++) x + 1;
/* ... */
- }
+ }
+
x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
course these optimizations are valid if the implementation can rule out the nettlesome
cases.)
-+
This specification does not require support for trap handlers that maintain information about the order or count of floating-point exceptions. Therefore, between function calls, floating-point exceptions need not be precise: the actual order and number of occurrences of floating-point exceptions (> 1) may vary from what the source code expresses. Thus, - + the preceding loop could be treated as
- if (0 < n) x + 1;+ if (0 < n) x + 1; + -
+
x/2 <-> x x 0.5 Although similar transformations involving inexact constants
generally do not yield numerically equivalent expressions, if the
constants are exact then such transformations can be made on
- IEC 60559 machines and others that round perfectly.
+ IEC 60559 machines and others that round perfectly.
+
1 x x and x/1 -> x The expressions 1 x x, x/1, and x are equivalent (on IEC 60559
- machines, among others).355)+ machines, among others).355) + x/x -> 1.0 The expressions x/x and 1.0 are not equivalent if x can be zero,
- infinite, or NaN.+ infinite, or NaN. + x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x are equivalent (on
- IEC 60559 machines, among others).+ IEC 60559 machines, among others). + x - y <-> -(y - x) The expressions x - y and -(y - x) are not equivalent because 1 - 1
- is +0 but -(1 - 1) is -0 (in the default rounding direction).356)+ is +0 but -(1 - 1) is -0 (in the default rounding direction).356) + x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if x is a NaN or
- infinite.+ infinite. + 0 x x -> 0.0 The expressions 0 x x and 0.0 are not equivalent if x is a NaN,
- infinite, or -0.+ infinite, or -0. + x+0-> x The expressions x + 0 and x are not equivalent if x is -0, because
- (-0) + (+0) yields +0 (in the default rounding direction), not -0.+ (-0) + (+0) yields +0 (in the default rounding direction), not -0. + x-0-> x (+0) - (+0) yields -0 when rounding is downward (toward -(inf)), but
+0 otherwise, and (-0) - (+0) always yields -0; so, if the state of the
FENV_ACCESS pragma is ''off'', promising default rounding, then
- the implementation can replace x - 0 by x, even if x might be zero.
+ the implementation can replace x - 0 by x, even if x might be zero.
+
-x <-> 0 - x The expressions -x and 0 - x are not equivalent if x is +0, because
-(+0) yields -0, but 0 - (+0) yields +0 (unless rounding is
- downward).
+ downward).
+
-
+
355) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
@@ -24342,16 +25612,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Examples include:
- 1/(1/ (+-) (inf)) is (+-) (inf)
+ 1/(1/ (+-) (inf)) is (+-) (inf)
+
and
- conj(csqrt(z)) is csqrt(conj(z)),
+ conj(csqrt(z)) is csqrt(conj(z)),
+
for complex z.
-F.9.3 Relational operators
-
+
x != x -> false The expression x != x is true if x is a NaN. x = x -> true The expression x = x is false if x is a NaN. x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically equal, these @@ -24361,49 +25633,55 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. transformation, which would be desirable if extra code were required to cause the ''invalid'' floating-point exception for unordered cases, could be performed provided the state of the FENV_ACCESS pragma - is ''off''. + is ''off''. + The sense of relational operators shall be maintained. This includes handling unordered cases as expressed by the source code. -
+
EXAMPLE
// calls g and raises ''invalid'' if a and b are unordered
if (a < b)
f();
else
- g();
+ g();
+
is not equivalent to
// calls f and raises ''invalid'' if a and b are unordered
if (a >= b)
g();
else
- f();
+ f();
+
nor to
// calls f without raising ''invalid'' if a and b are unordered
if (isgreaterequal(a,b))
g();
else
- f();
+ f();
+
nor, unless the state of the FENV_ACCESS pragma is ''off'', to
// calls g without raising ''invalid'' if a and b are unordered
if (isless(a,b))
f();
else
- g();
+ g();
+
but is equivalent to
-
+
if (!(a < b))
g();
else
- f();
+ f();
+
-+
The implementation shall honor floating-point exceptions raised by execution-time constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See F.8.4 and F.8.5.) An operation on constants that raises no floating-point exception can be @@ -24417,57 +25695,57 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
357) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
-F.10 Mathematics
-
+
This subclause contains specifications of <math.h> facilities that are particularly suited for IEC 60559 implementations. -
+
The Standard C macro HUGE_VAL and its float and long double analogs, HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive infinities. -
+
Special cases for functions in <math.h> are covered directly or indirectly by IEC 60559. The functions that IEC 60559 specifies directly are identified in F.3. The other functions in <math.h> treat infinities, NaNs, signed zeros, subnormals, and (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags in a manner consistent with the basic arithmetic operations covered by IEC 60559. -
+
The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a nonzero value. -
+
The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in subsequent subclauses of this annex. -
+
The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value whose magnitude is too large. -
+
The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially subnormal or zero) and suffers loss of accuracy.358) - -
+ +
Whether or when library functions raise the ''inexact'' floating-point exception is unspecified, unless explicitly specified otherwise. -
+
Whether or when library functions raise an undeserved ''underflow'' floating-point exception is unspecified.359) Otherwise, as implied by F.8.6, the <math.h> functions do not raise spurious floating-point exceptions (detectable by the user), other than the ''inexact'' floating-point exception. -
+
Whether the functions honor the rounding direction mode is implementation-defined, unless explicitly specified otherwise. -
+
Functions with a NaN argument return a NaN result and raise no floating-point exception, except where stated otherwise. -
+
The specifications in the following subclauses append to the definitions in <math.h>. For families of functions, the specifications apply to all of the functions even though only the principal function is shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument and the result, the result has the same sign as the argument. - Recommended practice -
+
If a function with one or more NaN arguments returns a NaN result, the result should be
the same as one of the NaN arguments (after possible type conversion), except perhaps
for the sign.
@@ -24480,18 +25758,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
avoiding them would be too costly.
-F.10.1 Trigonometric functions
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
frexp raises no floating-point exceptions. -
+
When the radix of the argument is a power of 2, the returned value is exact and is independent of the current rounding direction mode. -
+
On a binary system, the body of the frexp function might be
{
*exp = (value == 0) ? 0 : (int)(1 + logb(value));
return scalbn(value, -(*exp));
- }
+ }
+
-+
When the correct result is representable in the range of the return type, the returned value is exact and is independent of the current rounding direction mode. -
+
If the correct result is outside the range of the return type, the numeric result is
unspecified and the ''invalid'' floating-point exception is raised.
-
+
-F.10.3.6 The ldexp functions
-
+
On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
-F.10.3.7 The log functions
-
+
+
+
+
+
+
The returned value is exact and is independent of the current rounding direction mode.
-
+
-F.10.3.12 The modf functions
-
+
+
The returned values are exact and are independent of the current rounding direction mode. -
+
modf behaves as though implemented by
#include <math.h>
@@ -24739,48 +26018,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
return copysign(
isinf(value) ? 0.0 :
value - (*iptr), value);
- }
+ }
+
-+
+
If the calculation does not overflow or underflow, the returned value is exact and
independent of the current rounding direction mode.
-
+
-F.10.4 Power and absolute value functions
+
+
+
+
The returned value is exact and is independent of the current rounding direction mode.
-F.10.4.3 The hypot functions
-
+
+
+
sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value
is dependent on the current rounding direction mode.
-F.10.5 Error and gamma functions
+
+
+
+
+
+
+
The returned value is independent of the current rounding direction mode. -
+
The double version of ceil behaves as though implemented by -
#include <math.h>
#include <fenv.h>
@@ -24876,41 +26155,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
result = rint(x); // or nearbyint instead of rint
fesetround(save_round);
return result;
- }
+ }
+
+
The ceil functions may, but are not required to, raise the ''inexact'' floating-point
exception for finite non-integer arguments, as this implementation does.
-F.10.6.2 The floor functions
-
+
+
The returned value and is independent of the current rounding direction mode. -
+
See the sample implementation for ceil in F.10.6.1. The floor functions may, but are
not required to, raise the ''inexact'' floating-point exception for finite non-integer
arguments, as that implementation does.
-F.10.6.3 The nearbyint functions
-
+
The nearbyint functions use IEC 60559 rounding according to the current rounding direction. They do not raise the ''inexact'' floating-point exception if the result differs in value from the argument.
+
The rint functions differ from the nearbyint functions only in that they do raise the
''inexact'' floating-point exception if the result differs in value from the argument.
-F.10.6.5 The lrint and llrint functions
-
+
The lrint and llrint functions provide floating-to-integer conversion as prescribed
by IEC 60559. They round according to the current rounding direction. If the rounded
value is outside the range of the return type, the numeric result is unspecified and the
@@ -24918,15 +26199,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
exception and the result differs from the argument, they raise the ''inexact'' floating-point
exception.
-F.10.6.6 The round functions
-
+
+
The returned value is independent of the current rounding direction mode. -
+
The double version of round behaves as though implemented by
#include <math.h>
@@ -24944,47 +26225,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
}
feupdateenv(&save_env);
return result;
- }
+ }
+
The round functions may, but are not required to, raise the ''inexact'' floating-point
exception for finite non-integer numeric arguments, as this implementation does.
-
+
-+
The lround and llround functions differ from the lrint and llrint functions
with the default rounding direction just in that the lround and llround functions
round halfway cases away from zero and need not raise the ''inexact'' floating-point
exception for non-integer arguments that round to within the range of the return type.
-F.10.6.8 The trunc functions
-
+
The trunc functions use IEC 60559 rounding toward zero (regardless of the current rounding direction). The returned value is exact.
+
The returned value is independent of the current rounding direction mode. The trunc
functions may, but are not required to, raise the ''inexact'' floating-point exception for
finite non-integer arguments.
-F.10.7 Remainder functions
+
+
+
When subnormal results are supported, the returned value is exact and is independent of the current rounding direction mode. -
+
The double version of fmod behaves as though implemented by - +
#include <math.h>
#include <fenv.h>
@@ -24995,91 +26277,93 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
result = remainder(fabs(x), (y = fabs(y)));
if (signbit(result)) result += y;
return copysign(result, x);
- }
+ }
+
-+
The remainder functions are fully specified as a basic arithmetic operation in IEC 60559. -
+
When subnormal results are supported, the returned value is exact and is independent of
the current rounding direction mode.
-F.10.7.3 The remquo functions
-
+
The remquo functions follow the specifications for the remainder functions. They have no further specifications special to IEC 60559 implementations. -
+
When subnormal results are supported, the returned value is exact and is independent of
the current rounding direction mode.
-F.10.8 Manipulation functions
+
+
copysign is specified in the Appendix to IEC 60559. -
+
The returned value is exact and is independent of the current rounding direction mode.
-F.10.8.2 The nan functions
-
+
All IEC 60559 implementations support quiet NaNs, in all floating formats. -
+
The returned value is exact and is independent of the current rounding direction mode.
-F.10.8.3 The nextafter functions
-
+
+
Even though underflow or overflow can occur, the returned value is independent of the
current rounding direction mode.
-F.10.8.4 The nexttoward functions
-
+
No additional requirements beyond those on nextafter. -
+
Even though underflow or overflow can occur, the returned value is independent of the
current rounding direction mode.
-
+
-F.10.9 Maximum, minimum, and positive difference functions
+
+
No additional requirements.
-F.10.9.2 The fmax functions
-
+
If just one argument is a NaN, the fmax functions return the other argument (if both arguments are NaNs, the functions return a NaN). -
+
The returned value is exact and is independent of the current rounding direction mode. -
+
The body of the fmax function might be361)
{ return (isgreaterequal(x, y) ||
- isnan(y)) ? x : y; }
+ isnan(y)) ? x : y; }
+
361) Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
return +0; however, implementation in software might be impractical.
-F.10.9.3 The fmin functions
-
+
The fmin functions are analogous to the fmax functions (see F.10.9.2). -
+
The returned value is exact and is independent of the current rounding direction mode.
-F.10.10 Floating multiply-add
+
+
+
Relational operators and their corresponding comparison macros (7.12.14) produce
equivalent result values, even if argument values are represented in wider formats. Thus,
comparison macro arguments represented in formats wider than their semantic types are
@@ -25104,15 +26388,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
of relational operators to their semantic types. The standard wide evaluation methods
characterized by FLT_EVAL_METHOD equal to 1 or 2 (5.2.4.2.2), do not convert
operands of relational operators to their semantic types.
-
+
-Annex G
+
(normative)
- IEC 60559-compatible complex arithmetic
+ IEC 60559-compatible complex arithmetic
+
-+
This annex supplements annex F to specify complex arithmetic for compatibility with
IEC 60559 real floating-point arithmetic. An implementation that defines *
__STDC_IEC_559_COMPLEX__ shall conform to the specifications in this annex.362)
@@ -25122,27 +26407,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
to these specifications.
-G.2 Types
-
+
There is a new keyword _Imaginary, which is used to specify imaginary types. It is used as a type specifier within declaration specifiers in the same way as _Complex is (thus, _Imaginary float is a valid type name). -
+
There are three imaginary types, designated as float _Imaginary, double _Imaginary, and long double _Imaginary. The imaginary types (along with the real floating and complex types) are floating types. -
+
For imaginary types, the corresponding real type is given by deleting the keyword _Imaginary from the type name. -
+
Each imaginary type has the same representation and alignment requirements as the corresponding real type. The value of an object of imaginary type is the value of the real representation times the imaginary unit. -
+
The imaginary type domain comprises the imaginary types.
-G.3 Conventions
-
+
A complex or imaginary value with at least one infinite part is regarded as an infinity
(even if its other part is a NaN). A complex or imaginary value is a finite number if each
of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
@@ -25151,20 +26436,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-G.4 Conversions
+
+
Conversions among imaginary types follow rules analogous to those for real floating
types.
-G.4.2 Real and imaginary
-
+
When a value of imaginary type is converted to a real type other than _Bool,363) the result is a positive zero. -
+
When a value of real type is converted to an imaginary type, the result is a positive imaginary zero. @@ -25172,21 +26457,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
363) See 6.3.1.2.
-G.4.3 Imaginary and complex
-
+
When a value of imaginary type is converted to a complex type, the real part of the complex result value is a positive zero and the imaginary part of the complex result value is determined by the conversion rules for the corresponding real types. -
+
When a value of complex type is converted to an imaginary type, the real part of the
complex value is discarded and the value of the imaginary part is converted according to
the conversion rules for the corresponding real types.
-G.5 Binary operators
-
+
The following subclauses supplement 6.5 in order to specify the type of the result for an operation with an imaginary operand. -
+
For most operand types, the value of the result of a binary operator with an imaginary or
complex operand is completely determined, with reference to real arithmetic, by the usual
mathematical formula. For some operand types, the usual mathematical formula is
@@ -25197,43 +26482,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
-
+
-G.5.1 Multiplicative operators
+
+
If one operand has real type and the other operand has imaginary type, then the result has imaginary type. If both operands have imaginary type, then the result has real type. (If either operand has complex type, then the result has complex type.) -
+
If the operands are not both complex, then the result and floating-point exception behavior of the * operator is defined by the usual mathematical formula:
- * u iv u + iv+ * u iv u + iv +
- x xu i(xv) (xu) + i(xv)+ x xu i(xv) (xu) + i(xv) +
- iy i(yu) -yv (-yv) + i(yu)+ iy i(yu) -yv (-yv) + i(yu) + -
- x + iy (xu) + i(yu) (-yv) + i(xv)+ x + iy (xu) + i(yu) (-yv) + i(xv) + +
If the second operand is not complex, then the result and floating-point exception behavior of the / operator is defined by the usual mathematical formula:
- / u iv+ / u iv +
- x x/u i(-x/v)+ x x/u i(-x/v) +
- iy i(y/u) y/v+ iy i(y/u) y/v + -
- x + iy (x/u) + i(y/u) (y/v) + i(-x/v)+ x + iy (x/u) + i(y/u) (y/v) + i(-x/v) + +
The * and / operators satisfy the following infinity properties for all real, imaginary, and complex operands:364)
+
If both operands of the * operator are complex or if the second operand of the / operator is complex, the operator raises floating-point exceptions if appropriate for the calculation of the parts of the result, and may raise spurious floating-point exceptions. -
+
EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note that the imaginary unit I has imaginary type (see G.6). - -
+
#include <math.h>
#include <complex.h>
@@ -25307,14 +26599,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
}
}
return x + I * y;
- }
+ }
+
+This implementation achieves the required treatment of infinities at the cost of only one isnan test in ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur. -
+
EXAMPLE 2 Division of two double _Complex operands could be implemented as follows. - -
+
#include <math.h>
#include <complex.h>
@@ -25358,7 +26651,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
}
}
return x + I * y;
- }
+ }
+
+
Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
for multiplication. In the spirit of the multiplication example above, this code does not defend against
overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
@@ -25370,77 +26665,86 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(at least where the state for CX_LIMITED_RANGE is ''off'').
