@@ -44,6 +45,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.+
ISO (the International Organization for Standardization) and IEC (the International @@ -692,6 +695,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. are also for information only. +
With the introduction of new devices and extended character sets, new features may be @@ -726,11 +730,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
This International Standard specifies the form and establishes the interpretation of @@ -762,11 +768,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
1) This International Standard is designed to promote the portability of C programs among a variety of data-processing systems. It is intended for use by implementors and programmers. +
The following referenced documents are indispensable for the application of this @@ -794,6 +801,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. designated IEC 559:1989). +
For the purposes of this International Standard, the following definitions apply. Other @@ -803,6 +811,7 @@ 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. +
access
@@ -817,12 +826,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
NOTE 3 Expressions that are not evaluated do not access objects.
+
alignment
requirement that objects of a particular type be located on storage boundaries with
addresses that are particular multiples of a byte address
+
argument
@@ -832,11 +843,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expression, or a sequence of preprocessing tokens in the comma-separated list bounded
by the parentheses in a function-like macro invocation
+
behavior
external appearance or action
+
implementation-defined behavior
@@ -846,6 +859,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
when a signed integer is shifted right.
+
locale-specific behavior
@@ -857,6 +871,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
characters other than the 26 lowercase Latin letters.
+
undefined behavior
@@ -872,6 +887,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
EXAMPLE An example of undefined behavior is the behavior on integer overflow.
+
unspecified behavior
@@ -883,6 +899,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
evaluated.
+
bit
@@ -892,6 +909,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
NOTE It need not be possible to express the address of each individual bit of an object.
+
byte
@@ -906,12 +924,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
bit.
+
character
<abstract> member of a set of elements used for the organization, control, or
representation of data
+
character
@@ -919,6 +939,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
<C> bit representation that fits in a byte
+
multibyte character
@@ -928,36 +949,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
NOTE The extended character set is a superset of the basic character set.
+
wide character
bit representation that fits in an object of type wchar_t, capable of representing any
character in the current locale
+
constraint
restriction, either syntactic or semantic, by which the exposition of language elements is
to be interpreted
+
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
+
diagnostic message
message belonging to an implementation-defined subset of the implementation's message
output
+
forward reference
reference to a later subclause of this International Standard that contains additional
information relevant to this subclause
+
implementation
@@ -965,11 +992,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
control options, that performs translation of programs for, and supports execution of
functions in, a particular execution environment
+
implementation limit
restriction imposed upon programs by the implementation
+
memory location
@@ -995,13 +1024,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -1011,6 +1042,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
NOTE When referenced, an object may be interpreted as having a particular type; see 6.3.2.1.
+
parameter
@@ -1020,12 +1052,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
+
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
+
runtime-constraint
@@ -1039,21 +1073,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
constraints for a library function are not violated by the program; see K.3.1.4.
+
value
precise meaning of the contents of an object when interpreted as having a specific type
+
implementation-defined value
unspecified value where each implementation documents how the choice is made
+
indeterminate value
either an unspecified value or a trap representation
+
unspecified value
@@ -1063,11 +1101,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
NOTE An unspecified value cannot be a trap representation.
+
trap representation
an object representation that need not represent a value of the object type
+
perform a trap
@@ -1077,11 +1117,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
''representation'', this is the intended usage.2)
-
Footnotes
2) For example, ''Trapping or stopping (if supported) is disabled...'' (F.8.2). Note that fetching a trap representation might perform a trap but is not required to (see 6.2.6.1). +
[^ x^]
@@ -1090,6 +1131,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
+
[_ x_]
@@ -1102,6 +1144,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
+
In this International Standard, ''shall'' is to be interpreted as a requirement on an @@ -1155,7 +1198,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
3) A strictly conforming program can use conditional features (see 6.10.8.3) provided the use is guarded by an appropriate conditional inclusion preprocessing directive using the related macro. For example: @@ -1164,7 +1207,8 @@ 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 @@ -1175,6 +1219,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation. +
An implementation translates C source files and executes C programs in two data- @@ -1185,10 +1230,13 @@ 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. +
A C program need not all be translated at the same time. The text of the program is kept @@ -1204,6 +1252,7 @@ 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). +
The precedence among the syntax rules of translation is specified by the following @@ -1255,7 +1304,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
6) Implementations shall behave as if these separate phases occur, even though many are typically folded together in practice. Source files, translation units, and translated translation units need not necessarily be stored as files, nor need there be any one-to-one correspondence between these entities @@ -1269,6 +1318,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. character. +
A conforming implementation shall produce at least one diagnostic message (identified in @@ -1280,17 +1330,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
-Footnotes
9) The intent is that an implementation should identify the nature of, and where possible localize, each violation. Of course, an implementation is free to produce any number of diagnostics as long as a 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, @@ -1301,6 +1353,7 @@ 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). +
In a freestanding environment (in which C program execution may take place without any @@ -1311,6 +1364,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. The effect of program termination in a freestanding environment is implementation- defined. +
A hosted environment need not be provided, but shall conform to the following @@ -1321,17 +1375,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
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 @@ -1356,11 +1413,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. startup and program termination. -
Footnotes
10) Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as char ** argv, and so on. +
In a hosted environment, a program may use all the functions, macros, type definitions, @@ -1371,6 +1429,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
If the return type of the main function is a type compatible with int, a return from the @@ -1380,11 +1439,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. termination status returned to the host environment is unspecified.
Forward references: definition of terms (7.1.1), the exit function (7.22.4.4). -
Footnotes
11) In accordance with 6.2.4, the lifetimes of objects with automatic storage duration declared in main will have ended in the former case, even where they would not have in the latter. +
The semantic descriptions in this International Standard describe the behavior of an @@ -1458,7 +1518,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -1470,7 +1531,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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).
@@ -1485,7 +1547,8 @@ 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.
@@ -1501,31 +1564,37 @@ 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 @@ -1539,10 +1608,12 @@ 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. @@ -1550,7 +1621,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: expressions (6.5), type qualifiers (6.7.3), statements (6.8), the signal function (7.14), files (7.21.3). -
Footnotes
12) The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status flags and control modes. Floating-point operations implicitly set the status flags; modes affect result values of floating-point operations. Implementations that support such floating-point state are @@ -1562,6 +1633,7 @@ 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 @@ -1768,7 +1840,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. is not tolerant of races or provides hardware race detection. -
Footnotes
14) The execution can usually be viewed as an interleaving of all of the threads. However, some kinds of atomic operations, for example, allow executions inconsistent with a simple interleaving as described below. @@ -1780,8 +1852,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. release/consume in place of release/acquire. +
Two sets of characters and their associated collating sequences shall be defined: the set in @@ -1802,18 +1876,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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
@@ -1834,6 +1912,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). +
Before any other processing takes place, each occurrence of one of the following @@ -1842,31 +1921,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
??= # ??) ] ??! |
??( [ ??' ^ ??> }
- ??/ \ ??< { ??- ~
+ ??/ \ ??< { ??- ~
+
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");
+
-Footnotes
17) The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set. +
The source character set may contain multibyte characters, used to represent members of @@ -1898,6 +1983,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. of a sequence of valid multibyte characters. +
The active position is that location on a display device where the next character output by @@ -1914,28 +2000,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. \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). +
Functions shall be implemented such that they may be interrupted at any time by a signal, @@ -1945,6 +2036,7 @@ 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. +
Both the translation and execution environments constrain the implementation of @@ -1952,6 +2044,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. environmental limits on a conforming implementation; the library-related limits are discussed in clause 7. +
The implementation shall be able to translate and execute at least one program that @@ -1974,7 +2067,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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)
+
Footnotes
18) Implementations should avoid imposing fixed translation limits whenever possible.
19) See ''future language directions'' (6.11.3). +
An implementation is required to document all the limits specified in this subclause, @@ -2006,7 +2101,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. specified in <stdint.h>.
Forward references: integer types <stdint.h> (7.20). -
Contents +
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 @@ -2066,29 +2162,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. UCHAR_MAX.20) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
Forward references: representations of types (6.2.6), conditional inclusion (6.10.1). -
Footnotes
Contents +
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 @@ -2136,7 +2235,8 @@ 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. @@ -2157,18 +2257,20 @@ 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: @@ -2190,7 +2292,8 @@ 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 +2303,8 @@ 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
@@ -2221,7 +2326,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
- [ ]+ [ ] + FLT_MIN_10_EXP -37 DBL_MIN_10_EXP -37 LDBL_MIN_10_EXP -37 @@ -2230,25 +2336,28 @@ 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
+
Recommended practice
Conversion from (at least) double to decimal with DECIMAL_DIG digits and back should be the identity function. @@ -2281,7 +2392,8 @@ 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
@@ -2294,7 +2406,8 @@ 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 @@ -2304,13 +2417,15 @@ 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
@@ -2318,7 +2433,8 @@ 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
+
@@ -2350,7 +2466,8 @@ 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.
@@ -2361,7 +2478,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
(7.22), input/output <stdio.h> (7.21), mathematics <math.h> (7.12).
-Footnotes
21) The floating-point model is intended to clarify the description of each floating-point characteristic and does not require the floating-point arithmetic of the implementation to be identical. @@ -2390,8 +2507,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. limits are one less than shown here. +
In the syntax notation used in this clause, syntactic categories (nonterminals) are @@ -2400,7 +2519,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -2408,8 +2528,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
A summary of the language syntax is given in annex A. +
An identifier can denote an object; a function; a tag or a member of a structure, union, or @@ -2466,6 +2588,7 @@ 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). +
An identifier declared in different scopes or in the same scope more than once can be @@ -2505,7 +2628,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: declarations (6.7), expressions (6.5), external definitions (6.9), statements (6.8). -
Footnotes
29) There is no linkage between different identifiers.
30) A function declaration can contain the storage-class specifier static only if it is at file scope; see @@ -2514,6 +2637,7 @@ 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. +
If more than one declaration of a particular identifier is visible at any point in a @@ -2535,10 +2659,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
32) There is only one name space for tags even though three are possible. +
An object has a storage duration that determines its lifetime. There are four storage @@ -2597,7 +2722,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: array declarators (6.7.6.2), compound literals (6.5.2.5), declarators (6.7.6), function calls (6.5.2.2), initialization (6.7.9), statements (6.8). -
Footnotes
33) The term ''constant address'' means that two pointers to the object constructed at possibly different times will compare equal. The address may be different during two different executions of the same program. @@ -2610,6 +2735,7 @@ 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. +
The meaning of a value stored in an object or returned by a function is determined by the @@ -2786,7 +2912,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -2808,7 +2934,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: compatible type and composite type (6.2.7), declarations (6.7). -
Footnotes
37) A type may be incomplete or complete throughout an entire translation unit, or it may change states at different points within a translation unit. @@ -2846,8 +2972,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. arguments to functions, return values from functions, and members of unions. +
The representations of all types are unspecified except as stated in this subclause. @@ -2899,7 +3027,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: declarations (6.7), expressions (6.5), lvalues, arrays, and function designators (6.3.2.1), order and consistency (7.17.3). -
Footnotes
49) A positional representation for integers that uses the binary digits 0 and 1, in which the values
represented by successive bits are additive, begin with 1, and are multiplied by successive integral
powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
@@ -2908,7 +3036,8 @@ 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. @@ -2922,6 +3051,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. on values of type T may distinguish between them. +
For unsigned integer types other than unsigned char, the bits of the object @@ -2981,7 +3111,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
53) Some combinations of padding bits might generate trap representations, for example, if one padding bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap representation other than as part of an exceptional condition such as an overflow, and this cannot occur @@ -2995,6 +3125,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. bits. +
Two types have compatible type if their types are the same. Additional rules for @@ -3053,18 +3184,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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]); + -
Footnotes
55) Two types need not be identical to be compatible.
56) As specified in 6.2.1, the later declaration might hide the prior declaration. +
Complete object types have alignment requirements which place restrictions on the @@ -3107,11 +3241,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
57) Every over-aligned type is, or contains, a structure or union type with a member to which an extended alignment has been applied. +
Several operators convert operand values from one type to another automatically. This @@ -3124,8 +3259,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. representation.
Forward references: cast operators (6.5.4). +
Every integer type has an integer conversion rank defined as follows: @@ -3171,21 +3308,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: enumeration specifiers (6.7.2.2), structure and union specifiers (6.7.2.1). -
Footnotes
58) The integer promotions are applied only: as part of the usual arithmetic conversions, to certain argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the shift operators, as specified by their respective subclauses. +
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) -
Footnotes
59) NaNs do not compare equal to 0 and thus convert to 1. +
When a value with integer type is converted to another integer type other than _Bool, if @@ -3198,10 +3337,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
60) The rules describe arithmetic on the mathematical value, not the value of a given type of expression. +
When a finite value of real floating type is converted to an integer type other than _Bool, @@ -3220,12 +3360,13 @@ 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. -
Footnotes
61) The remaindering operation performed when a value of integer type is converted to unsigned type need not be performed when a value of real floating type is converted to unsigned type. Thus, the range of portable real floating values is (-1, Utype_MAX+1). +
When a value of real floating type is converted to a real floating type, if the value being @@ -3237,11 +3378,13 @@ 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. +
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. +
When a value of real type is converted to a complex type, the real part of the complex @@ -3252,6 +3395,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. complex value is discarded and the value of the real part is converted according to the conversion rules for the corresponding real type. +
Many operators that expect operands of arithmetic type cause conversions and yield result @@ -3262,7 +3406,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +3431,9 @@ 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) @@ -3298,15 +3443,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
62) For example, addition of a double _Complex and a float entails just the conversion of the float operand to double (and yields a double _Complex result).
63) The cast and assignment operators are still required to remove extra range and precision. +
An lvalue is an expression (with an object type other than void) that potentially @@ -3349,7 +3496,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. increment and decrement operators (6.5.2.4), prefix increment and decrement operators (6.5.3.1), the sizeof operator (6.5.3.4), structure and union members (6.5.2.3). -
Footnotes
64) The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described @@ -3361,6 +3508,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. designator and violates the constraint in 6.5.3.4. +
The (nonexistent) value of a void expression (an expression that has type void) shall not @@ -3369,6 +3517,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. expression, its value or designator is discarded. (A void expression is evaluated for its side effects.) +
A pointer to void may be converted to or from a pointer to any object type. A pointer to @@ -3420,7 +3569,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
66) The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.19.
67) The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to @@ -3431,8 +3580,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. correctly aligned for a pointer to type C. +
Syntax
token:
@@ -3448,12 +3598,13 @@ 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
-Constraints
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. -
Semantics
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. @@ -3498,13 +3649,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (6.5.3.1), preprocessing directives (6.10), preprocessing numbers (6.4.8), string literals (6.4.5). -
Footnotes
69) An additional category, placemarkers, is used internally in translation phase 4 (see 6.10.3.3); it cannot occur in source files. +
Syntax
keyword: one of
@@ -3522,22 +3674,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
enum static _Noreturn
extern struct _Static_assert
float switch _Thread_local
- for typedef
-Semantics
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) -
Footnotes
70) One possible specification for imaginary types appears in annex G. +
Syntax
identifier:
@@ -3554,8 +3709,9 @@ 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
-Semantics
An identifier is a sequence of nondigit characters (including the underscore _, the lowercase and uppercase Latin letters, and other characters) and digits, which designates @@ -3576,7 +3732,7 @@ 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 +
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 @@ -3588,20 +3744,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. identifiers differ only in nonsignificant characters, the behavior is undefined.
Forward references: universal character names (6.4.3), macro replacement (6.10.3). -
Footnotes
71) On systems in which linkers cannot accept extended characters, an encoding of the universal character name may be used in forming valid external identifiers. For example, some otherwise unused character or sequence of characters may be used to encode the \u in a universal character name. Extended characters may produce a long external identifier. +
Semantics
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 @@ -3615,10 +3773,12 @@ 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). @@ -3627,13 +3787,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
Syntax
universal-character-name:
@@ -3641,17 +3802,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
\U hex-quad hex-quad
hex-quad:
hexadecimal-digit hexadecimal-digit
- hexadecimal-digit hexadecimal-digit
-Constraints
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) -
Description
Universal character names may be used in identifiers, character constants, and string literals to designate characters that are not in the basic character set. -
Semantics
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 @@ -3663,7 +3825,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
73) The disallowed characters are the characters in the basic character set and the code positions reserved by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by UTF-16). @@ -3672,32 +3834,35 @@ 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. +
Syntax
constant:
integer-constant
floating-constant
enumeration-constant
- character-constant
-Constraints
Each constant shall have a type and the value of a constant shall be in the range of representable values for its type. -
Semantics
Each constant has a type, determined by its form and value, as detailed later. +
Syntax
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
@@ -3718,17 +3883,18 @@ 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
-Description
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. @@ -3738,7 +3904,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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. @@ -3747,7 +3913,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. be represented.
- Octal or Hexadecimal+ Octal or Hexadecimal + Suffix Decimal Constant Constant none int int @@ -3756,25 +3923,29 @@ 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 @@ -3788,8 +3959,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. its list and has no extended integer type, then the integer constant has no type. +
Syntax
@@ -3797,37 +3969,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
-Description
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 @@ -3836,7 +4009,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence. 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. -
Semantics
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 @@ -3856,7 +4029,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
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 @@ -3869,7 +4042,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
75) 1.23, 1.230, 123e-2, 123e-02, and 1.23L are all different source forms and thus need not convert to the same internal format and value. @@ -3877,19 +4050,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. floating constants (see 7.22.1.3). +
Syntax
enumeration-constant:
- identifier
-Semantics
An identifier declared as an enumeration constant has type int.
Forward references: enumeration specifiers (6.7.2.2). +
Syntax
@@ -3919,8 +4095,9 @@ 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
-Description
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 @@ -3931,14 +4108,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 \\. @@ -3962,7 +4140,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t, and \v.77) -
Constraints
The value of an octal or hexadecimal escape sequence shall be in the range of representable values for the corresponding type: @@ -3971,8 +4149,9 @@ 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 -
Semantics
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 @@ -4025,17 +4204,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: common definitions <stddef.h> (7.19), the mbtowc function (7.22.7.2), Unicode utilities <uchar.h> (7.27). -
Footnotes
77) The semantics of these characters were discussed in 5.2.2. If any other character follows a backslash, the result is not a token and a diagnostic is required. See ''future language directions'' (6.11.4). +
Syntax
string-literal:
- encoding-prefixopt " s-char-sequenceopt "
+ encoding-prefixopt " s-char-sequenceopt "
encoding-prefix:
u8
u
@@ -4047,12 +4227,13 @@ 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
-Constraints
A sequence of adjacent string literal tokens shall not include both a wide string literal and a UTF-8 string literal. -
Description
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. @@ -4064,7 +4245,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. representable either by itself or by the escape sequence \', but the double-quote " shall be represented by the escape sequence \". -
Semantics
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 @@ -4098,7 +4279,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. @@ -4113,30 +4295,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. "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). -
Footnotes
78) A string literal need not be a string (see 7.1.1), because a null character may be embedded in it by a \0 escape sequence. +
Syntax
punctuator: one of
@@ -4146,8 +4333,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
? : ; ...
= *= /= %= += -= <<= >>= &= ^= |=
, # ##
- <: :> <% %> %: %:%:
-Semantics
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 @@ -4158,23 +4346,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). -
Footnotes
79) These tokens are sometimes called ''digraphs''.
80) Thus [ and <: behave differently when ''stringized'' (see 6.10.3.2), but can otherwise be freely interchanged. +
Syntax
header-name:
@@ -4191,8 +4382,9 @@ 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 "
-Semantics
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. @@ -4212,24 +4404,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). -
Footnotes
81) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
82) For an example of a header name preprocessing token used in a #pragma directive, see 6.10.9. +
Syntax
pp-number:
@@ -4241,15 +4436,16 @@ 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 .
-Description
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. -
Semantics
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 @@ -4258,6 +4454,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Except within a character constant, a string literal, or a comment, the characters /* @@ -4283,17 +4480,19 @@ 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; + -
Footnotes
83) Thus, /* ... */ comments do not nest. +
An expression is a sequence of operators and operands that specifies computation of a @@ -4358,17 +4557,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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 @@ -4399,8 +4600,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. documented. +
Syntax
primary-expression:
@@ -4408,8 +4610,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
constant
string-literal
( expression )
- generic-selection
-Semantics
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 @@ -4426,12 +4629,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. designator, or a void expression.
Forward references: declarations (6.7). -
Footnotes
91) Thus, an undeclared identifier is a violation of the syntax. +
Syntax
generic-selection:
@@ -4441,8 +4645,9 @@ 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
-Constraints
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 @@ -4453,7 +4658,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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 @@ -4472,18 +4677,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. long double: cbrtl, \ default: cbrt, \ float: cbrtf \ - )(X) + )(X) + +
Syntax
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 ++
@@ -4492,14 +4699,16 @@ 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
+
+Constraints
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''. -
Semantics
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 [] @@ -4518,7 +4727,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -4530,8 +4740,9 @@ 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). +
Constraints
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. @@ -4543,7 +4754,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. have a type such that its value may be assigned to an object with the unqualified version of the type of its corresponding parameter. -
Semantics
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 @@ -4604,14 +4815,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
Forward references: function declarators (including prototypes) (6.7.6.3), function definitions (6.9.1), the return statement (6.8.6.4), simple assignment (6.5.16.1). -
Footnotes
92) Most often, this is the result of converting an identifier that is a function designator.
93) A function may change the values of its parameters, but these changes cannot affect the values of the @@ -4622,8 +4834,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
94) In other words, function executions do not ''interleave'' with each other. +
Constraints
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. @@ -4631,7 +4844,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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 @@ -4666,7 +4879,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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
@@ -4674,7 +4888,8 @@ 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
+
@@ -4701,7 +4916,8 @@ 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; };
@@ -4720,13 +4936,14 @@ 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). -
Footnotes
95) If the member used to read the contents of a union object is not the same as the member last used to store a value in the object, the appropriate part of the object representation of the value is reinterpreted as an object representation in the new type as described in 6.2.6 (a process sometimes called ''type @@ -4740,12 +4957,13 @@ 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. +
Constraints
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. -
Semantics
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 @@ -4762,7 +4980,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. it).
Forward references: additive operators (6.5.6), compound assignment (6.5.16.2). -
Footnotes
98) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence where T is the type of E: @@ -4771,18 +4989,20 @@ 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. +
Constraints
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. -
Semantics
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 @@ -4809,7 +5029,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -4823,7 +5044,8 @@ 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.
@@ -4833,7 +5055,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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:
@@ -4841,19 +5064,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -4862,7 +5088,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -4872,7 +5099,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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: @@ -4886,7 +5114,8 @@ 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 @@ -4896,7 +5125,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: type names (6.7.7), initialization (6.7.9). -
Footnotes
99) Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types or void only, and the result of a cast expression is not an lvalue. @@ -4906,8 +5135,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the same or overlapping representations. +
Syntax
unary-expression:
@@ -4919,14 +5149,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
sizeof ( type-name )
alignof ( type-name )
unary-operator: one of
- & * + - ~ !
+ & * + - ~ !
+
+Constraints
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. -
Semantics
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). @@ -4937,15 +5169,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operand is decremented.
Forward references: additive operators (6.5.6), compound assignment (6.5.16.2). +
Constraints
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. -
Semantics
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, @@ -4965,7 +5198,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: storage-class specifiers (6.7.1), structure and union specifiers (6.7.2.1). -
Footnotes
102) Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is always true that if E is a function designator or an lvalue that is a valid operand of the unary & operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of @@ -4975,12 +5208,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. end of its lifetime. +
Constraints
The operand of the unary + or - operator shall have arithmetic type; of the ~ operator, integer type; of the ! operator, scalar type. -
Semantics
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. @@ -5002,14 +5236,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Constraints
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. -
Semantics
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 @@ -5035,20 +5270,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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> + @@ -5064,24 +5302,27 @@ 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). -
Footnotes
103) When applied to a parameter declared to have array or function type, the sizeof operator yields the size of the adjusted (pointer) type (see 6.9.1). +
Syntax
cast-expression:
unary-expression
- ( type-name ) cast-expression
-Constraints
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. @@ -5091,7 +5332,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
A pointer type shall not be converted to any floating type. A floating type shall not be converted to any pointer type. -
Semantics
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 @@ -5106,25 +5347,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
Syntax
multiplicative-expression:
cast-expression
multiplicative-expression * cast-expression
multiplicative-expression / cast-expression
- multiplicative-expression % cast-expression
-Constraints
Each of the operands shall have arithmetic type. The operands of the % operator shall have integer type. -
Semantics
The usual arithmetic conversions are performed on the operands.
