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. @@ -616,8 +616,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
argument
- actual argument
- actual parameter (deprecated)
+ actual argument
+ actual parameter (deprecated)
expression in the comma-separated list bounded by the parentheses in a function call
expression, or a sequence of preprocessing tokens in the comma-separated list bounded
by the parentheses in a function-like macro invocation
@@ -811,18 +811,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- ??? x???
+ [^ x ^]
ceiling of x: the least integer greater than or equal to x
- EXAMPLE ???2.4??? is 3, ???-2.4??? is -2. + EXAMPLE [^2.4^] is 3, [^-2.4^] is -2.
- ??? x???
+ [_ x _]
floor of x: the greatest integer less than or equal to x
- EXAMPLE ???2.4??? is 2, ???-2.4??? is -3. + EXAMPLE [_2.4_] is 2, [_-2.4_] is -3.
Footnotes
2) A strictly conforming program can use conditional features (such as those in annex F) provided the use is guarded by a #ifdef directive with the appropriate macro. For example: @@ -887,7 +887,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 /* ... */ fesetround(FE_UPWARD); /* ... */ - #endif + #endif +
3) This implies that a conforming implementation reserves no identifiers other than those explicitly
@@ -978,7 +979,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
-footnotes
+
Footnotes
5) 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
@@ -1003,12 +1004,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
Footnotes
8) 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.
@@ -1050,11 +1052,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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;9) or in some other implementation-defined manner.
If they are declared, the parameters to the main function shall obey the following @@ -1079,7 +1083,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 startup and program termination. -
Footnotes
9) 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. @@ -1102,7 +1106,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 termination status returned to the host environment is unspecified.
Forward references: definition of terms (7.1.1), the exit function (7.20.4.3). -
Footnotes
10) 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. @@ -1171,7 +1175,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -1183,7 +1188,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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).
@@ -1198,7 +1204,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -1214,30 +1221,36 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -1251,10 +1264,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -1263,7 +1278,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 signal function (7.14), files (7.19.3). -
Footnotes
11) 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
@@ -1294,18 +1309,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -1334,27 +1353,32 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
??= # ??) ] ??! |
??( [ ??' ^ ??> }
- ??/ \ ??< { ??- ~
+ ??/ \ ??< { ??- ~
+
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
12) 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. @@ -1402,26 +1426,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Alphabetic escape sequences representing nongraphic characters in the execution character set are intended to produce actions on display devices as follows: - \a (alert) Produces an audible or visible alert without changing the active position. - \b (backspace) Moves the active position to the previous position on the current line. If -
+
- 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 -
+ device is unspecified. +
-
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 @@ -1484,7 +1506,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Footnotes
13) Implementations should avoid imposing fixed translation limits whenever possible.
14) See ''future language directions'' (6.11.3). @@ -1497,7 +1519,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 specified in <stdint.h>.
Forward references: integer types <stdint.h> (7.18). -
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 @@ -1510,82 +1532,121 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (absolute value) to those shown, with the same sign.