-G.5.2 Additive operators
+
+
If both operands have imaginary type, then the result has imaginary type. (If one operand has real type and the other operand has imaginary type, or if either operand has complex type, then the result has complex type.) -
+
In all cases the result and floating-point exception behavior of a + or - operator is defined by the usual mathematical formula:
- + or - u iv u + iv+ + or - u iv u + iv +
- x x(+-)u x (+-) iv (x (+-) u) (+-) iv+ x x(+-)u x (+-) iv (x (+-) u) (+-) iv +
- iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)+ iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v) +
- x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)+ x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v) + -
+
The macros
- imaginary+ imaginary + and
- _Imaginary_I+ _Imaginary_I + are defined, respectively, as _Imaginary and a constant expression of type const float _Imaginary with the value of the imaginary unit. The macro
- I+ I + is defined to be _Imaginary_I (not _Complex_I as stated in 7.3). Notwithstanding the provisions of 7.1.3, a program may undefine and then perhaps redefine the macro imaginary. -
+
This subclause contains specifications for the <complex.h> functions that are particularly suited to IEC 60559 implementations. For families of functions, the specifications apply to all of the functions even though only the principal function is - + shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument and the result, the result has the same sign as the argument. -
+
The functions are continuous onto both sides of their branch cuts, taking into account the sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. - -
+
Since complex and imaginary values are composed of real values, each function may be regarded as computing real values from real values. Except as noted, the functions treat real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a manner consistent with the specifications for real functions in F.10.365) -
+
The functions cimag, conj, cproj, and creal are fully specified for all implementations, including IEC 60559 ones, in 7.3.9. These functions raise no floating- point exceptions. -
+
Each of the functions cabs and carg is specified by a formula in terms of a real function (whose special cases are covered in annex F): -
cabs(x + iy) = hypot(x, y)
- carg(x + iy) = atan2(y, x)
+ carg(x + iy) = atan2(y, x)
+
+Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by a formula in terms of other complex functions (whose special cases are specified below): -
casin(z) = -i casinh(iz)
catan(z) = -i catanh(iz)
ccos(z) = ccosh(iz)
csin(z) = -i csinh(iz)
- ctan(z) = -i ctanh(iz)
+ ctan(z) = -i ctanh(iz)
+
+For the other functions, the following subclauses specify behavior for special cases, including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For families of functions, the specifications apply to all of the functions even though only the @@ -25448,23 +26752,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. specifications for the upper half-plane imply the specifications for the lower half-plane; if the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the specifications for the first quadrant imply the specifications for the other three quadrants. -
+
In the following subclauses, cis(y) is defined as cos(y) + i sin(y). - +
365) As noted in G.3, a complex value with at least one infinite part is regarded as an infinity even if its
other part is a NaN.
-G.6.1 Trigonometric functions
+
+
+
+
+
+
+
+
+
+
+
The cpow functions raise floating-point exceptions if appropriate for the calculation of
the parts of the result, and may also raise spurious floating-point exceptions.366)
@@ -25682,8 +26986,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
implementations that treat special cases more carefully.
-G.6.4.2 The csqrt functions
-
+
+
Type-generic macros that accept complex arguments also accept imaginary arguments. If an argument is imaginary, the macro expands to an expression whose type is real, imaginary, or complex, as appropriate for the particular function: if the argument is imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and the types of the others are complex. -
+
Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh, sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real functions: - +
cos(iy) = cosh(y)
sin(iy) = i sinh(y)
@@ -25728,32 +27032,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
asin(iy) = i asinh(y)
atan(iy) = i atanh(y)
asinh(iy) = i asin(y)
- atanh(iy) = i atan(y)
+ atanh(iy) = i atan(y)
+
-
(informative)
- Language independent arithmetic
+ Language independent arithmetic
+
-+
This annex documents the extent to which the C language supports the ISO/IEC 10967-1
standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
IEC 60559 (annex F) in that it covers integer and diverse floating-point arithmetics.
-H.2 Types
-
+
The relevant C arithmetic types meet the requirements of LIA-1 types if an
implementation adds notification of exceptional arithmetic operations and meets the 1
unit in the last place (ULP) accuracy requirement (LIA-1 subclause 5.2.8).
-H.2.1 Boolean type
-
+
The LIA-1 data type Boolean is implemented by the C data type bool with values of
true and false, all from <stdbool.h>.
-H.2.2 Integer types
-
+
The signed C integer types int, long int, long long int, and the corresponding unsigned types are compatible with LIA-1. If an implementation adds support for the LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are @@ -25761,19 +27067,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. in that overflows or out-of-bounds results silently wrap. An implementation that defines signed integer types as also being modulo need not detect integer overflow, in which case, only integer divide-by-zero need be detected. -
+
The parameters for the integer data types can be accessed by the following: maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
- ULLONG_MAX+ ULLONG_MAX + minint INT_MIN, LONG_MIN, LLONG_MIN -
+
The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
is always 0 for the unsigned types, and is not provided for those types.
-
+
-H.2.2.1 Integer operations
-
+
The integer operations on integer types are the following:
addI x + y
subI x - y
@@ -25790,8 +27097,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
geqI x >= y
where x and y are expressions of the same integer type.
-H.2.3 Floating-point types
-
+
The C floating-point types float, double, and long double are compatible with
LIA-1. If an implementation adds support for the LIA-1 exceptional values
''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
@@ -25799,23 +27106,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
operations (see annex F) along with IEC 60559 status flags and traps has LIA-1
conformant types.
-H.2.3.1 Floating-point parameters
-
+
The parameters for a floating point data type can be accessed by the following: r FLT_RADIX p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP -
+
The derived constants for the floating point types are accessed by the following:
-
+
fmax FLT_MAX, DBL_MAX, LDBL_MAX
fminN FLT_MIN, DBL_MIN, LDBL_MIN
epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
rnd_style FLT_ROUNDS
-H.2.3.2 Floating-point operations
-
+
The floating-point operations on floating-point types are the following: addF x + y subF x - y @@ -25826,7 +27133,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x) scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
- scalblnf(x, li), scalbln(x, li), scalblnl(x, li)+ scalblnf(x, li), scalbln(x, li), scalblnl(x, li) + intpartF modff(x, &y), modf(x, &y), modfl(x, &y) fractpartF modff(x, &y), modf(x, &y), modfl(x, &y) eqF x == y @@ -25838,40 +27146,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. where x and y are expressions of the same floating point type, n is of type int, and li is of type long int. -
+
The C Standard requires all floating types to use the same radix and rounding style, so that only one identifier for each is provided to map to LIA-1. -
+
The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
truncate FLT_ROUNDS == 0
-
+
nearest FLT_ROUNDS == 1
other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
provided that an implementation extends FLT_ROUNDS to cover the rounding style used
in all relevant LIA-1 operations, not just addition as in C.
-H.2.4 Type conversions
-
+
The LIA-1 type conversions are the following type casts: cvtI' -> I (int)i, (long int)i, (long long int)i,
(unsigned int)i, (unsigned long int)i,
- (unsigned long long int)i
+ (unsigned long long int)i
+
cvtF -> I (int)x, (long int)x, (long long int)x,
(unsigned int)x, (unsigned long int)x,
- (unsigned long long int)x
+ (unsigned long long int)x
+
cvtI -> F (float)i, (double)i, (long double)i
cvtF' -> F (float)x, (double)x, (long double)x
-+
In the above conversions from floating to integer, the use of (cast)x can be replaced with (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x), (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer conversion functions, lrint(), llrint(), lround(), and llround(), can be used. They all meet LIA-1's requirements on floating to integer rounding for in-range values. For out-of-range values, the conversions shall silently wrap for the modulo types. -
+
The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g., fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x), 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0 @@ -25880,93 +27190,94 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the range -32767.0 to +32768.0 which is not, in general, in the range of signed short int. -
+
C's conversions (casts) from floating-point to floating-point can meet LIA-1 requirements if an implementation uses round-to-nearest (IEC 60559 default). -
+
C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
implementation uses round-to-nearest.
-
+
-H.3 Notification
-
+
Notification is the process by which a user or program is informed that an exceptional
arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
allows an implementation to cause a notification to occur when any arithmetic operation
returns an exceptional value as defined in LIA-1 clause 5.
-H.3.1 Notification alternatives
-
+
LIA-1 requires at least the following two alternatives for handling of notifications: setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and- resume. -
+
An implementation need only support a given notification alternative for the entire program. An implementation may support the ability to switch between notification alternatives during execution, but is not required to do so. An implementation can provide separate selection for each kind of notification, but this is not required. -
+
C allows an implementation to provide notification. C's SIGFPE (for traps) and FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators) can provide LIA-1 notification. -
+
C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
math library function calls. User-provided signal handlers for SIGFPE allow for trap-
and-resume behavior with the same constraint.
-H.3.1.1 Indicators
-
+
C's <fenv.h> status flags are compatible with the LIA-1 indicators. -
+
The following mapping is for floating-point types: undefined FE_INVALID, FE_DIVBYZERO floating_overflow FE_OVERFLOW underflow FE_UNDERFLOW -
+
The floating-point indicator interrogation and manipulation operations are: set_indicators feraiseexcept(i) clear_indicators feclearexcept(i) test_indicators fetestexcept(i) current_indicators fetestexcept(FE_ALL_EXCEPT) where i is an expression of type int representing a subset of the LIA-1 indicators. -
+
C allows an implementation to provide the following LIA-1 required behavior: at program termination if any indicator is set the implementation shall send an unambiguous - + and ''hard to ignore'' message (see LIA-1 subclause 6.1.2) -
+
LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
This documentation makes that distinction because <fenv.h> covers only the floating-
point indicators.
-H.3.1.2 Traps
-
+
C is compatible with LIA-1's trap requirements for arithmetic operations, but not for math library functions (which are not permitted to invoke a user's signal handler for SIGFPE). An implementation can provide an alternative of notification through termination with a ''hard-to-ignore'' message (see LIA-1 subclause 6.1.3). -
+
LIA-1 does not require that traps be precise. -
+
C does require that SIGFPE be the signal corresponding to LIA-1 arithmetic exceptions, if there is any signal raised for them. -
+
C supports signal handlers for SIGFPE and allows trapping of LIA-1 arithmetic
exceptions. When LIA-1 arithmetic exceptions do trap, C's signal-handler mechanism
allows trap-and-terminate (either default implementation behavior or user replacement for
it) or trap-and-resume, at the programmer's option.
-
+
-Annex I
-
+
(informative)
- Common warnings
+ Common warnings
+
+An implementation may generate warnings in many situations, none of which are specified as part of this International Standard. The following are a few of the more common situations. -
+
+
(informative)
- Portability issues
+ Portability issues
+
+
This annex collects some information about portability that appears in this International
Standard.
-J.1 Unspecified behavior
-
+
The following are unspecified:
+
The behavior is undefined in the following circumstances:
+
A conforming implementation is required to document its choice of behavior in each of
the areas listed in this subclause. The following are implementation-defined:
-
+
-J.3.1 Translation
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
The following characteristics of a hosted environment are locale-specific and are required to be documented by the implementation:
+
The following extensions are widely used in many systems, but are not portable to all
implementations. The inclusion of any extension that may cause a strictly conforming
program to become invalid renders an implementation nonconforming. Examples of such
extensions are new keywords, extra library functions declared in standard headers, or
predefined macros with names that do not begin with an underscore.
-J.5.1 Environment arguments
-
+
In a hosted environment, the main function receives a third argument, char *envp[],
that points to a null-terminated array of pointers to char, each of which points to a string
that provides information about the environment for this execution of the program
(5.1.2.2.1).
-J.5.2 Specialized identifiers
-
+
Characters other than the underscore _, letters, and digits, that are not part of the basic
source character set (such as the dollar sign $, or characters in national character sets)
may appear in an identifier (6.4.2).
-J.5.3 Lengths and cases of identifiers
-
+
All characters in identifiers (with or without external linkage) are significant (6.4.2).
-J.5.4 Scopes of identifiers
-
+
A function identifier, or the identifier of an object the declaration of which contains the
keyword extern, has file scope (6.2.1).
-J.5.5 Writable string literals
-
+
String literals are modifiable (in which case, identical string literals should denote distinct
objects) (6.4.5).
-
+
-J.5.6 Other arithmetic types
-
+
Additional arithmetic types, such as __int128 or double double, and their
appropriate conversions are defined (6.2.5, 6.3.1). Additional floating types may have
more range or precision than long double, may be used for evaluating expressions of
other floating types, and may be used to define float_t or double_t.
-J.5.7 Function pointer casts
-
+
A pointer to an object or to void may be cast to a pointer to a function, allowing data to be invoked as a function (6.5.4). -
+
A pointer to a function may be cast to a pointer to an object or to void, allowing a
function to be inspected or modified (for example, by a debugger) (6.5.4).
-J.5.8 Extended bit-field types
-
+
A bit-field may be declared with a type other than _Bool, unsigned int, or
signed int, with an appropriate maximum width (6.7.2.1).
-J.5.9 The fortran keyword
-
+
The fortran function specifier may be used in a function declaration to indicate that
calls suitable for FORTRAN should be generated, or that a different representation for the
external name is to be generated (6.7.4).
-J.5.10 The asm keyword
-
+
The asm keyword may be used to insert assembly language directly into the translator output (6.8). The most common implementation is via a statement of the form:
- asm ( character-string-literal );+ asm ( character-string-literal ); + -
+
There may be more than one external definition for the identifier of an object, with or
without the explicit use of the keyword extern; if the definitions disagree, or more than
one is initialized, the behavior is undefined (6.9.2).
-J.5.12 Predefined macro names
-
+
Macro names that do not begin with an underscore, describing the translation and
execution environments, are defined by the implementation before translation begins
(6.10.8).
-
+
-J.5.13 Floating-point status flags
-
+
If any floating-point status flags are set on normal termination after all calls to functions
registered by the atexit function have been made (see 7.22.4.4), the implementation
writes some diagnostics indicating the fact to the stderr stream, if it is still open,
-J.5.14 Extra arguments for signal handlers
-
+
Handlers for specific signals are called with extra arguments in addition to the signal
number (7.14.1.1).
-J.5.15 Additional stream types and file-opening modes
-
+
Additional mappings from files to streams are supported (7.21.2). -
+
Additional file-opening modes may be specified by characters appended to the mode
argument of the fopen function (7.21.5.3).
-J.5.16 Defined file position indicator
-
+
The file position indicator is decremented by each successful call to the ungetc or
ungetwc function for a text stream, except if its value was zero before a call (7.21.7.10,
7.28.3.10).
-J.5.17 Math error reporting
-
+
Functions declared in <complex.h> and <math.h> raise SIGFPE to report errors
instead of, or in addition to, setting errno or raising floating-point exceptions (7.3,
7.12).