@@ -5139,19 +5382,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (a/b)*b + a%b shall equal a; otherwise, the behavior of both a/b and a%b is undefined. -
Footnotes
105) This is often called ''truncation toward zero''. +
Syntax
additive-expression:
multiplicative-expression
additive-expression + multiplicative-expression
- additive-expression - multiplicative-expression
-Constraints
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 @@ -5171,7 +5416,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. integer type. (Decrementing is equivalent to subtracting 1.) -
Semantics
If both operands have arithmetic type, the usual arithmetic conversions are performed on them. @@ -5217,7 +5462,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +5470,9 @@ 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. @@ -5234,7 +5480,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: array declarators (6.7.6.2), common definitions <stddef.h> (7.19). -
Footnotes
106) Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In this scheme the integer expression added to or subtracted from the converted pointer is first multiplied by the size of the object originally pointed to, and the resulting pointer is converted back to the @@ -5245,18 +5491,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. element'' requirements. +
Syntax
shift-expression:
additive-expression
shift-expression << additive-expression
- shift-expression >> additive-expression
-Constraints
Each of the operands shall have integer type. -
Semantics
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 @@ -5275,8 +5523,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the resulting value is implementation-defined. +
Syntax
relational-expression:
@@ -5284,8 +5533,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
relational-expression < shift-expression
relational-expression > shift-expression
relational-expression <= shift-expression
- relational-expression >= shift-expression
-Constraints
One of the following shall hold:
Semantics
If both of the operands have arithmetic type, the usual arithmetic conversions are performed. @@ -5319,20 +5569,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (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. -
Footnotes
107) The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''. +
Syntax
equality-expression:
relational-expression
equality-expression == relational-expression
- equality-expression != relational-expression
-Constraints
One of the following shall hold:
Semantics
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 @@ -5375,7 +5627,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
108) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
109) Two objects may be adjacent in memory because they are adjacent elements of a larger array or @@ -5385,17 +5637,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. behavior. +
Syntax
AND-expression:
equality-expression
- AND-expression & equality-expression
-Constraints
Each of the operands shall have integer type. -
Semantics
The usual arithmetic conversions are performed on the operands.
@@ -5408,17 +5662,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Syntax
exclusive-OR-expression:
AND-expression
- exclusive-OR-expression ^ AND-expression
-Constraints
Each of the operands shall have integer type. -
Semantics
The usual arithmetic conversions are performed on the operands.
@@ -5426,17 +5682,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. in the result is set if and only if exactly one of the corresponding bits in the converted operands is set). +
Syntax
inclusive-OR-expression:
exclusive-OR-expression
- inclusive-OR-expression | exclusive-OR-expression
-Constraints
Each of the operands shall have integer type. -
Semantics
The usual arithmetic conversions are performed on the operands.
@@ -5445,17 +5703,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operands is set). +
Syntax
logical-AND-expression:
inclusive-OR-expression
- logical-AND-expression && inclusive-OR-expression
-Constraints
Each of the operands shall have scalar type. -
Semantics
The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0. The result has type int. @@ -5465,17 +5725,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the first and second operands. If the first operand compares equal to 0, the second operand is not evaluated. +
Syntax
logical-OR-expression:
logical-AND-expression
- logical-OR-expression || logical-AND-expression
-Constraints
Each of the operands shall have scalar type. -
Semantics
The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0. The result has type int. @@ -5486,14 +5748,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. not evaluated. +
Syntax
conditional-expression:
logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
-Constraints
The first operand shall have scalar type.
@@ -5507,7 +5771,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Semantics
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 @@ -5542,7 +5806,8 @@ 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):
@@ -5551,26 +5816,29 @@ 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 *
+
-Footnotes
110) A conditional expression does not yield an lvalue. +
Syntax
assignment-expression:
conditional-expression
unary-expression assignment-operator assignment-expression
assignment-operator: one of
- = *= /= %= += -= <<= >>= &= ^= |=
-Constraints
An assignment operator shall have a modifiable lvalue as its left operand. -
Semantics
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 @@ -5584,13 +5852,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
Constraints
One of the following shall hold:112)
Semantics
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 @@ -5634,7 +5903,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -5647,7 +5917,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. @@ -5660,20 +5931,22 @@ 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. -
Footnotes
112) The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion (specified in 6.3.2.1) that changes lvalues to ''the value of the expression'' and thus removes any type qualifiers that were applied to the type category of the expression (for example, it removes const but not volatile from the type int volatile * const). +
Constraints
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 @@ -5684,7 +5957,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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 @@ -5694,7 +5967,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. read-modify-write operation with memory_order_seq_cst memory order semantics.113) -
Footnotes
113) Where a pointer to an atomic object can be formed, this is equivalent to the following code sequence where T is the type of E1: @@ -5703,18 +5976,21 @@ 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. +
Syntax
expression:
assignment-expression
- expression , assignment-expression
-Semantics
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 @@ -5725,7 +6001,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). @@ -5735,21 +6012,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
114) A comma operator does not yield an lvalue. +
Syntax
constant-expression:
- conditional-expression
-Description
A constant expression can be evaluated during translation rather than runtime, and accordingly may be used in any place that a constant may be. -
Constraints
Constant expressions shall not contain assignment, increment, decrement, function-call, or comma operators, except when they are contained within a subexpression that is not @@ -5757,7 +6036,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Each constant expression shall evaluate to a constant that is in the range of representable values for its type. -
Semantics
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 @@ -5810,7 +6089,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
115) The operand of a sizeof operator is usually not evaluated (6.5.3.4).
116) The use of evaluation formats as characterized by FLT_EVAL_METHOD also applies to evaluation in @@ -5824,30 +6103,33 @@ 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.
+
Syntax
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
-Constraints
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 @@ -5860,7 +6142,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
All declarations in the same scope that refer to the same object or function shall specify compatible types. -
Semantics
A declaration specifies the interpretation and attributes of a set of identifiers. A definition of an identifier is a declaration for that identifier that: @@ -5888,12 +6170,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: declarators (6.7.6), enumeration specifiers (6.7.2.2), initialization (6.7.9), type names (6.7.7), type qualifiers (6.7.3). -
Footnotes
119) Function definitions have a different syntax, described in 6.9.1. +
Syntax
storage-class-specifier:
@@ -5902,8 +6185,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
static
_Thread_local
auto
- register
-Constraints
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) @@ -5912,7 +6196,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. _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. -
Semantics
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 @@ -5935,7 +6219,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. or union member objects.
Forward references: type definitions (6.7.8). -
Footnotes
120) See ''future language directions'' (6.11.5).
121) The implementation may treat any register declaration simply as an auto declaration. However, @@ -5946,8 +6230,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. register is sizeof. +
Syntax
type-specifier:
@@ -5965,8 +6250,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atomic-type-specifier
struct-or-union-specifier
enum-specifier
- typedef-name
-Constraints
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 @@ -6006,7 +6292,7 @@ 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). -
Semantics
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 @@ -6018,12 +6304,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). +
Syntax
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
@@ -6032,18 +6319,19 @@ 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
-Constraints
A struct-declaration that does not declare an anonymous structure or anonymous union shall contain a struct-declarator-list. @@ -6064,7 +6352,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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 @@ -6154,20 +6442,24 @@ 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).
@@ -6176,22 +6468,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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: @@ -6199,38 +6495,44 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Footnotes
122) While the number of bits in a _Bool object is at least CHAR_BIT, the width (number of sign and value bits) of a _Bool may be just 1 bit. @@ -6247,25 +6549,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. layouts. +
Syntax
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
-Constraints
The expression that defines the value of an enumeration constant shall be an integer constant expression that has a value representable as an int. -
Semantics
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 @@ -6294,13 +6598,14 @@ 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 }.
Forward references: tags (6.7.2.3). -
Footnotes
127) Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from each other and from other identifiers declared in ordinary declarators. @@ -6308,8 +6613,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. been seen. +
Constraints
A specific type shall have its content defined at most once.
@@ -6318,9 +6624,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
A type specifier of the form
- enum identifier+ enum identifier + without an enumerator list shall only appear after the type it specifies is complete. -
Semantics
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 @@ -6339,35 +6646,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
- 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. @@ -6377,7 +6691,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -6386,7 +6701,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
- 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 @@ -6399,25 +6715,28 @@ 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.
Forward references: declarators (6.7.6), type definitions (6.7.8). -
Footnotes
129) An incomplete type may only by used when the size of an object of that type is not needed. It is not needed, for example, when a typedef name is declared to be a specifier for a structure or union, or when a pointer to or a function returning a structure or union is being declared. (See incomplete types @@ -6431,43 +6750,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
131) A similar construction with enum does not exist. +
Syntax
atomic-type-specifier:
- _Atomic ( type-name )
-Constraints
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. -
Semantics
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. +
Syntax
type-qualifier:
const
restrict
volatile
- _Atomic
-Constraints
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. -
Semantics
The properties associated with qualified types are meaningful only for expressions that are lvalues.132) @@ -6513,7 +6836,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -6531,7 +6855,8 @@ 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 *'' + @@ -6539,11 +6864,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Footnotes
132) The implementation may place a const object that is not volatile in a read-only region of storage. Moreover, the implementation need not allocate storage for such an object if its address is never used. @@ -6563,6 +6889,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
136) Both of these can occur through the use of typedefs. +
Let D be a declaration of an ordinary identifier that provides a means of designating an @@ -6598,7 +6925,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -6611,7 +6939,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{
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.
@@ -6626,7 +6955,8 @@ 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 @@ -6636,7 +6966,8 @@ 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. @@ -6646,7 +6977,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +6988,9 @@ 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. @@ -6670,24 +7002,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. t.n = n; t.v = malloc(n * sizeof (float)); return t; - } + } + -
Footnotes
137) In other words, E depends on the value of P itself rather than on the value of an object referenced indirectly through P. For example, if identifier p has type (int **restrict), then the pointer expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer expressions *p and p[1] are not. +
Syntax
function-specifier:
inline
- _Noreturn
-Constraints
Function specifiers shall be used only in the declaration of an identifier for a function.
@@ -6696,7 +7031,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. to an identifier with internal linkage.
In a hosted environment, no function specifier(s) shall appear in a declaration of main. -
Semantics
A function specifier may appear more than once; the behavior is the same as if it appeared only once. @@ -6722,7 +7057,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
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. @@ -6730,7 +7065,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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)
{
@@ -6745,7 +7079,9 @@ 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 @@ -6764,11 +7100,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. } _Noreturn void g (int i) { // causes undefined behavior if i <= 0 if (i > 0) abort(); - } + } +
Forward references: function definitions (6.9.1). -
Footnotes
138) By using, for example, an alternative to the usual function call mechanism, such as ''inline substitution''. Inline substitution is not textual substitution, nor does it create a new function. Therefore, for example, the expansion of a macro used within the body of the function uses the @@ -6785,14 +7122,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. duration are also distinct in each of the definitions. +
Syntax
alignment-specifier:
_Alignas ( type-name )
- _Alignas ( constant-expression )
-Constraints
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 @@ -6805,7 +7144,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
The first form is equivalent to _Alignas(alignof(type-name)).
@@ -6824,29 +7163,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
141) An alignment specification of zero also does not affect other alignment specifications in the same declaration. +
Syntax
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
@@ -6858,11 +7198,12 @@ 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
-Semantics
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 @@ -6877,35 +7218,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +
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). +
Semantics
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. @@ -6918,7 +7264,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -6928,12 +7275,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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''.
+Constraints
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 @@ -6947,14 +7296,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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.)
@@ -6985,14 +7335,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -7010,7 +7362,8 @@ 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
- }
+ }
+
@@ -7042,19 +7395,21 @@ 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). -
Footnotes
142) When several ''array of'' specifications are adjacent, a multidimensional array is declared.
143) Thus, * can be used only in function declarations that are not definitions (see 6.7.6.3). +
Constraints
A function declarator shall not specify a return type that is a function type or an array type. @@ -7066,15 +7421,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Semantics
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 ''. @@ -7137,7 +7494,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -7154,7 +7512,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. @@ -7162,7 +7521,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -7189,7 +7549,8 @@ 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. @@ -7197,20 +7558,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Footnotes
144) The macros defined in the <stdarg.h> header (7.16) may be used to access arguments that correspond to the ellipsis. @@ -7219,26 +7582,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
146) If both function types are ''old style'', parameter types are not compared. +
Syntax
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 )
-Semantics
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 @@ -7253,7 +7618,8 @@ 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 @@ -7266,21 +7632,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
Syntax
typedef-name:
- identifier
-Constraints
If a typedef name specifies a variably modified type then it shall have block scope. -
Semantics
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 @@ -7290,7 +7658,8 @@ 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
@@ -7300,13 +7669,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -7315,7 +7686,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -7328,7 +7700,8 @@ 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
@@ -7339,7 +7712,8 @@ 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.
@@ -7352,7 +7726,8 @@ 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 @@ -7367,10 +7742,12 @@ 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]; - } + } + +
Syntax
initializer:
@@ -7378,8 +7755,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{ initializer-list }
{ initializer-list , }
initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
+ designationopt initializer
+ initializer-list , designationopt initializer
designation:
designator-list =
designator-list:
@@ -7387,8 +7764,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
designator-list designator
designator:
[ constant-expression ]
- . identifier
-Constraints
No initializer shall attempt to provide a value for an object not contained within the entity being initialized. @@ -7404,18 +7782,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Semantics
An initializer specifies the initial value stored in an object.
@@ -7511,13 +7891,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
@@ -7528,7 +7910,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{ 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
@@ -7536,7 +7919,8 @@ 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].
@@ -7545,13 +7929,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -7566,7 +7952,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
{ 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 +7967,8 @@ 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] = {
@@ -7594,7 +7982,8 @@ 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 @@ -7604,27 +7993,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. @@ -7637,39 +8032,44 @@ 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). -
Footnotes
148) If the initializer list for a subaggregate or contained union does not begin with a left brace, its subobjects are initialized as usual, but the subaggregate or contained union does not become the current object: current objects are associated only with brace-enclosed initializer lists. @@ -7686,16 +8086,18 @@ 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. +
Syntax
static_assert-declaration:
- _Static_assert ( constant-expression , string-literal ) ;
-Constraints
The constant expression shall compare unequal to 0. -
Semantics
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 @@ -7705,8 +8107,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: diagnostics (7.2). +
Syntax
statement:
@@ -7715,8 +8118,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
expression-statement
selection-statement
iteration-statement
- jump-statement
-Semantics
A statement specifies an action to be performed. Except as indicated, statements are executed in sequence. @@ -7738,51 +8142,57 @@ 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). +
Syntax
labeled-statement:
identifier : statement
case constant-expression : statement
- default : statement
-Constraints
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. -
Semantics
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). +
Syntax
compound-statement:
- { block-item-listopt }
+ { block-item-listopt }
block-item-list:
block-item
block-item-list block-item
block-item:
declaration
- statement
-Semantics
A compound statement is a block. +
Syntax
expression-statement:
- expressionopt ;
-Semantics
The expression in an expression statement is evaluated as a void expression for its side effects.153) @@ -7795,7 +8205,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int p(int);
/* ... */
- (void)p(0);
+ (void)p(0);
+
@@ -7806,7 +8217,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
char *s;
/* ... */
while (*s++ != '\0')
- ;
+ ;
+
a null statement is used to supply an empty loop body to the iteration statement.
@@ -7823,23 +8235,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. } /* ... */ end_loop1: ; - } + } +
Forward references: iteration statements (6.8.5). -
Footnotes
153) Such as assignments, and function calls which have side effects. +
Syntax
selection-statement:
if ( expression ) statement
if ( expression ) statement else statement
- switch ( expression ) statement
-Semantics
A selection statement selects among a set of statements depending on the value of a controlling expression. @@ -7848,11 +8263,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. enclosing block. Each associated substatement is also a block whose scope is a strict subset of the scope of the selection statement. +
Constraints
The controlling expression of an if statement shall have scalar type. -
Semantics
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 @@ -7863,8 +8279,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. An else is associated with the lexically nearest preceding if that is allowed by the syntax. +
Constraints
The controlling expression of a switch statement shall have integer type.
@@ -7878,7 +8295,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (Any enclosed switch statement may have a default label or case constant expressions with values that duplicate case constant expressions in the enclosing switch statement.) -
Semantics
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 @@ -7892,7 +8309,7 @@ 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 +
Implementation limits
As discussed in 5.2.4.1, the implementation may limit the number of case values in a switch statement. @@ -7913,33 +8330,36 @@ 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. -
Footnotes
154) That is, the declaration either precedes the switch statement, or it follows the last case or default label associated with the switch that is in the block containing the declaration. +
Syntax
iteration-statement:
while ( expression ) statement
do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
-Constraints
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. -
Semantics
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 @@ -7957,7 +8377,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. a for statement) its expression-3, may be assumed by the implementation to terminate.157) -
Footnotes
155) Code jumped over is not executed. In particular, the controlling expression of a for or while statement is not evaluated before entering the loop body, nor is clause-1 of a for statement. @@ -7967,21 +8387,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. termination cannot be proven. +
The evaluation of the controlling expression takes place before each execution of the loop body. +
The evaluation of the controlling expression takes place after each execution of the loop body. +
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 @@ -7993,38 +8417,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a nonzero constant. -
Footnotes
158) Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration, such that execution of the loop continues until the expression compares equal to 0; and expression-3 specifies an operation (such as incrementing) that is performed after each iteration. +
Syntax
jump-statement:
goto identifier ;
continue ;
break ;
- return expressionopt ;
+ return expressionopt ;
+
-Semantics
A jump statement causes an unconditional jump to another place. +
Constraints
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. -
Semantics
A goto statement causes an unconditional jump to the statement prefixed by the named label in the enclosing function. @@ -8037,8 +8464,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
/* ... */
goto first_time;
@@ -8055,7 +8480,10 @@ 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.
@@ -8070,14 +8498,16 @@ 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.
+
+Constraints
A continue statement shall appear only in or as a loop body. -
Semantics
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 @@ -8086,21 +8516,23 @@ 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
case it is interpreted within that statement), it is equivalent to goto contin;.159)
-Footnotes
159) Following the contin: label is a null statement. +
Constraints
A break statement shall appear only in or as a switch body or loop body. -
Semantics
A break statement terminates execution of the smallest enclosing switch or iteration statement. @@ -8109,13 +8541,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Constraints
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. -
Semantics
A return statement terminates execution of the current function and returns control to its caller. A function may have any number of return statements. @@ -8143,7 +8576,8 @@ 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). @@ -8152,14 +8586,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
160) The return statement is not an assignment. The overlap restriction of subclause 6.5.16.1 does not apply to the case of function return. The representation of floating-point values may have wider range or precision than implied by the type; a cast may be used to remove this extra range and precision. +
Syntax
translation-unit:
@@ -8167,8 +8602,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
translation-unit external-declaration
external-declaration:
function-definition
- declaration
-Constraints
The storage-class specifiers auto and register shall not appear in the declaration specifiers in an external declaration. @@ -8178,7 +8614,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Semantics
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'' @@ -8198,21 +8634,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
161) Thus, if an identifier declared with external linkage is not used in an expression, there need be no external definition for it. +
Syntax
function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement
+ declaration-specifiers declarator declaration-listopt compound-statement
declaration-list:
declaration
- declaration-list declaration
-Constraints
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) @@ -8238,7 +8676,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Semantics
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 @@ -8271,11 +8709,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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:
@@ -8288,7 +8728,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -8298,24 +8739,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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)(); ... */
- }
+ }
+
-Footnotes
162) The intent is that the type category in a function definition cannot be inherited from a typedef:
@@ -8329,15 +8773,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
F *e(void) { /* ... */ } // e returns a pointer to a function
F *((e))(void) { /* ... */ } // same: parentheses irrelevant
int (*fp)(void); // fp points to a function that has type F
- F *Fp; // Fp points to a function that has type F
+ F *Fp; // Fp points to a function that has type F
+
163) See ''future language directions'' (6.11.7).
164) A parameter identifier cannot be redeclared in the function body except in an enclosed block. +
Semantics
If the declaration of an identifier for an object has file scope and an initializer, the declaration is an external definition for the identifier. @@ -8370,23 +8816,26 @@ 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. +
Syntax
preprocessing-file:
- groupopt
+ groupopt
group:
group-part
group group-part
@@ -8396,47 +8845,48 @@ 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
-Description
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 @@ -8455,14 +8905,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Constraints
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). -
Semantics
The implementation can process and skip sections of source files conditionally, include other source files, and replace macros. These capabilities are called preprocessing, @@ -8474,29 +8924,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
-Footnotes
165) Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic significance, as all white space is equivalent except in certain situations during preprocessing (see the # character string literal creation operator in 6.10.3.2, for example). +
Constraints
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 @@ -8507,12 +8961,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Semantics
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 @@ -8541,8 +8996,9 @@ 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. @@ -8558,7 +9014,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: macro replacement (6.10.3), source file inclusion (6.10.2), largest integer types (7.20.1.5). -
Footnotes
166) Because the controlling constant expression is evaluated during translation phase 4, all identifiers either are or are not macro names -- there simply are no keywords, enumeration constants, etc. @@ -8576,16 +9032,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. including within a preprocessing directive. +
Constraints
A #include directive shall identify a header or source file that can be processed by the implementation. -
Semantics
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 @@ -8593,7 +9051,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -8602,13 +9061,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -8630,7 +9091,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
#include <stdio.h>
- #include "myprog.h"
+ #include "myprog.h"
+
@@ -8646,17 +9108,19 @@ 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). -
Footnotes
170) Note that adjacent string literals are not concatenated into a single string literal (see the translation phases in 5.1.1.2); thus, an expansion that results in two string literals is an invalid directive. +
Constraints
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 @@ -8685,7 +9149,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
A parameter identifier in a function-like macro shall be uniquely declared within its scope. -
Semantics
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 @@ -8698,7 +9162,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -8706,9 +9171,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -8737,7 +9203,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
merger, the number of arguments is one more than the number of parameters in the macro
definition (excluding the ...).
-Footnotes
171) Since, by macro-replacement time, all character constants and string literals are preprocessing tokens, not sequences possibly containing identifier-like subsequences (see 5.1.1.2, translation phases), they are never scanned for macro names or parameters. @@ -8745,6 +9211,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
172) Despite the name, a non-directive is a preprocessing directive. +
After the arguments for the invocation of a function-like macro have been identified, @@ -8759,12 +9226,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. were a parameter, and the variable arguments shall form the preprocessing tokens used to replace it. +
Constraints
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. -
Semantics
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 @@ -8783,12 +9251,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ## operators is unspecified. +
Constraints
A ## preprocessing token shall not occur at the beginning or at the end of a replacement list for either form of macro definition. -
Semantics
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 @@ -8814,25 +9283,28 @@ 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.
-Footnotes
173) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that exist only within translation phase 4. +
After all parameters in the replacement list have been substituted and # and ## @@ -8851,6 +9323,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
A macro definition lasts (independent of block structure) until a corresponding #undef @@ -8859,14 +9332,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. @@ -8875,7 +9350,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
@@ -8899,13 +9375,15 @@ 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 @@ -8925,7 +9403,8 @@ 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
@@ -8935,7 +9414,8 @@ 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);
@@ -8944,7 +9424,8 @@ 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"
+
Space around the # and ## tokens in the macro definition is optional.