CHAR_BIT 8 +
+ SCHAR_MIN -127 // -(27 - 1) +
+ SCHAR_MAX +127 // 27 - 1 +
+ UCHAR_MAX 255 // 28 - 1 +
CHAR_MIN see below +
CHAR_MAX see below +
MB_LEN_MAX 1 +
+ SHRT_MIN -32767 // -(215 - 1) +
+ SHRT_MAX +32767 // 215 - 1 +
+ USHRT_MAX 65535 // 216 - 1 +
+ INT_MIN -32767 // -(215 - 1) +
+ INT_MAX +32767 // 215 - 1 +
+ UINT_MAX 65535 // 216 - 1 +
+ LONG_MIN -2147483647 // -(231 - 1) +
+ LONG_MAX +2147483647 // 231 - 1 +
+ ULONG_MAX 4294967295 // 232 - 1 +
+ LLONG_MIN -9223372036854775807 // -(263 - 1) +
+ LLONG_MAX +9223372036854775807 // 263 - 1 +
+ ULLONG_MAX 18446744073709551615 // 264 - 1 +
If the value of an object of type char is treated as a signed integer when used in an expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of - UCHAR_MAX.15) The value UCHAR_MAX shall equal 2CHAR_BIT - 1. + UCHAR_MAX.15) The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
Forward references: representations of types (6.2.6), conditional inclusion (6.10.1). -
Footnotes
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.16) 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 ,
+ x = s be (Sum) fk b-k , emin <= e <= emax
k=1
- emin <= e <= emax
+
- In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be + In addition to normalized floating-point numbers ( f1 > 0 if x != 0), floating types may be able to contain other kinds of floating-point numbers, such as subnormal floating-point - numbers (x != 0, e = emin , f 1 = 0) and unnormalized floating-point numbers (x != 0, - e > emin , f 1 = 0), and values that are not floating-point numbers, such as infinities and + numbers (x != 0, e = emin , f1 = 0) and unnormalized floating-point numbers (x != 0, + e > emin , f1 = 0), and values that are not floating-point numbers, such as infinities and NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates through almost every arithmetic operation without raising a floating-point exception; a signaling NaN generally raises a floating-point exception when occurring as an @@ -1609,8 +1670,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 All integer values in the <float.h> header, except FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing directives; all floating values shall be constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX, - and FLT_ROUNDS have separate names for all three floating-point types. The floating- - point model representation is provided for all values except FLT_EVAL_METHOD and + and FLT_ROUNDS have separate names for all three floating-point types. The floating-point + model representation is provided for all values except FLT_EVAL_METHOD and FLT_ROUNDS.
The rounding mode for floating-point addition is characterized by the implementation- @@ -1620,7 +1681,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -1642,7 +1704,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -1651,19 +1714,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 those shown, with the same sign:
FLT_RADIX 2 +
FLT_MANT_DIG
DBL_MANT_DIG
LDBL_MANT_DIG
+
- ??? pmax log10 b if b is a power of 10 - ??? - ??? ???1 + pmax log10 b??? otherwise+ { pmax log10 b if b is a power of 10 + { + { [^1 + pmax log10 b^] otherwise + +
DECIMAL_DIG 10
+
- ??? p log10 b if b is a power of 10 - ??? - ??? ???( p - 1) log10 b??? otherwise+ { p log10 b if b is a power of 10 + { + { [_( p - 1) log10 b_] otherwise + +
FLT_DIG 6 DBL_DIG 10 LDBL_DIG 10 +
FLT_MIN_EXP DBL_MIN_EXP LDBL_MIN_EXP +
- ??? ???FLT_MIN_10_EXP -37 DBL_MIN_10_EXP -37 LDBL_MIN_10_EXP -37 +
FLT_MAX_EXP DBL_MAX_EXP LDBL_MAX_EXP +
FLT_MAX_10_EXP +37 DBL_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 +
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
-
FLT_MIN 1E-37
DBL_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. @@ -1736,9 +1821,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 float:
6
- x = s16e (Sum) f k 16-k ,
+ x = s 16e (Sum) fk 16-k , -31 <= e <= +32
k=1
- -31 <= e <= +32
+
FLT_RADIX 16
@@ -1750,7 +1835,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -1758,22 +1844,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 <float.h> header for types float and double:
24
- x f = s2e (Sum) f k 2-k ,
+ xf = s 2e (Sum) fk 2-k , -125 <= e <= +128
k=1
- -125 <= e <= +128
+
53
- x d = s2e (Sum) f k 2-k ,
+ xd = s 2e (Sum) fk 2-k , -1021 <= e <= +1024
k=1
- -1021 <= e <= +1024
+
+
FLT_RADIX 2
DECIMAL_DIG 17
FLT_MANT_DIG 24
FLT_EPSILON 1.19209290E-07F // decimal constant
- FLT_EPSILON 0X1P-23F // hex constant
+ FLT_EPSILON 0X1P-23F // hex constant
+
@@ -1798,7 +1886,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -1809,7 +1898,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
(7.20), input/output <stdio.h> (7.19), mathematics <math.h> (7.12).
-Footnotes
16) 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. @@ -1839,7 +1928,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -1940,7 +2030,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: declarations (6.7), expressions (6.5), external definitions (6.9), statements (6.8). -
Footnotes
21) There is no linkage between different identifiers.