-
+
-Annex K
+
(normative)
- Bounds-checking interfaces
+ Bounds-checking interfaces
+
-+
Traditionally, the C Library has contained many functions that trust the programmer to provide output character arrays big enough to hold the result being produced. Not only do these functions not check that the arrays are big enough, they frequently lack the information needed to perform such checks. While it is possible to write safe, robust, and error-free code using the existing library, the library tends to promote programming styles that lead to mysterious failures if a result is too big for the provided array. -
+
A common programming style is to declare character arrays large enough to handle most practical cases. However, if these arrays are not large enough to handle the resulting strings, data can be written past the end of the array overwriting other data and program structures. The program never gets any indication that a problem exists, and so never has a chance to recover or to fail gracefully. -
+
Worse, this style of programming has compromised the security of computers and networks. Buffer overflows can often be exploited to run arbitrary code with the permissions of the vulnerable (defective) program. -
+
If the programmer writes runtime checks to verify lengths before calling library functions, then those runtime checks frequently duplicate work done inside the library functions, which discover string lengths as a side effect of doing their job. -
+
This annex provides alternative library functions that promote safer, more secure programming. The alternative functions verify that output buffers are large enough for the intended result and return a failure indicator if they are not. Data is never written past the end of an array. All string results are null terminated. -
+
This annex also addresses another problem that complicates writing robust code:
functions that are not reentrant because they return pointers to static objects owned by the
function. Such functions can be troublesome since a previously returned result can
change if the function is called again, perhaps by another thread.
-
+
-K.2 Scope
-
+
This annex specifies a series of optional extensions that can be useful in the mitigation of security vulnerabilities in programs, and comprise new functions, macros, and types declared or defined in existing standard headers. -
+
An implementation that defines __STDC_LIB_EXT1__ shall conform to the specifications in this annex.367) -
+
Subclause K.3 should be read as if it were merged into the parallel structure of named
subclauses of clause 7.
@@ -27100,34 +28414,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
specifications.
-K.3 Library
+
+
The functions, macros, and types declared or defined in K.3 and its subclauses are not declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is defined as a macro which expands to the integer constant 0 at the point in the source file where the appropriate header is first included. -
+
The functions, macros, and types declared or defined in K.3 and its subclauses are declared and defined by their respective headers if __STDC_WANT_LIB_EXT1__ is defined as a macro which expands to the integer constant 1 at the point in the source file where the appropriate header is first included.368) -
+
It is implementation-defined whether the functions, macros, and types declared or defined in K.3 and its subclauses are declared or defined by their respective headers if __STDC_WANT_LIB_EXT1__ is not defined as a macro at the point in the source file where the appropriate header is first included.369) -
+
Within a preprocessing translation unit, __STDC_WANT_LIB_EXT1__ shall be defined identically for all inclusions of any headers from subclause K.3. If __STDC_WANT_LIB_EXT1__ is defined differently for any such inclusion, the implementation shall issue a diagnostic as if a preprocessor error directive were used. - +
368) Future revisions of this International Standard may define meanings for other values of
@@ -27140,51 +28454,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
implementation is not conforming.
-K.3.1.2 Reserved identifiers
-
+
Each macro name in any of the following subclauses is reserved for use as specified if it is defined by any of its associated headers when included; unless explicitly stated otherwise (see 7.1.4). -
+
All identifiers with external linkage in any of the following subclauses are reserved for use as identifiers with external linkage if any of them are used by the program. None of them are reserved if none of them are used. -
+
Each identifier with file scope listed in any of the following subclauses is reserved for use
as a macro name and as an identifier with file scope in the same name space if it is
defined by any of its associated headers when included.
-K.3.1.3 Use of errno
-
+
An implementation may set errno for the functions defined in this annex, but is not
required to.
-K.3.1.4 Runtime-constraint violations
-
+
Most functions in this annex include as part of their specification a list of runtime- constraints. These runtime-constraints are requirements on the program using the library.370) -
+
Implementations shall verify that the runtime-constraints for a function are not violated by the program. If a runtime-constraint is violated, the implementation shall call the currently registered runtime-constraint handler (see set_constraint_handler_s in <stdlib.h>). Multiple runtime-constraint violations in the same call to a library function result in only one call to the runtime-constraint handler. It is unspecified which one of the multiple runtime-constraint violations cause the handler to be called. -
+
If the runtime-constraints section for a function states an action to be performed when a runtime-constraint violation occurs, the function shall perform the action before calling the runtime-constraint handler. If the runtime-constraints section lists actions that are prohibited when a runtime-constraint violation occurs, then such actions are prohibited to the function both before calling the handler and after the handler returns. -
+
The runtime-constraint handler might not return. If the handler does return, the library function whose runtime-constraint was violated shall return some indication of failure as given by the returns section in the function's specification. - +
370) Although runtime-constraints replace many cases of undefined behavior, undefined behavior still
@@ -27193,13 +28507,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
from the definition of undefined behavior.
-K.3.2 Errors
-
+
The header <errno.h> defines a type. -
+
The type is
- errno_t+ errno_t + which is type int.371)
+
The header <stddef.h> defines a type. -
+
The type is
- rsize_t+ rsize_t + which is the type size_t.372)
372) See the description of the RSIZE_MAX macro in <stdint.h>.
-K.3.4 Integer types
-
+
The header <stdint.h> defines a macro. -
+
The macro is
- RSIZE_MAX+ RSIZE_MAX + which expands to a value373) of type size_t. Functions that have parameters of type rsize_t consider it a runtime-constraint violation if the values of those parameters are greater than RSIZE_MAX. - Recommended practice -
+
Extremely large object sizes are frequently a sign that an object's size was calculated incorrectly. For example, negative numbers appear as very large positive numbers when converted to an unsigned type like size_t. Also, some implementations do not support objects as large as the maximum value that can be represented by type size_t. -
+
For those reasons, it is sometimes beneficial to restrict the range of object sizes to detect programming errors. For implementations targeting machines with large address spaces, it is recommended that RSIZE_MAX be defined as the smaller of the size of the largest @@ -27245,105 +28562,111 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. some legitimate, but very large, objects. Implementations targeting machines with small address spaces may wish to define RSIZE_MAX as SIZE_MAX, which means that there - + is no object size that is considered a runtime-constraint violation.
373) The macro RSIZE_MAX need not expand to a constant expression.
-K.3.5 Input/output
-
+
The header <stdio.h> defines several macros and two types. -
+
The macros are
- L_tmpnam_s+ L_tmpnam_s + which expands to an integer constant expression that is the size needed for an array of char large enough to hold a temporary file name string generated by the tmpnam_s function;
- TMP_MAX_S+ TMP_MAX_S + which expands to an integer constant expression that is the maximum number of unique file names that can be generated by the tmpnam_s function. -
+
The types are
- errno_t+ errno_t + which is type int; and
- rsize_t+ rsize_t + which is the type size_t. -
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
- errno_t tmpfile_s(FILE * restrict * restrict streamptr);
+ errno_t tmpfile_s(FILE * restrict * restrict streamptr);
+
Runtime-constraints
-+
streamptr shall not be a null pointer. -
+
If there is a runtime-constraint violation, tmpfile_s does not attempt to create a file.
+
The tmpfile_s function creates a temporary binary file that is different from any other existing file and that will automatically be removed when it is closed or at program termination. If the program terminates abnormally, whether an open temporary file is removed is implementation-defined. The file is opened for update with "wb+" mode with the meaning that mode has in the fopen_s function (including the mode's effect on exclusive access and file permissions). - -
+ +
If the file was created successfully, then the pointer to FILE pointed to by streamptr will be set to the pointer to the object controlling the opened file. Otherwise, the pointer to FILE pointed to by streamptr will be set to a null pointer. - Recommended practice +
+
The tmpfile_s function returns zero if it created the file. If it did not create the file or
there was a runtime-constraint violation, tmpfile_s returns a nonzero value.
-K.3.5.1.2 The tmpnam_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
- errno_t tmpnam_s(char *s, rsize_t maxsize);
+ errno_t tmpnam_s(char *s, rsize_t maxsize);
+
Runtime-constraints
-+
s shall not be a null pointer. maxsize shall be less than or equal to RSIZE_MAX. maxsize shall be greater than the length of the generated file name string.
+
The tmpnam_s function generates a string that is a valid file name and that is not the same as the name of an existing file.374) The function is potentially capable of generating TMP_MAX_S different strings, but any or all of them may already be in use by existing files and thus not be suitable return values. The lengths of these strings shall be less than the value of the L_tmpnam_s macro. -
+
The tmpnam_s function generates a different string each time it is called. -
+
It is assumed that s points to an array of at least maxsize characters. This array will be set to generated string, as specified below. - -
+ +
The implementation shall behave as if no library function except tmpnam calls the tmpnam_s function.375) - Recommended practice -
+
After a program obtains a file name using the tmpnam_s function and before the program creates a file with that name, the possibility exists that someone else may create a file with that same name. To avoid this race condition, the tmpfile_s function @@ -27351,15 +28674,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. of the tmpnam_s function is when the program needs to create a temporary directory rather than a temporary file.
+
If no suitable string can be generated, or if there is a runtime-constraint violation, the tmpnam_s function writes a null character to s[0] (only if s is not null and maxsize is greater than zero) and returns a nonzero value. -
+
Otherwise, the tmpnam_s function writes the string in the array pointed to by s and returns zero. - Environmental limits -
+
The value of the macro TMP_MAX_S shall be at least 25.
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
errno_t fopen_s(FILE * restrict * restrict streamptr,
const char * restrict filename,
- const char * restrict mode);
+ const char * restrict mode);
+
Runtime-constraints
-+
None of streamptr, filename, or mode shall be a null pointer. -
+
If there is a runtime-constraint violation, fopen_s does not attempt to open a file. Furthermore, if streamptr is not a null pointer, fopen_s sets *streamptr to the null pointer. @@ -27397,46 +28721,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The fopen_s function opens the file whose name is the string pointed to by filename, and associates a stream with it. -
+
The mode string shall be as described for fopen, with the addition that modes starting with the character 'w' or 'a' may be preceded by the character 'u', see below: uw truncate to zero length or create text file for writing, default
- permissions+ permissions + uwx create text file for writing, default permissions ua append; open or create text file for writing at end-of-file, default
- permissions+ permissions + uwb truncate to zero length or create binary file for writing, default
- permissions+ permissions + uwbx create binary file for writing, default permissions uab append; open or create binary file for writing at end-of-file, default
- permissions+ permissions + uw+ truncate to zero length or create text file for update, default
- permissions+ permissions + uw+x create text file for update, default permissions ua+ append; open or create text file for update, writing at end-of-file,
- default permissions+ default permissions + uw+b or uwb+ truncate to zero length or create binary file for update, default
- permissions+ permissions + uw+bx or uwb+x create binary file for update, default permissions ua+b or uab+ append; open or create binary file for update, writing at end-of-file, -
- default permissions+ default permissions + +
Opening a file with exclusive mode ('x' as the last character in the mode argument) fails if the file already exists or cannot be created. -
+
To the extent that the underlying system supports the concepts, files opened for writing shall be opened with exclusive (also known as non-shared) access. If the file is being created, and the first character of the mode string is not 'u', to the extent that the @@ -27444,15 +28776,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. users on the system from accessing the file. If the file is being created and first character of the mode string is 'u', then by the time the file has been closed, it shall have the system default file access permissions.376) -
+
If the file was opened successfully, then the pointer to FILE pointed to by streamptr will be set to the pointer to the object controlling the opened file. Otherwise, the pointer - + to FILE pointed to by streamptr will be set to a null pointer.
+
The fopen_s function returns zero if it opened the file. If it did not open the file or if there was a runtime-constraint violation, fopen_s returns a nonzero value. @@ -27460,85 +28792,87 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
376) These are the same permissions that the file would have been created with by fopen.
-K.3.5.2.2 The freopen_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
errno_t freopen_s(FILE * restrict * restrict newstreamptr,
const char * restrict filename,
const char * restrict mode,
- FILE * restrict stream);
+ FILE * restrict stream);
+
Runtime-constraints
-+
None of newstreamptr, mode, and stream shall be a null pointer. -
+
If there is a runtime-constraint violation, freopen_s neither attempts to close any file associated with stream nor attempts to open a file. Furthermore, if newstreamptr is not a null pointer, fopen_s sets *newstreamptr to the null pointer.
+
The freopen_s function opens the file whose name is the string pointed to by filename and associates the stream pointed to by stream with it. The mode argument has the same meaning as in the fopen_s function (including the mode's effect on exclusive access and file permissions). -
+
If filename is a null pointer, the freopen_s function attempts to change the mode of the stream to that specified by mode, as if the name of the file currently associated with the stream had been used. It is implementation-defined which changes of mode are permitted (if any), and under what circumstances. -
+
The freopen_s function first attempts to close any file that is associated with stream. Failure to close the file is ignored. The error and end-of-file indicators for the stream are cleared. -
+
If the file was opened successfully, then the pointer to FILE pointed to by newstreamptr will be set to the value of stream. Otherwise, the pointer to FILE pointed to by newstreamptr will be set to a null pointer.
+
The freopen_s function returns zero if it opened the file. If it did not open the file or
there was a runtime-constraint violation, freopen_s returns a nonzero value.
-
+
-K.3.5.3 Formatted input/output functions
-
+
Unless explicitly stated otherwise, if the execution of a function described in this
subclause causes copying to take place between objects that overlap, the objects take on
unspecified values.
-K.3.5.3.1 The fprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int fprintf_s(FILE * restrict stream,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. The %n specifier377) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to fprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation,378) the fprintf_s function does not attempt to produce further output, and it is unspecified to what extent fprintf_s produced output before discovering the runtime-constraint violation.
+
The fprintf_s function is equivalent to the fprintf function except for the explicit runtime-constraints listed above.
+
The fprintf_s function returns the number of characters transmitted, or a negative value if an output error, encoding error, or runtime-constraint violation occurred. - +
377) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
@@ -27550,24 +28884,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
constraint violation.
-K.3.5.3.2 The fscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int fscanf_s(FILE * restrict stream,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation,379) the fscanf_s function does not attempt to perform further input, and it is unspecified to what extent fscanf_s performed input before discovering the runtime-constraint violation.
+
The fscanf_s function is equivalent to fscanf except that the c, s, and [ conversion specifiers apply to a pair of arguments (unless assignment suppression is indicated by a *). The first of these arguments is the same as for fscanf. That argument is @@ -27575,42 +28910,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. rsize_t and gives the number of elements in the array pointed to by the first argument of the pair. If the first argument points to a scalar object, it is considered to be an array of one element.380) -
+
A matching failure occurs if the number of elements in a receiving object is insufficient to hold the converted input (including any trailing null character).
+
The fscanf_s function returns the value of the macro EOF if an input failure occurs before any conversion or if there is a runtime-constraint violation. Otherwise, the - + fscanf_s function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure. -
+
EXAMPLE 1 The call:
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
/* ... */
int n, i; float x; char name[50];
- n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
+ n = fscanf_s(stdin, "%d%f%s", &i, &x, name, (rsize_t) 50);
+
with the input line:
- 25 54.32E-1 thompson+ 25 54.32E-1 thompson + will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence thompson\0. -
+
EXAMPLE 2 The call:
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
/* ... */
int n; char s[5];
- n = fscanf_s(stdin, "%s", s, sizeof s);
+ n = fscanf_s(stdin, "%s", s, sizeof s);
+
with the input line:
- hello+ hello + will assign to n the value 0 since a matching failure occurred because the sequence hello\0 requires an array of six characters to store it. @@ -27632,31 +28971,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compatible with rsize_t. -
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
- int printf_s(const char * restrict format, ...);
+ int printf_s(const char * restrict format, ...);
+
Runtime-constraints
-+
format shall not be a null pointer. The %n specifier381) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to printf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the printf_s function does not attempt to produce further output, and it is unspecified to what extent printf_s produced output before discovering the runtime-constraint violation. - +
+
The printf_s function is equivalent to the printf function except for the explicit runtime-constraints listed above.