@@ -8952,11 +9433,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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. @@ -8966,13 +9449,15 @@ 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: @@ -8985,21 +9470,24 @@ 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));
+
+Constraints
The string literal of a #line directive, if present, shall be a character string literal. -
Semantics
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 @@ -9007,7 +9495,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -9015,13 +9504,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -9029,21 +9520,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. previous forms and is then processed as appropriate. +
Semantics
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. +
Semantics
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 @@ -9059,7 +9554,8 @@ 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). @@ -9068,7 +9564,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
174) An implementation is not required to perform macro replacement in pragmas, but it is permitted except for in standard pragmas (where STDC immediately follows pragma). If the result of macro replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still @@ -9078,14 +9574,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
175) See ''future language directions'' (6.11.8). +
Semantics
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 @@ -9100,10 +9599,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. in any standard header.
Forward references: standard headers (7.1.2). -
Footnotes
176) See ''future language directions'' (6.11.9). +
The following macro names shall be defined by the implementation: @@ -9113,15 +9613,18 @@ 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. + @@ -9132,10 +9635,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). -
Footnotes
177) The presumed source file name and line number can be changed by the #line directive.
178) This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in @@ -9144,6 +9648,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Standard. +
The following macro names are conditionally defined by the implementation: @@ -9155,22 +9660,26 @@ 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). @@ -9178,50 +9687,60 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
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__. -
Footnotes
179) The intention is that this will remain an integer constant of type long int that is increased with each revision of this International Standard. +
Semantics
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 @@ -9235,69 +9754,85 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. +
Declaring an identifier with internal linkage at file scope without the static storage- class specifier is an obsolescent feature. +
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. +
Lowercase letters as escape sequences are reserved for future standardization. Other characters may be used in extensions. +
The placement of a storage-class specifier other than at the beginning of the declaration specifiers in a declaration is an obsolescent feature. +
The use of function declarators with empty parentheses (not prototype-format parameter type declarators) is an obsolescent feature. +
The use of function definitions with separate parameter identifier and declaration lists (not prototype-format parameter type and identifier declarators) is an obsolescent feature. +
Pragmas whose first preprocessing token is STDC are reserved for future standardization. +
Macro names beginning with __STDC_ are reserved for future standardization. +
A string is a contiguous sequence of characters terminated by and including the first null @@ -9331,7 +9866,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
180) The functions that make use of the decimal-point character are the numeric conversion functions (7.22.1, 7.28.4.1) and the formatted input/output functions (7.21.6, 7.28.2). @@ -9341,6 +9876,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation's choice. +
Each library function is declared, with a type that includes a prototype, in a header,182) @@ -9350,7 +9886,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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>
@@ -9358,7 +9893,9 @@ 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. @@ -9388,7 +9925,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. A summary of the contents of the standard headers is given in annex B.
Forward references: diagnostics (7.2). -
Footnotes
182) A header is not necessarily a source file, nor are the < and > delimited sequences in header names necessarily valid source file names. @@ -9396,6 +9933,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementations need not support; see 6.10.8.3. +
Each header declares or defines all identifiers listed in its associated subclause, and @@ -9430,11 +9968,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
184) The list of reserved identifiers with external linkage includes math_errhandling, setjmp, va_copy, and va_end. +
Each of the following statements applies unless explicitly stated otherwise in the detailed @@ -9494,7 +10033,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #include <stdlib.h> const char *str; /* ... */ - i = atoi(str); + i = atoi(str); +
#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);
+
-Footnotes
185) This means that an implementation shall provide an actual function for each library function, even if it also provides a macro for that function. @@ -9534,13 +10077,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. appropriate header could specify
- #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. @@ -9554,17 +10099,20 @@ 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. -
Contents +
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.
@@ -9574,18 +10122,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The macro
- static_assert+ static_assert + expands to _Static_assert. +
Synopsis
#include <assert.h>
- void assert(scalar expression);
-Description
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, @@ -9599,19 +10151,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The assert macro returns no value.
Forward references: the abort function (7.22.4.1). -
Footnotes
191) The message written might be of the form: Assertion failed: expression, function abc, file xyz, line nnn. -
Contents +
The header <complex.h> defines macros and declares functions that support complex @@ -9627,26 +10181,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -9656,7 +10215,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: IEC 60559-compatible complex arithmetic (annex G). -
Footnotes
192) See ''future library directions'' (7.30.1).
193) The imaginary unit is a number i such that i 2 = -1. @@ -9664,11 +10223,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
194) A specification for imaginary types is in informative annex G. +
Values are interpreted as radians, not degrees. An implementation may set errno but is not required to. +
Some of the functions below have branch cuts, across which the function is @@ -9688,13 +10249,15 @@ 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. +
Synopsis
#include <complex.h>
- #pragma STDC CX_LIMITED_RANGE on-off-switch
-Description
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 @@ -9712,50 +10275,56 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compound statement. If this pragma is used in any other context, the behavior is undefined. The default state for the pragma is ''off''. -
Footnotes
195) The purpose of the pragma is to allow the implementation to use the formulas:
(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.
+
Synopsis
#include <complex.h>
double complex cacos(double complex z);
float complex cacosf(float complex z);
- long double complex cacosl(long double complex z);
-Description
The cacos functions compute the complex arc cosine of z, with branch cuts outside the interval [-1, +1] along the real axis. -
Returns
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. +
Synopsis
#include <complex.h>
double complex casin(double complex z);
float complex casinf(float complex z);
- long double complex casinl(long double complex z);
-Description
The casin functions compute the complex arc sine of z, with branch cuts outside the interval [-1, +1] along the real axis. -
Returns
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] @@ -9763,229 +10332,259 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. along the real axis. +
Synopsis
#include <complex.h>
double complex catan(double complex z);
float complex catanf(float complex z);
- long double complex catanl(long double complex z);
-Description
The catan functions compute the complex arc tangent of z, with branch cuts outside the interval [-i, +i] along the imaginary axis. -
Returns
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. +
Synopsis
#include <complex.h>
double complex ccos(double complex z);
float complex ccosf(float complex z);
- long double complex ccosl(long double complex z);
-Description
The ccos functions compute the complex cosine of z. -
Returns
The ccos functions return the complex cosine value. +
Synopsis
#include <complex.h>
double complex csin(double complex z);
float complex csinf(float complex z);
- long double complex csinl(long double complex z);
-Description
The csin functions compute the complex sine of z. -
Returns
The csin functions return the complex sine value. +
Synopsis
#include <complex.h>
double complex ctan(double complex z);
float complex ctanf(float complex z);
- long double complex ctanl(long double complex z);
-Description
The ctan functions compute the complex tangent of z. -
Returns
The ctan functions return the complex tangent value. +
Synopsis
#include <complex.h>
double complex cacosh(double complex z);
float complex cacoshf(float complex z);
- long double complex cacoshl(long double complex z);
-Description
The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch cut at values less than 1 along the real axis. -
Returns
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. +
Synopsis
#include <complex.h>
double complex casinh(double complex z);
float complex casinhf(float complex z);
- long double complex casinhl(long double complex z);
-Description
The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts outside the interval [-i, +i] along the imaginary axis. -
Returns
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. +
Synopsis
#include <complex.h>
double complex catanh(double complex z);
float complex catanhf(float complex z);
- long double complex catanhl(long double complex z);
-Description
The catanh functions compute the complex arc hyperbolic tangent of z, with branch cuts outside the interval [-1, +1] along the real axis. -
Returns
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. +
Synopsis
#include <complex.h>
double complex ccosh(double complex z);
float complex ccoshf(float complex z);
- long double complex ccoshl(long double complex z);
-Description
The ccosh functions compute the complex hyperbolic cosine of z. -
Returns
The ccosh functions return the complex hyperbolic cosine value. +
Synopsis
#include <complex.h>
double complex csinh(double complex z);
float complex csinhf(float complex z);
- long double complex csinhl(long double complex z);
-Description
The csinh functions compute the complex hyperbolic sine of z. -
Returns
The csinh functions return the complex hyperbolic sine value. +
Synopsis
#include <complex.h>
double complex ctanh(double complex z);
float complex ctanhf(float complex z);
- long double complex ctanhl(long double complex z);
-Description
The ctanh functions compute the complex hyperbolic tangent of z. -
Returns
The ctanh functions return the complex hyperbolic tangent value. +
Synopsis
#include <complex.h>
double complex cexp(double complex z);
float complex cexpf(float complex z);
- long double complex cexpl(long double complex z);
-Description
The cexp functions compute the complex base-e exponential of z. -
Returns
The cexp functions return the complex base-e exponential value. +
Synopsis
#include <complex.h>
double complex clog(double complex z);
float complex clogf(float complex z);
- long double complex clogl(long double complex z);
-Description
The clog functions compute the complex natural (base-e) logarithm of z, with a branch cut along the negative real axis. -
Returns
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. +
Synopsis
#include <complex.h>
double cabs(double complex z);
float cabsf(float complex z);
- long double cabsl(long double complex z);
-Description
The cabs functions compute the complex absolute value (also called norm, modulus, or magnitude) of z. -
Returns
The cabs functions return the complex absolute value. +
Synopsis
@@ -9993,88 +10592,98 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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);
-Description
The cpow functions compute the complex power function xy , with a branch cut for the first parameter along the negative real axis. -
Returns
The cpow functions return the complex power function value. +
Synopsis
#include <complex.h>
double complex csqrt(double complex z);
float complex csqrtf(float complex z);
- long double complex csqrtl(long double complex z);
-Description
The csqrt functions compute the complex square root of z, with a branch cut along the negative real axis. -
Returns
The csqrt functions return the complex square root value, in the range of the right half- plane (including the imaginary axis). +
Synopsis
#include <complex.h>
double carg(double complex z);
float cargf(float complex z);
- long double cargl(long double complex z);
-Description
The carg functions compute the argument (also called phase angle) of z, with a branch cut along the negative real axis. -
Returns
The carg functions return the value of the argument in the interval [-pi , +pi ]. +
Synopsis
#include <complex.h>
double cimag(double complex z);
float cimagf(float complex z);
- long double cimagl(long double complex z);
-Description
The cimag functions compute the imaginary part of z.196) -
Returns
The cimag functions return the imaginary part value (as a real). -
Footnotes
196) For a variable z of complex type, z == creal(z) + cimag(z)*I. +
Synopsis
#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);
-Description
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 +
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. -
Returns
The CMPLX macros return the complex value x + i y.
@@ -10085,62 +10694,70 @@ 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))) + +
Synopsis
#include <complex.h>
double complex conj(double complex z);
float complex conjf(float complex z);
- long double complex conjl(long double complex z);
-Description
The conj functions compute the complex conjugate of z, by reversing the sign of its imaginary part. -
Returns
The conj functions return the complex conjugate value. +
Synopsis
#include <complex.h>
double complex cproj(double complex z);
float complex cprojf(float complex z);
- long double complex cprojl(long double complex z);
-Description
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))-
Returns
The cproj functions return the value of the projection onto the Riemann sphere. +
Synopsis
#include <complex.h>
double creal(double complex z);
float crealf(float complex z);
- long double creall(long double complex z);
-Description
The creal functions compute the real part of z.197) -
Returns
The creal functions return the real part value. @@ -10149,11 +10766,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
197) For a variable z of complex type, z == creal(z) + cimag(z)*I. -
Contents +
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 @@ -10169,7 +10787,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. characters.199) All letters and digits are printing characters.
Forward references: EOF (7.21.1), localization (7.11). -
Footnotes
198) See ''future library directions'' (7.30.2).
199) In an implementation that uses the seven-bit US ASCII character set, the printing characters are those @@ -10177,28 +10795,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL). +
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. +
Synopsis
#include <ctype.h>
- int isalnum(int c);
-Description
The isalnum function tests for any character for which isalpha or isdigit is true. +
Synopsis
#include <ctype.h>
- int isalpha(int c);
-Description
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 @@ -10209,18 +10832,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
200) The functions islower and isupper test true or false separately for each of these additional characters; all four combinations are possible. +
Synopsis
#include <ctype.h>
- int isblank(int c);
-Description
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 @@ -10228,84 +10853,98 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only for the standard blank characters. +
Synopsis
#include <ctype.h>
- int iscntrl(int c);
-Description
The iscntrl function tests for any control character. +
Synopsis
#include <ctype.h>
- int isdigit(int c);
-Description
The isdigit function tests for any decimal-digit character (as defined in 5.2.1). +
Synopsis
#include <ctype.h>
- int isgraph(int c);
+ int isgraph(int c);
+
-Description
The isgraph function tests for any printing character except space (' '). +
Synopsis
#include <ctype.h>
- int islower(int c);
-Description
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). +
Synopsis
#include <ctype.h>
- int isprint(int c);
-Description
The isprint function tests for any printing character including space (' '). +
Synopsis
#include <ctype.h>
- int ispunct(int c);
-Description
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. +
Synopsis
#include <ctype.h>
- int isspace(int c);
-Description
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 @@ -10314,41 +10953,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ('\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. +
Synopsis
#include <ctype.h>
- int isupper(int c);
-Description
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). +
Synopsis
#include <ctype.h>
- int isxdigit(int c);
-Description
The isxdigit function tests for any hexadecimal-digit character (as defined in 6.4.4.1). +
Synopsis
#include <ctype.h>
- int tolower(int c);
-Description
The tolower function converts an uppercase letter to a corresponding lowercase letter. -
Returns
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, @@ -10356,16 +11002,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. for any given locale); otherwise, the argument is returned unchanged. +
Synopsis
#include <ctype.h>
- int toupper(int c);
-Description
The toupper function converts a lowercase letter to a corresponding uppercase letter. -
Returns
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, @@ -10373,7 +11021,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. for any given locale); otherwise, the argument is returned unchanged. -
Contents +
The header <errno.h> defines several macros, all relating to the reporting of error conditions. @@ -10382,11 +11031,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -10406,7 +11057,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
201) The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue resulting from a function call (for example, *errno()). @@ -10418,7 +11069,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
203) See ''future library directions'' (7.30.3). -
Contents +
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 @@ -10447,12 +11099,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. @@ -10465,7 +11119,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -10476,7 +11131,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -10485,7 +11141,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -10499,7 +11156,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
- FE_DFL_ENV+ FE_DFL_ENV + represents the default floating-point environment -- the one installed at program startup
Footnotes
204) This header is designed to support the floating-point exception status flags and directed-rounding control modes required by IEC 60559, and other similar floating-point state information. It is also designed to facilitate code portability among all systems. @@ -10531,13 +11189,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. FLT_ROUNDS, they are not required to do so. +
Synopsis
#include <fenv.h>
- #pragma STDC FENV_ACCESS on-off-switch
-Description
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 @@ -10564,7 +11224,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
EXAMPLE -
#include <fenv.h>
void f(double x)
@@ -10576,13 +11235,15 @@ 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) -
Footnotes
210) The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag tests and mode changes (e.g., global common subexpression elimination, code motion, and constant folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default @@ -10593,6 +11254,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ''off'', just one evaluation of x + 1 would suffice. +
The following functions provide access to the floating-point status flags.212) The int @@ -10601,7 +11263,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these functions is undefined. -
Footnotes
212) The functions fetestexcept, feraiseexcept, and feclearexcept support the basic abstraction of flags that are either set or clear. An implementation may endow floating-point status flags with more information -- for example, the address of the code which first raised the floating- @@ -10609,17 +11271,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. content of flags. +
Synopsis
#include <fenv.h>
- int feclearexcept(int excepts);
-Description
The feclearexcept function attempts to clear the supported floating-point exceptions represented by its argument. -
Returns
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. @@ -10627,37 +11291,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <fenv.h>
int fegetexceptflag(fexcept_t *flagp,
- int excepts);
-Description
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. -
Returns
The fegetexceptflag function returns zero if the representation was successfully stored. Otherwise, it returns a nonzero value. +
Synopsis
#include <fenv.h>
- int feraiseexcept(int excepts);
-Description
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. -
Returns
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. @@ -10667,20 +11335,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
213) The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations. Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification in F.8.6 is in the same spirit. +
Synopsis
#include <fenv.h>
int fesetexceptflag(const fexcept_t *flagp,
- int excepts);
-Description
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 @@ -10688,24 +11358,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. fegetexceptflag whose second argument represented at least those floating-point exceptions represented by the argument excepts. This function does not raise floating- point exceptions, but only sets the state of the flags. -
Returns
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. +
Synopsis
#include <fenv.h>
- int fetestexcept(int excepts);
-Description
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) -
Returns
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 @@ -10729,45 +11401,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. if (set_excepts & FE_INVALID) f(); if (set_excepts & FE_OVERFLOW) g(); /* ... */ - } + } + -
Footnotes
214) This mechanism allows testing several floating-point exceptions with just one function call. +
The fegetround and fesetround functions provide control of rounding direction modes. +
Synopsis
#include <fenv.h>
- int fegetround(void);
-Description
The fegetround function gets the current rounding direction. -
Returns
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. +
Synopsis
#include <fenv.h>
- int fesetround(int round);
-Description
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. -
Returns
The fesetround function returns zero if and only if the requested rounding direction was established. @@ -10789,86 +11467,96 @@ 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. +
Synopsis
#include <fenv.h>
- int fegetenv(fenv_t *envp);
-Description
The fegetenv function attempts to store the current floating-point environment in the object pointed to by envp. -
Returns
The fegetenv function returns zero if the environment was successfully stored. Otherwise, it returns a nonzero value. +
Synopsis
#include <fenv.h>
- int feholdexcept(fenv_t *envp);
-Description
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) -
Returns
The feholdexcept function returns zero if and only if non-stop floating-point exception handling was successfully installed. -
Footnotes
215) IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For such systems, the feholdexcept function can be used in conjunction with the feupdateenv function to write routines that hide spurious floating-point exceptions from their callers. +
Synopsis
#include <fenv.h>
- int fesetenv(const fenv_t *envp);
-Description
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. -
Returns
The fesetenv function returns zero if the environment was successfully established. Otherwise, it returns a nonzero value. +
Synopsis
#include <fenv.h>
- int feupdateenv(const fenv_t *envp);
-Description
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. -
Returns
The feupdateenv function returns zero if all the actions were successfully carried out. Otherwise, it returns a nonzero value. @@ -10896,9 +11584,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. if (feupdateenv(&save_env)) return /* indication of an environmental problem */; return result; - } + } + -
Contents +
The header <float.h> defines several macros that expand to various limits and parameters of the standard floating-point types. @@ -10907,7 +11597,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. in 5.2.4.2.2. -
Contents +
The header <inttypes.h> includes the header <stdint.h> and extends it with additional facilities provided by hosted implementations. @@ -10915,17 +11606,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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)
Forward references: integer types <stdint.h> (7.20), formatted input/output functions (7.21.6), formatted wide character input/output functions (7.28.2). -
Footnotes
216) See ''future library directions'' (7.30.4). +
Each of the following object-like macros expands to a character string literal containing a * @@ -10939,32 +11632,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -10980,28 +11677,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wprintf(L"The largest integer value is %020" PRIxMAX "\n", i); return 0; - } + } + -
Footnotes
217) Separate macros are given for use with fprintf and fscanf functions because, in the general case, different format specifiers may be required for fprintf and fscanf, even when the type is the same. +
Synopsis
#include <inttypes.h>
- intmax_t imaxabs(intmax_t j);
-Description
The imaxabs function computes the absolute value of an integer j. If the result cannot be represented, the behavior is undefined.218) -
Returns
The imaxabs function returns the absolute value. @@ -11010,42 +11711,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
218) The absolute value of the most negative number cannot be represented in two's complement. +
Synopsis
#include <inttypes.h>
- imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
-Description
The imaxdiv function computes numer / denom and numer % denom in a single operation. -
Returns
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. +
Synopsis
#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);
-Description
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. -
Returns
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 @@ -11056,8 +11761,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (7.22.1.4). +
Synopsis
#include <stddef.h> // for wchar_t
@@ -11065,13 +11771,14 @@ 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);
-Description
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. -
Returns
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 @@ -11082,7 +11789,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (7.28.4.1.2). -
Contents +
The header <iso646.h> defines the following eleven macros (on the left) that expand to the corresponding tokens (on the right): @@ -11098,9 +11806,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. or || or_eq |= xor ^ - xor_eq ^= + xor_eq ^= + -
Contents +
The header <limits.h> defines several macros that expand to various limits and parameters of the standard integer types. @@ -11109,19 +11819,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. in 5.2.4.2.1. -
Contents +
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 +11857,9 @@ 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
@@ -11154,27 +11867,31 @@ 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
implementation.
-Footnotes
219) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
220) See ''future library directions'' (7.30.5). +
Synopsis
#include <locale.h>
- char *setlocale(int category, const char *locale);
-Description
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 @@ -11197,13 +11914,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Returns
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 @@ -11223,7 +11941,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (7.22.8), numeric conversion functions (7.22.1), the strcoll function (7.23.4.3), the strftime function (7.26.3.5), the strxfrm function (7.23.4.5). -
Footnotes
221) The only functions in 7.4 whose behavior is not affected by the current locale are isdigit and isxdigit. @@ -11231,15 +11949,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. locale when category has the value LC_ALL. +
Synopsis
#include <locale.h>
- struct lconv *localeconv(void);
-Description
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) @@ -11257,128 +11978,156 @@ 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.