22) A function declaration can contain the storage-class specifier static only if it is at file scope; see
@@ -1973,7 +2063,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
-footnotes
+
Footnotes
24) There is only one name space for tags even though three are possible. @@ -2017,7 +2107,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
25) 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. @@ -2186,7 +2276,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 qualifiers (if any) of the type from which it is derived.
A pointer to void shall have the same representation and alignment requirements as a - pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of + pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of compatible types shall have the same representation and alignment requirements. All @@ -2208,7 +2298,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: compatible type and composite type (6.2.7), declarations (6.7). -
Footnotes
28) Implementation-defined keywords shall have the form of an identifier reserved for any use as described in 7.1.3. @@ -2294,16 +2384,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: declarations (6.7), expressions (6.5), lvalues, arrays, and function designators (6.3.2.1). -
Footnotes
40) 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
Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
- type unsigned char range from 0 to 2
-
-
- CHAR_BIT
- - 1.
+ type unsigned char range from 0 to 2CHAR_BIT- 1.
41) 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. @@ -2322,8 +2408,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 For unsigned integer types other than unsigned char, the bits of the object representation shall be divided into two groups: value bits and padding bits (there need not be any of the latter). If there are N value bits, each bit shall represent a different - power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of - representing values from 0 to 2 N - 1 using a pure binary representation; this shall be + power of 2 between 1 and 2N-1 , so that objects of that type shall be capable of + representing values from 0 to 2N - 1 using a pure binary representation; this shall be known as the value representation. The values of any padding bits are unspecified.44)
For signed integer types, the bits of the object representation shall be divided into three @@ -2337,8 +2423,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 modified in one of the following ways:
Footnotes
44) 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
@@ -2432,13 +2518,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
Footnotes
46) Two types need not be identical to be compatible.
47) As specified in 6.2.1, the later declaration might hide the prior declaration. @@ -2501,7 +2589,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: enumeration specifiers (6.7.2.2), structure and union specifiers (6.7.2.1). -
Footnotes
48) 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.
@@ -2524,7 +2612,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
Footnotes
49) The rules describe arithmetic on the mathematical value, not the value of a given type of expression. @@ -2543,7 +2631,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 in an implementation-defined manner. If the value being converted is outside the range of values that can be represented, the behavior is undefined. -
Footnotes
50) 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). @@ -2589,33 +2677,36 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 +
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.52) @@ -2625,7 +2716,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
51) 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). @@ -2671,7 +2762,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
53) 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
@@ -2737,7 +2828,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
capable of holding object pointers (7.18.1.4), simple assignment (6.5.16.1).
-footnotes
+
Footnotes
55) The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.17.
56) The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to @@ -2749,7 +2840,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
token:
@@ -2765,12 +2856,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -2815,13 +2907,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (6.5.3.1), preprocessing directives (6.10), preprocessing numbers (6.4.8), string literals (6.4.5). -
Footnotes
58) 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
@@ -2834,8 +2926,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
default inline struct _Imaginary
do int switch
double long typedef
- else register union
-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 @@ -2845,14 +2938,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
59) One possible specification for imaginary types appears in annex G.
Syntax
identifier:
@@ -2869,8 +2962,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -2890,7 +2984,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 - 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 @@ -2902,7 +2996,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 identifiers differ only in nonsignificant characters, the behavior is undefined.