+
The printf_s function returns the number of characters transmitted, or a negative
value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -27666,61 +29006,63 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.4 The scanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
- int scanf_s(const char * restrict format, ...);
+ int scanf_s(const char * restrict format, ...);
+
Runtime-constraints
-+
format shall not be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the scanf_s function does not attempt to perform further input, and it is unspecified to what extent scanf_s performed input before discovering the runtime-constraint violation.
+
The scanf_s function is equivalent to fscanf_s with the argument stdin interposed before the arguments to scanf_s.
+
The scanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
scanf_s function returns the number of input items assigned, which can be fewer than
provided for, or even zero, in the event of an early matching failure.
-K.3.5.3.5 The snprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int snprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The %n specifier382) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to - + snprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the snprintf_s function sets s[0] to the null character.
+
The snprintf_s function is equivalent to the snprintf function except for the explicit runtime-constraints listed above. -
+
The snprintf_s function, unlike sprintf_s, will truncate the result to fit within the array pointed to by s.
+
The snprintf_s function returns the number of characters that would have been
written had n been sufficiently large, not counting the terminating null character, or a
negative value if a runtime-constraint violation occurred. Thus, the null-terminated
@@ -27733,16 +29075,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.6 The sprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int sprintf_s(char * restrict s, rsize_t n,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The number of characters (including the trailing null) required for the result to be written to the array pointed to by s shall not be greater than n. The %n @@ -27752,20 +29095,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the sprintf_s function sets s[0] to the null character.
+
The sprintf_s function is equivalent to the sprintf function except for the parameter n and the explicit runtime-constraints listed above. -
+
The sprintf_s function, unlike snprintf_s, treats a result too big for the array pointed to by s as a runtime-constraint violation.
+
If no runtime-constraint violation occurred, the sprintf_s function returns the number
of characters written in the array, not counting the terminating null character. If an
encoding error occurred, sprintf_s returns a negative value. If any other runtime-
@@ -27777,62 +29120,64 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.7 The sscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int sscanf_s(const char * restrict s,
- const char * restrict format, ...);
+ const char * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the sscanf_s function does not attempt to perform further input, and it is unspecified to what extent sscanf_s performed input before discovering the runtime-constraint violation.
+
The sscanf_s function is equivalent to fscanf_s, except that input is obtained from a string (specified by the argument s) rather than from a stream. Reaching the end of the string is equivalent to encountering end-of-file for the fscanf_s function. If copying takes place between objects that overlap, the objects take on unspecified values.
+
The sscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
sscanf_s function returns the number of input items assigned, which can be fewer than
provided for, or even zero, in the event of an early matching failure.
-
+
-K.3.5.3.8 The vfprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vfprintf_s(FILE * restrict stream,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. The %n specifier384) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to vfprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vfprintf_s function does not attempt to produce further output, and it is unspecified to what extent vfprintf_s produced output before discovering the runtime-constraint violation.
+
The vfprintf_s function is equivalent to the vfprintf function except for the explicit runtime-constraints listed above.
+
The vfprintf_s function returns the number of characters transmitted, or a negative
value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -27842,37 +29187,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.9 The vfscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vfscanf_s(FILE * restrict stream,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
-
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vfscanf_s function does not attempt to perform further input, and it is unspecified to what extent vfscanf_s performed input before discovering the runtime-constraint violation.
+
The vfscanf_s function is equivalent to fscanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfscanf_s function does not invoke the va_end macro.385)
+
The vfscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
vfscanf_s function returns the number of input items assigned, which can be fewer
@@ -27884,32 +29230,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
indeterminate.
-K.3.5.3.10 The vprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vprintf_s(const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
format shall not be a null pointer. The %n specifier386) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to vprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vprintf_s function does not attempt to produce further output, and it is unspecified to what extent vprintf_s produced output before discovering the runtime-constraint violation. - +
+
The vprintf_s function is equivalent to the vprintf function except for the explicit runtime-constraints listed above.
+
The vprintf_s function returns the number of characters transmitted, or a negative
value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -27919,31 +29266,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.11 The vscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vscanf_s(const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
format shall not be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vscanf_s function does not attempt to perform further input, and it is unspecified to what extent vscanf_s performed input before discovering the runtime-constraint violation.
+
The vscanf_s function is equivalent to scanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vscanf_s function does not invoke the va_end macro.387)
+
The vscanf_s function returns the value of the macro EOF if an input failure occurs before any conversion or if there is a runtime-constraint violation. Otherwise, the vscanf_s function returns the number of input items assigned, which can be fewer than @@ -27952,7 +29300,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
387) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s,
@@ -27960,36 +29308,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
indeterminate.
-K.3.5.3.12 The vsnprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vsnprintf_s(char * restrict s, rsize_t n,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The %n specifier388) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to vsnprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the vsnprintf_s function sets s[0] to the null character.
+
The vsnprintf_s function is equivalent to the vsnprintf function except for the explicit runtime-constraints listed above. -
+
The vsnprintf_s function, unlike vsprintf_s, will truncate the result to fit within the array pointed to by s.
+
The vsnprintf_s function returns the number of characters that would have been written had n been sufficiently large, not counting the terminating null character, or a negative value if a runtime-constraint violation occurred. Thus, the null-terminated @@ -27999,7 +29348,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
388) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
@@ -28007,37 +29356,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.13 The vsprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vsprintf_s(char * restrict s, rsize_t n,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The number of characters (including the trailing null) required for the result to be written to the array pointed to by s shall not be greater than n. The %n specifier389) (modified or not by flags, field width, or precision) shall not appear in the string pointed to by format. Any argument to vsprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the vsprintf_s function sets s[0] to the null character.
+
The vsprintf_s function is equivalent to the vsprintf function except for the parameter n and the explicit runtime-constraints listed above. -
+
The vsprintf_s function, unlike vsnprintf_s, treats a result too big for the array pointed to by s as a runtime-constraint violation.
+
If no runtime-constraint violation occurred, the vsprintf_s function returns the number of characters written in the array, not counting the terminating null character. If an encoding error occurred, vsprintf_s returns a negative value. If any other @@ -28046,7 +29396,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
389) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed
@@ -28054,32 +29404,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
format string was %%n.
-K.3.5.3.14 The vsscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
int vsscanf_s(const char * restrict s,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vsscanf_s function does not attempt to perform further input, and it is unspecified to what extent vsscanf_s performed input before discovering the runtime-constraint violation.
+
The vsscanf_s function is equivalent to sscanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vsscanf_s function does not invoke the va_end macro.390)
+
The vsscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
vscanf_s function returns the number of input items assigned, which can be fewer than
@@ -28091,49 +29442,50 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
indeterminate.
-K.3.5.4 Character input/output functions
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
- char *gets_s(char *s, rsize_t n);
+ char *gets_s(char *s, rsize_t n);
+
-
+
Runtime-constraints
-+
s shall not be a null pointer. n shall neither be equal to zero nor be greater than RSIZE_MAX. A new-line character, end-of-file, or read error shall occur within reading n-1 characters from stdin.391) -
+
If there is a runtime-constraint violation, s[0] is set to the null character, and characters are read and discarded from stdin until a new-line character is read, or end-of-file or a read error occurs.
+
The gets_s function reads at most one less than the number of characters specified by n from the stream pointed to by stdin, into the array pointed to by s. No additional characters are read after a new-line character (which is discarded) or after end-of-file. The discarded new-line character does not count towards number of characters read. A null character is written immediately after the last character read into the array. -
+
If end-of-file is encountered and no characters have been read into the array, or if a read error occurs during the operation, then s[0] is set to the null character, and the other elements of s take unspecified values. - Recommended practice -
+
The fgets function allows properly-written programs to safely process input lines too long to store in the result array. In general this requires that callers of fgets pay attention to the presence or absence of a new-line character in the result array. Consider using fgets (along with any needed processing based on new-line characters) instead of gets_s.
+
The gets_s function returns s if successful. If there was a runtime-constraint violation, or if end-of-file is encountered and no characters have been read into the array, or if a read error occurs during the operation, then a null pointer is returned. @@ -28141,7 +29493,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
391) The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for
@@ -28150,44 +29502,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expect such a relationship.
-K.3.6 General utilities
-
+
The header <stdlib.h> defines three types. -
+
The types are
- errno_t+ errno_t + which is type int; and
- rsize_t+ rsize_t + which is the type size_t; and
- constraint_handler_t+ constraint_handler_t + which has the following definition
typedef void (*constraint_handler_t)(
const char * restrict msg,
void * restrict ptr,
- errno_t error);
+ errno_t error);
+
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
+ constraint_handler_t handler);
+
+
The set_constraint_handler_s function sets the runtime-constraint handler to be handler. The runtime-constraint handler is the function to be called when a library function detects a runtime-constraint violation. Only the most recent handler registered with set_constraint_handler_s is called when a runtime-constraint violation occurs. -
+
When the handler is called, it is passed the following arguments in the following order:
+
The implementation has a default constraint handler that is used if no calls to the set_constraint_handler_s function have been made. The behavior of the default handler is implementation-defined, and it may cause the program to exit or abort. -
+
If the handler argument to set_constraint_handler_s is a null pointer, the implementation default handler becomes the current constraint handler.
+
The set_constraint_handler_s function returns a pointer to the previously
registered handler.392)
@@ -28214,55 +29571,57 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
pointer argument, a pointer to the implementation default handler is returned (not NULL).
-K.3.6.1.2 The abort_handler_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
void abort_handler_s(
const char * restrict msg,
void * restrict ptr,
- errno_t error);
+ errno_t error);
+
+
A pointer to the abort_handler_s function shall be a suitable argument to the set_constraint_handler_s function. -
+
The abort_handler_s function writes a message on the standard error stream in an implementation-defined format. The message shall include the string pointed to by msg. The abort_handler_s function then calls the abort function.393)
+
The abort_handler_s function does not return to its caller. - +
393) Many implementations invoke a debugger when the abort function is called.
-K.3.6.1.3 The ignore_handler_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
void ignore_handler_s(
const char * restrict msg,
void * restrict ptr,
- errno_t error);
+ errno_t error);
+
+
A pointer to the ignore_handler_s function shall be a suitable argument to the set_constraint_handler_s function. -
+
The ignore_handler_s function simply returns to its caller.394)
+
The ignore_handler_s function returns no value.
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
errno_t getenv_s(size_t * restrict len,
char * restrict value, rsize_t maxsize,
- const char * restrict name);
+ const char * restrict name);
+
Runtime-constraints
-+
name shall not be a null pointer. maxsize shall neither equal zero nor be greater than RSIZE_MAX. If maxsize is not equal to zero, then value shall not be a null pointer. -
+
If there is a runtime-constraint violation, the integer pointed to by len is set to 0 (if len is not null), and the environment list is not searched.
+
The getenv_s function searches an environment list, provided by the host environment, for a string that matches the string pointed to by name. - -
+ +
If that name is found then getenv_s performs the following actions. If len is not a null pointer, the length of the string associated with the matched list member is stored in the integer pointed to by len. If the length of the associated string is less than maxsize, then the associated string is copied to the array pointed to by value. -
+
If that name is not found then getenv_s performs the following actions. If len is not a null pointer, zero is stored in the integer pointed to by len. If maxsize is greater than zero, then value[0] is set to the null character. -
+
The set of environment names and the method for altering the environment list are implementation-defined.
+
The getenv_s function returns zero if the specified name is found and the associated
string was successfully stored in value. Otherwise, a nonzero value is returned.
-K.3.6.3 Searching and sorting utilities
-
+
These utilities make use of a comparison function to search or sort arrays of unspecified type. Where an argument declared as size_t nmemb specifies the length of the array for a function, if nmemb has the value zero on a call to that function, then the comparison function is not called, a search finds no matching element, sorting performs no rearrangement, and the pointer to the array may be null. -
+
The implementation shall ensure that the second argument of the comparison function (when called from bsearch_s), or both arguments (when called from qsort_s), are pointers to elements of the array.395) The first argument when called from bsearch_s shall equal key. -
+
The comparison function shall not alter the contents of either the array or search key. The implementation may reorder elements of the array between calls to the comparison function, but shall not otherwise alter the contents of any individual element. -
+
When the same objects (consisting of size bytes, irrespective of their current positions in the array) are passed more than once to the comparison function, the results shall be consistent with one another. That is, for qsort_s they shall define a total ordering on @@ -28340,8 +29700,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
A sequence point occurs immediately before and immediately after each call to the comparison function, and also between any call to the comparison function and any movement of the objects passed as arguments to that call. @@ -28352,12 +29712,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
((char *)p - (char *)base) % size == 0
(char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
+ (char *)p < (char *)base + nmemb * size
+
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
@@ -28365,20 +29726,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
rsize_t nmemb, rsize_t size,
int (*compar)(const void *k, const void *y,
void *context),
- void *context);
+ void *context);
+
Runtime-constraints
-+
Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to zero, then none of key, base, or compar shall be a null pointer. -
+
If there is a runtime-constraint violation, the bsearch_s function does not search the array.
+
The bsearch_s function searches an array of nmemb objects, the initial element of which is pointed to by base, for an element that matches the object pointed to by key. The size of each element of the array is specified by size. -
+
The comparison function pointed to by compar is called with three arguments. The first two point to the key object and to an array element, in that order. The function shall return an integer less than, equal to, or greater than zero if the key object is considered, @@ -28392,9 +29754,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The bsearch_s function returns a pointer to a matching element of the array, or a null
pointer if no match is found or there is a runtime-constraint violation. If two elements
compare as equal, which element is matched is unspecified.
@@ -28406,27 +29768,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, it might specify a collating sequence used by the comparison function.
-K.3.6.3.2 The qsort_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
errno_t qsort_s(void *base, rsize_t nmemb, rsize_t size,
int (*compar)(const void *x, const void *y,
void *context),
- void *context);
+ void *context);
+
Runtime-constraints
-+
Neither nmemb nor size shall be greater than RSIZE_MAX. If nmemb is not equal to zero, then neither base nor compar shall be a null pointer. -
+
If there is a runtime-constraint violation, the qsort_s function does not sort the array.
+
The qsort_s function sorts an array of nmemb objects, the initial element of which is pointed to by base. The size of each object is specified by size. -
+
The contents of the array are sorted into ascending order according to a comparison function pointed to by compar, which is called with three arguments. The first two point to the objects being compared. The function shall return an integer less than, equal @@ -28434,26 +29797,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. equal to, or greater than the second. The third argument to the comparison function is the context argument passed to qsort_s. The sole use of context by qsort_s is to pass it to the comparison function.398) -
+
If two elements compare as equal, their relative order in the resulting sorted array is unspecified.
+
The qsort_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. - +
398) The context argument is for the use of the comparison function in performing its duties. For
example, it might specify a collating sequence used by the comparison function.
-K.3.6.4 Multibyte/wide character conversion functions
-
+
The behavior of the multibyte character functions is affected by the LC_CTYPE category
of the current locale. For a state-dependent encoding, each function is placed into its
initial conversion state by a call for which its character pointer argument, s, is a null
@@ -28468,110 +29831,112 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
character codes, but are grouped with an adjacent multibyte character.
-K.3.6.4.1 The wctomb_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
errno_t wctomb_s(int * restrict status,
char * restrict s,
rsize_t smax,
- wchar_t wc);
+ wchar_t wc);
+
Runtime-constraints
-+
Let n denote the number of bytes needed to represent the multibyte character corresponding to the wide character given by wc (including any shift sequences). -
+
If s is not a null pointer, then smax shall not be less than n, and smax shall not be greater than RSIZE_MAX. If s is a null pointer, then smax shall equal zero. -
+
If there is a runtime-constraint violation, wctomb_s does not modify the int pointed to by status, and if s is not a null pointer, no more than smax elements in the array pointed to by s will be accessed.