@@ -11393,7 +12142,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The implementation shall behave as if no library function calls the localeconv function. -
Returns
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 @@ -11404,7 +12153,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -11416,7 +12166,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 "." "." "." "," @@ -11444,7 +12195,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -11453,7 +12205,8 @@ 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 $+ 1.25$ + +
@@ -11461,9 +12214,11 @@ 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
+
-Contents +
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 @@ -11475,7 +12230,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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
@@ -11485,17 +12241,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -11506,7 +12265,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -11516,7 +12276,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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, @@ -11524,20 +12285,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -11548,10 +12312,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -11562,7 +12328,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in <fenv.h>. -
Footnotes
223) Particularly on systems with wide expression evaluation, a <math.h> function might pass arguments and return values in wider format than the synopsis prototype indicates. @@ -11580,6 +12346,7 @@ 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 @@ -11643,7 +12410,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
228) In an implementation that supports infinities, this allows an infinity as an argument to be a domain error if the mathematical domain of the function does not include the infinity. @@ -11653,13 +12420,15 @@ 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. +
Synopsis
#include <math.h>
- #pragma STDC FP_CONTRACT on-off-switch
-Description
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 @@ -11674,24 +12443,27 @@ 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. +
In the synopses in this subclause, real-floating indicates that the argument shall be an expression of real floating type. +
Synopsis
#include <math.h>
- int fpclassify(real-floating x);
-Description
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) -
Returns
The fpclassify macro returns the value of the number classification macro appropriate to the value of its argument. * @@ -11699,52 +12471,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
231) Since an expression can be evaluated with more range and precision than its type has, it is important to know the type that classification is based on. For example, a normal long double value might become subnormal when converted to double, and zero when converted to float. +
Synopsis
#include <math.h>
- int isfinite(real-floating x);
-Description
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. -
Returns
The isfinite macro returns a nonzero value if and only if its argument has a finite value. +
Synopsis
#include <math.h>
- int isinf(real-floating x);
-Description
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. -
Returns
The isinf macro returns a nonzero value if and only if its argument has an infinite value. +
Synopsis
#include <math.h>
- int isnan(real-floating x);
-Description
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. @@ -11752,42 +12530,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The isnan macro returns a nonzero value if and only if its argument has a NaN value. -
Footnotes
232) For the isnan macro, the type for determination does not matter unless the implementation supports NaNs in the evaluation type but not in the semantic type. +
Synopsis
#include <math.h>
- int isnormal(real-floating x);
-Description
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. -
Returns
The isnormal macro returns a nonzero value if and only if its argument has a normal value. +
Synopsis
#include <math.h>
- int signbit(real-floating x);
-Description
The signbit macro determines whether the sign of its argument value is negative.233) -
Returns
The signbit macro returns a nonzero value if and only if the sign of its argument value is negative. @@ -11797,291 +12579,328 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
233) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is unsigned, it is treated as positive. +
Synopsis
#include <math.h>
double acos(double x);
float acosf(float x);
- long double acosl(long double x);
-Description
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]. -
Returns
The acos functions return arccos x in the interval [0, pi ] radians. +
Synopsis
#include <math.h>
double asin(double x);
float asinf(float x);
- long double asinl(long double x);
-Description
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]. -
Returns
The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians. +
Synopsis
#include <math.h>
double atan(double x);
float atanf(float x);
- long double atanl(long double x);
-Description
The atan functions compute the principal value of the arc tangent of x. -
Returns
The atan functions return arctan x in the interval [-pi /2, +pi /2] radians. +
Synopsis
#include <math.h>
double atan2(double y, double x);
float atan2f(float y, float x);
- long double atan2l(long double y, long double x);
-Description
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. -
Returns
The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians. +
Synopsis
#include <math.h>
double cos(double x);
float cosf(float x);
- long double cosl(long double x);
-Description
The cos functions compute the cosine of x (measured in radians). -
Returns
The cos functions return cos x. +
Synopsis
#include <math.h>
double sin(double x);
float sinf(float x);
- long double sinl(long double x);
-Description
The sin functions compute the sine of x (measured in radians). -
Returns
The sin functions return sin x. +
Synopsis
#include <math.h>
double tan(double x);
float tanf(float x);
- long double tanl(long double x);
-Description
The tan functions return the tangent of x (measured in radians). -
Returns
The tan functions return tan x. +
Synopsis
#include <math.h>
double acosh(double x);
float acoshf(float x);
- long double acoshl(long double x);
-Description
The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain error occurs for arguments less than 1. -
Returns
The acosh functions return arcosh x in the interval [0, +(inf)]. +
Synopsis
#include <math.h>
double asinh(double x);
float asinhf(float x);
- long double asinhl(long double x);
-Description
The asinh functions compute the arc hyperbolic sine of x. -
Returns
The asinh functions return arsinh x. +
Synopsis
#include <math.h>
double atanh(double x);
float atanhf(float x);
- long double atanhl(long double x);
-Description
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. -
Returns
The atanh functions return artanh x. +
Synopsis
#include <math.h>
double cosh(double x);
float coshf(float x);
- long double coshl(long double x);
-Description
The cosh functions compute the hyperbolic cosine of x. A range error occurs if the magnitude of x is too large. -
Returns
The cosh functions return cosh x. +
Synopsis
#include <math.h>
double sinh(double x);
float sinhf(float x);
- long double sinhl(long double x);
-Description
The sinh functions compute the hyperbolic sine of x. A range error occurs if the magnitude of x is too large. -
Returns
The sinh functions return sinh x. +
Synopsis
#include <math.h>
double tanh(double x);
float tanhf(float x);
- long double tanhl(long double x);
-Description
The tanh functions compute the hyperbolic tangent of x. -
Returns
The tanh functions return tanh x. +
Synopsis
#include <math.h>
double exp(double x);
float expf(float x);
- long double expl(long double x);
-Description
The exp functions compute the base-e exponential of x. A range error occurs if the magnitude of x is too large. -
Returns
The exp functions return ex . +
Synopsis
#include <math.h>
double exp2(double x);
float exp2f(float x);
- long double exp2l(long double x);
-Description
The exp2 functions compute the base-2 exponential of x. A range error occurs if the magnitude of x is too large. -
Returns
The exp2 functions return 2x . +
Synopsis
#include <math.h>
double expm1(double x);
float expm1f(float x);
- long double expm1l(long double x);
-Description
The expm1 functions compute the base-e exponential of the argument, minus 1. A range error occurs if x is too large.234) -
Returns
The expm1 functions return ex - 1. -
Footnotes
234) For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1. +
Synopsis
#include <math.h>
double frexp(double value, int *exp);
float frexpf(float value, int *exp);
- long double frexpl(long double value, int *exp);
-Description
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. -
Returns
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, @@ -12093,15 +12912,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <math.h>
int ilogb(double x);
int ilogbf(float x);
- int ilogbl(long double x);
-Description
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 @@ -12109,74 +12930,82 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the corresponding logb function and casting the returned value to type int. A domain 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. -
Returns
The ilogb functions return the exponent of x as a signed int value.
Forward references: the logb functions (7.12.6.11). +
Synopsis
#include <math.h>
double ldexp(double x, int exp);
float ldexpf(float x, int exp);
- long double ldexpl(long double x, int exp);
-Description
The ldexp functions multiply a floating-point number by an integral power of 2. A range error may occur. -
Returns
The ldexp functions return x x 2exp . +
Synopsis
#include <math.h>
double log(double x);
float logf(float x);
- long double logl(long double x);
-Description
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. -
Returns
The log functions return loge x. +
Synopsis
#include <math.h>
double log10(double x);
float log10f(float x);
- long double log10l(long double x);
-Description
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. -
Returns
The log10 functions return log10 x. +
Synopsis
#include <math.h>
double log1p(double x);
float log1pf(float x);
- long double log1pl(long double x);
-Description
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. -
Returns
The log1p functions return loge (1 + x). @@ -12185,66 +13014,74 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
235) For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x). +
Synopsis
#include <math.h>
double log2(double x);
float log2f(float x);
- long double log2l(long double x);
-Description
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. -
Returns
The log2 functions return log2 x. +
Synopsis
#include <math.h>
double logb(double x);
float logbf(float x);
- long double logbl(long double x);
-Description
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. -
Returns
The logb functions return the signed exponent of x. +
Synopsis
#include <math.h>
double modf(double value, double *iptr);
float modff(float value, float *iptr);
- long double modfl(long double value, long double *iptr);
-Description
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. -
Returns
The modf functions return the signed fractional part of value. +
Synopsis
#include <math.h>
@@ -12253,262 +13090,299 @@ 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);
-Description
The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not normally by computing FLT_RADIXn explicitly. A range error may occur. -
Returns
The scalbn and scalbln functions return x x FLT_RADIXn . +
Synopsis
#include <math.h>
double cbrt(double x);
float cbrtf(float x);
- long double cbrtl(long double x);
-Description
The cbrt functions compute the real cube root of x. -
Returns
The cbrt functions return x1/3 . +
Synopsis
#include <math.h>
double fabs(double x);
float fabsf(float x);
- long double fabsl(long double x);
-Description
The fabs functions compute the absolute value of a floating-point number x. -
Returns
The fabs functions return | x |. +
Synopsis
#include <math.h>
double hypot(double x, double y);
float hypotf(float x, float y);
- long double hypotl(long double x, long double y);
-Description
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.
-
Returns
The hypot functions return (sqrt)x2 + y2 .
-
- -----
+ -----
+
+Synopsis
#include <math.h>
double pow(double x, double y);
float powf(float x, float y);
- long double powl(long double x, long double y);
-Description
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. -
Returns
The pow functions return xy . +
Synopsis
#include <math.h>
double sqrt(double x);
float sqrtf(float x);
- long double sqrtl(long double x);
-Description
The sqrt functions compute the nonnegative square root of x. A domain error occurs if the argument is less than zero. -
Returns
The sqrt functions return (sqrt)x.
-
- -
+ -
+
+Synopsis
#include <math.h>
double erf(double x);
float erff(float x);
- long double erfl(long double x);
-Description
The erf functions compute the error function of x. -
Returns
2 x
(integral) e-t dt.
- 2
+ 2
+
The erf functions return erf x =
(sqrt)pi
-
- - 0
+ - 0
+
+Synopsis
#include <math.h>
double erfc(double x);
float erfcf(float x);
- long double erfcl(long double x);
-Description
The erfc functions compute the complementary error function of x. A range error occurs if x is too large. -
Returns
2 (inf)
(integral) e-t dt.
- 2
+ 2
+
The erfc functions return erfc x = 1 - erf x =
(sqrt)pi
-
- - x
+ - x
+
+Synopsis
#include <math.h>
double lgamma(double x);
float lgammaf(float x);
- long double lgammal(long double x);
-Description
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. -
Returns
The lgamma functions return loge | (Gamma)(x) |. +
Synopsis
#include <math.h>
double tgamma(double x);
float tgammaf(float x);
- long double tgammal(long double x);
-Description
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. -
Returns
The tgamma functions return (Gamma)(x). +
Synopsis
#include <math.h>
double ceil(double x);
float ceilf(float x);
- long double ceill(long double x);
-Description
The ceil functions compute the smallest integer value not less than x. -
Returns
The ceil functions return [^x^], expressed as a floating-point number. +
Synopsis
#include <math.h>
double floor(double x);
float floorf(float x);
- long double floorl(long double x);
-Description
The floor functions compute the largest integer value not greater than x. -
Returns
The floor functions return [_x_], expressed as a floating-point number. +
Synopsis
#include <math.h>
double nearbyint(double x);
float nearbyintf(float x);
- long double nearbyintl(long double x);
-Description
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. -
Returns
The nearbyint functions return the rounded integer value. +
Synopsis
#include <math.h>
double rint(double x);
float rintf(float x);
- long double rintl(long double x);
-Description
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. -
Returns
The rint functions return the rounded integer value. +
Synopsis
#include <math.h>
@@ -12517,37 +13391,41 @@ 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);
-Description
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. -
Returns
The lrint and llrint functions return the rounded integer value. +
Synopsis
#include <math.h>
double round(double x);
float roundf(float x);
- long double roundl(long double x);
-Description
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. -
Returns
The round functions return the rounded integer value. +
Synopsis
#include <math.h>
@@ -12556,63 +13434,71 @@ 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);
-Description
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. -
Returns
The lround and llround functions return the rounded integer value. +
Synopsis
#include <math.h>
double trunc(double x);
float truncf(float x);
- long double truncl(long double x);
-Description
The trunc functions round their argument to the integer value, in floating format, nearest to but no larger in magnitude than the argument. -
Returns
The trunc functions return the truncated integer value. +
Synopsis
#include <math.h>
double fmod(double x, double y);
float fmodf(float x, float y);
- long double fmodl(long double x, long double y);
-Description
The fmod functions compute the floating-point remainder of x/y. -
Returns
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. +
Synopsis
#include <math.h>
double remainder(double x, double y);
float remainderf(float x, float y);
- long double remainderl(long double x, long double y);
-Description
The remainder functions compute the remainder x REM y required by IEC 60559.236) @@ -12620,69 +13506,76 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The remainder functions return x REM y. If y is zero, whether a domain error occurs or the functions return zero is implementation defined. -
Footnotes
236) ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever | n - x/y | = 1/2, then n is even. If r = 0, its sign shall be that of x.'' This definition is applicable for * all implementations. +
Synopsis
#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);
-Description
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. -
Returns
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. +
Synopsis
#include <math.h>
double copysign(double x, double y);
float copysignf(float x, float y);
- long double copysignl(long double x, long double y);
-Description
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. -
Returns
The copysign functions return a value with the magnitude of x and the sign of y. +
Synopsis
#include <math.h>
double nan(const char *tagp);
float nanf(const char *tagp);
- long double nanl(const char *tagp);
-Description
The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char- sequence)", (char**) NULL); the call nan("") is equivalent to @@ -12690,28 +13583,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. sequence or an empty string, the call is equivalent to strtod("NAN", (char**) NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof and strtold. -
Returns
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). +
Synopsis
#include <math.h>
double nextafter(double x, double y);
float nextafterf(float x, float y);
- long double nextafterl(long double x, long double y);
-Description
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. -
Returns
The nextafter functions return the next representable value in the specified format after x in the direction of y. @@ -12719,112 +13614,125 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
237) The argument values are converted to the type of the function, even by a macro implementation of the function. +
Synopsis
#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);
-Description
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) -
Footnotes
238) The result of the nexttoward functions is determined in the type of the function, without loss of range or precision in a floating second argument. +
Synopsis
#include <math.h>
double fdim(double x, double y);
float fdimf(float x, float y);
- long double fdiml(long double x, long double y);
-Description
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.
-Returns
The fdim functions return the positive difference value. +
Synopsis
#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);
+
-Description
The fmax functions determine the maximum numeric value of their arguments.239) -
Returns
The fmax functions return the maximum numeric value of their arguments. -
Footnotes
239) NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the fmax functions choose the numeric value. See F.10.9.2. +
Synopsis
#include <math.h>
double fmin(double x, double y);
float fminf(float x, float y);
- long double fminl(long double x, long double y);
-Description
The fmin functions determine the minimum numeric value of their arguments.240) -
Returns
The fmin functions return the minimum numeric value of their arguments. -
Footnotes
240) The fmin functions are analogous to the fmax functions in their treatment of NaNs. +
Synopsis
#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);
-Description
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. -
Returns
The fma functions return (x x y) + z, rounded as one ternary operation. @@ -12833,6 +13741,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
The relational and equality operators support the usual mathematical relationships @@ -12846,7 +13755,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the synopses in this subclause, real-floating indicates that the argument shall be an expression of real floating type242) (both arguments need not have the same type).243) -
Footnotes
241) IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if the operands compare unordered, as an error indicator for programs written without consideration of NaNs; the result in these cases is false. @@ -12858,115 +13767,129 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. type is unspecified. +
Synopsis
#include <math.h>
- int isgreater(real-floating x, real-floating y);
-Description
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. -
Returns
The isgreater macro returns the value of (x) > (y). +
Synopsis
#include <math.h>
- int isgreaterequal(real-floating x, real-floating y);
+ int isgreaterequal(real-floating x, real-floating y);
+
-Description
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. -
Returns
The isgreaterequal macro returns the value of (x) >= (y). +
Synopsis
#include <math.h>
- int isless(real-floating x, real-floating y);
-Description
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. -
Returns
The isless macro returns the value of (x) < (y). +
Synopsis
#include <math.h>
- int islessequal(real-floating x, real-floating y);
-Description
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. -
Returns
The islessequal macro returns the value of (x) <= (y). +
Synopsis
#include <math.h>
- int islessgreater(real-floating x, real-floating y);
-Description
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). -
Returns
The islessgreater macro returns the value of (x) < (y) || (x) > (y). +
Synopsis
#include <math.h>
- int isunordered(real-floating x, real-floating y);
-Description
The isunordered macro determines whether its arguments are unordered. -
Returns
The isunordered macro returns 1 if its arguments are unordered and 0 otherwise. -
Contents +
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 @@ -12978,29 +13901,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
244) These functions are useful for dealing with unusual conditions encountered in a low-level function of a program. +
Synopsis
#include <setjmp.h>
- int setjmp(jmp_buf env);
-Description
The setjmp macro saves its calling environment in its jmp_buf argument for later use by the longjmp function. -
Returns
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 +
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. +
Synopsis
#include <setjmp.h>
- _Noreturn void longjmp(jmp_buf env, int val);
-Description
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 @@ -13041,7 +13970,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. invocation of the corresponding setjmp macro that do not have volatile-qualified type and have been changed between the setjmp invocation and longjmp call are indeterminate. -
Returns
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 @@ -13077,23 +14006,26 @@ 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 - } + } + -
Footnotes
245) For example, by executing a return statement or because another longjmp call has caused a transfer to a setjmp invocation in a function earlier in the set of nested calls.
246) This includes, but is not limited to, the floating-point status flags and the state of open files. -
Contents +
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.
@@ -13101,13 +14033,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +14047,9 @@ 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 @@ -13128,21 +14062,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
247) See ''future library directions'' (7.30.6). The names of the signal numbers reflect the following terms (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation, and termination. +
Synopsis
#include <signal.h>
- void (*signal(int sig, void (*func)(int)))(int);
-Description
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 @@ -13180,15 +14117,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Returns
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 @@ -13196,47 +14135,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: the abort function (7.22.4.1), the exit function (7.22.4.4), the _Exit function (7.22.4.5), the quick_exit function (7.22.4.7). -
Footnotes
248) This includes functions called indirectly via standard library functions (e.g., a SIGABRT handler called via the abort function).
249) If any signal is generated by an asynchronous signal handler, the behavior is undefined. +
Synopsis
#include <signal.h>
- int raise(int sig);
-Description
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. -
Returns
The raise function returns zero if successful, nonzero if unsuccessful. -
Contents +
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. -
Contents +
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 @@ -13249,7 +14195,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -13258,11 +14205,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. value of ap in the calling function is indeterminate and shall be passed to the va_end macro prior to any further reference to ap.250) -
Footnotes
250) It is permitted to create a pointer to a va_list and pass that pointer to another function, in which 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 @@ -13273,13 +14221,15 @@ 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. +
Synopsis
#include <stdarg.h>
- type va_arg(va_list ap, type);
-Description
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 @@ -13298,36 +14248,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. type, and the value is representable in both types;
Returns
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. +
Synopsis
#include <stdarg.h>
- void va_copy(va_list dest, va_list src);
-Description
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. -
Returns
The va_copy macro returns no value. +
Synopsis
#include <stdarg.h>
- void va_end(va_list ap);
-Description
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 @@ -13337,17 +14291,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The va_end macro returns no value. +
Synopsis
#include <stdarg.h>
- void va_start(va_list ap, parmN);
-Description
The va_start macro shall be invoked before any access to the unnamed arguments.
@@ -13360,7 +14316,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The va_start macro returns no value.
@@ -13383,10 +14339,12 @@ 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 @@ -13418,10 +14376,13 @@ 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); - } + } + -
Contents +
The header <stdatomic.h> defines several macros and declares several types and @@ -13440,25 +14401,31 @@ 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.
@@ -13480,15 +14447,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operations to volatile objects. +
Synopsis
#include <stdatomic.h>
- #define ATOMIC_VAR_INIT(C value)
-Description
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 @@ -13502,16 +14472,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
EXAMPLE
- atomic_int guide = ATOMIC_VAR_INIT(42);+ atomic_int guide = ATOMIC_VAR_INIT(42); + +
Synopsis
#include <stdatomic.h>
- void atomic_init(volatile A *obj, C value);
-Description
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 @@ -13521,29 +14494,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -13609,12 +14585,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
// 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:
@@ -13625,22 +14603,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
+Recommended practice
The requirements do not forbid r1 == 42 && r2 == 42 in the following example, with x and y initially zero: @@ -13648,37 +14629,42 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. // 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. -
Footnotes
251) Among other implications, atomic variables shall not decay. +
Synopsis
#include <stdatomic.h>
- type kill_dependency(type y);
-Description
The kill_dependency macro terminates a dependency chain; the argument does not carry a dependency to the return value. -
Returns
The kill_dependency macro returns the value of y. +
This subclause introduces synchronization primitives called fences. Fences can have @@ -13702,13 +14688,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
Synopsis
#include <stdatomic.h>
- void atomic_thread_fence(memory_order order);
-Description
Depending on the value of order, this operation:
Returns
The atomic_thread_fence function returns no value. +
Synopsis
#include <stdatomic.h>
- void atomic_signal_fence(memory_order order);
-Description
Equivalent to atomic_thread_fence(order), except that ''synchronizes with'' relationships are established only between a thread and a signal handler executed in the @@ -13746,10 +14736,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. atomic_thread_fence, but the hardware fence instructions that atomic_thread_fence would have inserted are not emitted. -
Returns
The atomic_signal_fence function returns no value. +
The atomic lock-free macros indicate the lock-free property of integer and address atomic @@ -13762,29 +14753,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. process more than once and memory shared between two processes. +
Synopsis
#include <stdatomic.h>
- _Bool atomic_is_lock_free(atomic_type const volatile *obj);
-Description
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. -
Returns
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. +
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
@@ -13822,7 +14815,9 @@ 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. @@ -13836,64 +14831,72 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. to port existing code. +
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. +
Synopsis
#include <stdatomic.h>
void atomic_store(volatile A *object, C desired);
void atomic_store_explicit(volatile A *object,
- C desired, memory_order order);
-Description
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. -
Returns
The atomic_store generic functions return no value. +
Synopsis
#include <stdatomic.h>
C atomic_load(volatile A *object);
C atomic_load_explicit(volatile A *object,
- memory_order order);
-Description
The order argument shall not be memory_order_release nor memory_order_acq_rel. Memory is affected according to the value of order. -
Returns Atomically returns the value pointed to by object. +
Synopsis
#include <stdatomic.h>
C atomic_exchange(volatile A *object, C desired);
C atomic_exchange_explicit(volatile A *object,
- C desired, memory_order order);
-Description
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). -
Returns
Atomically returns the value pointed to by object immediately before the effects. +
Synopsis
#include <stdatomic.h>
@@ -13906,8 +14909,9 @@ 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);
-Description
The failure argument shall not be memory_order_release nor memory_order_acq_rel. The failure argument shall be no stronger than the @@ -13924,7 +14928,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. if (*object == *expected) *object = desired; else - *expected = *object; + *expected = *object; +
The weak compare-and-exchange operations may fail spuriously, that is, return zero @@ -13940,15 +14945,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The result of the comparison. +
The following operations perform arithmetic and bitwise computations. All of these @@ -13961,14 +14968,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. or | bitwise inclusive or xor ^ bitwise exclusive or and & bitwise and -
Synopsis
#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);
-Description
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 @@ -13978,7 +14986,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
Atomically, the value pointed to by object immediately before the effects.
@@ -13989,6 +14997,7 @@ 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. +
The atomic_flag type provides the classic test-and-set functionality. It has two @@ -14008,65 +15017,75 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
EXAMPLE
- atomic_flag guard = ATOMIC_FLAG_INIT;+ atomic_flag guard = ATOMIC_FLAG_INIT; + +
Synopsis
#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);
-Description
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). -
Returns
Atomically, the value of the object immediately before the effects. +
Synopsis
#include <stdatomic.h>
void atomic_flag_clear(volatile atomic_flag *object);
void atomic_flag_clear_explicit(
- volatile atomic_flag *object, memory_order order);
-Description
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. -
Returns
The atomic_flag_clear functions return no value. -
Contents +
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 @@ -14077,28 +15096,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
252) See ''future library directions'' (7.30.7). -
Contents +
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 @@ -14108,19 +15132,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +
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 @@ -14129,7 +15156,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: localization (7.11). -
Contents +
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 @@ -14155,12 +15183,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. shall provide those types described as ''required'', but need not provide any of the others (described as ''optional''). -
Footnotes
253) See ''future library directions'' (7.30.8).
254) Some of these types may denote implementation-defined extended integer types. +
When typedef names differing only in the absence or presence of the initial u are defined, @@ -14175,6 +15204,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
The typedef name intN_t designates a signed integer type with width N , no padding @@ -14189,6 +15219,7 @@ margin: deleted text is marked with ''*'', new or changed text 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. +
The typedef name int_leastN_t designates a signed integer type with a width of at @@ -14205,9 +15236,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -14227,41 +15260,49 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
255) The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear grounds for choosing one type over another, it will simply pick some integer type satisfying the signedness and width requirements. +
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 * @@ -14276,50 +15317,60 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. except where stated to be exactly the given value. +
- 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 * @@ -14388,13 +15441,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN shall be 0 and the value of WINT_MAX shall be no less than 65535. -
Footnotes
256) A freestanding implementation need not provide all of these types.
257) The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended character set. +
The following function-like macros expand to integer constants suitable for initializing * @@ -14409,6 +15463,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
The macro INTN_C(value) shall expand to an integer constant expression @@ -14422,20 +15477,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
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) + -
Contents +
The header <stdio.h> defines several macros, and declares three types and many @@ -14443,13 +15503,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -14457,47 +15519,56 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
_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.