Forward references: universal character names (6.4.3), macro replacement (6.10.3). -
Footnotes
60) 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. @@ -2910,12 +3004,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.61)
This name is encoded as if the implicit declaration had been written in the source @@ -2929,10 +3024,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 { 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). @@ -2941,13 +3038,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
61) 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:
@@ -2955,17 +3052,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
\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.62) -
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.63) Similarly, the universal @@ -2977,7 +3075,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
62) 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). @@ -2986,31 +3084,32 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -3031,17 +3130,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -3051,7 +3151,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -3059,38 +3159,69 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The type of an integer constant is the first of the corresponding list in which its value can be represented. -
- Octal or Hexadecimal- Suffix Decimal Constant Constant - - none int int -
- long int unsigned int - long long int long int - unsigned long int - 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- - l or L long int long int -
- long long int unsigned long int - 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- - Both u or U unsigned long long int unsigned long long int - and ll or LL +
| Suffix | Decimal Constant | Octal or Hexadecimal Constant + |
|---|---|---|
| none + | +int +long int +long long int ++ | +int +unsigned int +long int +unsigned long int +long long int +unsigned long long int ++ |
| u or U + | +unsigned int +unsigned long int +unsigned long long int ++ | +unsigned int +unsigned long int +unsigned long long int ++ |
| l or L + | +long int +long long int ++ | +long int +unsigned long int +long long int +unsigned long long int ++ |
| Both u or U and l or L + | +unsigned long int +unsigned long long int ++ | +unsigned long int +unsigned long long int ++ |
| ll or LL + | +long long int ++ | +long long int +unsigned long long int ++ |
| Both u or U and ll or LL + | +unsigned long long int ++ | +unsigned long long int ++ |
If an integer constant cannot be represented by any type in its list, it may have an extended integer type, if the extended integer type can represent its value. If all of the @@ -3102,7 +3233,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
@@ -3110,37 +3241,38 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -3149,7 +3281,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -3168,7 +3300,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 Floating constants are converted to internal format as if at translation-time. The conversion of a floating constant shall not raise an exceptional condition or a floating- point exception at execution time. - 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 @@ -3184,24 +3316,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
64) The specification for the library functions recommends more accurate conversion than required for floating constants (see 7.20.1.3).
Syntax
enumeration-constant:
- identifier
-Semantics
An identifier declared as an enumeration constant has type int.
Forward references: enumeration specifiers (6.7.2.2).
Syntax
@@ -3229,8 +3362,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
\ 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 @@ -3241,14 +3375,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 \\. @@ -3276,12 +3411,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Constraints
The value of an octal or hexadecimal escape sequence shall be in the range of representable values for the type unsigned char for an integer character constant, or the unsigned type corresponding to wchar_t for a wide character constant. -
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 @@ -3327,26 +3462,27 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (7.20.7.2). -
Footnotes
65) 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:
- " s-char-sequenceopt "
- L" s-char-sequenceopt "
+ " s-char-sequenceopt "
+ L" s-char-sequenceopt "
s-char-sequence:
s-char
s-char-sequence s-char
s-char:
any member of the source character set except
the double-quote ", backslash \, or new-line character
- escape-sequence
-Description
A character string literal is a sequence of zero or more multibyte characters enclosed in double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the @@ -3357,7 +3493,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 character constant, except that the single-quote ' is representable either by itself or by the escape sequence \', but the double-quote " shall be represented by the escape sequence \". -
Semantics
In translation phase 6, the multibyte character sequences specified by any sequence of adjacent character and wide string literal tokens are concatenated into a single multibyte @@ -3384,7 +3520,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
EXAMPLE 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. @@ -3392,13 +3529,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: common definitions <stddef.h> (7.17), the mbstowcs function (7.20.8.1). -
Footnotes
66) A character 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
@@ -3408,8 +3545,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
? : ; ...
= *= /= %= += -= <<= >>= &= ^= |=
, # ##
- <: :> <% %> %: %:%:
-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 @@ -3420,15 +3558,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
In all aspects of the language, the six tokens67)
- <: :> <% %> %: %:%:+ <: :> <% %> %: %:%: + behave, respectively, the same as the six tokens
- [ ] { } # ##
+ [ ] { } # ##
+
except for their spelling.68)
Forward references: expressions (6.5), declarations (6.7), preprocessing directives (6.10), statements (6.8). -
Footnotes
67) These tokens are sometimes called ''digraphs''.
68) Thus [ and <: behave differently when ''stringized'' (see 6.10.3.2), but can otherwise be freely @@ -3436,7 +3576,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
header-name:
@@ -3453,8 +3593,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -3474,24 +3615,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
69) Thus, sequences of characters that resemble escape sequences cause undefined behavior.
70) For an example of a header name preprocessing token used in a #pragma directive, see 6.10.9.