+
The wctomb_s function determines n and stores the multibyte character representation of wc in the array whose first element is pointed to by s (if s is not a null pointer). The number of characters stored never exceeds MB_CUR_MAX or smax. If wc is a null wide character, a null byte is stored, preceded by any shift sequence needed to restore the initial shift state, and the function is left in the initial conversion state. -
+
The implementation shall behave as if no library function calls the wctomb_s function. - -
+ +
If s is a null pointer, the wctomb_s function stores into the int pointed to by status a nonzero or zero value, if multibyte character encodings, respectively, do or do not have state-dependent encodings. -
+
If s is not a null pointer, the wctomb_s function stores into the int pointed to by status either n or -1 if wc, respectively, does or does not correspond to a valid multibyte character. -
+
In no case will the int pointed to by status be set to a value greater than the MB_CUR_MAX macro.
+
The wctomb_s function returns zero if successful, and a nonzero value if there was a
runtime-constraint violation or wc did not correspond to a valid multibyte character.
-K.3.6.5 Multibyte/wide string conversion functions
-
+
The behavior of the multibyte string functions is affected by the LC_CTYPE category of
the current locale.
-K.3.6.5.1 The mbstowcs_s function
+
+
#include <stdlib.h>
errno_t mbstowcs_s(size_t * restrict retval,
wchar_t * restrict dst, rsize_t dstmax,
- const char * restrict src, rsize_t len);
+ const char * restrict src, rsize_t len);
+
Runtime-constraints
-+
Neither retval nor src shall be a null pointer. If dst is not a null pointer, then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null character shall occur within the first dstmax multibyte characters of the array pointed to by src. -
+
If there is a runtime-constraint violation, then mbstowcs_s does the following. If retval is not a null pointer, then mbstowcs_s sets *retval to (size_t)(-1). If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX, then mbstowcs_s sets dst[0] to the null wide character.
+
The mbstowcs_s function converts a sequence of multibyte characters that begins in the initial shift state from the array pointed to by src into a sequence of corresponding wide characters. If dst is not a null pointer, the converted characters are stored into the array pointed to by dst. Conversion continues up to and including a terminating null character, which is also stored. Conversion stops earlier in two cases: when a sequence of - + bytes is encountered that does not form a valid multibyte character, or (if dst is not a null pointer) when len wide characters have been stored into the array pointed to by dst.400) If dst is not a null pointer and no null wide character was stored into the array pointed to by dst, then dst[len] is set to the null wide character. Each conversion takes place as if by a call to the mbrtowc function. -
+
Regardless of whether dst is or is not a null pointer, if the input conversion encounters a sequence of bytes that do not form a valid multibyte character, an encoding error occurs: the mbstowcs_s function stores the value (size_t)(-1) into *retval. Otherwise, the mbstowcs_s function stores into *retval the number of multibyte characters successfully converted, not including the terminating null character (if any). -
+
All elements following the terminating null wide character (if any) written by mbstowcs_s in the array of dstmax wide characters pointed to by dst take unspecified values when mbstowcs_s returns.401) -
+
If copying takes place between objects that overlap, the objects take on unspecified values.
+
The mbstowcs_s function returns zero if no runtime-constraint violation and no
encoding error occurred. Otherwise, a nonzero value is returned.
@@ -28582,16 +29947,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
terminating null character did not occur where required.
-K.3.6.5.2 The wcstombs_s function
+
+
#include <stdlib.h>
errno_t wcstombs_s(size_t * restrict retval,
char * restrict dst, rsize_t dstmax,
- const wchar_t * restrict src, rsize_t len);
+ const wchar_t * restrict src, rsize_t len);
+
Runtime-constraints
-+
Neither retval nor src shall be a null pointer. If dst is not a null pointer, then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal @@ -28602,14 +29968,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - -
+ +
If there is a runtime-constraint violation, then wcstombs_s does the following. If retval is not a null pointer, then wcstombs_s sets *retval to (size_t)(-1). If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX, then wcstombs_s sets dst[0] to the null character.
+
The wcstombs_s function converts a sequence of wide characters from the array pointed to by src into a sequence of corresponding multibyte characters that begins in the initial shift state. If dst is not a null pointer, the converted characters are then stored @@ -28627,25 +29993,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pointer, then a null character is stored into the array pointed to by dst immediately following any multibyte characters already stored. Each conversion takes place as if by a call to the wcrtomb function.402) -
+
Regardless of whether dst is or is not a null pointer, if the input conversion encounters a wide character that does not correspond to a valid multibyte character, an encoding error occurs: the wcstombs_s function stores the value (size_t)(-1) into *retval. Otherwise, the wcstombs_s function stores into *retval the number of bytes in the resulting multibyte character sequence, not including the terminating null character (if any). -
+
All elements following the terminating null character (if any) written by wcstombs_s in the array of dstmax elements pointed to by dst take unspecified values when wcstombs_s returns.403) -
+
If copying takes place between objects that overlap, the objects take on unspecified values. - +
+
The wcstombs_s function returns zero if no runtime-constraint violation and no
encoding error occurred. Otherwise, a nonzero value is returned.
@@ -28659,104 +30025,109 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
runtime-constraint violation.
-K.3.7 String handling
-
+
The header <string.h> defines two types. -
+
The types are
- errno_t+ errno_t + which is type int; and
- rsize_t+ rsize_t + which is the type size_t. -
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t memcpy_s(void * restrict s1, rsize_t s1max,
- const void * restrict s2, rsize_t n);
+ const void * restrict s2, rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, the memcpy_s function stores zeros in the first s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than RSIZE_MAX.
+
The memcpy_s function copies n characters from the object pointed to by s2 into the object pointed to by s1.
+
The memcpy_s function returns zero if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
-
+
-K.3.7.1.2 The memmove_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t memmove_s(void *s1, rsize_t s1max,
- const void *s2, rsize_t n);
+ const void *s2, rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n shall not be greater than s1max. -
+
If there is a runtime-constraint violation, the memmove_s function stores zeros in the first s1max characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than RSIZE_MAX.
+
The memmove_s function copies n characters from the object pointed to by s2 into the object pointed to by s1. This copying takes place as if the n characters from the object pointed to by s2 are first copied into a temporary array of n characters that does not overlap the objects pointed to by s1 or s2, and then the n characters from the temporary array are copied into the object pointed to by s1.
+
The memmove_s function returns zero if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
-K.3.7.1.3 The strcpy_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t strcpy_s(char * restrict s1,
rsize_t s1max,
- const char * restrict s2);
+ const char * restrict s2);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall not equal zero. s1max shall be greater than strnlen_s(s2, s1max). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the null character. - +
+
The strcpy_s function copies the string pointed to by s2 (including the terminating null character) into the array pointed to by s1. -
+
All elements following the terminating null character (if any) written by strcpy_s in the array of s1max characters pointed to by s1 take unspecified values when strcpy_s returns.404)
+
The strcpy_s function returns zero405) if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
@@ -28769,44 +30140,45 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
within the array pointed to by s1 and that the result in s1 is null terminated.
-K.3.7.1.4 The strncpy_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t strncpy_s(char * restrict s1,
rsize_t s1max,
const char * restrict s2,
- rsize_t n);
+ rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max shall be greater than strnlen_s(s2, s1max). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then strncpy_s sets s1[0] to the null character.
+
The strncpy_s function copies not more than n successive characters (characters that follow a null character are not copied) from the array pointed to by s2 to the array pointed to by s1. If no null character was copied from s2, then s1[n] is set to a null character. - -
+ +
All elements following the terminating null character (if any) written by strncpy_s in the array of s1max characters pointed to by s1 take unspecified values when strncpy_s returns.406)
+
The strncpy_s function returns zero407) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
+
EXAMPLE 1 The strncpy_s function can be used to copy a string without the danger that the result will not be null terminated or that characters will be written past the end of the destination array.
@@ -28819,7 +30191,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int r1, r2, r3;
r1 = strncpy_s(dst1, 6, src1, 100);
r2 = strncpy_s(dst2, 5, src2, 7);
- r3 = strncpy_s(dst3, 5, src2, 4);
+ r3 = strncpy_s(dst3, 5, src2, 4);
+
The first call will assign to r1 the value zero and to dst1 the sequence hello\0.
The second call will assign to r2 a nonzero value and to dst2 the sequence \0.
The third call will assign to r3 the value zero and to dst3 the sequence good\0.
@@ -28834,45 +30207,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
within the array pointed to by s1 and that the result in s1 is null terminated.
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t strcat_s(char * restrict s1,
rsize_t s1max,
- const char * restrict s2);
+ const char * restrict s2);
+
Runtime-constraints
-+
Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to strcat_s. - -
+ +
Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.408) m shall be greater than strnlen_s(s2, m). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then strcat_s sets s1[0] to the null character.
+
The strcat_s function appends a copy of the string pointed to by s2 (including the terminating null character) to the end of the string pointed to by s1. The initial character from s2 overwrites the null character at the end of s1. -
+
All elements following the terminating null character (if any) written by strcat_s in the array of s1max characters pointed to by s1 take unspecified values when strcat_s returns.409)
+
The strcat_s function returns zero410) if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
@@ -28887,48 +30261,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
appended to the string pointed to by s1 and that the result in s1 is null terminated.
-K.3.7.2.2 The strncat_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t strncat_s(char * restrict s1,
rsize_t s1max,
const char * restrict s2,
- rsize_t n);
+ rsize_t n);
+
Runtime-constraints
-+
Let m denote the value s1max - strnlen_s(s1, s1max) upon entry to strncat_s. -
+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.411) If n is not less - + than m, then m shall be greater than strnlen_s(s2, m). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then strncat_s sets s1[0] to the null character.
+
The strncat_s function appends not more than n successive characters (characters that follow a null character are not copied) from the array pointed to by s2 to the end of the string pointed to by s1. The initial character from s2 overwrites the null character at the end of s1. If no null character was copied from s2, then s1[s1max-m+n] is set to a null character. -
+
All elements following the terminating null character (if any) written by strncat_s in the array of s1max characters pointed to by s1 take unspecified values when strncat_s returns.412)
+
The strncat_s function returns zero413) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
+
EXAMPLE 1 The strncat_s function can be used to copy a string without the danger that the result will not be null terminated or that characters will be written past the end of the destination array.
@@ -28944,12 +30319,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
r1 = strncat_s(s1, 100, s5, 1000);
r2 = strncat_s(s2, 6, "", 1);
r3 = strncat_s(s3, 6, "X", 2);
- r4 = strncat_s(s4, 7, "defghijklmn", 3);
+ r4 = strncat_s(s4, 7, "defghijklmn", 3);
+
After the first call r1 will have the value zero and s1 will contain the sequence goodbye\0.
-
+
After the second call r2 will have the value zero and s2 will contain the sequence hello\0.
After the third call r3 will have a nonzero value and s3 will contain the sequence \0.
After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0.
@@ -28966,36 +30342,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
appended to the string pointed to by s1 and that the result in s1 is null terminated.
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
char *strtok_s(char * restrict s1,
rsize_t * restrict s1max,
const char * restrict s2,
- char ** restrict ptr);
+ char ** restrict ptr);
+
Runtime-constraints
-+
None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX. The end of the token found shall occur within the first *s1max characters of s1 for the first call, and shall occur within the first *s1max characters of where searching resumes on subsequent calls. -
+
If there is a runtime-constraint violation, the strtok_s function does not indirect through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
+
A sequence of calls to the strtok_s function breaks the string pointed to by s1 into a sequence of tokens, each of which is delimited by a character from the string pointed to by s2. The fourth argument points to a caller-provided char pointer into which the strtok_s function stores information necessary for it to continue scanning the same string. -
+
The first call in a sequence has a non-null first argument and s1max points to an object whose value is the number of elements in the character array pointed to by the first argument. The first call stores an initial value in the object pointed to by ptr and @@ -29004,28 +30381,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. objects pointed to by s1max and ptr are required to have the values stored by the previous call in the sequence, which are then updated. The separator string pointed to by s2 may be different from call to call. -
+
The first call in the sequence searches the string pointed to by s1 for the first character that is not contained in the current separator string pointed to by s2. If no such character is found, then there are no tokens in the string pointed to by s1 and the strtok_s function returns a null pointer. If such a character is found, it is the start of the first token. - -
+ +
The strtok_s function then searches from there for the first character in s1 that is contained in the current separator string. If no such character is found, the current token extends to the end of the string pointed to by s1, and subsequent searches in the same string for a token return a null pointer. If such a character is found, it is overwritten by a null character, which terminates the current token. -
+
In all cases, the strtok_s function stores sufficient information in the pointer pointed to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start searching just past the element overwritten by a null character (if any).
+
The strtok_s function returns a pointer to the first character of a token, or a null pointer if there is no token or there is a runtime-constraint violation. -
+
EXAMPLE
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29039,29 +30416,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
t = strtok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
t = strtok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
t = strtok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
+ t = strtok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
+
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
- errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
+ errno_t memset_s(void *s, rsize_t smax, int c, rsize_t n)
+
Runtime-constraints
-+
s shall not be a null pointer. Neither smax nor n shall be greater than RSIZE_MAX. n shall not be greater than smax. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and smax is not greater than RSIZE_MAX, the memset_s function stores the value of c (converted to an unsigned char) into each of the first smax characters of the object pointed to by s. - +
+
The memset_s function copies the value of c (converted to an unsigned char) into each of the first n characters of the object pointed to by s. Unlike memset, any call to the memset_s function shall be evaluated strictly according to the rules of the abstract @@ -29069,75 +30448,78 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. assume that the memory indicated by s and n may be accessible in the future and thus must contain the values indicated by c.
+
The memset_s function returns zero if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
-K.3.7.4.2 The strerror_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
errno_t strerror_s(char *s, rsize_t maxsize,
- errno_t errnum);
+ errno_t errnum);
+
Runtime-constraints
-+
s shall not be a null pointer. maxsize shall not be greater than RSIZE_MAX. maxsize shall not equal zero. -
+
If there is a runtime-constraint violation, then the array (if any) pointed to by s is not modified.
+
The strerror_s function maps the number in errnum to a locale-specific message string. Typically, the values for errnum come from errno, but strerror_s shall map any value of type int to a message. -
+
If the length of the desired string is less than maxsize, then the string is copied to the array pointed to by s. -
+
Otherwise, if maxsize is greater than zero, then maxsize-1 characters are copied from the string to the array pointed to by s and then s[maxsize-1] is set to the null character. Then, if maxsize is greater than 3, then s[maxsize-2], s[maxsize-3], and s[maxsize-4] are set to the character period (.).
+
The strerror_s function returns zero if the length of the desired string was less than
maxsize and there was no runtime-constraint violation. Otherwise, the strerror_s
function returns a nonzero value.
-
+
-K.3.7.4.3 The strerrorlen_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
- size_t strerrorlen_s(errno_t errnum);
+ size_t strerrorlen_s(errno_t errnum);
+
+
The strerrorlen_s function calculates the length of the (untruncated) locale-specific message string that the strerror_s function maps to errnum.
+
The strerrorlen_s function returns the number of characters (not including the null
character) in the full message string.
-K.3.7.4.4 The strnlen_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
- size_t strnlen_s(const char *s, size_t maxsize);
+ size_t strnlen_s(const char *s, size_t maxsize);
+
+
The strnlen_s function computes the length of the string pointed to by s.
+
If s is a null pointer,414) then the strnlen_s function returns zero. -
+
Otherwise, the strnlen_s function returns the number of characters that precede the terminating null character. If there is no null character in the first maxsize characters of s then strnlen_s returns maxsize. At most the first maxsize characters of s shall @@ -29146,7 +30528,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
414) Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints
@@ -29154,20 +30536,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
strnlen_s useful in algorithms that gracefully handle such exceptional data.
-K.3.8 Date and time
-
+
The header <time.h> defines two types. -
+
The types are
- errno_t+ errno_t + which is type int; and
- rsize_t+ rsize_t + which is the type size_t. -
+
A broken-down time is normalized if the values of the members of the tm structure are in their normal rages.415) @@ -29175,40 +30559,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
415) The normal ranges are defined in 7.26.1.