@@ -14529,13 +15600,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Forward references: files (7.21.3), the fseek function (7.21.9.2), streams (7.21.2), the tmpnam function (7.21.4.4), <wchar.h> (7.28). -
Footnotes
258) If the implementation imposes no practical limit on the length of file name strings, the value of FILENAME_MAX should instead be the recommended size of an array intended to hold a file name string. Of course, file name string contents are subject to other system-specific constraints; therefore all possible strings of length FILENAME_MAX cannot be expected to be opened successfully. +
Input and output, whether to or from physical devices such as terminals and tape drives, @@ -14592,7 +15664,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
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 @@ -14606,7 +15678,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
259) An implementation need not distinguish between text streams and binary streams. In such an implementation, there need be no new-line characters in a text stream nor any limit to the length of a line. @@ -14614,6 +15686,7 @@ 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. +
A stream is associated with an external file (which may be a physical device) by opening @@ -14710,7 +15783,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
Environmental limits
The value of FOPEN_MAX shall be at least eight, including the three standard text streams. @@ -14720,84 +15793,93 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. fputwc function (7.28.3.3), conversion state (7.28.6), the mbrtowc function (7.28.6.3.2), the wcrtomb function (7.28.6.3.3). -
Footnotes
261) Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has undefined behavior for a binary stream (because of possible trailing null characters) or for any stream with state-dependent encoding that does not assuredly end in the initial shift state. +
Synopsis
#include <stdio.h>
- int remove(const char *filename);
-Description
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. -
Returns
The remove function returns zero if the operation succeeds, nonzero if it fails. +
Synopsis
#include <stdio.h>
- int rename(const char *old, const char *new);
-Description
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. -
Returns
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. -
Footnotes
262) Among the reasons the implementation may cause the rename function to fail are that the file is open or that it is necessary to copy its contents to effectuate its renaming. +
Synopsis
#include <stdio.h>
- FILE *tmpfile(void);
-Description
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 +
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). -
Returns
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). +
Synopsis
#include <stdio.h>
- char *tmpnam(char *s);
-Description
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 @@ -14812,7 +15894,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -14820,26 +15902,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
Environmental limits
The value of the macro TMP_MAX shall be at least 25. -
Footnotes
263) Files created using strings generated by the tmpnam function are temporary only in the sense that their names should not collide with those generated by conventional naming rules for the implementation. It is still necessary to use the remove function to remove such files when their use is ended, and before program termination. +
Synopsis
#include <stdio.h>
- int fclose(FILE *stream);
-Description
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 @@ -14847,19 +15932,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. are discarded. Whether or not the call succeeds, the stream is disassociated from the file and any buffer set by the setbuf or setvbuf function is disassociated from the stream (and deallocated if it was automatically allocated). -
Returns
The fclose function returns zero if the stream was successfully closed, or EOF if any errors were detected. +
Synopsis
#include <stdio.h>
- int fflush(FILE *stream);
-Description
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 @@ -14868,20 +15955,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If stream is a null pointer, the fflush function performs this flushing action on all streams for which the behavior is defined above. -
Returns
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). +
Synopsis
#include <stdio.h>
FILE *fopen(const char * restrict filename,
- const char * restrict mode);
-Description
The fopen function opens the file whose name is the string pointed to by filename, and associates a stream with it. @@ -14934,28 +16023,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Returns
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). -
Footnotes
264) If the string begins with one of the above sequences, the implementation might choose to ignore the remaining characters, or it might use them to select different kinds of a file (some of which might not conform to the properties in 7.21.2). +
Synopsis
#include <stdio.h>
FILE *freopen(const char * restrict filename,
const char * restrict mode,
- FILE * restrict stream);
-Description
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 @@ -14969,25 +16060,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The freopen function returns a null pointer if the open operation fails. Otherwise, freopen returns the value of stream. -
Footnotes
265) The primary use of the freopen function is to change the file associated with a standard text stream (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value returned by the fopen function may be assigned. +
Synopsis
#include <stdio.h>
void setbuf(FILE * restrict stream,
- char * restrict buf);
-Description
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 @@ -14997,20 +16090,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The setbuf function returns no value.
Forward references: the setvbuf function (7.21.5.6). +
Synopsis
#include <stdio.h>
int setvbuf(FILE * restrict stream,
char * restrict buf,
- int mode, size_t size);
-Description
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 @@ -15022,7 +16117,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. specifies the size of the array; otherwise, size may determine the size of a buffer allocated by the setvbuf function. The contents of the array at any time are indeterminate. -
Returns
The setvbuf function returns zero on success, or nonzero if an invalid value is given for mode or if the request cannot be honored. @@ -15032,28 +16127,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
The formatted input/output functions shall behave as if there is a sequence point after the actions associated with each specifier.267) -
Footnotes
267) The fprintf functions perform writes to memory for the %n specifier. +
Synopsis
#include <stdio.h>
int fprintf(FILE * restrict stream,
- const char * restrict format, ...);
-Description
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 @@ -15103,15 +16201,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +16222,22 @@ 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 +16245,16 @@ 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
@@ -15156,30 +16262,36 @@ 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.
@@ -15189,7 +16301,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +16310,8 @@ 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
@@ -15212,12 +16326,14 @@ 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
+
@@ -15229,7 +16345,8 @@ 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 +16360,8 @@ 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
@@ -15252,7 +16370,8 @@ 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
+
@@ -15267,7 +16386,8 @@ 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 +16395,8 @@ 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
@@ -15293,26 +16414,31 @@ 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. @@ -15323,7 +16449,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +
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 @@ -15341,11 +16467,11 @@ 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. -
Returns
The fprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. - Environmental limits +
Environmental limits
The number of characters that can be produced by any single conversion shall be at least 4095. @@ -15360,7 +16486,8 @@ 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 @@ -15369,7 +16496,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +16506,8 @@ 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|
@@ -15387,12 +16516,13 @@ 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). -
Footnotes
268) Note that 0 is taken as a flag, not as the beginning of a field width.
269) The results of all floating conversions of a negative zero, and of negative values that round to zero, @@ -15420,14 +16550,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the case of fixed-point conversion by the source value as well. +
Synopsis
#include <stdio.h>
int fscanf(FILE * restrict stream,
- const char * restrict format, ...);
-Description
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 @@ -15492,39 +16624,47 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
@@ -15533,32 +16673,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +16718,9 @@ 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
@@ -15585,17 +16732,19 @@ 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 +
@@ -15614,7 +16763,8 @@ 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 +16772,8 @@ 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
@@ -15630,11 +16781,13 @@ 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, @@ -15647,7 +16800,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -15659,10 +16812,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. @@ -15672,16 +16827,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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>
/* ... */
@@ -15689,7 +16845,9 @@ 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:
@@ -15698,7 +16856,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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");
@@ -15709,7 +16868,8 @@ 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: @@ -15717,7 +16877,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. @@ -15733,10 +16894,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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.
@@ -15746,7 +16909,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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.
@@ -15757,7 +16921,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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.
@@ -15768,7 +16933,8 @@ 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. @@ -15776,7 +16942,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. strtol, strtoll, strtoul, and strtoull functions (7.22.1.4), conversion state (7.28.6), the wcrtomb function (7.28.6.3.3). -
Footnotes
277) These white-space characters are not counted against a specified field width.
278) fscanf pushes back at most one input character onto the input stream. Therefore, some sequences @@ -15789,47 +16955,53 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
280) See ''future library directions'' (7.30.9). +
Synopsis
#include <stdio.h>
- int printf(const char * restrict format, ...);
-Description
The printf function is equivalent to fprintf with the argument stdout interposed before the arguments to printf. -
Returns
The printf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. +
Synopsis
#include <stdio.h>
- int scanf(const char * restrict format, ...);
-Description
The scanf function is equivalent to fscanf with the argument stdin interposed before the arguments to scanf. -
Returns
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. +
Synopsis
#include <stdio.h>
int snprintf(char * restrict s, size_t n,
- const char * restrict format, ...);
-Description
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, @@ -15837,68 +17009,74 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. discarded rather than being written to the array, and a null character is written at the end of the characters actually written into the array. If copying takes place between objects that overlap, the behavior is undefined. -
Returns
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. +
Synopsis
#include <stdio.h>
int sprintf(char * restrict s,
- const char * restrict format, ...);
-Description
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. -
Returns
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. +
Synopsis
#include <stdio.h>
int sscanf(const char * restrict s,
- const char * restrict format, ...);
-Description
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. -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vfprintf(FILE * restrict stream,
const char * restrict format,
- va_list arg);
-Description
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) -
Returns
The vfprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. @@ -15921,138 +17099,151 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. // print out remainder of message vfprintf(stderr, format, args); va_end(args); - } + } + -
Footnotes
281) As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vfscanf(FILE * restrict stream,
const char * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vprintf(const char * restrict format,
- va_list arg);
-Description
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) -
Returns
The vprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vscanf(const char * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vsnprintf(char * restrict s, size_t n,
const char * restrict format,
- va_list arg);
-Description
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. -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vsprintf(char * restrict s,
const char * restrict format,
- va_list arg);
-Description
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. -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <stdio.h>
int vsscanf(const char * restrict s,
const char * restrict format,
- va_list arg);
-Description
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) -
Returns
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 @@ -16060,21 +17251,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
Synopsis
#include <stdio.h>
- int fgetc(FILE *stream);
-Description
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). -
Returns
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 @@ -16082,24 +17276,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. If a read error occurs, the error indicator for the stream is set and the fgetc function returns EOF.282) -
Footnotes
282) An end-of-file and a read error can be distinguished by use of the feof and ferror functions. +
Synopsis
#include <stdio.h>
char *fgets(char * restrict s, int n,
- FILE * restrict stream);
-Description
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. -
Returns
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 @@ -16108,129 +17304,145 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <stdio.h>
- int fputc(int c, FILE *stream);
-Description
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. -
Returns
The fputc function returns the character written. If a write error occurs, the error indicator for the stream is set and fputc returns EOF. +
Synopsis
#include <stdio.h>
int fputs(const char * restrict s,
- FILE * restrict stream);
-Description
The fputs function writes the string pointed to by s to the stream pointed to by stream. The terminating null character is not written. -
Returns
The fputs function returns EOF if a write error occurs; otherwise it returns a nonnegative value. +
Synopsis
#include <stdio.h>
- int getc(FILE *stream);
-Description
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. -
Returns
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. +
Synopsis
#include <stdio.h>
- int getchar(void);
-Description
The getchar function is equivalent to getc with the argument stdin. -
Returns
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. * +
Synopsis
#include <stdio.h>
- int putc(int c, FILE *stream);
-Description
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. -
Returns
The putc function returns the character written. If a write error occurs, the error indicator for the stream is set and putc returns EOF. +
Synopsis
#include <stdio.h>
- int putchar(int c);
-Description
The putchar function is equivalent to putc with the second argument stdout. -
Returns
The putchar function returns the character written. If a write error occurs, the error indicator for the stream is set and putchar returns EOF. +
Synopsis
#include <stdio.h>
- int puts(const char *s);
-Description
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. -
Returns
The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative value. +
Synopsis
#include <stdio.h>
- int ungetc(int c, FILE *stream);
-Description
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 @@ -16255,27 +17467,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The ungetc function returns the character pushed back after conversion, or EOF if the operation fails.
Forward references: file positioning functions (7.21.9). -
Footnotes
283) See ''future library directions'' (7.30.9). +
Synopsis
#include <stdio.h>
size_t fread(void * restrict ptr,
size_t size, size_t nmemb,
- FILE * restrict stream);
-Description
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 @@ -16284,7 +17499,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. indicator for the stream (if defined) is advanced by the number of characters successfully 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. -
Returns
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, @@ -16296,15 +17511,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <stdio.h>
size_t fwrite(const void * restrict ptr,
size_t size, size_t nmemb,
- FILE * restrict stream);
-Description
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, @@ -16313,41 +17530,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. stream (if defined) is advanced by the number of characters successfully written. If an error occurs, the resulting value of the file position indicator for the stream is indeterminate. -
Returns
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. +
Synopsis
#include <stdio.h>
int fgetpos(FILE * restrict stream,
- fpos_t * restrict pos);
-Description
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. -
Returns
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). +
Synopsis
#include <stdio.h>
- int fseek(FILE *stream, long int offset, int whence);
-Description
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. @@ -16366,18 +17588,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The fseek function returns nonzero only for a request that cannot be satisfied.
Forward references: the ftell function (7.21.9.4). +
Synopsis
#include <stdio.h>
- int fsetpos(FILE *stream, const fpos_t *pos);
-Description
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 @@ -16390,18 +17614,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. parse state and position. After a successful fsetpos call, the next operation on an update stream may be either input or output. -
Returns
If successful, the fsetpos function returns zero; on failure, the fsetpos function returns nonzero and stores an implementation-defined positive value in errno. +
Synopsis
#include <stdio.h>
- long int ftell(FILE *stream);
-Description
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 @@ -16410,82 +17636,94 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. stream to its position at the time of the ftell call; the difference between two such return values is not necessarily a meaningful measure of the number of characters written or read. -
Returns
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. +
Synopsis
#include <stdio.h>
- void rewind(FILE *stream);
-Description
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. -
Returns
The rewind function returns no value. +
Synopsis
#include <stdio.h>
- void clearerr(FILE *stream);
-Description
The clearerr function clears the end-of-file and error indicators for the stream pointed to by stream. -
Returns
The clearerr function returns no value. +
Synopsis
#include <stdio.h>
- int feof(FILE *stream);
-Description
The feof function tests the end-of-file indicator for the stream pointed to by stream. -
Returns
The feof function returns nonzero if and only if the end-of-file indicator is set for stream. +
Synopsis
#include <stdio.h>
- int ferror(FILE *stream);
-Description
The ferror function tests the error indicator for the stream pointed to by stream. -
Returns
The ferror function returns nonzero if and only if the error indicator is set for stream. +
Synopsis
#include <stdio.h>
- void perror(const char *s);
-Description
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 @@ -16493,43 +17731,51 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. string pointed to by s followed by a colon (:) and a space; then an appropriate error 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. -
Returns
The perror function returns no value.
Forward references: the strerror function (7.23.6.2). -
Contents +
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. @@ -16539,42 +17785,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
284) See ''future library directions'' (7.30.10). +
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. +
Synopsis
#include <stdlib.h>
- double atof(const char *nptr);
-Description
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)-
Returns
The atof function returns the converted value.
Forward references: the strtod, strtof, and strtold functions (7.22.1.3). +
Synopsis
#include <stdlib.h>
int atoi(const char *nptr);
long int atol(const char *nptr);
- long long int atoll(const char *nptr);
-Description
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. @@ -16582,16 +17834,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
atoi: (int)strtol(nptr, (char **)NULL, 10)
atol: strtol(nptr, (char **)NULL, 10)
- atoll: strtoll(nptr, (char **)NULL, 10)
-Returns
The atoi, atol, and atoll functions return the converted value.
Forward references: the strtol, strtoll, strtoul, and strtoull functions (7.22.1.4). +
Synopsis
#include <stdlib.h>
@@ -16600,8 +17854,9 @@ 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);
-Description
The strtod, strtof, and strtold functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation, @@ -16620,13 +17875,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
n-char-sequence:
digit
nondigit
n-char-sequence digit
- n-char-sequence nondigit
+ n-char-sequence nondigit
+
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
@@ -16643,7 +17899,7 @@ 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
@@ -16658,7 +17914,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
+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 @@ -16677,7 +17933,7 @@ 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.287) -
Returns
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), @@ -16687,7 +17943,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. no greater than the smallest normalized positive number in the return type; whether errno acquires the value ERANGE is implementation-defined. -
Footnotes
285) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by negating the value resulting from converting the corresponding unsigned sequence (see F.5); the two methods may yield different results if rounding is toward positive or negative infinity. In either case, @@ -16700,8 +17956,9 @@ 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. +
Synopsis
#include <stdlib.h>
@@ -16720,8 +17977,9 @@ 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);
-Description
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 @@ -16766,7 +18024,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -16775,41 +18033,46 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. and sign of the value, if any), and the value of the macro ERANGE is stored in errno. +
Synopsis
#include <stdlib.h>
- int rand(void);
-Description
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. -
Returns
The rand function returns a pseudo-random integer. - Environmental limits +
Environmental limits
The value of the RAND_MAX macro shall be at least 32767. -
Footnotes
288) There are no guarantees as to the quality of the random sequence produced and some implementations are known to produce sequences with distressingly non-random low-order bits. Applications with particular requirements should use a generator that is known to be sufficient for their needs. +
Synopsis
#include <stdlib.h>
- void srand(unsigned int seed);
-Description
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 @@ -16818,7 +18081,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The srand function returns no value. @@ -16838,9 +18101,11 @@ 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 @@ -16856,67 +18121,75 @@ 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. +
Synopsis
#include <stdlib.h>
- void *aligned_alloc(size_t alignment, size_t size);
-Description
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. -
Returns
The aligned_alloc function returns either a null pointer or a pointer to the allocated space. +
Synopsis
#include <stdlib.h>
- void *calloc(size_t nmemb, size_t size);
-Description
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) -
Returns
The calloc function returns either a null pointer or a pointer to the allocated space. -
Footnotes
289) Note that this need not be the same as the representation of floating-point zero or a null pointer constant. +
Synopsis
#include <stdlib.h>
- void free(void *ptr);
-Description
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. -
Returns
The free function returns no value. +
Synopsis
#include <stdlib.h>
- void *malloc(size_t size);
-Description
The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate. @@ -16925,17 +18198,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The malloc function returns either a null pointer or a pointer to the allocated space. +
Synopsis
#include <stdlib.h>
- void *realloc(void *ptr, size_t size);
-Description
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 @@ -16948,21 +18223,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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. +
Synopsis
#include <stdlib.h>
- _Noreturn void abort(void);
-Description
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 @@ -16971,48 +18249,52 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. unsuccessful termination is returned to the host environment by means of the function call raise(SIGABRT). -
Returns
The abort function does not return to its caller. +
Synopsis
#include <stdlib.h>
- int atexit(void (*func)(void));
-Description
The atexit function registers the function pointed to by func, to be called without arguments at normal program termination.290) - Environmental limits +
Environmental limits
The implementation shall support the registration of at least 32 functions. -
Returns
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). -
Footnotes
290) The atexit function registrations are distinct from the at_quick_exit registrations, so applications may need to call both registration functions with the same argument. +
Synopsis
#include <stdlib.h>
- int at_quick_exit(void (*func)(void));
-Description
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 +
Environmental limits
The implementation shall support the registration of at least 32 functions. -
Returns
The at_quick_exit function returns zero if the registration succeeds, nonzero if it fails. @@ -17021,18 +18303,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
Synopsis
#include <stdlib.h>
- _Noreturn void exit(int status);
-Description
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 @@ -17053,22 +18337,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The exit function cannot return to its caller. -
Footnotes
292) Each function is called as many times as it was registered, and in the correct order with respect to other registered functions. +
Synopsis
#include <stdlib.h>
- _Noreturn void _Exit(int status);
-Description
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 @@ -17080,17 +18366,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The _Exit function cannot return to its caller. +
Synopsis
#include <stdlib.h>
- char *getenv(const char *name);
-Description
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 @@ -17099,24 +18387,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the environment list.293)
The implementation shall behave as if no library function calls the getenv function. -
Returns
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 be found, a null pointer is returned. -
Footnotes
293) Many implementations provide non-standard functions that modify the environment list. +
Synopsis
#include <stdlib.h>
- _Noreturn void quick_exit(int status);
-Description
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 @@ -17134,34 +18424,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Then control is returned to the host environment by means of the function call _Exit(status). -
Returns
The quick_exit function cannot return to its caller. -
Footnotes
294) Each function is called as many times as it was registered, and in the correct order with respect to other registered functions. +
Synopsis
#include <stdlib.h>
- int system(const char *string);
-Description
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. -
Returns
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. +
These utilities make use of a comparison function to search or sort arrays of unspecified @@ -17194,25 +18487,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. comparison function, and also between any call to the comparison function and any movement of the objects passed as arguments to that call. -
Footnotes
295) That is, if the value passed is p, then the following expressions are always nonzero:
((char *)p - (char *)base) % size == 0
(char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
+ (char *)p < (char *)base + nmemb * size
+
+
Synopsis
#include <stdlib.h>
void *bsearch(const void *key, const void *base,
size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
-Description
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 @@ -17224,7 +18520,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. respectively, to be less than, to match, or to be greater than the array element. The array 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) -
Returns
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 @@ -17233,18 +18529,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. matched is unspecified. -
Footnotes
296) In practice, the entire array is sorted according to the comparison function. +
Synopsis
#include <stdlib.h>
void qsort(void *base, size_t nmemb, size_t size,
- int (*compar)(const void *, const void *));
-Description
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. @@ -17256,25 +18554,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. or greater than the second.
If two elements compare as equal, their order in the resulting sorted array is unspecified. -
Returns
The qsort function returns no value. +
Synopsis
#include <stdlib.h>
int abs(int j);
long int labs(long int j);
- long long int llabs(long long int j);
-Description
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) -
Returns
The abs, labs, and llabs, functions return the absolute value. @@ -17283,23 +18584,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
297) The absolute value of the most negative number cannot be represented in two's complement. +
Synopsis
#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);
-Description
The div, ldiv, and lldiv, functions compute numer / denom and numer % denom in a single operation. -
Returns
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 @@ -17307,6 +18610,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
The behavior of the multibyte character functions is affected by the LC_CTYPE category @@ -17318,18 +18622,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. if encodings have state dependency, and zero otherwise.298) Changing the LC_CTYPE category causes the conversion state of these functions to be indeterminate. -
Footnotes
298) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide character codes, but are grouped with an adjacent multibyte character. +
Synopsis
#include <stdlib.h>
- int mblen(const char *s, size_t n);
-Description
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 @@ -17338,12 +18644,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
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. -
Returns
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 @@ -17353,15 +18660,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. multibyte character).
Forward references: the mbtowc function (7.22.7.2). +
Synopsis
#include <stdlib.h>
int mbtowc(wchar_t * restrict pwc,
const char * restrict s,
- size_t n);
-Description
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 @@ -17372,7 +18681,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. character, the function is left in the initial conversion state.
The implementation shall behave as if no library function calls the mbtowc function. -
Returns
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 @@ -17385,13 +18694,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. macro. +
Synopsis
#include <stdlib.h>
- int wctomb(char *s, wchar_t wc);
-Description
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 @@ -17402,7 +18713,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. conversion state.
The implementation shall behave as if no library function calls the wctomb function. -
Returns
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 @@ -17412,20 +18723,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
In no case will the value returned be greater than the value of the MB_CUR_MAX macro. +
The behavior of the multibyte string functions is affected by the LC_CTYPE category of the current locale. +
Synopsis
#include <stdlib.h>
size_t mbstowcs(wchar_t * restrict pwcs,
const char * restrict s,
- size_t n);
-Description
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 @@ -17438,25 +18752,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Returns
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) -
Footnotes
299) The array will not be null-terminated if the value returned is n. +
Synopsis
#include <stdlib.h>
size_t wcstombs(char * restrict s,
const wchar_t * restrict pwcs,
- size_t n);
-Description
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 @@ -17467,20 +18783,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Returns
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) -
Contents +
The header <string.h> declares one type and several functions, and defines one @@ -17502,26 +18820,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. unsigned char (and therefore every possible object representation is valid and has a different value). -
Footnotes
300) See ''future library directions'' (7.30.11). +
Synopsis
#include <string.h>
void *memcpy(void * restrict s1,
const void * restrict s2,
- size_t n);
-Description
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. -
Returns
The memcpy function returns the value of s1. @@ -17530,48 +18851,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <string.h>
- void *memmove(void *s1, const void *s2, size_t n);
-Description
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. -
Returns
The memmove function returns the value of s1. +
Synopsis
#include <string.h>
char *strcpy(char * restrict s1,
- const char * restrict s2);
-Description
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. -
Returns
The strcpy function returns the value of s1. +
Synopsis
#include <string.h>
char *strncpy(char * restrict s1,
const char * restrict s2,
- size_t n);
-Description
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 @@ -17581,43 +18908,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The strncpy function returns the value of s1. -
Footnotes
301) Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will not be null-terminated. +
Synopsis
#include <string.h>
char *strcat(char * restrict s1,
- const char * restrict s2);
-Description
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. -
Returns
The strcat function returns the value of s1. +
Synopsis
#include <string.h>
char *strncat(char * restrict s1,
const char * restrict s2,
- size_t n);
-Description
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 @@ -17626,16 +18958,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. takes place between objects that overlap, the behavior is undefined. -
Returns
The strncat function returns the value of s1.