Syntax
pp-number:
@@ -3503,15 +3646,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -3545,14 +3689,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
71) Thus, /* ... */ comments do not nest. @@ -3619,7 +3764,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
72) A floating-point status flag is not an object and can be set more than once within an expression.
73) This paragraph renders undefined statement expressions such as
@@ -3627,9 +3772,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
i = ++i + 1;
a[i++] = i;
+
while allowing
+
i = i + 1;
- a[i] = i;
+ a[i] = i;
+
74) The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
@@ -3640,9 +3788,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
parentheses () (6.5.1), subscripting brackets [] (6.5.2.1), function-call parentheses () (6.5.2.2), and
the conditional operator ?: (6.5.15).
-
- Within each major subclause, the operators have the same precedence. Left- or right-associativity is
- indicated in each subclause by the syntax for the expressions discussed therein.
+ Within each major subclause, the operators have the same precedence. Left- or right-associativity is
+ indicated in each subclause by the syntax for the expressions discussed therein.
75) Allocated objects have no declared type. @@ -3657,15 +3804,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
primary-expression:
identifier
constant
string-literal
- ( expression )
-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 @@ -3682,24 +3830,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 designator, or a void expression.
Forward references: declarations (6.7). -
Footnotes
79) Thus, an undeclared identifier is a violation of the syntax.
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 ++
postfix-expression --
( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
+ ( type-name ) { initializer-list , }
+
@@ -3708,14 +3857,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 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 [] @@ -3734,7 +3884,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -3748,7 +3899,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
The expression that denotes the called function80) shall have type pointer to function returning void or returning an object type other than an array type. @@ -3757,7 +3908,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 number of arguments shall agree with the number of parameters. Each argument shall have a type such that its value may be assigned to an object with the unqualified version of the type of its corresponding parameter. -
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 @@ -3819,14 +3970,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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) (6.7.5.3), function definitions (6.9.1), the return statement (6.8.6.4), simple assignment (6.5.16.1). -
Footnotes
80) Most often, this is the result of converting an identifier that is a function designator.
81) A function may change the values of its parameters, but these changes cannot affect the values of the @@ -3836,7 +3988,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
The first operand of the . operator shall have a qualified or unqualified structure or union type, and the second operand shall name a member of that type. @@ -3845,7 +3997,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 structure'' or ''pointer to 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,82) and is an lvalue if @@ -3875,7 +4027,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -3883,7 +4036,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
cs.i const int
cs.ci const int
vs.i volatile int
- vs.ci volatile const int
+ vs.ci volatile const int
+
@@ -3910,7 +4064,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
/* ... */
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; };
@@ -3929,13 +4084,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
} 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
82) If the member used to access 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 @@ -3946,11 +4102,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
The operand of the postfix increment or decrement operator shall have 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. After the result is obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate @@ -3965,7 +4121,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: additive operators (6.5.6), compound assignment (6.5.16.2).
Constraints
The type name shall specify an object type or an array of unknown size, but not a variable length array type. @@ -3975,7 +4131,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
If the compound literal occurs outside the body of a function, the initializer list shall consist of constant expressions. -
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 @@ -4003,7 +4159,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -4017,7 +4174,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
/*...*/
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.
@@ -4027,16 +4185,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
created using compound literals can be passed to functions without depending on member order:
drawline((struct point){.x=1, .y=1},
- (struct point){.x=3, .y=4});
+ (struct point){.x=3, .y=4});
+
Or, if drawline instead expected pointers to struct point:
drawline(&(struct point){.x=1, .y=1},
- &(struct point){.x=3, .y=4});
+ &(struct point){.x=3, .y=4});
+
EXAMPLE 4 A read-only compound literal can be specified through constructions like:
- (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
+ (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}
+
@@ -4047,7 +4208,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
"/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.
@@ -4056,7 +4218,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -4066,7 +4229,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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: @@ -4080,7 +4244,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -4090,7 +4255,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: type names (6.7.6), initialization (6.7.8). -
Footnotes
84) 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. @@ -4101,7 +4266,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
unary-expression:
@@ -4112,14 +4277,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
sizeof unary-expression
sizeof ( type-name )
unary-operator: one of
- & * + - ~ !