-K.3.8.2 Time conversion functions
-
+
Like the strftime function, the asctime_s and ctime_s functions do not return a
pointer to a static object, and other library functions are permitted to call them.
-K.3.8.2.1 The asctime_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <time.h>
errno_t asctime_s(char *s, rsize_t maxsize,
- const struct tm *timeptr);
+ const struct tm *timeptr);
+
Runtime-constraints
-+
Neither s nor timeptr shall be a null pointer. maxsize shall not be less than 26 and shall not be greater than RSIZE_MAX. The broken-down time pointed to by timeptr shall be normalized. The calendar year represented by the broken-down time pointed to by timeptr shall not be less than calendar year 0 and shall not be greater than calendar year 9999. -
+
If there is a runtime-constraint violation, there is no attempt to convert the time, and s[0] is set to a null character if s is not a null pointer and maxsize is not zero and is not greater than RSIZE_MAX.
+
The asctime_s function converts the normalized broken-down time in the structure pointed to by timeptr into a 26 character (including the null character) string in the - + form
- Sun Sep 16 01:03:52 1973\n\0+ Sun Sep 16 01:03:52 1973\n\0 + The fields making up this string are (in order):
+
The asctime_s function returns zero if the time was successfully converted and stored
into the array pointed to by s. Otherwise, it returns a nonzero value.
-
+
-K.3.8.2.2 The ctime_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <time.h>
errno_t ctime_s(char *s, rsize_t maxsize,
- const time_t *timer);
+ const time_t *timer);
+
Runtime-constraints
-+
Neither s nor timer shall be a null pointer. maxsize shall not be less than 26 and shall not be greater than RSIZE_MAX. -
+
If there is a runtime-constraint violation, s[0] is set to a null character if s is not a null pointer and maxsize is not equal zero and is not greater than RSIZE_MAX.
+
The ctime_s function converts the calendar time pointed to by timer to local time in the form of a string. It is equivalent to
- asctime_s(s, maxsize, localtime_s(timer))- Recommended practice + asctime_s(s, maxsize, localtime_s(timer)) + +
+
The ctime_s function returns zero if the time was successfully converted and stored
into the array pointed to by s. Otherwise, it returns a nonzero value.
-K.3.8.2.3 The gmtime_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <time.h>
struct tm *gmtime_s(const time_t * restrict timer,
- struct tm * restrict result);
+ struct tm * restrict result);
+
Runtime-constraints
-+
Neither timer nor result shall be a null pointer. -
+
If there is a runtime-constraint violation, there is no attempt to convert the time.
+
The gmtime_s function converts the calendar time pointed to by timer into a broken- down time, expressed as UTC. The broken-down time is stored in the structure pointed - + to by result.
+
The gmtime_s function returns result, or a null pointer if the specified time cannot
be converted to UTC or there is a runtime-constraint violation.
-K.3.8.2.4 The localtime_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <time.h>
struct tm *localtime_s(const time_t * restrict timer,
- struct tm * restrict result);
+ struct tm * restrict result);
+
Runtime-constraints
-+
Neither timer nor result shall be a null pointer. -
+
If there is a runtime-constraint violation, there is no attempt to convert the time.
+
The localtime_s function converts the calendar time pointed to by timer into a broken-down time, expressed as local time. The broken-down time is stored in the structure pointed to by result.
+
The localtime_s function returns result, or a null pointer if the specified time
cannot be converted to local time or there is a runtime-constraint violation.
-K.3.9 Extended multibyte and wide character utilities
-
+
The header <wchar.h> defines two types. -
+
The types are
- errno_t+ errno_t + which is type int; and
- rsize_t+ rsize_t + which is the type size_t. -
+
Unless explicitly stated otherwise, if the execution of a function described in this
subclause causes copying to take place between objects that overlap, the objects take on
unspecified values.
-
+
-K.3.9.1 Formatted wide character input/output functions
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
int fwprintf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. The %n specifier416) (modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by format. Any argument to fwprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the fwprintf_s function does not attempt to produce further output, and it is unspecified to what extent fwprintf_s produced output before discovering the runtime-constraint violation.
+
The fwprintf_s function is equivalent to the fwprintf function except for the explicit runtime-constraints listed above.
+
The fwprintf_s function returns the number of wide characters transmitted, or a
negative value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -29374,28 +30767,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.2 The fwscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <wchar.h>
int fwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. - -
+ +
If there is a runtime-constraint violation, the fwscanf_s function does not attempt to perform further input, and it is unspecified to what extent fwscanf_s performed input before discovering the runtime-constraint violation.
+
The fwscanf_s function is equivalent to fwscanf except that the c, s, and [ conversion specifiers apply to a pair of arguments (unless assignment suppression is indicated by a *). The first of these arguments is the same as for fwscanf. That @@ -29403,11 +30797,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. type size_t and gives the number of elements in the array pointed to by the first argument of the pair. If the first argument points to a scalar object, it is considered to be an array of one element.417) -
+
A matching failure occurs if the number of elements in a receiving object is insufficient to hold the converted input (including any trailing null character).
+
The fwscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
fwscanf_s function returns the number of input items assigned, which can be fewer
@@ -29426,37 +30820,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
compatible with rsize_t.
-K.3.9.1.3 The snwprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
int snwprintf_s(wchar_t * restrict s,
rsize_t n,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The %n specifier418) (modified or not by flags, field width, or - + precision) shall not appear in the wide string pointed to by format. Any argument to snwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the snwprintf_s function sets s[0] to the null wide character.
+
The snwprintf_s function is equivalent to the swprintf function except for the explicit runtime-constraints listed above. -
+
The snwprintf_s function, unlike swprintf_s, will truncate the result to fit within the array pointed to by s.
+
The snwprintf_s function returns the number of wide characters that would have
been written had n been sufficiently large, not counting the terminating wide null
character, or a negative value if a runtime-constraint violation occurred. Thus, the null-
@@ -29469,16 +30864,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.4 The swprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
int swprintf_s(wchar_t * restrict s, rsize_t n,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The number of wide characters (including the trailing null) required for the result to be written to the array pointed to by s shall not be greater than n. The %n @@ -29487,20 +30883,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %s specifier shall not be a null pointer. No encoding error shall occur. - -
+ +
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the swprintf_s function sets s[0] to the null wide character.
+
The swprintf_s function is equivalent to the swprintf function except for the explicit runtime-constraints listed above. -
+
The swprintf_s function, unlike snwprintf_s, treats a result too big for the array pointed to by s as a runtime-constraint violation.
+
If no runtime-constraint violation occurred, the swprintf_s function returns the
number of wide characters written in the array, not counting the terminating null wide
character. If an encoding error occurred or if n or more wide characters are requested to
@@ -29513,39 +30909,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.5 The swscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
int swscanf_s(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
+ const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the swscanf_s function does not attempt to perform further input, and it is unspecified to what extent swscanf_s performed input before discovering the runtime-constraint violation.
+
The swscanf_s function is equivalent to fwscanf_s, except that the argument s specifies a wide string from which the input is to be obtained, rather than from a stream. Reaching the end of the wide string is equivalent to encountering end-of-file for the fwscanf_s function.
+
The swscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
swscanf_s function returns the number of input items assigned, which can be fewer
than provided for, or even zero, in the event of an early matching failure.
-
+
-K.3.9.1.6 The vfwprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
@@ -29553,23 +30950,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#include <wchar.h>
int vfwprintf_s(FILE * restrict stream,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. The %n specifier420) (modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by format. Any argument to vfwprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vfwprintf_s function does not attempt to produce further output, and it is unspecified to what extent vfwprintf_s produced output before discovering the runtime-constraint violation.
+
The vfwprintf_s function is equivalent to the vfwprintf function except for the explicit runtime-constraints listed above.
+
The vfwprintf_s function returns the number of wide characters transmitted, or a
negative value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -29579,36 +30977,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.7 The vfwscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
int vfwscanf_s(FILE * restrict stream,
- const wchar_t * restrict format, va_list arg);
+ const wchar_t * restrict format, va_list arg);
+
-
+
Runtime-constraints
-+
Neither stream nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vfwscanf_s function does not attempt to perform further input, and it is unspecified to what extent vfwscanf_s performed input before discovering the runtime-constraint violation.
+
The vfwscanf_s function is equivalent to fwscanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vfwscanf_s function does not invoke the va_end macro.421)
+
The vfwscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
vfwscanf_s function returns the number of input items assigned, which can be fewer
@@ -29619,9 +31018,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
value of arg after the return is indeterminate.
-K.3.9.1.8 The vsnwprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
@@ -29629,29 +31028,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int vsnwprintf_s(wchar_t * restrict s,
rsize_t n,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The %n specifier422) (modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by format. Any argument to vsnwprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. - -
+ +
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the vsnwprintf_s function sets s[0] to the null wide character.
+
The vsnwprintf_s function is equivalent to the vswprintf function except for the explicit runtime-constraints listed above. -
+
The vsnwprintf_s function, unlike vswprintf_s, will truncate the result to fit within the array pointed to by s.
+
The vsnwprintf_s function returns the number of wide characters that would have
been written had n been sufficiently large, not counting the terminating null character, or
a negative value if a runtime-constraint violation occurred. Thus, the null-terminated
@@ -29664,9 +31064,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.9 The vswprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
@@ -29674,30 +31074,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int vswprintf_s(wchar_t * restrict s,
rsize_t n,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. n shall neither equal zero nor be greater than RSIZE_MAX. The number of wide characters (including the trailing null) required for the result to be written to the array pointed to by s shall not be greater than n. The %n specifier423) (modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by format. Any argument to vswprintf_s corresponding to a %s specifier shall not be a null pointer. No encoding error shall occur. -
+
If there is a runtime-constraint violation, then if s is not a null pointer and n is greater than zero and less than RSIZE_MAX, then the vswprintf_s function sets s[0] to the null wide character. - +
+
The vswprintf_s function is equivalent to the vswprintf function except for the explicit runtime-constraints listed above. -
+
The vswprintf_s function, unlike vsnwprintf_s, treats a result too big for the array pointed to by s as a runtime-constraint violation.
+
If no runtime-constraint violation occurred, the vswprintf_s function returns the
number of wide characters written in the array, not counting the terminating null wide
character. If an encoding error occurred or if n or more wide characters are requested to
@@ -29710,26 +31111,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.10 The vswscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <wchar.h>
int vswscanf_s(const wchar_t * restrict s,
const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
Neither s nor format shall be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vswscanf_s function does not attempt to perform further input, and it is unspecified to what extent vswscanf_s performed input before discovering the runtime-constraint violation.
+
The vswscanf_s function is equivalent to swscanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vswscanf_s function does not invoke the @@ -29738,9 +31140,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
+
The vswscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
vswscanf_s function returns the number of input items assigned, which can be fewer
@@ -29751,37 +31153,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
value of arg after the return is indeterminate.
-K.3.9.1.11 The vwprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <wchar.h>
int vwprintf_s(const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
format shall not be a null pointer. The %n specifier425) (modified or not by flags, field width, or precision) shall not appear in the wide string pointed to by format. Any argument to vwprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vwprintf_s function does not attempt to produce further output, and it is unspecified to what extent vwprintf_s produced output before discovering the runtime-constraint violation.
+
The vwprintf_s function is equivalent to the vwprintf function except for the explicit runtime-constraints listed above.
+
The vwprintf_s function returns the number of wide characters transmitted, or a negative value if an output error, encoding error, or runtime-constraint violation occurred. - +
425) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide
@@ -29789,31 +31192,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.12 The vwscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdarg.h>
#include <wchar.h>
int vwscanf_s(const wchar_t * restrict format,
- va_list arg);
+ va_list arg);
+
Runtime-constraints
-+
format shall not be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the vwscanf_s function does not attempt to perform further input, and it is unspecified to what extent vwscanf_s performed input before discovering the runtime-constraint violation.
+
The vwscanf_s function is equivalent to wscanf_s, with the variable argument list replaced by arg, which shall have been initialized by the va_start macro (and possibly subsequent va_arg calls). The vwscanf_s function does not invoke the va_end macro.426)
+
The vwscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
vwscanf_s function returns the number of input items assigned, which can be fewer
@@ -29824,30 +31228,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
value of arg after the return is indeterminate.
-K.3.9.1.13 The wprintf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
- int wprintf_s(const wchar_t * restrict format, ...);
+ int wprintf_s(const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
format shall not be a null pointer. The %n specifier427) (modified or not by flags, field - + width, or precision) shall not appear in the wide string pointed to by format. Any argument to wprintf_s corresponding to a %s specifier shall not be a null pointer. -
+
If there is a runtime-constraint violation, the wprintf_s function does not attempt to produce further output, and it is unspecified to what extent wprintf_s produced output before discovering the runtime-constraint violation.
+
The wprintf_s function is equivalent to the wprintf function except for the explicit runtime-constraints listed above.
+
The wprintf_s function returns the number of wide characters transmitted, or a
negative value if an output error, encoding error, or runtime-constraint violation occurred.
@@ -29857,72 +31262,74 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
example, if the entire format string was L"%%n".
-K.3.9.1.14 The wscanf_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
- int wscanf_s(const wchar_t * restrict format, ...);
+ int wscanf_s(const wchar_t * restrict format, ...);
+
Runtime-constraints
-+
format shall not be a null pointer. Any argument indirected though in order to store converted input shall not be a null pointer. -
+
If there is a runtime-constraint violation, the wscanf_s function does not attempt to perform further input, and it is unspecified to what extent wscanf_s performed input before discovering the runtime-constraint violation.
+
The wscanf_s function is equivalent to fwscanf_s with the argument stdin interposed before the arguments to wscanf_s.
+
The wscanf_s function returns the value of the macro EOF if an input failure occurs
before any conversion or if there is a runtime-constraint violation. Otherwise, the
wscanf_s function returns the number of input items assigned, which can be fewer than
provided for, or even zero, in the event of an early matching failure.
-
+
-K.3.9.2 General wide string utilities
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wcscpy_s(wchar_t * restrict s1,
rsize_t s1max,
- const wchar_t * restrict s2);
+ const wchar_t * restrict s2);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall not equal zero. s1max shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then wcscpy_s sets s1[0] to the null wide character.
+
The wcscpy_s function copies the wide string pointed to by s2 (including the terminating null wide character) into the array pointed to by s1. -
+
All elements following the terminating null wide character (if any) written by wcscpy_s in the array of s1max wide characters pointed to by s1 take unspecified values when wcscpy_s returns.428)
+
The wcscpy_s function returns zero429) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. - +
428) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking
@@ -29933,41 +31340,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
fit within the array pointed to by s1 and that the result in s1 is null terminated.
-K.3.9.2.1.2 The wcsncpy_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wcsncpy_s(wchar_t * restrict s1,
rsize_t s1max,
const wchar_t * restrict s2,
- rsize_t n);
+ rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. s1max shall not equal zero. If n is not less than s1max, then s1max shall be greater than wcsnlen_s(s2, s1max). Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then wcsncpy_s sets s1[0] to the null wide character.
+
The wcsncpy_s function copies not more than n successive wide characters (wide characters that follow a null wide character are not copied) from the array pointed to by s2 to the array pointed to by s1. If no null wide character was copied from s2, then s1[n] is set to a null wide character. -
+
All elements following the terminating null wide character (if any) written by wcsncpy_s in the array of s1max wide characters pointed to by s1 take unspecified values when wcsncpy_s returns.430)
+
The wcsncpy_s function returns zero431) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
+
EXAMPLE 1 The wcsncpy_s function can be used to copy a wide string without the danger that the result will not be null terminated or that wide characters will be written past the end of the destination array. @@ -29975,7 +31383,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
@@ -29986,7 +31394,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int r1, r2, r3;
r1 = wcsncpy_s(dst1, 6, src1, 100);
r2 = wcsncpy_s(dst2, 5, src2, 7);
- r3 = wcsncpy_s(dst3, 5, src2, 4);
+ r3 = wcsncpy_s(dst3, 5, src2, 4);
+
The first call will assign to r1 the value zero and to dst1 the sequence of wide characters hello\0.