Forward references: the strlen function (7.23.6.3). -
Footnotes
302) Thus, the maximum number of characters that can end up in the array pointed to by s1 is strlen(s1)+n+1. +
The sign of a nonzero value returned by the comparison functions memcmp, strcmp, @@ -17643,39 +18976,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pair of characters (both interpreted as unsigned char) that differ in the objects being compared. +
Synopsis
#include <string.h>
- int memcmp(const void *s1, const void *s2, size_t n);
-Description
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) -
Returns
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. -
Footnotes
303) The contents of ''holes'' used as padding for purposes of alignment within structure objects are indeterminate. Strings shorter than their allocated space and unions may also cause problems in comparison. +
Synopsis
#include <string.h>
- int strcmp(const char *s1, const char *s2);
-Description
The strcmp function compares the string pointed to by s1 to the string pointed to by s2. -
Returns
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 @@ -17683,48 +19020,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. pointed to by s2. +
Synopsis
#include <string.h>
- int strcoll(const char *s1, const char *s2);
-Description
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. -
Returns
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. +
Synopsis
#include <string.h>
- int strncmp(const char *s1, const char *s2, size_t n);
-Description
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. -
Returns
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. +
Synopsis
#include <string.h>
size_t strxfrm(char * restrict s1,
const char * restrict s2,
- size_t n);
-Description
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 @@ -17735,7 +19078,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -17744,130 +19087,148 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) + +
Synopsis
#include <string.h>
- void *memchr(const void *s, int c, size_t n);
-Description
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. -
Returns
The memchr function returns a pointer to the located character, or a null pointer if the character does not occur in the object. +
Synopsis
#include <string.h>
- char *strchr(const char *s, int c);
-Description
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. -
Returns
The strchr function returns a pointer to the located character, or a null pointer if the character does not occur in the string. +
Synopsis
#include <string.h>
- size_t strcspn(const char *s1, const char *s2);
-Description
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. -
Returns
The strcspn function returns the length of the segment. +
Synopsis
#include <string.h>
- char *strpbrk(const char *s1, const char *s2);
-Description
The strpbrk function locates the first occurrence in the string pointed to by s1 of any character from the string pointed to by s2. -
Returns
The strpbrk function returns a pointer to the character, or a null pointer if no character from s2 occurs in s1. +
Synopsis
#include <string.h>
- char *strrchr(const char *s, int c);
-Description
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. -
Returns
The strrchr function returns a pointer to the character, or a null pointer if c does not occur in the string. +
Synopsis
#include <string.h>
- size_t strspn(const char *s1, const char *s2);
-Description
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. -
Returns
The strspn function returns the length of the segment. +
Synopsis
#include <string.h>
- char *strstr(const char *s1, const char *s2);
-Description
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. -
Returns
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. +
Synopsis
#include <string.h>
char *strtok(char * restrict s1,
- const char * restrict s2);
-Description
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 @@ -17893,7 +19254,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The strtok function is not required to avoid data races. The implementation shall behave as if no library function calls the strtok function. -
Returns
The strtok function returns a pointer to the first character of a token, or a null pointer if there is no token. @@ -17906,33 +19267,39 @@ 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 + +
Synopsis
#include <string.h>
- void *memset(void *s, int c, size_t n);
-Description
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. -
Returns
The memset function returns the value of s. +
Synopsis
#include <string.h>
- char *strerror(int errnum);
-Description
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 @@ -17940,28 +19307,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The strerror function is not required to avoid data races. The implementation shall behave as if no library function calls the strerror function. -
Returns
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. +
Synopsis
#include <string.h>
- size_t strlen(const char *s);
-Description
The strlen function computes the length of the string pointed to by s. -
Returns
The strlen function returns the number of characters that precede the terminating null character. -
Contents +
The header <tgmath.h> includes the headers <math.h> and <complex.h> and defines several type-generic macros. @@ -18012,7 +19382,8 @@ 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.
@@ -18029,7 +19400,8 @@ 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. @@ -18039,7 +19411,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -18051,7 +19424,8 @@ 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:
@@ -18076,9 +19450,10 @@ 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)
+
-Footnotes
304) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to make available the corresponding ordinary function. @@ -18086,8 +19461,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the behavior is undefined. -
Contents +
The header <threads.h> defines macros, and declares types, enumeration constants, @@ -18098,179 +19475,213 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. +
Synopsis
#include <threads.h>
- void call_once(once_flag *flag, void (*func)(void));
-Description
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. -
Returns
The call_once function returns no value. +
Synopsis
#include <threads.h>
- int cnd_broadcast(cnd_t *cond);
-Description
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. -
Returns
The cnd_broadcast function returns thrd_success on success, or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- void cnd_destroy(cnd_t *cond);
-Description
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. -
Returns
The cnd_destroy function returns no value. +
Synopsis
#include <threads.h>
- int cnd_init(cnd_t *cond);
-Description
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. -
Returns
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. +
Synopsis
#include <threads.h>
- int cnd_signal(cnd_t *cond);
-Description
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. -
Returns
The cnd_signal function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
int cnd_timedwait(cnd_t *cond, mtx_t *mtx,
- const xtime *xt);
-Description
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 @@ -18278,19 +19689,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. object pointed to by xt. When the calling thread becomes unblocked it locks the variable 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. -
Returns
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. +
Synopsis
#include <threads.h>
- int cnd_wait(cnd_t *cond, mtx_t *mtx);
-Description
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 @@ -18298,35 +19711,40 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. locks the mutex pointed to by mtx before it returns. If the mutex pointed to by mtx is not locked by the calling thread, the cnd_wait function will act as if the abort function is called. -
Returns
The cnd_wait function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- void mtx_destroy(mtx_t *mtx);
-Description
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. -
Returns
The mtx_destroy function returns no value. +
Synopsis
#include <threads.h>
- int mtx_init(mtx_t *mtx, int type);
-Description
The mtx_init function creates a mutex object with properties indicated by type, which must have one of the six values: @@ -18339,92 +19757,103 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If the mtx_init function succeeds, it sets the mutex pointed to by mtx to a value that uniquely identifies the newly created mutex. -
Returns
The mtx_init function returns thrd_success on success, or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- int mtx_lock(mtx_t *mtx);
-Description
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. -
Returns
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. +
Synopsis
#include <threads.h>
- int mtx_timedlock(mtx_t *mtx, const xtime *xt);
-Description
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. -
Returns
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. +
Synopsis
#include <threads.h>
- int mtx_trylock(mtx_t *mtx);
-Description
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. -
Returns
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. +
Synopsis
#include <threads.h>
- int mtx_unlock(mtx_t *mtx);
-Description
The mtx_unlock function unlocks the mutex pointed to by mtx. The mutex pointed to by mtx shall be locked by the calling thread. -
Returns
The mtx_unlock function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
int thrd_create(thrd_t *thr, thrd_start_t func,
- void *arg);
-Description
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 @@ -18432,78 +19861,88 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the original thread has exited and either been detached or joined to another thread.) The completion of the thrd_create function synchronizes with the beginning of the execution of the new thread. -
Returns
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. +
Synopsis
#include <threads.h>
- thrd_t thrd_current(void);
-Description
The thrd_current function identifies the thread that called it. -
Returns
The thrd_current function returns the identifier of the thread that called it. +
Synopsis
#include <threads.h>
- int thrd_detach(thrd_t thr);
-Description
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. -
Returns
The thrd_detach function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- int thrd_equal(thrd_t thr0, thrd_t thr1);
-Description
The thrd_equal function will determine whether the thread identified by thr0 refers to the thread identified by thr1. -
Returns
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. +
Synopsis
#include <threads.h>
- void thrd_exit(int res);
-Description
The thrd_exit function terminates execution of the calling thread and sets its result code to res. -
Returns
The thrd_exit function returns no value. +
Synopsis
#include <threads.h>
- int thrd_join(thrd_t thr, int *res);
-Description
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, @@ -18511,117 +19950,133 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The thrd_join function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- void thrd_sleep(const xtime *xt);
-Description
The thrd_sleep function suspends execution of the calling thread until after the time specified by the xtime object pointed to by xt. -
Returns
The thrd_sleep function returns no value. +
Synopsis
#include <threads.h>
- void thrd_yield(void);
-Description
The thrd_yield function endeavors to permit other threads to run, even if the current thread would ordinarily continue to run. -
Returns
The thrd_yield function returns no value. +
Synopsis
#include <threads.h>
- int tss_create(tss_t *key, tss_dtor_t dtor);
-Description
The tss_create function creates a thread-specific storage pointer with destructor dtor, which may be null. -
Returns
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. +
Synopsis
#include <threads.h>
- void tss_delete(tss_t key);
-Description
The tss_delete function releases any resources used by the thread-specific storage identified by key. -
Returns
The tss_delete function returns no value. +
Synopsis
#include <threads.h>
- void *tss_get(tss_t key);
-Description
The tss_get function returns the value for the current thread held in the thread-specific storage identified by key. -
Returns
The tss_get function returns the value for the current thread if successful, or zero if unsuccessful. +
Synopsis
#include <threads.h>
- int tss_set(tss_t key, void *val);
-Description
The tss_set function sets the value for the current thread held in the thread-specific storage identified by key to val. -
Returns
The tss_set function returns thrd_success on success or thrd_error if the request could not be honored. +
Synopsis
#include <threads.h>
- int xtime_get(xtime *xt, int base);
-Description
The xtime_get function sets the xtime object pointed to by xt to hold the current time based on the time base base. -
Returns
If the xtime_get function is successful it returns the nonzero value base, which must be TIME_UTC; otherwise, it returns zero.306) @@ -18631,13 +20086,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
306) Although an xtime object describes times with nanosecond resolution, the actual resolution in an xtime object is system dependent. -
Contents +
The header <time.h> defines two macros, and declares several types and functions for @@ -18649,19 +20106,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -18677,7 +20138,8 @@ 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 + @@ -18685,22 +20147,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Footnotes
307) The range [0, 60] for tm_sec allows for a positive leap second. +
Synopsis
#include <time.h>
- clock_t clock(void);
-Description
The clock function determines the processor time used. -
Returns
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 @@ -18709,22 +20174,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the processor time used is not available or its value cannot be represented, the function returns the value (clock_t)(-1).308) -
Footnotes
308) In order to measure the time spent in a program, the clock function should be called at the start of the program and its return value subtracted from the value returned by subsequent calls. +
Synopsis
#include <time.h>
- double difftime(time_t time1, time_t time0);
-Description
The difftime function computes the difference between two calendar times: time1 - time0. -
Returns
The difftime function returns the difference expressed in seconds as a double. @@ -18733,13 +20200,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <time.h>
- time_t mktime(struct tm *timeptr);
-Description
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 @@ -18750,7 +20219,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. set appropriately, and the other components are set to represent the specified calendar 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. -
Returns
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 @@ -18765,7 +20234,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. "Thursday", "Friday", "Saturday", "-unknown-" }; struct tm time_str; - /* ... */ + /* ... */ + @@ -18781,32 +20251,36 @@ 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]); + -
Footnotes
309) Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time. +
Synopsis
#include <time.h>
- time_t time(time_t *timer);
-Description
The time function determines the current calendar time. The encoding of the value is unspecified. -
Returns
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. +
Except for the strftime function, these functions each return a pointer to one of two @@ -18816,19 +20290,22 @@ 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. +
Synopsis
#include <time.h>
- char *asctime(const struct tm *timeptr);
-Description
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) { @@ -18847,75 +20324,84 @@ 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. -
Returns
The asctime function returns a pointer to the string. -
Footnotes
Synopsis
#include <time.h>
- char *ctime(const time_t *timer);
-Description
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)) + -
Returns
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). +
Synopsis
#include <time.h>
- struct tm *gmtime(const time_t *timer);
-Description
The gmtime function converts the calendar time pointed to by timer into a broken- down time, expressed as UTC. -
Returns
The gmtime function returns a pointer to the broken-down time, or a null pointer if the specified time cannot be converted to UTC. +
Synopsis
#include <time.h>
- struct tm *localtime(const time_t *timer);
-Description
The localtime function converts the calendar time pointed to by timer into a broken-down time, expressed as local time. -
Returns
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. +
Synopsis
@@ -18923,8 +20409,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
size_t strftime(char * restrict s,
size_t maxsize,
const char * restrict format,
- const struct tm * restrict timeptr);
-Description
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, @@ -18947,24 +20434,30 @@ 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] @@ -18975,42 +20468,52 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %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 @@ -19019,47 +20522,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %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 @@ -19085,7 +20599,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. %x equivalent to ''%m/%d/%y''. %X equivalent to %T. %Z implementation-defined. -
Returns
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 @@ -19093,7 +20607,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. zero is returned and the contents of the array are indeterminate. -
Contents +
The header <uchar.h> declares types and functions for manipulating Unicode characters. @@ -19101,14 +20616,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -19119,19 +20637,22 @@ 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. +
Synopsis
#include <uchar.h>
size_t mbrtoc16(char16_t * restrict pc16,
const char * restrict s, size_t n,
- mbstate_t * restrict ps);
-Description
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 @@ -19144,47 +20665,55 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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.
+
-Footnotes
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). +
Synopsis
#include <uchar.h>
size_t c16rtomb(char * restrict s, char16_t c16,
- mbstate_t * restrict ps);
-Description
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 @@ -19196,26 +20725,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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. +
Synopsis
#include <uchar.h>
size_t mbrtoc32(char32_t * restrict pc32,
const char * restrict s, size_t n,
- mbstate_t * restrict ps);
-Description
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 @@ -19227,48 +20759,56 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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.
+
-Footnotes
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). +
Synopsis
#include <uchar.h>
size_t c32rtomb(char * restrict s, char32_t c32,
- mbstate_t * restrict ps);
-Description
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 @@ -19277,7 +20817,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If 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. -
Returns
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: @@ -19289,8 +20829,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Contents +
The header <wchar.h> defines four macros, and declares four data types, one tag, and @@ -19298,24 +20840,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -19340,7 +20886,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. subclause causes copying to take place between objects that overlap, the behavior is undefined. -
Footnotes
313) See ''future library directions'' (7.30.12).
314) wchar_t and wint_t can be the same integer type. @@ -19348,24 +20894,27 @@ 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. +
The formatted wide character input/output functions shall behave as if there is a sequence point after the actions associated with each specifier.316) -
Footnotes
316) The fwprintf functions perform writes to memory for the %n specifier. +
Synopsis
#include <stdio.h>
#include <wchar.h>
int fwprintf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
-Description
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 @@ -19416,20 +20965,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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,
+
@@ -19438,15 +20991,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +21009,16 @@ 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
@@ -19469,30 +21026,36 @@ 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.
@@ -19502,7 +21065,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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
@@ -19510,7 +21074,8 @@ 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 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
@@ -19526,7 +21091,8 @@ 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 +21105,8 @@ 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),
@@ -19553,14 +21120,16 @@ 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
+
@@ -19576,12 +21145,14 @@ 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
@@ -19598,24 +21169,29 @@ 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. @@ -19626,7 +21202,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 +
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 @@ -19641,13 +21217,13 @@ 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. -
Returns
The fwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. - Environmental limits +
Environmental limits
The number of wide characters that can be produced by any single conversion shall be at least 4095. @@ -19663,12 +21239,13 @@ 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). -
Footnotes
317) Note that 0 is taken as a flag, not as the beginning of a field width.
318) The results of all floating conversions of a negative zero, and of negative values that round to zero, @@ -19692,15 +21269,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. the case of fixed-point conversion by the source value as well. +
Synopsis
#include <stdio.h>
#include <wchar.h>
int fwscanf(FILE * restrict stream,
- const wchar_t * restrict format, ...);
-Description
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 @@ -19769,35 +21348,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
@@ -19806,32 +21393,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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).
@@ -19843,7 +21436,8 @@ 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.
@@ -19857,7 +21451,8 @@ 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 +21478,8 @@ 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
@@ -19891,7 +21487,8 @@ 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
@@ -19901,11 +21498,13 @@ 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, @@ -19914,7 +21513,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -19927,10 +21526,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. @@ -19941,10 +21542,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. @@ -19954,7 +21557,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wcstol, wcstoll, wcstoul, and wcstoull functions (7.28.4.1.2), the wcrtomb function (7.28.6.3.3). -
Footnotes
324) These white-space wide characters are not counted against a specified field width.
325) fwscanf pushes back at most one input wide character onto the input stream. Therefore, some @@ -19963,40 +21566,44 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
326) See ''future library directions'' (7.30.12). +
Synopsis
#include <wchar.h>
int swprintf(wchar_t * restrict s,
size_t n,
- const wchar_t * restrict format, ...);
-Description
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). -
Returns
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. +
Synopsis
#include <wchar.h>
int swscanf(const wchar_t * restrict s,
- const wchar_t * restrict format, ...);
-Description
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. -
Returns
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 @@ -20004,8 +21611,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. zero, in the event of an early matching failure. +
Synopsis
#include <stdarg.h>
@@ -20013,14 +21621,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#include <wchar.h>
int vfwprintf(FILE * restrict stream,
const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
The vfwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. @@ -20040,20 +21649,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. // print out remainder of message vfwprintf(stderr, format, args); va_end(args); - } + } + -
Footnotes
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. +
Synopsis
#include <stdarg.h>
@@ -20061,22 +21672,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#include <wchar.h>
int vfwscanf(FILE * restrict stream,
const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <stdarg.h>
@@ -20084,132 +21697,146 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
int vswprintf(wchar_t * restrict s,
size_t n,
const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <wchar.h>
int vswscanf(const wchar_t * restrict s,
const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <stdarg.h>
#include <wchar.h>
int vwprintf(const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
The vwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. +
Synopsis
#include <stdarg.h>
#include <wchar.h>
int vwscanf(const wchar_t * restrict format,
- va_list arg);
-Description
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) -
Returns
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. +
Synopsis
#include <wchar.h>
- int wprintf(const wchar_t * restrict format, ...);
-Description
The wprintf function is equivalent to fwprintf with the argument stdout interposed before the arguments to wprintf. -
Returns
The wprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. +
Synopsis
#include <wchar.h>
- int wscanf(const wchar_t * restrict format, ...);
-Description
The wscanf function is equivalent to fwscanf with the argument stdin interposed before the arguments to wscanf. -
Returns
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. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- wint_t fgetwc(FILE *stream);
-Description
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). -
Returns
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, @@ -20218,20 +21845,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. function returns WEOF. If an encoding error occurs (including too few bytes), the value of the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.328) -
Footnotes
328) An end-of-file and a read error can be distinguished by use of the feof and ferror functions. Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs. +
Synopsis
#include <stdio.h>
#include <wchar.h>
wchar_t *fgetws(wchar_t * restrict s,
- int n, FILE * restrict stream);
-Description
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 @@ -20241,147 +21870,163 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- wint_t fputwc(wchar_t c, FILE *stream);
-Description
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. -
Returns
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. +
Synopsis
#include <stdio.h>
#include <wchar.h>
int fputws(const wchar_t * restrict s,
- FILE * restrict stream);
-Description
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. -
Returns
The fputws function returns EOF if a write or encoding error occurs; otherwise, it returns a nonnegative value. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- int fwide(FILE *stream, int mode);
-Description
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. -
Returns
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. -
Footnotes
329) If the orientation of the stream has already been determined, fwide does not change it. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- wint_t getwc(FILE *stream);
-Description
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. -
Returns
The getwc function returns the next wide character from the input stream pointed to by stream, or WEOF. +
Synopsis
#include <wchar.h>
- wint_t getwchar(void);
+ wint_t getwchar(void);
+
-Description
The getwchar function is equivalent to getwc with the argument stdin. -
Returns
The getwchar function returns the next wide character from the input stream pointed to by stdin, or WEOF. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- wint_t putwc(wchar_t c, FILE *stream);
-Description
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. -
Returns
The putwc function returns the wide character written, or WEOF. +
Synopsis
#include <wchar.h>
- wint_t putwchar(wchar_t c);
-Description
The putwchar function is equivalent to putwc with the second argument stdout. -
Returns
The putwchar function returns the character written, or WEOF. +
Synopsis
#include <stdio.h>
#include <wchar.h>
- wint_t ungetwc(wint_t c, FILE *stream);
-Description
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 @@ -20406,11 +22051,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. back. For a text or binary stream, the value of its file position indicator after a successful call to the ungetwc function is unspecified until all pushed-back wide characters are read or discarded. -
Returns
The ungetwc function returns the wide character pushed back, or WEOF if the operation fails. +
The header <wchar.h> declares a number of functions useful for wide string @@ -20427,10 +22073,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. zero wide characters. +
Synopsis
#include <wchar.h>
@@ -20439,8 +22087,9 @@ 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);
-Description
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, @@ -20461,14 +22110,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. decimal-point wide character, then an optional binary exponent part as defined in 6.4.4.2;
n-wchar-sequence:
digit
nondigit
n-wchar-sequence digit
- n-wchar-sequence nondigit
+ n-wchar-sequence nondigit
+
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.
@@ -20487,7 +22137,7 @@ 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
@@ -20502,7 +22152,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
+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 @@ -20523,7 +22173,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.332) -
Returns
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), @@ -20538,7 +22188,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
330) It is unspecified whether a minus-signed sequence is converted to a negative number directly or by negating the value resulting from converting the corresponding unsigned sequence (see F.5); the two methods may yield different results if rounding is toward positive or negative infinity. In either case, @@ -20551,8 +22201,9 @@ 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. +
Synopsis
#include <wchar.h>
@@ -20571,8 +22222,9 @@ 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);
-Description
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, @@ -20617,7 +22269,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -20625,33 +22277,38 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
Synopsis
#include <wchar.h>
wchar_t *wcscpy(wchar_t * restrict s1,
- const wchar_t * restrict s2);
-Description
The wcscpy function copies the wide string pointed to by s2 (including the terminating null wide character) into the array pointed to by s1. -
Returns
The wcscpy function returns the value of s1. +
Synopsis
#include <wchar.h>
wchar_t *wcsncpy(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
-Description
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 @@ -20660,28 +22317,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The wcsncpy function returns the value of s1. -
Footnotes
333) Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the result will not be null-terminated. +
Synopsis
#include <wchar.h>
wchar_t *wmemcpy(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
-Description
The wmemcpy function copies n wide characters from the object pointed to by s2 to the object pointed to by s1. -
Returns
The wmemcpy function returns the value of s1. @@ -20690,51 +22349,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Synopsis
#include <wchar.h>
wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
- size_t n);
-Description
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. -
Returns
The wmemmove function returns the value of s1. +
Synopsis
#include <wchar.h>
wchar_t *wcscat(wchar_t * restrict s1,
- const wchar_t * restrict s2);
-Description
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. -
Returns
The wcscat function returns the value of s1. +
Synopsis
#include <wchar.h>
wchar_t *wcsncat(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
-Description
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 @@ -20742,49 +22408,54 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The wcsncat function returns the value of s1. -
Footnotes
334) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is wcslen(s1)+n+1. +
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. +
Synopsis
#include <wchar.h>
- int wcscmp(const wchar_t *s1, const wchar_t *s2);
-Description
The wcscmp function compares the wide string pointed to by s1 to the wide string pointed to by s2. -
Returns
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. +
Synopsis
#include <wchar.h>
- int wcscoll(const wchar_t *s1, const wchar_t *s2);
-Description
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. -
Returns
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 @@ -20794,33 +22465,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wide string pointed to by s2 when both are interpreted as appropriate to the current locale. +
Synopsis
#include <wchar.h>
int wcsncmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
size_t wcsxfrm(wchar_t * restrict s1,
const wchar_t * restrict s2,
- size_t n);
-Description
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 @@ -20829,7 +22504,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. applied to the same two original wide strings. No more than n wide characters are placed 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. -
Returns
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 @@ -20839,131 +22514,149 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. transformation of the wide string pointed to by s:
- 1 + wcsxfrm(NULL, s, 0)+ 1 + wcsxfrm(NULL, s, 0) + +
Synopsis
#include <wchar.h>
int wmemcmp(const wchar_t *s1, const wchar_t *s2,
- size_t n);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
- wchar_t *wcschr(const wchar_t *s, wchar_t c);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
- size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
-Description
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. -
Returns
The wcscspn function returns the length of the segment. +
Synopsis
#include <wchar.h>
- wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
- wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
-Description
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. -
Returns
The wcsrchr function returns a pointer to the wide character, or a null pointer if c does not occur in the wide string. +
Synopsis
#include <wchar.h>
- size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
-Description
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. -
Returns
The wcsspn function returns the length of the segment. +
Synopsis
#include <wchar.h>
- wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
wchar_t *wcstok(wchar_t * restrict s1,
const wchar_t * restrict s2,
- wchar_t ** restrict ptr);
-Description
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 @@ -20994,7 +22687,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Returns
The wcstok function returns a pointer to the first wide character of a token, or a null pointer if there is no token. @@ -21009,60 +22702,70 @@ 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 + +
Synopsis
#include <wchar.h>
wchar_t *wmemchr(const wchar_t *s, wchar_t c,
- size_t n);
-Description
The wmemchr function locates the first occurrence of c in the initial n wide characters of the object pointed to by s. -
Returns
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. +
Synopsis
#include <wchar.h>
- size_t wcslen(const wchar_t *s);
-Description
The wcslen function computes the length of the wide string pointed to by s. -
Returns
The wcslen function returns the number of wide characters that precede the terminating null wide character. +
Synopsis
#include <wchar.h>
- wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
-Description
The wmemset function copies the value of c into each of the first n wide characters of the object pointed to by s. -
Returns
The wmemset function returns the value of s. +
Synopsis
#include <time.h>
@@ -21070,8 +22773,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
size_t wcsftime(wchar_t * restrict s,
size_t maxsize,
const wchar_t * restrict format,
- const struct tm * restrict timeptr);
-Description
The wcsftime function is equivalent to the strftime function, except that:
Returns
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 @@ -21091,6 +22795,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wide character. Otherwise, zero is returned and the contents of the array are indeterminate. +
The header <wchar.h> declares an extended set of functions useful for conversion @@ -21122,65 +22827,74 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
335) Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and mbsrtowcs functions as long as they are used to step sequentially through the same multibyte character string. +
Synopsis
#include <wchar.h> *
- wint_t btowc(int c);
-Description
The btowc function determines whether c constitutes a valid single-byte character in the initial shift state. -
Returns
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. +
Synopsis
#include <wchar.h> *
- int wctob(wint_t c);
-Description
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. -
Returns
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. +
Synopsis
#include <wchar.h>
- int mbsinit(const mbstate_t *ps);
-Description
If ps is not a null pointer, the mbsinit function determines whether the referenced mbstate_t object describes an initial conversion state. -
Returns
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. +
These functions differ from the corresponding multibyte character functions of 7.22.7 @@ -21195,42 +22909,48 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Also unlike their corresponding functions, the return value does not represent whether the encoding is state-dependent. +
Synopsis
#include <wchar.h>
size_t mbrlen(const char * restrict s,
size_t n,
- mbstate_t * restrict ps);
-Description
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. -
Returns
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). +
Synopsis
#include <wchar.h>
size_t mbrtowc(wchar_t * restrict pwc,
const char * restrict s,
size_t n,
- mbstate_t * restrict ps);
-Description
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 @@ -21240,47 +22960,54 @@ 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 resulting state described is the initial conversion state. -
Returns
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.