+ & * + - ~ !
+
Constraints
The operand of the prefix increment or decrement operator shall have 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). @@ -4131,14 +4297,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -4158,7 +4324,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: storage-class specifiers (6.7.1), structure and union specifiers (6.7.2.1). -
Footnotes
87) 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 @@ -4169,11 +4335,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -4197,12 +4363,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. -
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 @@ -4224,14 +4390,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -4242,7 +4410,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 { char b[n+3]; // variable length array return sizeof b; // execution time sizeof - } + } + @@ -4253,31 +4422,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 size_t size; size = fsize3(10); // fsize3 returns 13 return 0; - } + } +
Forward references: common definitions <stddef.h> (7.17), declarations (6.7), structure and union specifiers (6.7.2.1), type names (6.7.6), array declarators (6.7.5.2). -
Footnotes
88) 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 qualified or unqualified scalar type and the operand shall have scalar type.
Conversions that involve pointers, other than where permitted by the constraints of 6.5.16.1, shall be specified by means of an explicit cast. -
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.89) A cast that specifies @@ -4294,25 +4465,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
89) 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.
@@ -4326,19 +4498,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 fractional part discarded.90) If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a. -
Footnotes
90) 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 an object type and the other shall have integer type. (Incrementing is @@ -4356,7 +4529,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Semantics
If both operands have arithmetic type, the usual arithmetic conversions are performed on them. @@ -4402,7 +4575,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 expression (Q)+1 does not point to an element of the array object.91)
EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types. -
{
int n = 4, m = 3;
@@ -4411,7 +4583,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -4419,7 +4593,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: array declarators (6.7.5.2), common definitions <stddef.h> (7.17). -
Footnotes
91) 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 @@ -4431,17 +4605,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -4464,7 +4639,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 resulting value is implementation-defined.
Syntax
relational-expression:
@@ -4472,8 +4647,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -4509,20 +4685,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.92) The result has type int. -
Footnotes
92) 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.93) Each of the operators yields 1 if the @@ -4564,7 +4741,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
93) Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
94) Two objects may be adjacent in memory because they are adjacent elements of a larger array or @@ -4575,16 +4752,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -4598,16 +4776,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -4616,16 +4795,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -4635,16 +4815,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -4654,16 +4835,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -4674,13 +4856,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
conditional-expression:
logical-OR-expression
- logical-OR-expression ? expression : conditional-expression
-Constraints
The first operand shall have scalar type.
@@ -4694,7 +4877,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Semantics
The first operand is evaluated; there is a sequence point after its evaluation. The second operand is evaluated only if the first compares unequal to 0; the third operand is evaluated @@ -4730,7 +4913,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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):
@@ -4739,26 +4923,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
c_ip v_ip const volatile int *
vp c_cp const void *
ip c_ip const int *
- vp ip void *
+ vp ip void *
+
-Footnotes
95) 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, but is not an @@ -4773,7 +4959,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
One of the following shall hold:96)
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 @@ -4807,7 +4993,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -4824,7 +5011,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -4837,12 +5025,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
96) 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 @@ -4850,7 +5039,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
For the operators += and -= only, either the left operand shall be a pointer to an object type and the right shall have integer type, or the left operand shall have qualified or @@ -4858,20 +5047,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
For the other operators, 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 differs from the simple assignment expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
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 after its evaluation. Then the right operand is evaluated; the result has its @@ -4883,7 +5073,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (6.7.8). @@ -4893,21 +5084,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
97) 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 @@ -4915,7 +5107,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -4968,7 +5160,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
98) The operand of a sizeof operator is usually not evaluated (6.5.3.4).