The second call will assign to r2 a nonzero value and to dst2 the sequence of wide characters \0.
The third call will assign to r3 the value zero and to dst3 the sequence of wide characters good\0.
@@ -30001,98 +31410,101 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
fit within the array pointed to by s1 and that the result in s1 is null terminated.
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wmemcpy_s(wchar_t * restrict s1,
rsize_t s1max,
const wchar_t * restrict s2,
- rsize_t n);
+ rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n shall not be greater than s1max. Copying shall not take place between objects that overlap. -
+
If there is a runtime-constraint violation, the wmemcpy_s function stores zeros in the first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than RSIZE_MAX.
+
The wmemcpy_s function copies n successive wide characters from the object pointed to by s2 into the object pointed to by s1.
+
The wmemcpy_s function returns zero if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
-
+
-K.3.9.2.1.4 The wmemmove_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wmemmove_s(wchar_t *s1, rsize_t s1max,
- const wchar_t *s2, rsize_t n);
+ const wchar_t *s2, rsize_t n);
+
Runtime-constraints
-+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. n shall not be greater than s1max. -
+
If there is a runtime-constraint violation, the wmemmove_s function stores zeros in the first s1max wide characters of the object pointed to by s1 if s1 is not a null pointer and s1max is not greater than RSIZE_MAX.
+
The wmemmove_s function copies n successive wide characters from the object pointed to by s2 into the object pointed to by s1. This copying takes place as if the n wide characters from the object pointed to by s2 are first copied into a temporary array of n wide characters that does not overlap the objects pointed to by s1 or s2, and then the n wide characters from the temporary array are copied into the object pointed to by s1.
+
The wmemmove_s function returns zero if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
-K.3.9.2.2 Wide string concatenation functions
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wcscat_s(wchar_t * restrict s1,
rsize_t s1max,
- const wchar_t * restrict s2);
+ const wchar_t * restrict s2);
+
Runtime-constraints
-+
Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to wcscat_s. -
+
Neither s1 nor s2 shall be a null pointer. s1max shall not be greater than RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.432) m shall be greater than wcsnlen_s(s2, m). Copying shall not take place between objects that overlap. - -
+ +
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then wcscat_s sets s1[0] to the null wide character.
+
The wcscat_s function appends a copy of the wide string pointed to by s2 (including the terminating null wide character) to the end of the wide string pointed to by s1. The initial wide character from s2 overwrites the null wide character at the end of s1. -
+
All elements following the terminating null wide character (if any) written by wcscat_s in the array of s1max wide characters pointed to by s1 take unspecified values when wcscat_s returns.433)
+
The wcscat_s function returns zero434) if there was no runtime-constraint violation.
Otherwise, a nonzero value is returned.
@@ -30107,48 +31519,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
-K.3.9.2.2.2 The wcsncat_s function
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
errno_t wcsncat_s(wchar_t * restrict s1,
rsize_t s1max,
const wchar_t * restrict s2,
- rsize_t n);
+ rsize_t n);
+
Runtime-constraints
-+
Let m denote the value s1max - wcsnlen_s(s1, s1max) upon entry to wcsncat_s. -
+
Neither s1 nor s2 shall be a null pointer. Neither s1max nor n shall be greater than RSIZE_MAX. s1max shall not equal zero. m shall not equal zero.435) If n is not less than m, then m shall be greater than wcsnlen_s(s2, m). Copying shall not take place between objects that overlap. - -
+ +
If there is a runtime-constraint violation, then if s1 is not a null pointer and s1max is greater than zero and not greater than RSIZE_MAX, then wcsncat_s sets s1[0] to the null wide character.
+
The wcsncat_s function appends not more than n successive wide characters (wide characters that follow a null wide character are not copied) from the array pointed to by s2 to the end of the wide string pointed to by s1. The initial wide character from s2 overwrites the null wide character at the end of s1. If no null wide character was copied from s2, then s1[s1max-m+n] is set to a null wide character. -
+
All elements following the terminating null wide character (if any) written by wcsncat_s in the array of s1max wide characters pointed to by s1 take unspecified values when wcsncat_s returns.436)
+
The wcsncat_s function returns zero437) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
+
EXAMPLE 1 The wcsncat_s function can be used to copy a wide string without the danger that the result will not be null terminated or that wide characters will be written past the end of the destination array. @@ -30165,7 +31578,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. r1 = wcsncat_s(s1, 100, s5, 1000); r2 = wcsncat_s(s2, 6, L"", 1); r3 = wcsncat_s(s3, 6, L"X", 2); - r4 = wcsncat_s(s4, 7, L"defghijklmn", 3); + r4 = wcsncat_s(s4, 7, L"defghijklmn", 3); + After the first call r1 will have the value zero and s1 will be the wide character sequence goodbye\0. After the second call r2 will have the value zero and s2 will be the wide character sequence hello\0. After the third call r3 will have a nonzero value and s3 will be the wide character sequence \0. @@ -30174,7 +31588,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - +
435) Zero means that s1 was not null terminated upon entry to wcsncat_s.
@@ -30187,36 +31601,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
s2 were appended to the wide string pointed to by s1 and that the result in s1 is null terminated.
-K.3.9.2.3 Wide string search functions
+
+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
wchar_t *wcstok_s(wchar_t * restrict s1,
rsize_t * restrict s1max,
const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
+ wchar_t ** restrict ptr);
+
Runtime-constraints
-+
None of s1max, s2, or ptr shall be a null pointer. If s1 is a null pointer, then *ptr shall not be a null pointer. The value of *s1max shall not be greater than RSIZE_MAX. The end of the token found shall occur within the first *s1max wide characters of s1 for the first call, and shall occur within the first *s1max wide characters of where searching resumes on subsequent calls. -
+
If there is a runtime-constraint violation, the wcstok_s function does not indirect through the s1 or s2 pointers, and does not store a value in the object pointed to by ptr.
+
A sequence of calls to the wcstok_s function breaks the wide string pointed to by s1 into a sequence of tokens, each of which is delimited by a wide character from the wide string pointed to by s2. The fourth argument points to a caller-provided wchar_t pointer into which the wcstok_s function stores information necessary for it to continue scanning the same wide string. -
+
The first call in a sequence has a non-null first argument and s1max points to an object whose value is the number of elements in the wide character array pointed to by the first argument. The first call stores an initial value in the object pointed to by ptr and @@ -30225,29 +31640,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. objects pointed to by s1max and ptr are required to have the values stored by the previous call in the sequence, which are then updated. The separator wide string pointed to by s2 may be different from call to call. -
+
The first call in the sequence searches the wide string pointed to by s1 for the first wide character that is not contained in the current separator wide string pointed to by s2. If no such wide character is found, then there are no tokens in the wide string pointed to by s1 and the wcstok_s function returns a null pointer. If such a wide character is found, it is the start of the first token. - -
+ +
The wcstok_s function then searches from there for the first wide character in s1 that is contained in the current separator wide string. If no such wide character is found, the current token extends to the end of the wide string pointed to by s1, and subsequent searches in the same wide string for a token return a null pointer. If such a wide character is found, it is overwritten by a null wide character, which terminates the current token. -
+
In all cases, the wcstok_s function stores sufficient information in the pointer pointed to by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer value for ptr, shall start searching just past the element overwritten by a null wide character (if any).
+
The wcstok_s function returns a pointer to the first wide character of a token, or a null pointer if there is no token or there is a runtime-constraint violation. -
+
EXAMPLE
#define __STDC_WANT_LIB_EXT1__ 1
@@ -30261,29 +31676,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
t = wcstok_s(NULL, &max1, ",", &ptr1); // t points to the token "??b"
t = wcstok_s(str2, &max2, " \t", &ptr2); // t is a null pointer
t = wcstok_s(NULL, &max1, "#,", &ptr1); // t points to the token "c"
- t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
+ t = wcstok_s(NULL, &max1, "?", &ptr1); // t is a null pointer
+
-+
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
+ size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
+
+
The wcsnlen_s function computes the length of the wide string pointed to by s.
+
If s is a null pointer,438) then the wcsnlen_s function returns zero. -
+
Otherwise, the wcsnlen_s function returns the number of wide characters that precede the terminating null wide character. If there is no null wide character in the first maxsize wide characters of s then wcsnlen_s returns maxsize. At most the first - + maxsize wide characters of s shall be accessed by wcsnlen_s.
+
Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the
conversion state) to be a null pointer.
-K.3.9.3.1.1 The wcrtomb_s function
+
+
#include <wchar.h>
errno_t wcrtomb_s(size_t * restrict retval,
char * restrict s, rsize_t smax,
- wchar_t wc, mbstate_t * restrict ps);
+ wchar_t wc, mbstate_t * restrict ps);
+
Runtime-constraints
-+
Neither retval nor ps shall be a null pointer. If s is not a null pointer, then smax shall not equal zero and shall not be greater than RSIZE_MAX. If s is not a null pointer, then smax shall be not be less than the number of bytes to be stored in the array pointed to by s. If s is a null pointer, then smax shall equal zero. -
+
If there is a runtime-constraint violation, then wcrtomb_s does the following. If s is not a null pointer and smax is greater than zero and not greater than RSIZE_MAX, then wcrtomb_s sets s[0] to the null character. If retval is not a null pointer, then wcrtomb_s sets *retval to (size_t)(-1).
+
If s is a null pointer, the wcrtomb_s function is equivalent to the call
- wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps)+ wcrtomb_s(&retval, buf, sizeof buf, L'\0', ps) + where retval and buf are internal variables of the appropriate types, and the size of buf is greater than MB_CUR_MAX. -
+
If s is not a null pointer, the wcrtomb_s function determines the number of bytes needed to represent the multibyte character that corresponds to the wide character given by wc (including any shift sequences), and stores the multibyte character representation @@ -30334,47 +31753,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. sequence needed to restore the initial shift state; the resulting state described is the initial conversion state. - -
+ +
If wc does not correspond to a valid multibyte character, an encoding error occurs: the wcrtomb_s function stores the value (size_t)(-1) into *retval and the conversion state is unspecified. Otherwise, the wcrtomb_s function stores into *retval the number of bytes (including any shift sequences) stored in the array pointed to by s.
+
The wcrtomb_s function returns zero if no runtime-constraint violation and no
encoding error occurred. Otherwise, a nonzero value is returned.
-K.3.9.3.2 Restartable multibyte/wide string conversion functions
-
+
Unlike mbsrtowcs and wcsrtombs, mbsrtowcs_s and wcsrtombs_s do not
permit the ps parameter (the pointer to the conversion state) to be a null pointer.
-K.3.9.3.2.1 The mbsrtowcs_s function
+
+
#include <wchar.h>
errno_t mbsrtowcs_s(size_t * restrict retval,
wchar_t * restrict dst, rsize_t dstmax,
const char ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
Runtime-constraints
-+
None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer, then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal zero. If dst is not a null pointer and len is not less than dstmax, then a null character shall occur within the first dstmax multibyte characters of the array pointed to by *src. -
+
If there is a runtime-constraint violation, then mbsrtowcs_s does the following. If retval is not a null pointer, then mbsrtowcs_s sets *retval to (size_t)(-1). If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX, then mbsrtowcs_s sets dst[0] to the null wide character.
+
The mbsrtowcs_s function converts a sequence of multibyte characters that begins in the conversion state described by the object pointed to by ps, from the array indirectly pointed to by src into a sequence of corresponding wide characters. If dst is not a null @@ -30382,33 +31802,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. continues up to and including a terminating null character, which is also stored. Conversion stops earlier in two cases: when a sequence of bytes is encountered that does not form a valid multibyte character, or (if dst is not a null pointer) when len wide - + characters have been stored into the array pointed to by dst.439) If dst is not a null pointer and no null wide character was stored into the array pointed to by dst, then dst[len] is set to the null wide character. Each conversion takes place as if by a call to the mbrtowc function. -
+
If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if conversion stopped due to reaching a terminating null character) or the address just past the last multibyte character converted (if any). If conversion stopped due to reaching a terminating null character and if dst is not a null pointer, the resulting state described is the initial conversion state. -
+
Regardless of whether dst is or is not a null pointer, if the input conversion encounters a sequence of bytes that do not form a valid multibyte character, an encoding error occurs: the mbsrtowcs_s function stores the value (size_t)(-1) into *retval and the conversion state is unspecified. Otherwise, the mbsrtowcs_s function stores into *retval the number of multibyte characters successfully converted, not including the terminating null character (if any). -
+
All elements following the terminating null wide character (if any) written by mbsrtowcs_s in the array of dstmax wide characters pointed to by dst take unspecified values when mbsrtowcs_s returns.440) -
+
If copying takes place between objects that overlap, the objects take on unspecified values.
+
The mbsrtowcs_s function returns zero if no runtime-constraint violation and no
encoding error occurred. Otherwise, a nonzero value is returned.
@@ -30419,35 +31839,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
terminating null character did not occur where required.
-K.3.9.3.2.2 The wcsrtombs_s function
+
+
#include <wchar.h>
errno_t wcsrtombs_s(size_t * restrict retval,
char * restrict dst, rsize_t dstmax,
const wchar_t ** restrict src, rsize_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
-
+
Runtime-constraints
-+
None of retval, src, *src, or ps shall be null pointers. If dst is not a null pointer, then neither len nor dstmax shall be greater than RSIZE_MAX. If dst is a null pointer, then dstmax shall equal zero. If dst is not a null pointer, then dstmax shall not equal zero. If dst is not a null pointer and len is not less than dstmax, then the conversion shall have been stopped (see below) because a terminating null wide character was reached or because an encoding error occurred. -
+
If there is a runtime-constraint violation, then wcsrtombs_s does the following. If retval is not a null pointer, then wcsrtombs_s sets *retval to (size_t)(-1). If dst is not a null pointer and dstmax is greater than zero and less than RSIZE_MAX, then wcsrtombs_s sets dst[0] to the null character.
+
The wcsrtombs_s function converts a sequence of wide characters from the array indirectly pointed to by src into a sequence of corresponding multibyte characters that begins in the conversion state described by the object pointed to by ps. If dst is not a @@ -30466,7 +31887,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pointer, then a null character is stored into the array pointed to by dst immediately following any multibyte characters already stored. Each conversion takes place as if by a call to the wcrtomb function.441) -
+
If dst is not a null pointer, the pointer object pointed to by src is assigned either a null pointer (if conversion stopped due to reaching a terminating null wide character) or the address just past the last wide character converted (if any). If conversion stopped due to @@ -30474,30 +31895,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. conversion state. - -
+ +
Regardless of whether dst is or is not a null pointer, if the input conversion encounters a wide character that does not correspond to a valid multibyte character, an encoding error occurs: the wcsrtombs_s function stores the value (size_t)(-1) into *retval and the conversion state is unspecified. Otherwise, the wcsrtombs_s function stores into *retval the number of bytes in the resulting multibyte character sequence, not including the terminating null character (if any). -
+
All elements following the terminating null character (if any) written by wcsrtombs_s in the array of dstmax elements pointed to by dst take unspecified values when wcsrtombs_s returns.442) -
+
If copying takes place between objects that overlap, the objects take on unspecified values.
+
The wcsrtombs_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. - +
441) If conversion stops because a terminating null wide character has been reached, the bytes stored
@@ -30509,15 +31930,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
runtime-constraint violation.
-Annex L
+
(normative)
- Analyzability
+ Analyzability
+
-+
This annex specifies optional behavior that can aid in the analyzability of C programs. -
+
An implementation that defines __STDC_ANALYZABLE__ shall conform to the
specifications in this annex.443)
@@ -30526,43 +31948,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
specifications.
-L.2 Definitions
+
+
out-of-bounds store
an (attempted) access (3.1) that, at run time, for a given computational state, would
modify (or, for an object declared volatile, fetch) one or more bytes that lie outside
the bounds permitted by this Standard.