+
-Footnotes
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). +
Synopsis
#include <wchar.h>
size_t wcrtomb(char * restrict s,
wchar_t wc,
- mbstate_t * restrict ps);
-Description
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 @@ -21289,13 +23016,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. array whose first element is pointed to by s. At most MB_CUR_MAX bytes 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; the resulting state described is the initial conversion state. -
Returns
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. +
These functions differ from the corresponding multibyte string functions of 7.22.8 @@ -21313,16 +23041,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. to reflect the amount of the source processed by that invocation. +
Synopsis
#include <wchar.h>
size_t mbsrtowcs(wchar_t * restrict dst,
const char ** restrict src,
size_t len,
- mbstate_t * restrict ps);
-Description
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 @@ -21339,7 +23069,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -21352,20 +23082,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
337) Thus, the value of len is ignored if dst is a null pointer. +
Synopsis
#include <wchar.h>
size_t wcsrtombs(char * restrict dst,
const wchar_t ** restrict src,
size_t len,
- mbstate_t * restrict ps);
-Description
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 @@ -21383,7 +23115,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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 @@ -21396,13 +23128,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. -
Contents +
The header <wctype.h> defines one macro, and declares three data types and many @@ -21410,14 +23144,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
@@ -21443,10 +23180,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
339) See ''future library directions'' (7.30.13). +
The header <wctype.h> declares several functions useful for classifying wide @@ -21457,6 +23195,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. term control wide character refers to a member of a locale-specific set of wide characters that are not printing wide characters. +
The functions in this subclause return nonzero (true) if and only if the value of the @@ -21469,31 +23208,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. both printing and white-space wide characters.340)
Forward references: the wctob function (7.28.6.1.2). -
Footnotes
340) For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc) && iswspace(wc) is true, but not both. +
Synopsis
#include <wctype.h>
- int iswalnum(wint_t wc);
-Description
The iswalnum function tests for any wide character for which iswalpha or iswdigit is true. +
Synopsis
#include <wctype.h>
- int iswalpha(wint_t wc);
-Description
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 @@ -21502,18 +23245,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace is true.341) -
Footnotes
341) The functions iswlower and iswupper test true or false separately for each of these additional wide characters; all four combinations are possible. +
Synopsis
#include <wctype.h>
- int iswblank(wint_t wc);
-Description
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 @@ -21521,135 +23266,156 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C" locale, iswblank returns true only for the standard blank characters. +
Synopsis
#include <wctype.h>
- int iswcntrl(wint_t wc);
-Description
The iswcntrl function tests for any control wide character. +
Synopsis
#include <wctype.h>
- int iswdigit(wint_t wc);
-Description
The iswdigit function tests for any wide character that corresponds to a decimal-digit character (as defined in 5.2.1). +
Synopsis
#include <wctype.h>
- int iswgraph(wint_t wc);
+ int iswgraph(wint_t wc);
+
-Description
The iswgraph function tests for any wide character for which iswprint is true and iswspace is false.342) -
Footnotes
342) Note that the behavior of the iswgraph and iswpunct functions may differ from their corresponding functions in 7.4.1 with respect to printing, white-space, single-byte execution characters other than ' '. +
Synopsis
#include <wctype.h>
- int iswlower(wint_t wc);
-Description
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. +
Synopsis
#include <wctype.h>
- int iswprint(wint_t wc);
-Description
The iswprint function tests for any printing wide character. +
Synopsis
#include <wctype.h>
- int iswpunct(wint_t wc);
-Description
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) +
Synopsis
#include <wctype.h>
- int iswspace(wint_t wc);
+ int iswspace(wint_t wc);
+
-Description
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. +
Synopsis
#include <wctype.h>
- int iswupper(wint_t wc);
-Description
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. +
Synopsis
#include <wctype.h>
- int iswxdigit(wint_t wc);
-Description
The iswxdigit function tests for any wide character that corresponds to a hexadecimal-digit character (as defined in 6.4.4.1). +
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). +
Synopsis
#include <wctype.h>
- int iswctype(wint_t wc, wctype_t desc);
-Description
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 @@ -21670,50 +23436,57 @@ 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) -
Returns
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). +
Synopsis
#include <wctype.h>
- wctype_t wctype(const char *property);
-Description
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. -
Returns
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. +
The header <wctype.h> declares several functions useful for mapping wide characters. +
Synopsis
#include <wctype.h>
- wint_t towlower(wint_t wc);
-Description
The towlower function converts an uppercase letter to a corresponding lowercase letter. -
Returns
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 @@ -21721,16 +23494,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. characters (always the same one for any given locale); otherwise, the argument is returned unchanged. +
Synopsis
#include <wctype.h>
- wint_t towupper(wint_t wc);
-Description
The towupper function converts a lowercase letter to a corresponding uppercase letter. -
Returns
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 @@ -21738,6 +23513,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. characters (always the same one for any given locale); otherwise, the argument is returned unchanged. +
The functions wctrans and towctrans provide extensible wide character mapping as @@ -21745,13 +23521,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. previous subclause (7.29.3.1). +
Synopsis
#include <wctype.h>
- wint_t towctrans(wint_t wc, wctrans_t desc);
-Description
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 @@ -21761,78 +23539,91 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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)
-Returns
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. +
Synopsis
#include <wctype.h>
- wctrans_t wctrans(const char *property);
-Description
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. -
Returns
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. +
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. -
Contents +
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.
-Contents +
Function names that begin with either is or to, and a lowercase letter may be added to the declarations in the <ctype.h> header. -
Contents +
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. -
Contents +
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. -
Contents +
Macros that begin with LC_ and an uppercase letter may be added to the definitions in the <locale.h> header. -
Contents +
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. -
Contents +
The ability to undefine and perhaps then redefine the macros bool, true, and false is an obsolescent feature. -
Contents +
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 @@ -21840,7 +23631,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. <stdint.h> header. -
Contents +
Lowercase letters may be added to the conversion specifiers and length modifiers in fprintf and fscanf. Other characters may be used in extensions. @@ -21848,17 +23640,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. The use of ungetc on a binary stream where the file position indicator is zero prior to * the call is an obsolescent feature. -
Contents +
Function names that begin with str and a lowercase letter may be added to the declarations in the <stdlib.h> header. -
Contents +
Function names that begin with str, mem, or wcs and a lowercase letter may be added to the declarations in the <string.h> header. -
Contents +
Function names that begin with wcs and a lowercase letter may be added to the declarations in the <wchar.h> header. @@ -21866,6 +23661,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Lowercase letters may be added to the conversion specifiers and length modifiers in fwprintf and fwscanf. Other characters may be used in extensions. +
@@ -21873,16 +23669,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. declarations in the <wctype.h> header. +
(informative)
- Language syntax summary
+ Language syntax summary
+
+NOTE The notation is described in 6.1. +
@@ -21890,7 +23690,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
identifier
constant
string-literal
- punctuator
+ punctuator
+
(6.4) preprocessing-token:
@@ -21900,8 +23701,10 @@ 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
+
+
@@ -21919,199 +23722,247 @@ 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
+
+
< 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 "
+
+
@@ -22169,33 +24031,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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:
@@ -22205,103 +24073,126 @@ 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 +24200,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
static
_Thread_local
auto
- register
+ register
+
(6.7.2) type-specifier:
void
@@ -22326,151 +24218,185 @@ 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 ) ; + +
@@ -22479,145 +24405,181 @@ 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
+
-Contents +
NDEBUG
static_assert
- void assert(scalar expression);
+ void assert(scalar expression);
+
-Contents +
@@ -22694,9 +24656,11 @@ 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);
+
-Contents +
int isalnum(int c);
int isalpha(int c);
@@ -22711,15 +24675,19 @@ 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);
+
-Contents +
EDOM EILSEQ ERANGE errno
__STDC_WANT_LIB_EXT1__
- errno_t
+ errno_t
+
-Contents +
fenv_t FE_OVERFLOW FE_TOWARDZERO
@@ -22739,9 +24707,11 @@ 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);
+
-Contents +
FLT_ROUNDS DBL_DIG FLT_MAX
FLT_EVAL_METHOD LDBL_DIG DBL_MAX
@@ -22756,9 +24726,11 @@ 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
+
-Contents +
imaxdiv_t
@@ -22782,30 +24754,38 @@ 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);
+
-Contents +
and bitor not_eq xor
and_eq compl or xor_eq
- bitand not or_eq
+ bitand not or_eq
+
-Contents +
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
+
-Contents +
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);
+
-Contents +
Contents +
jmp_buf
int setjmp(jmp_buf env);
- _Noreturn void longjmp(jmp_buf env, int val);
+ _Noreturn void longjmp(jmp_buf env, int val);
+
-Contents +
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);
+
-Contents +
alignas
- __alignas_is_defined
+ __alignas_is_defined
+
-Contents +
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);
+
-Contents +
@@ -23100,24 +25090,30 @@ 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);
+
-Contents +
bool
true
false
- __bool_true_false_are_defined
+ __bool_true_false_are_defined
+
-Contents +
ptrdiff_t max_align_t NULL
size_t wchar_t
offsetof(type, member-designator)
__STDC_WANT_LIB_EXT1__
- rsize_t
+ rsize_t
+
-Contents +
intN_t INT_LEASTN_MIN PTRDIFF_MAX
@@ -23134,9 +25130,11 @@ 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
+
-Contents +
Contents +
@@ -23355,9 +25355,11 @@ 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);
+
-Contents +
@@ -23421,9 +25423,11 @@ 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);
+
-Contents +
acos sqrt fmod nextafter
asin fabs frexp nexttoward
@@ -23439,9 +25443,11 @@ 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
+
-Contents +
ONCE_FLAG_INIT mtx_plain
@@ -23481,9 +25487,11 @@ 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);
+
-Contents +
NULL size_t time_t
@@ -23510,9 +25518,11 @@ 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);
+
-Contents +
mbstate_t size_t char16_t char32_t
size_t mbrtoc16(char16_t * restrict pc16,
@@ -23524,9 +25534,11 @@ 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);
+
-Contents +
Contents +
wint_t wctrans_t wctype_t WEOF
@@ -23730,13 +25744,16 @@ 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. +
00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6, @@ -23791,21 +25811,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD, B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD +
0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F +
(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
@@ -23825,7 +25847,9 @@ 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 @@ -23833,15 +25857,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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
@@ -23865,14 +25889,17 @@ 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: @@ -23882,13 +25909,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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 @@ -23905,11 +25936,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. negative and positive infinity are representable in IEC 60559 formats, all real numbers lie within the range of representable values. -
Footnotes
343) Implementations that do not define __STDC_IEC_559__ are not required to conform to these specifications. +
The C floating types match the IEC 60559 formats as follows: @@ -23926,11 +25958,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. - Recommended practice +
Recommended practice
The long double type should match an IEC 60559 extended format. -
Footnotes
344) ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit and quadruple 128-bit IEC 60559 formats. @@ -23938,17 +25970,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. all double values. +
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. -
Footnotes
346) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are sufficient for closure of the arithmetic. +
C operators and functions provide IEC 60559 required and recommended facilities as @@ -24030,6 +26064,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. macros defined in 7.12.3 do not distinguish signaling from quiet NaNs). +
If the integer type is _Bool, 6.3.1.2 applies and no floating-point exceptions are raised @@ -24041,7 +26076,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. conversion of a non-integral floating value raises the ''inexact'' floating-point exception is unspecified.347) -
Footnotes
347) ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those cases where it matters, library functions can be used to effect such conversions with or without raising @@ -24049,6 +26084,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. <math.h>. +
Conversion from the widest supported IEC 60559 format to decimal with @@ -24069,32 +26105,35 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation cannot convert a minus-signed sequence by negating the converted unsigned sequence. -
Footnotes
348) If the minimum-width IEC 60559 extended format (64 bits of precision) is supported, DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and DBL_DIG are 18 and 15, respectively, for these formats.) +
Footnotes
349) Assignment removes any extra range and precision. +
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 +
Recommended practice
A contracted expression should raise floating-point exceptions in a manner generally consistent with the basic arithmetic operations. * +
The floating-point environment defined in <fenv.h> includes the IEC 60559 floating- @@ -24102,10 +26141,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. IEC 60559 dynamic rounding precision and trap enablement modes, if the implementation supports them.350) -
Footnotes
350) This specification does not require dynamic rounding precision nor trap enablement modes. +
IEC 60559 requires that floating-point operations implicitly raise floating-point exception @@ -24119,12 +26159,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
351) If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating- point control modes will be the default ones and the floating-point status flags will not be tested, which allows certain optimizations (see F.9). +
During translation the IEC 60559 default modes are in effect: @@ -24133,19 +26174,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Recommended practice
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. -
Footnotes
352) As floating constants are converted to appropriate internal representations at translation time, their conversion is subject to default rounding modes and raises no execution-time floating-point exceptions (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example strtod, provide execution-time conversion of numeric strings. +
At program startup the floating-point environment is initialized as prescribed by @@ -24158,6 +26200,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
An arithmetic constant expression of floating type, other than one in an initializer for an @@ -24171,7 +26214,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -24182,22 +26224,26 @@ 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. -
Footnotes
353) Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
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 @@ -24207,7 +26253,6 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. translation time.
EXAMPLE -
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -24220,7 +26265,9 @@ 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 @@ -24235,15 +26282,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. their internal representations occur at translation time in all cases. -
Footnotes
354) Use of float_t and double_t variables increases the likelihood of translation-time computation.
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 @@ -24256,11 +26305,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised before ''inexact''. +
This section identifies code transformations that might subvert IEC 60559-specified behavior, and others that do not. +
Floating-point arithmetic operations and external function calls may entail side effects @@ -24279,7 +26330,8 @@ 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 @@ -24292,49 +26344,61 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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).
+
-Footnotes
355) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and other transformations that remove arithmetic operators. @@ -24342,14 +26406,17 @@ 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. +
x != x -> false The expression x != x is true if x is a NaN. @@ -24361,7 +26428,8 @@ 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.
@@ -24371,37 +26439,43 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 @@ -24413,11 +26487,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. precision modes shall assure further that the result of the operation raises no floating- point exception when converted to the semantic type of the operation. -
Footnotes
357) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward. -
Contents +
This subclause contains specifications of <math.h> facilities that are particularly suited for IEC 60559 implementations. @@ -24466,13 +26541,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
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. -
Footnotes
358) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on when the floating-point exception is raised. @@ -24480,8 +26555,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. avoiding them would be too costly. +
Footnotes
360) atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise the ''divide-by-zero'' floating-point exception. +
When the correct result is representable in the range of the return type, the returned value @@ -24662,10 +26759,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. unspecified and the ''invalid'' floating-point exception is raised. +
On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp). +
The returned value is exact and is independent of the current rounding direction mode. +
sqrt is fully specified as a basic arithmetic operation in IEC 60559. The returned value is dependent on the current rounding direction mode. +
The double version of ceil behaves as though implemented by -
#include <math.h>
#include <fenv.h>
@@ -24876,10 +26994,13 @@ 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. +
The nearbyint functions use IEC 60559 rounding according to the current rounding @@ -24904,11 +27026,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. +
The lrint and llrint functions provide floating-to-integer conversion as prescribed @@ -24918,6 +27042,7 @@ 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. +
The lround and llround functions differ from the lrint and llrint functions @@ -24956,6 +27083,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
The trunc functions use IEC 60559 rounding toward zero (regardless of the current @@ -24969,8 +27097,10 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. functions may, but are not required to, raise the ''inexact'' floating-point exception for finite non-integer arguments. +
The remainder functions are fully specified as a basic arithmetic operation in @@ -25005,6 +27137,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. When subnormal results are supported, the returned value is exact and is independent of the current rounding direction mode. +
The remquo functions follow the specifications for the remainder functions. They @@ -25013,20 +27146,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. When subnormal results are supported, the returned value is exact and is independent of the current rounding direction mode. +
copysign is specified in the Appendix to IEC 60559.
The returned value is exact and is independent of the current rounding direction mode. +
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. +
No additional requirements beyond those on nextafter. @@ -25047,12 +27185,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. current rounding direction mode. +
No additional requirements. +
If just one argument is a NaN, the fmax functions return the other argument (if both @@ -25063,21 +27204,25 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. The body of the fmax function might be361)
{ return (isgreaterequal(x, y) ||
- isnan(y)) ? x : y; }
+ isnan(y)) ? x : y; }
+
-Footnotes
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. +
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. +
Relational operators and their corresponding comparison macros (7.12.14) produce @@ -25106,22 +27252,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. operands of relational operators to their semantic types. +
(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) -
Footnotes
362) Implementations that do not define __STDC_IEC_559_COMPLEX__ are not required to conform to these specifications. +
There is a new keyword _Imaginary, which is used to specify imaginary types. It is @@ -25141,6 +27291,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The imaginary type domain comprises the imaginary types. +
A complex or imaginary value with at least one infinite part is regarded as an infinity @@ -25153,13 +27304,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Conversions among imaginary types follow rules analogous to those for real floating types. +
When a value of imaginary type is converted to a real type other than _Bool,363) the @@ -25168,10 +27322,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. When a value of real type is converted to an imaginary type, the result is a positive imaginary zero. -
Footnotes
When a value of imaginary type is converted to a complex type, the real part of the @@ -25182,6 +27337,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. complex value is discarded and the value of the imaginary part is converted according to the conversion rules for the corresponding real types. +
The following subclauses supplement 6.5 in order to specify the type of the result for an @@ -25199,8 +27355,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
Semantics
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 @@ -25209,31 +27366,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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)
#include <math.h>
#include <complex.h>
@@ -25307,14 +27471,15 @@ 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>
@@ -25358,20 +27523,23 @@ 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 with division, provides better roundoff characteristics. -
Footnotes
364) These properties are already implied for those cases covered in the tables, but are required for all cases (at least where the state for CX_LIMITED_RANGE is ''off''). +
Semantics
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 @@ -25380,29 +27548,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) + -
Contents +
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. @@ -25428,19 +27604,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -25456,13 +27634,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
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) -
Footnotes
366) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding implementations that treat special cases more carefully. +
Contents +
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, @@ -25728,30 +27922,37 @@ 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. +
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). +
The LIA-1 data type Boolean is implemented by the C data type bool with values of true and false, all from <stdbool.h>. +
The signed C integer types int, long int, long long int, and the corresponding @@ -25765,13 +27966,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
The integer operations on integer types are the following: @@ -25790,6 +27993,7 @@ 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. +
The C floating-point types float, double, and long double are compatible with @@ -25799,6 +28003,7 @@ 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. +
The parameters for a floating point data type can be accessed by the following: @@ -25814,6 +28019,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON rnd_style FLT_ROUNDS +
The floating-point operations on floating-point types are the following: @@ -25826,7 +28032,8 @@ 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 @@ -25838,6 +28045,7 @@ 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 @@ -25851,17 +28059,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
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
@@ -25888,6 +28099,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation uses round-to-nearest. +
Notification is the process by which a user or program is informed that an exceptional @@ -25895,6 +28107,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. allows an implementation to cause a notification to occur when any arithmetic operation returns an exceptional value as defined in LIA-1 clause 5. +
LIA-1 requires at least the following two alternatives for handling of notifications: @@ -25915,6 +28128,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. math library function calls. User-provided signal handlers for SIGFPE allow for trap- and-resume behavior with the same constraint. +
C's <fenv.h> status flags are compatible with the LIA-1 indicators. @@ -25940,6 +28154,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. This documentation makes that distinction because <fenv.h> covers only the floating- point indicators. +
C is compatible with LIA-1's trap requirements for arithmetic operations, but not for @@ -25958,11 +28173,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. it) or trap-and-resume, at the programmer's option. +
(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. @@ -26002,14 +28219,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
(informative)
- Portability issues
+ Portability issues
+
+This annex collects some information about portability that appears in this International Standard. +
The following are unspecified: @@ -26124,6 +28344,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. G.6.2.4, G.6.2.5, G.6.2.6, G.6.3.1, G.6.4.2). +
The behavior is undefined in the following circumstances: @@ -26603,12 +28824,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (7.29.3.2.1). +
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: +
The following characteristics of a hosted environment are locale-specific and are required @@ -26931,6 +29167,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The following extensions are widely used in many systems, but are not portable to all @@ -26939,6 +29176,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. extensions are new keywords, extra library functions declared in standard headers, or predefined macros with names that do not begin with an underscore. +
In a hosted environment, the main function receives a third argument, char *envp[], @@ -26946,27 +29184,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. that provides information about the environment for this execution of the program (5.1.2.2.1). +
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). +
All characters in identifiers (with or without external linkage) are significant (6.4.2). +
A function identifier, or the identifier of an object the declaration of which contains the keyword extern, has file scope (6.2.1). +
String literals are modifiable (in which case, identical string literals should denote distinct objects) (6.4.5). +
Additional arithmetic types, such as __int128 or double double, and their @@ -26974,6 +29217,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
A pointer to an object or to void may be cast to a pointer to a function, allowing data to @@ -26982,30 +29226,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). +
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). +
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). +
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). +
Macro names that do not begin with an underscore, describing the translation and @@ -27013,17 +29263,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. (6.10.8). +
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, +
Handlers for specific signals are called with extra arguments in addition to the signal number (7.14.1.1). +
Additional mappings from files to streams are supported (7.21.2). @@ -27031,12 +29284,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Additional file-opening modes may be specified by characters appended to the mode argument of the fopen function (7.21.5.3). +
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). +
Functions declared in <complex.h> and <math.h> raise SIGFPE to report errors @@ -27044,11 +29299,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 7.12). +
(normative)
- Bounds-checking interfaces
+ Bounds-checking interfaces
+
+Traditionally, the C Library has contained many functions that trust the programmer to @@ -27083,6 +29341,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. change if the function is called again, perhaps by another thread. +
This annex specifies a series of optional extensions that can be useful in the mitigation of @@ -27095,15 +29354,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. Subclause K.3 should be read as if it were merged into the parallel structure of named subclauses of clause 7. -
Footnotes
367) Implementations that do not define __STDC_LIB_EXT1__ are not required to conform to these specifications. +
The functions, macros, and types declared or defined in K.3 and its subclauses are not @@ -27129,7 +29391,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
368) Future revisions of this International Standard may define meanings for other values of __STDC_WANT_LIB_EXT1__. @@ -27140,6 +29402,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. implementation is not conforming. +
Each macro name in any of the following subclauses is reserved for use as specified if it @@ -27154,11 +29417,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. +
An implementation may set errno for the functions defined in this annex, but is not required to. +
Most functions in this annex include as part of their specification a list of runtime- @@ -27186,52 +29451,58 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
370) Although runtime-constraints replace many cases of undefined behavior, undefined behavior still exists in this annex. Implementations are free to detect any case of undefined behavior and treat it as a runtime-constraint violation by calling the runtime-constraint handler. This license comes directly from the definition of undefined behavior. -
Contents +
The header <errno.h> defines a type.
The type is
- errno_t+ errno_t + which is type int.371) -
Footnotes
371) As a matter of programming style, errno_t may be used as the type of something that deals only with the values that might be found in errno. For example, a function which returns the value of errno might be declared as having the return type errno_t. -
Contents +
The header <stddef.h> defines a type.
The type is
- rsize_t+ rsize_t + which is the type size_t.372) -
Footnotes
372) See the description of the RSIZE_MAX macro in <stdint.h>. -
Contents +
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 +
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 @@ -27248,48 +29519,56 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. is no object size that is considered a runtime-constraint violation. -
Footnotes
373) The macro RSIZE_MAX need not expand to a constant expression. -
Contents +
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. +
Synopsis
#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. -
Description
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 @@ -27302,28 +29581,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
Recommended practice It should be possible to open at least TMP_MAX_S temporary files during the lifetime of the program (this limit may be shared with tmpnam_s) 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). -
Returns
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. +
Synopsis
#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. -
Description
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 @@ -27342,7 +29623,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The implementation shall behave as if no library function except tmpnam calls the tmpnam_s function.375) - Recommended practice +
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 @@ -27350,7 +29631,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. should be used instead of tmpnam_s when possible. One situation that requires the use of the tmpnam_s function is when the program needs to create a temporary directory rather than a temporary file. -
Returns
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 @@ -27358,11 +29639,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
Otherwise, the tmpnam_s function writes the string in the array pointed to by s and returns zero. - Environmental limits +
Environmental limits
The value of the macro TMP_MAX_S shall be at least 25. -
Footnotes
374) Files created using strings generated by the tmpnam_s function are temporary only in the sense that their names should not collide with those generated by conventional naming rules for the implementation. It is still necessary to use the remove function to remove such files when their use @@ -27375,17 +29656,20 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. convention for temporary files), but this is not required. +
Synopsis
#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. @@ -27398,7 +29682,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Description
The fopen_s function opens the file whose name is the string pointed to by filename, and associates a stream with it. @@ -27407,33 +29691,41 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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.
@@ -27451,17 +29743,18 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. to FILE pointed to by streamptr will be set to a null pointer. -
Returns
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. -
Footnotes
376) These are the same permissions that the file would have been created with by fopen. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -27469,7 +29762,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. @@ -27477,7 +29771,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -27496,26 +29790,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
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. +
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. +
Synopsis
#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 @@ -27526,11 +29823,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The fprintf_s function is equivalent to the fprintf function except for the explicit runtime-constraints listed above. -
Returns
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. @@ -27540,7 +29837,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
377) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. @@ -27550,14 +29847,16 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. constraint violation. +
Synopsis
#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 @@ -27566,7 +29865,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -27578,7 +29877,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). -
Returns
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 @@ -27593,10 +29892,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. @@ -27607,15 +29908,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. #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. -
Footnotes
379) Because an implementation may treat any undefined behavior as a runtime-constraint violation, an implementation may treat any unsupported specifiers in the string pointed to by format as a runtime- constraint violation. @@ -27632,13 +29935,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compatible with rsize_t. +
Synopsis
#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 @@ -27651,28 +29956,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Description
The printf_s function is equivalent to the printf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
381) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#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 @@ -27681,25 +29988,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The scanf_s function is equivalent to fscanf_s with the argument stdin interposed before the arguments to scanf_s. -
Returns
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. +
Synopsis
#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 @@ -27712,14 +30021,14 @@ 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 snprintf_s function sets s[0] to the null character. -
Description
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. -
Returns
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 @@ -27727,20 +30036,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. output has been completely written if and only if the returned value is nonnegative and less than n. -
Footnotes
382) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#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 @@ -27757,34 +30068,36 @@ 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. -
Description
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. -
Returns
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- constraint violation occurred, sprintf_s returns zero. -
Footnotes
383) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#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 @@ -27793,13 +30106,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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. -
Returns
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 @@ -27807,8 +30120,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. provided for, or even zero, in the event of an early matching failure. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -27816,7 +30130,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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 @@ -27827,23 +30142,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The vfprintf_s function is equivalent to the vfprintf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
384) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -27851,7 +30167,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#include <stdio.h>
int vfscanf_s(FILE * restrict stream,
const char * restrict format,
- va_list arg);
+ va_list arg);
+
@@ -27865,34 +30182,36 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
-Description
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) -
Returns
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 than provided for, or even zero, in the event of an early matching failure. -
Footnotes
385) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s, vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#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 @@ -27904,30 +30223,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. before discovering the runtime-constraint violation. -
Description
The vprintf_s function is equivalent to the vprintf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
386) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#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 @@ -27936,13 +30257,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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) -
Returns
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 @@ -27954,14 +30275,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
387) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s, vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -27969,7 +30291,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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 @@ -27981,14 +30304,14 @@ 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 vsnprintf_s function sets s[0] to the null character. -
Description
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. -
Returns
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 @@ -28001,14 +30324,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
388) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28016,7 +30340,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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 @@ -28029,14 +30354,14 @@ 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 vsprintf_s function sets s[0] to the null character. -
Description
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. -
Returns
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 @@ -28048,14 +30373,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
389) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointed at by format when those characters are not a interpreted as a %n specifier. For example, if the entire format string was %%n. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28063,7 +30389,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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 @@ -28072,34 +30399,37 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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) -
Returns
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 provided for, or even zero, in the event of an early matching failure. -
Footnotes
390) As the functions vfprintf_s, vfscanf_s, vprintf_s, vscanf_s, vsnprintf_s, vsprintf_s, and vsscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#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);
+
@@ -28114,7 +30444,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
-Description
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 @@ -28125,14 +30455,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 +
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. -
Returns
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 @@ -28143,44 +30473,52 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
391) The gets_s function, unlike the historical gets function, makes it a runtime-constraint violation for a line of input to overflow the buffer to store it. Unlike the fgets function, gets_s maintains a one-to-one relationship between input lines and successful calls to gets_s. Programs that use gets expect such a relationship. -
Contents +
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);
+
+Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
constraint_handler_t set_constraint_handler_s(
- constraint_handler_t handler);
-Description
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 @@ -28204,18 +30542,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If the handler argument to set_constraint_handler_s is a null pointer, the implementation default handler becomes the current constraint handler. -
Returns
The set_constraint_handler_s function returns a pointer to the previously registered handler.392) -
Footnotes
392) If the previous handler was registered by calling set_constraint_handler_s with a null pointer argument, a pointer to the implementation default handler is returned (not NULL). +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28223,8 +30562,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
void abort_handler_s(
const char * restrict msg,
void * restrict ptr,
- errno_t error);
-Description
A pointer to the abort_handler_s function shall be a suitable argument to the set_constraint_handler_s function. @@ -28232,7 +30572,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The abort_handler_s function does not return to its caller. @@ -28241,12 +30581,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
393) Many implementations invoke a debugger when the abort function is called. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28254,35 +30595,39 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
void ignore_handler_s(
const char * restrict msg,
void * restrict ptr,
- errno_t error);
-Description
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) -
Returns
The ignore_handler_s function returns no value. -
Footnotes
394) If the runtime-constraint handler is set to the ignore_handler_s function, any library function in which a runtime-constraint violation occurs will return to its caller. The caller can determine whether a runtime-constraint violation occurred based on the library function's specification (usually, the library function returns a nonzero errno_t). +
Synopsis
#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 @@ -28290,7 +30635,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Description
The getenv_s function searches an environment list, provided by the host environment, for a string that matches the string pointed to by name. @@ -28309,11 +30654,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
The set of environment names and the method for altering the environment list are implementation-defined. -
Returns
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. +
These utilities make use of a comparison function to search or sort arrays of unspecified @@ -28346,17 +30692,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. comparison function, and also between any call to the comparison function and any movement of the objects passed as arguments to that call. -
Footnotes
395) That is, if the value passed is p, then the following expressions are always valid and nonzero:
((char *)p - (char *)base) % size == 0
(char *)p >= (char *)base
- (char *)p < (char *)base + nmemb * size
+ (char *)p < (char *)base + nmemb * size
+
+
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28365,7 +30713,8 @@ 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 @@ -28373,7 +30722,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If there is a runtime-constraint violation, the bsearch_s function does not search the array. -
Description
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. @@ -28393,21 +30742,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
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. -
Footnotes
396) In practice, this means that the entire array has been sorted according to the comparison function.
397) 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28415,14 +30765,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Description
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. @@ -28437,7 +30788,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If two elements compare as equal, their relative order in the resulting sorted array is unspecified. -
Returns
The qsort_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -28447,11 +30798,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
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. +
The behavior of the multibyte character functions is affected by the LC_CTYPE category @@ -28463,13 +30815,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. encodings have state dependency, and zero otherwise.399) Changing the LC_CTYPE category causes the conversion state of these functions to be indeterminate. -
Footnotes
399) If the locale employs special bytes to change the shift state, these bytes do not produce separate wide character codes, but are grouped with an adjacent multibyte character. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28477,7 +30830,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -28489,7 +30843,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28514,24 +30868,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
In no case will the int pointed to by status be set to a value greater than the MB_CUR_MAX macro. -
Returns
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. +
The behavior of the multibyte string functions is affected by the LC_CTYPE category of the current locale. +
Synopsis
#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 @@ -28544,7 +30901,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28570,26 +30927,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If copying takes place between objects that overlap, the objects take on unspecified values. -
Returns
The mbstowcs_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. -
Footnotes
400) Thus, the value of len is ignored if dst is a null pointer.
401) This allows an implementation to attempt converting the multibyte string before discovering a terminating null character did not occur where required. +
Synopsis
#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 @@ -28608,7 +30967,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28644,12 +31003,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
The wcstombs_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. -
Footnotes
402) 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. However, if the conversion stops before a terminating null wide character has been reached, the result will be null @@ -28659,28 +31018,34 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. runtime-constraint violation. -
Contents +
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. +
Synopsis
#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 @@ -28690,24 +31055,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The memcpy_s function copies n characters from the object pointed to by s2 into the object pointed to by s1. -
Returns
The memcpy_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. +
Synopsis
#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 @@ -28716,27 +31083,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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. -
Returns
The memmove_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. +
Synopsis
#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. @@ -28747,7 +31116,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. greater than zero and not greater than RSIZE_MAX, then strcpy_s sets s1[0] to the null character. -
Description
The strcpy_s function copies the string pointed to by s2 (including the terminating null character) into the array pointed to by s1. @@ -28755,12 +31124,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The strcpy_s function returns zero405) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
Footnotes
404) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if any of those characters are null. Such an approach might write a character to every element of s1 before discovering that the first element should be set to the null character. @@ -28769,8 +31138,9 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28778,7 +31148,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -28789,7 +31160,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28802,7 +31173,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The strncpy_s function returns zero407) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -28819,13 +31190,14 @@ 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. -
Footnotes
406) This allows an implementation to copy characters from s2 to s1 while simultaneously checking if any of those characters are null. Such an approach might write a character to every element of s1 before discovering that the first element should be set to the null character. @@ -28834,17 +31206,20 @@ 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. +
Synopsis
#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 @@ -28862,7 +31237,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28871,12 +31246,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The strcat_s function returns zero410) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
Footnotes
408) Zero means that s1 was not null terminated upon entry to strcat_s.
409) This allows an implementation to append characters from s2 to s1 while simultaneously checking if @@ -28887,8 +31262,9 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28896,7 +31272,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -28913,7 +31290,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -28924,7 +31301,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The strncat_s function returns zero413) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -28944,7 +31321,8 @@ 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. @@ -28955,7 +31333,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. After the fourth call r4 will have the value zero and s4 will contain the sequence abcdef\0. -
Footnotes
411) Zero means that s1 was not null terminated upon entry to strncat_s.
412) This allows an implementation to append characters from s2 to s1 while simultaneously checking if @@ -28966,10 +31344,12 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -28977,7 +31357,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -28988,7 +31369,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Description
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 @@ -29021,7 +31402,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Returns
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. @@ -29039,18 +31420,22 @@ 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 + +
Synopsis
#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 @@ -29060,7 +31445,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -29068,19 +31453,21 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. machine as described in (5.1.2.3). That is, any call to the memset_s function shall assume that the memory indicated by s and n may be accessible in the future and thus must contain the values indicated by c. -
Returns
The memset_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. +
Synopsis
#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. @@ -29088,7 +31475,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If there is a runtime-constraint violation, then the array (if any) pointed to by s is not modified. -
Description
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 @@ -29101,40 +31488,44 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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 (.). -
Returns
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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
- size_t strerrorlen_s(errno_t errnum);
-Description
The strerrorlen_s function calculates the length of the (untruncated) locale-specific message string that the strerror_s function maps to errnum. -
Returns
The strerrorlen_s function returns the number of characters (not including the null character) in the full message string. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
- size_t strnlen_s(const char *s, size_t maxsize);
-Description
The strnlen_s function computes the length of the string pointed to by s. -
Returns
If s is a null pointer,414) then the strnlen_s function returns zero.
@@ -29148,46 +31539,53 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
414) Note that the strnlen_s function has no runtime-constraints. This lack of runtime-constraints along with the values returned for a null pointer or an unterminated string argument make strnlen_s useful in algorithms that gracefully handle such exceptional data. -
Contents +
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) -
Footnotes
415) The normal ranges are defined in 7.26.1. +
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. +
Synopsis
#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 @@ -29199,7 +31597,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -29208,7 +31606,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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):
Recommended practice The strftime function allows more flexible formatting and supports locale-specific behavior. If you do not require the exact form of the result string produced by the asctime_s function, consider using the strftime function instead. -
Returns
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. +
Synopsis
#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 @@ -29260,78 +31661,86 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Description
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)) + +
Recommended practice The strftime function allows more flexible formatting and supports locale-specific behavior. If you do not require the exact form of the result string produced by the ctime_s function, consider using the strftime function instead. -
Returns
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. +
Synopsis
#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. -
Description
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. -
Returns
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. +
Synopsis
#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. -
Description
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. -
Returns
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. -
Contents +
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 @@ -29339,16 +31748,19 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. unspecified values. +
Synopsis
#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 @@ -29359,30 +31771,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The fwprintf_s function is equivalent to the fwprintf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
416) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#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 @@ -29394,7 +31808,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -29406,14 +31820,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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). -
Returns
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 than provided for, or even zero, in the event of an early matching failure. -
Footnotes
417) If the format is known at translation time, an implementation may issue a diagnostic for any argument used to store the result from a c, s, or [ conversion specifier if that argument is not followed by an argument of a type compatible with rsize_t. A limited amount of checking may be done if even if @@ -29426,15 +31840,17 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. compatible with rsize_t. +
Synopsis
#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 @@ -29448,14 +31864,14 @@ 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 snwprintf_s function sets s[0] to the null wide character. -
Description
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. -
Returns
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 @@ -29463,20 +31879,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. terminated output has been completely written if and only if the returned value is nonnegative and less than n. -
Footnotes
418) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#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 @@ -29492,14 +31910,14 @@ 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 swprintf_s function sets s[0] to the null wide character. -
Description
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. -
Returns
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 @@ -29507,20 +31925,22 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. be written, swprintf_s returns a negative value. If any other runtime-constraint violation occurred, swprintf_s returns zero. -
Footnotes
419) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#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 @@ -29529,13 +31949,13 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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. -
Returns
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 @@ -29543,8 +31963,9 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. than provided for, or even zero, in the event of an early matching failure. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29553,7 +31974,8 @@ 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 @@ -29564,23 +31986,24 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The vfwprintf_s function is equivalent to the vfwprintf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
420) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29588,7 +32011,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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);
+
@@ -29601,26 +32025,27 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
-Description
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) -
Returns
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 than provided for, or even zero, in the event of an early matching failure. -
Footnotes
421) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29629,7 +32054,8 @@ 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 @@ -29643,14 +32069,14 @@ 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 vsnwprintf_s function sets s[0] to the null wide character. -
Description
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. -
Returns
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 @@ -29658,14 +32084,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. output has been completely written if and only if the returned value is nonnegative and less than n. -
Footnotes
422) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29674,7 +32101,8 @@ 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 @@ -29689,14 +32117,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. null wide character. -
Description
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. -
Returns
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 @@ -29704,14 +32132,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. be written, vswprintf_s returns a negative value. If any other runtime-constraint violation occurred, vswprintf_s returns zero. -
Footnotes
423) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29719,7 +32148,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
#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 @@ -29728,7 +32158,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -29739,27 +32169,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Returns
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 than provided for, or even zero, in the event of an early matching failure. -
Footnotes
424) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#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 @@ -29769,11 +32201,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The vwprintf_s function is equivalent to the vwprintf function except for the explicit runtime-constraints listed above. -
Returns
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. @@ -29783,21 +32215,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
425) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#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 @@ -29806,31 +32240,33 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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) -
Returns
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 than provided for, or even zero, in the event of an early matching failure. -
Footnotes
426) As the functions vfwscanf_s, vwscanf_s, and vswscanf_s invoke the va_arg macro, the value of arg after the return is indeterminate. +
Synopsis
#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 @@ -29842,28 +32278,30 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The wprintf_s function is equivalent to the wprintf function except for the explicit runtime-constraints listed above. -
Returns
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. -
Footnotes
427) It is not a runtime-constraint violation for the wide characters %n to appear in sequence in the wide string pointed at by format when those wide characters are not a interpreted as a %n specifier. For example, if the entire format string was L"%%n". +
Synopsis
#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 @@ -29872,11 +32310,11 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The wscanf_s function is equivalent to fwscanf_s with the argument stdin interposed before the arguments to wscanf_s. -
Returns
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 @@ -29884,19 +32322,23 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. provided for, or even zero, in the event of an early matching failure. +
Synopsis
#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. @@ -29906,7 +32348,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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. @@ -29914,7 +32356,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The wcscpy_s function returns zero429) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -29924,7 +32366,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
428) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking if any of those wide characters are null. Such an approach might write a wide character to every element of s1 before discovering that the first element should be set to the null wide character. @@ -29933,8 +32375,9 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -29942,7 +32385,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -29953,7 +32397,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -29963,7 +32407,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The wcsncpy_s function returns zero431) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -29986,13 +32430,14 @@ 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. -
Footnotes
430) This allows an implementation to copy wide characters from s2 to s1 while simultaneously checking if any of those wide characters are null. Such an approach might write a wide character to every element of s1 before discovering that the first element should be set to the null wide character. @@ -30001,8 +32446,9 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -30010,7 +32456,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -30020,24 +32467,26 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
The wmemcpy_s function copies n successive wide characters from the object pointed to by s2 into the object pointed to by s1. -
Returns
The wmemcpy_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. +
Synopsis
#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 @@ -30046,29 +32495,32 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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. -
Returns
The wmemmove_s function returns zero if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. +
Synopsis
#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 @@ -30082,7 +32534,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -30091,12 +32543,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The wcscat_s function returns zero434) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. -
Footnotes
432) Zero means that s1 was not null terminated upon entry to wcscat_s.
433) This allows an implementation to append wide characters from s2 to s1 while simultaneously @@ -30107,8 +32559,9 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -30116,7 +32569,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -30133,7 +32587,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -30144,7 +32598,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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) -
Returns
The wcsncat_s function returns zero437) if there was no runtime-constraint violation. Otherwise, a nonzero value is returned. @@ -30165,7 +32619,8 @@ 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. @@ -30176,7 +32631,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
435) Zero means that s1 was not null terminated upon entry to wcsncat_s.
436) This allows an implementation to append wide characters from s2 to s1 while simultaneously @@ -30187,10 +32642,12 @@ 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. +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
@@ -30198,7 +32655,8 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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 @@ -30209,7 +32667,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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. -
Description
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 @@ -30243,7 +32701,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Returns
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. @@ -30261,22 +32719,26 @@ 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 + +
Synopsis
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>
- size_t wcsnlen_s(const wchar_t *s, size_t maxsize);
-Description
The wcsnlen_s function computes the length of the wide string pointed to by s. -
Returns
If s is a null pointer,438) then the wcsnlen_s function returns zero.
@@ -30286,27 +32748,31 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. maxsize wide characters of s shall be accessed by wcsnlen_s. -
Footnotes
438) Note that the wcsnlen_s function has no runtime-constraints. This lack of runtime-constraints along with the values returned for a null pointer or an unterminated wide string argument make wcsnlen_s useful in algorithms that gracefully handle such exceptional data. +
Unlike wcrtomb, wcrtomb_s does not permit the ps parameter (the pointer to the conversion state) to be a null pointer. +
Synopsis
#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 @@ -30318,11 +32784,12 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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). -
Description
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.
@@ -30341,25 +32808,28 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Returns
The wcrtomb_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. +
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. +
Synopsis
#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, @@ -30373,7 +32843,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. 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. -
Description
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 @@ -30407,27 +32877,29 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If copying takes place between objects that overlap, the objects take on unspecified values. -
Returns
The mbsrtowcs_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. -
Footnotes
439) Thus, the value of len is ignored if dst is a null pointer.
440) This allows an implementation to attempt converting the multibyte string before discovering a terminating null character did not occur where required. +
Synopsis
#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);
+
@@ -30446,7 +32918,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
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.
-Description
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 @@ -30489,7 +32961,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''.
If copying takes place between objects that overlap, the objects take on unspecified values. -
Returns
The wcsrtombs_s function returns zero if no runtime-constraint violation and no encoding error occurred. Otherwise, a nonzero value is returned. @@ -30499,7 +32971,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. -
Footnotes
441) 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. However, if the conversion stops before a terminating null wide character has been reached, the result will be null @@ -30509,11 +32981,14 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. runtime-constraint violation. +
(normative)
- Analyzability
+ Analyzability
+
+This annex specifies optional behavior that can aid in the analyzability of C programs. @@ -30521,13 +32996,15 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. An implementation that defines __STDC_ANALYZABLE__ shall conform to the specifications in this annex.443) -
Footnotes
443) Implementations that do not define __STDC_ANALYZABLE__ are not required to conform to these specifications. +
out-of-bounds store @@ -30535,6 +33012,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. modify (or, for an object declared volatile, fetch) one or more bytes that lie outside the bounds permitted by this Standard. +
bounded undefined behavior @@ -30546,6 +33024,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. NOTE 2 Any values produced or stored might be indeterminate values. +
critical undefined behavior @@ -30558,6 +33037,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
If the program performs a trap (3.19.5), the implementation is permitted to invoke a @@ -30583,6 +33063,7 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. +
[^ x ^], 3.20 , (comma operator), 5.1.2.4, 6.5.17 @@ -32012,4 +34494,5 @@ margin: deleted text is marked with ''*'', new or changed text with '' ''. WINT_MIN macro, 7.20.3 wint_t type, 7.20.3, 7.21.6.1, 7.28.1, 7.28.2.1,+