-L.2.2
-
+
bounded undefined behavior undefined behavior (3.4.3) that does not perform an out-of-bounds store. -
+
NOTE 1 The behavior might perform a trap. -
+
NOTE 2 Any values produced or stored might be indeterminate values.
-L.2.3
-
+
critical undefined behavior undefined behavior that is not bounded undefined behavior. -
+
NOTE The behavior might perform an out-of-bounds store or perform a trap.
-
+
-L.3 Requirements
-
+
If the program performs a trap (3.19.5), the implementation is permitted to invoke a runtime-constraint handler. Any such semantics are implementation-defined. -
+
All undefined behavior shall be limited to bounded undefined behavior, except for the following which are permitted to result in critical undefined behavior:
[^ x ^], 3.20 , (comma operator), 5.1.2.4, 6.5.17 , (comma punctuator), 6.5.2, 6.7, 6.7.2.1, 6.7.2.2, @@ -30711,7 +32133,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ++ (postfix increment operator), 6.3.2.1, 6.5.2.4 <stdbool.h> header, 4, 7.18, 7.30.7, H ++ (prefix increment operator), 6.3.2.1, 6.5.3.1 <stddef.h> header, 4, 6.3.2.1, 6.3.2.3, 6.4.4.4, += (addition assignment operator), 6.5.16.2 - + 6.4.5, 6.5.3.4, 6.5.6, 7.19, K.3.3 \x hexadecimal digits (hexadecimal-character <stdint.h> header, 4, 5.2.4.2, 6.10.1, 7.8, escape sequence), 6.4.4.4 7.20, 7.30.8, K.3.3, K.3.4 ^ (bitwise exclusive OR operator), 6.2.6.2, 6.5.11 @@ -30763,7 +32185,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. \u (universal character names), 6.4.3 _IONBF macro, 7.21.1, 7.21.5.5, 7.21.5.6 \v (vertical-tab escape sequence), 5.2.2, 6.4.4.4, _Noreturn, 6.7.4 7.4.1.10 _Pragma operator, 5.1.1.2, 6.10.9 - + _Static_assert, 6.7.10, 7.2 allocated storage, order and contiguity, 7.22.3 _Thread_local storage-class specifier, 6.2.4, and macro, 7.9 6.7.1 AND operators @@ -30815,7 +32237,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. structure/union member, 6.7.2.1 asin functions, 7.12.4.2, F.10.1.2 alignment specifier, 6.7.5 asin type-generic macro, 7.24, G.7 alignof operator, 6.5.3, 6.5.3.4 asinh functions, 7.12.5.2, F.10.2.2 - + asinh type-generic macro, 7.24, G.7 atomic_is_lock_free generic function, asm keyword, J.5.10 7.17.5.1 assert macro, 7.2.1.1 ATOMIC_LLONG_LOCK_FREE macro, 7.17.1 @@ -30867,7 +32289,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 7.17.8.1 6.8.2 atomic_init generic function, 7.17.2.2 brackets operator ([ ]), 6.5.2.1, 6.5.3.2 ATOMIC_INT_LOCK_FREE macro, 7.17.1 brackets punctuator ([ ]), 6.7.6.2, 6.7.9 - + branch cuts, 7.3.3 type-generic macro for, 7.24 break statement, 6.8.6.3 ccosh functions, 7.3.6.4, G.6.2.4 broken-down time, 7.26.1, 7.26.2.3, 7.26.3, type-generic macro for, 7.24 @@ -30919,7 +32341,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. cbrt functions, 7.12.7.1, F.10.4.1 clock_t type, 7.26.1, 7.26.2.1 cbrt type-generic macro, 7.24 CLOCKS_PER_SEC macro, 7.26.1, 7.26.2.1 ccos functions, 7.3.5.4, G.6 clog functions, 7.3.7.2, G.6.3.2 - + type-generic macro for, 7.24 string, 7.23.3, K.3.7.2 clog10 function, 7.30.1 wide string, 7.28.4.3, K.3.9.2.2 clog1p function, 7.30.1 concatenation, preprocessing, see preprocessing @@ -30971,7 +32393,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compound statement, 6.8.2 imaginary, G.4.1 compound-literal operator (( ){ }), 6.5.2.5 imaginary and complex, G.4.3 concatenation functions implicit, 6.3 - + lvalues, 6.3.2.1 csinh functions, 7.3.6.5, G.6.2.5 pointer, 6.3.2.1, 6.3.2.3 type-generic macro for, 7.24 real and complex, 6.3.1.7 csqrt functions, 7.3.8.3, G.6.4.2 @@ -31023,7 +32445,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. critical undefined behavior, L.2.3 increment and decrement csin functions, 7.3.5.5, G.6 default argument promotions, 6.5.2.2 type-generic macro for, 7.24 default initialization, 6.7.9 - + default label, 6.8.1, 6.8.4.2 elif preprocessing directive, 6.10.1 define preprocessing directive, 6.10.3 ellipsis punctuator (...), 6.5.2.2, 6.7.6.3, 6.10.3 defined operator, 6.10.1, 6.10.8 else preprocessing directive, 6.10.1 @@ -31075,7 +32497,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 7.28.6.3.2, 7.28.6.3.3, 7.28.6.4.1, 7.28.6.4.2, ERANGE macro, 7.5, 7.8.2.3, 7.8.2.4, 7.12.1, see also encoding error 7.22.1.3, 7.22.1.4, 7.28.4.1.1, 7.28.4.1.2, see element type, 6.2.5 also range error, pole error - + erf functions, 7.12.8.1, F.10.5.1 exp2 functions, 7.12.6.2, F.10.3.2 erf type-generic macro, 7.24 exp2 type-generic macro, 7.24 erfc functions, 7.12.8.2, F.10.5.2 explicit conversion, 6.3 @@ -31127,7 +32549,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. EXIT_SUCCESS macro, 7.22, 7.22.4.4 FE_INEXACT macro, 7.6, F.3 exp functions, 7.12.6.1, F.10.3.1 FE_INVALID macro, 7.6, 7.12, F.3 exp type-generic macro, 7.24 FE_OVERFLOW macro, 7.6, 7.12, F.3 - + FE_TONEAREST macro, 7.6, F.3 float _Complex type conversion, 6.3.1.6, FE_TOWARDZERO macro, 7.6, F.3 6.3.1.7, 6.3.1.8 FE_UNDERFLOW macro, 7.6, F.3 float _Imaginary type, G.2 @@ -31179,7 +32601,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. status flag fmin type-generic macro, 7.24 flexible array member, 6.7.2.1 fmod functions, 7.12.10.1, F.10.7.1 float _Complex type, 6.2.5 fmod type-generic macro, 7.24 - + fopen function, 7.21.5.3, 7.21.5.4, K.3.5.2.1 K.3.5.3.7, K.3.5.3.9 FOPEN_MAX macro, 7.21.1, 7.21.3, 7.21.4.3, fseek function, 7.21.1, 7.21.5.3, 7.21.7.10, K.3.5.1.1 7.21.9.2, 7.21.9.4, 7.21.9.5, 7.28.3.10 @@ -31231,7 +32653,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. fscanf function, 7.8.1, 7.21.1, 7.21.6.2, fwscanf_s function, K.3.9.1.2, K.3.9.1.5, 7.21.6.4, 7.21.6.7, 7.21.6.9, F.3, K.3.5.3.2 K.3.9.1.7, K.3.9.1.14 fscanf_s function, K.3.5.3.2, K.3.5.3.4, - + gamma functions, 7.12.8, F.10.5 name spaces, 6.2.3 general utilities, 7.22, K.3.6 reserved, 6.4.1, 7.1.3, K.3.1.2 wide string, 7.28.4, K.3.9.2 scope, 6.2.1 @@ -31283,7 +32705,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. identifier, 6.4.2.1, 6.5.1 unsequenced linkage, see linkage indirection operator (*), 6.5.2.1, 6.5.3.2 maximum length, 6.4.2.1 inequality operator (!=), 6.5.9 - + infinitary, 7.12.1 extended, 6.2.5, 6.3.1.1, 6.4.4.1, 7.20 INFINITY macro, 7.3.9.5, 7.12, F.2.1 inter-thread happens before, 5.1.2.4 initial position, 5.2.2 interactive device, 5.1.2.3, 7.21.3, 7.21.5.3 @@ -31335,7 +32757,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. integer type conversion, 6.3.1.1, 6.3.1.3, 6.3.1.4, ispunct function, 7.4.1.2, 7.4.1.7, 7.4.1.9, F.3, F.4 7.4.1.11 integer types, 6.2.5, 7.20 isspace function, 7.4.1.2, 7.4.1.7, 7.4.1.9, - + 7.4.1.10, 7.4.1.11, 7.21.6.2, 7.22.1.3, LC_ALL macro, 7.11, 7.11.1.1, 7.11.2.1 7.22.1.4, 7.28.2.2 LC_COLLATE macro, 7.11, 7.11.1.1, 7.23.4.3, isunordered macro, 7.12.14.6, F.3 7.28.4.4.2 @@ -31387,7 +32809,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. future directions, 6.11 use of functions, 7.1.4 syntax summary, A lifetime, 6.2.4 Latin alphabet, 5.2.1, 6.4.2.1 limits - + environmental, see environmental limits 6.3.1.6, 6.3.1.7, 6.3.1.8 implementation, see implementation limits long double _Imaginary type, G.2 numerical, see numerical limits long double suffix, l or L, 6.4.4.2 @@ -31439,7 +32861,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. logical source lines, 5.1.1.2 malloc function, 7.22.3, 7.22.3.4, 7.22.3.5 long double _Complex type, 6.2.5 manipulation functions long double _Complex type conversion, complex, 7.3.9 - + real, 7.12.11, F.10.8 modf functions, 7.12.6.12, F.10.3.12 matching failure, 7.28.2.6, 7.28.2.8, 7.28.2.10, modifiable lvalue, 6.3.2.1 K.3.9.1.7, K.3.9.1.10, K.3.9.1.12 modification order, 5.1.2.4 @@ -31491,7 +32913,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. string, 7.23.6, K.3.7.4 nearbyint functions, 7.12.9.3, 7.12.9.4, F.3, wide string, 7.28.4.6, K.3.9.2.4 F.10.6.3 mktime function, 7.26.2.3 nearbyint type-generic macro, 7.24 - + nearest integer functions, 7.12.9, F.10.6 operating system, 5.1.2.1, 7.22.4.8 negation operator (!), 6.5.3.3 operations on files, 7.21.4, K.3.5.1 negative zero, 6.2.6.2, 7.12.11.1 operator, 6.4.6 @@ -31543,7 +32965,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ONCE_FLAG_INIT macro, 7.25.1 parentheses punctuator (( )), 6.7.6.3, 6.8.4, 6.8.5 ones' complement, 6.2.6.2 parenthesized expression, 6.5.1 operand, 6.4.6, 6.5 parse state, 7.21.2 - + perform a trap, 3.19.5 preprocessor, 6.10 permitted form of initializer, 6.6 PRIcFASTN macros, 7.8.1 perror function, 7.21.10.4 PRIcLEASTN macros, 7.8.1 @@ -31595,7 +33017,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. defined, 6.10.1 preprocessing tokens, 5.1.1.2, 6.4, 6.10 raise function, 7.14, 7.14.1.1, 7.14.2.1, 7.22.4.1 preprocessing translation unit, 5.1.1.1 rand function, 7.22, 7.22.2.1, 7.22.2.2 - + RAND_MAX macro, 7.22, 7.22.2.1 restrict-qualified type, 6.2.5, 6.7.3 range return statement, 6.8.6.4, F.6 excess, 5.2.4.2.2, 6.3.1.8, 6.8.6.4 rewind function, 7.21.5.3, 7.21.7.10, 7.21.9.5, @@ -31647,7 +33069,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. functions, 7.28.6.4, K.3.9.3.2 string, 7.23.5, K.3.7.3 restore calling environment function, 7.13.2 utility, 7.22.5, K.3.6.3 restrict type qualifier, 6.7.3, 6.7.3.1 wide string, 7.28.4.5, K.3.9.2.3 - + SEEK_CUR macro, 7.21.1, 7.21.9.2 sign and magnitude, 6.2.6.2 SEEK_END macro, 7.21.1, 7.21.9.2 sign bit, 6.2.6.2 SEEK_SET macro, 7.21.1, 7.21.9.2 signal function, 7.14.1.1, 7.22.4.5, 7.22.4.7 @@ -31699,7 +33121,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. SIGFPE macro, 7.12.1, 7.14, 7.14.1.1, J.5.17 7.4.1.10, 7.29.2.1.3 SIGILL macro, 7.14, 7.14.1.1 sprintf function, 7.21.6.6, 7.21.6.13, K.3.5.3.6 SIGINT macro, 7.14 sprintf_s function, K.3.5.3.5, K.3.5.3.6 - + sqrt functions, 7.12.7.5, F.3, F.10.4.5 do, 6.8.5.2 sqrt type-generic macro, 7.24 else, 6.8.4.1 srand function, 7.22.2.2 expression, 6.8.3 @@ -31751,7 +33173,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. break, 6.8.6.3 strcpy function, 7.23.2.3 compound, 6.8.2 strcpy_s function, K.3.7.1.3 continue, 6.8.6.2 strcspn function, 7.23.5.3 - + streams, 7.21.2, 7.22.4.4 7.22.1.4, 7.28.2.2 fully buffered, 7.21.3 strtoull function, 7.8.2.3, 7.22.1.2, 7.22.1.4 line buffered, 7.21.3 strtoumax function, 7.8.2.3 @@ -31803,7 +33225,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. strtold function, 7.12.11.2, 7.22.1.3, F.3 tan functions, 7.12.4.7, F.10.1.7 strtoll function, 7.8.2.3, 7.22.1.2, 7.22.1.4 tan type-generic macro, 7.24, G.7 strtoul function, 7.8.2.3, 7.21.6.2, 7.22.1.2, tanh functions, 7.12.5.6, F.10.2.6 - + tanh type-generic macro, 7.24, G.7 toupper function, 7.4.2.2 temporary lifetime, 6.2.4 towctrans function, 7.29.3.2.1, 7.29.3.2.2 tentative definition, 6.9.2 towlower function, 7.29.3.1.1, 7.29.3.2.1 @@ -31855,7 +33277,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. token concatenation, 6.10.3.3 imaginary, G token pasting, 6.10.3.3 restrict qualified, 6.7.3 tolower function, 7.4.2.1 volatile qualified, 6.7.3 - + uchar.h header, 6.4.4.4, 6.4.5, 7.27 universal character name, 6.4.3 UCHAR_MAX macro, 5.2.4.2.1 unnormalized floating-point numbers, 5.2.4.2.2 UINT_FASTN_MAX macros, 7.20.2.3 unqualified type, 6.2.5 @@ -31907,7 +33329,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. specifier, 6.7.2.1 K.3.9.1.10, K.3.9.1.12 tag, 6.2.3, 6.7.2.3 value, 3.19 type, 6.2.5, 6.7.2.1 value bits, 6.2.6.2 - + variable arguments, 6.10.3, 7.16 vswscanf function, 7.28.2.8 variable arguments header, 7.16 vswscanf_s function, K.3.9.1.10 variable length array, 6.7.6, 6.7.6.2, 6.10.8.3 vwprintf function, 7.21.1, 7.28.2.9, K.3.9.1.11 @@ -31959,7 +33381,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. vswprintf function, 7.28.2.7, K.3.9.1.8, 7.28.4.1.2 K.3.9.1.9 wcstold function, 7.28.4.1.1 vswprintf_s function, K.3.9.1.8, K.3.9.1.9 wcstoll function, 7.8.2.4, 7.28.4.1.2 - + wcstombs function, 7.22.8.2, 7.28.6.4 7.29.1 wcstombs_s function, K.3.6.5.2 wmemchr function, 7.28.4.5.8 wcstoul function, 7.8.2.4, 7.21.6.2, 7.28.2.2, wmemcmp function, 7.28.4.4.5