99) An integer constant expression is used to specify the size of a bit-field member of a structure, the @@ -4979,28 +5171,30 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
100) 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 ;
declaration-specifiers:
- storage-class-specifier declaration-specifiersopt
- type-specifier declaration-specifiersopt
- type-qualifier declaration-specifiersopt
- function-specifier declaration-specifiersopt
+ storage-class-specifier declaration-specifiersopt
+ type-specifier declaration-specifiersopt
+ type-qualifier declaration-specifiersopt
+ function-specifier declaration-specifiersopt
init-declarator-list:
init-declarator
init-declarator-list , init-declarator
init-declarator:
declarator
- declarator = initializer
-Constraints
A declaration shall declare at least a declarator (other than the parameters of a function or the members of a structure or union), a tag, or the members of an enumeration. @@ -5011,7 +5205,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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: @@ -5037,12 +5231,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: declarators (6.7.5), enumeration specifiers (6.7.2.2), initialization (6.7.8). -
Footnotes
101) Function definitions have a different syntax, described in 6.9.1.
Syntax
storage-class-specifier:
@@ -5050,12 +5244,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
extern
static
auto
- register
-Constraints
At most, one storage-class specifier may be given in the declaration specifiers in a declaration.102) -
Semantics
The typedef specifier is called a ''storage-class specifier'' for syntactic convenience only; it is discussed in 6.7.7. The meanings of the various linkages and storage durations @@ -5078,7 +5273,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 or union member objects.
Forward references: type definitions (6.7.7). -
Footnotes
102) See ''future language directions'' (6.11.5).
103) The implementation may treat any register declaration simply as an auto declaration. However, @@ -5090,7 +5285,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
type-specifier:
@@ -5107,8 +5302,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
_Complex
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 @@ -5144,7 +5340,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The type specifier _Complex shall not be used if the implementation does not provide complex types.104) -
Semantics
Specifiers for structures, unions, and enumerations are discussed in 6.7.2.1 through 6.7.2.3. Declarations of typedef names are discussed in 6.7.7. The characteristics of the @@ -5161,16 +5357,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
104) Freestanding implementations are not required to provide complex types. *
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
@@ -5181,15 +5377,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
struct-declaration:
specifier-qualifier-list struct-declarator-list ;
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 structure or union shall not contain a member with incomplete or function type (hence, a structure shall not contain an instance of itself, but may contain a pointer to an instance @@ -5206,7 +5403,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. -
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 @@ -5277,15 +5474,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
EXAMPLE 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).
@@ -5295,21 +5495,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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: @@ -5317,38 +5521,44 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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: tags (6.7.2.3). -
Footnotes
105) A structure or union can not contain a member with a variably modified type because member names are not ordinary identifiers as defined in 6.2.3. @@ -5363,24 +5573,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.109) An enumerator with = defines its @@ -5409,13 +5620,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
109) 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. @@ -5424,7 +5636,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Constraints
A specific type shall have its content defined at most once.
@@ -5433,9 +5645,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. The type is incomplete111) until the closing brace @@ -5447,13 +5660,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
A type specifier of the form
- struct-or-union identifieropt { struct-declaration-list }
+ struct-or-union identifieropt { struct-declaration-list }
+
or
- enum identifier { enumerator-list }
+ enum identifier { enumerator-list }
+
or
- enum identifier { enumerator-list , }
+ enum identifier { enumerator-list , }
+
declares a structure, union, or enumerated type. The list defines the structure content,
@@ -5462,22 +5678,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.113)
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.113) + declares the identifier as the tag of that type.113)
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. @@ -5487,11 +5707,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 struct tnode { int count; struct tnode *left, *right; - }; + }; + specifies a structure that contains an integer and two pointers to objects of the same type. Once this declaration has been given, the declaration
- struct tnode s, *sp;+ struct tnode s, *sp; + declares s to be an object of the given type and sp to be a pointer to an object of the given type. With these declarations, the expression sp->left refers to the left struct tnode pointer of the object to which sp points; the expression s.right->count designates the count member of the right struct @@ -5509,26 +5731,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (6.7.5), array declarators (6.7.5.2), type definitions (6.7.7). -
Footnotes
111) 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 @@ -5543,18 +5768,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
type-qualifier:
const
restrict
- volatile
-Constraints
Types other than pointer types derived from object or incomplete types shall not be restrict-qualified. -
Semantics
The properties associated with qualified types are meaningful only for expressions that are lvalues.114) @@ -5599,7 +5825,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -5621,10 +5848,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 *'' + -
Footnotes
114) 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.
@@ -5681,7 +5909,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -5692,7 +5921,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{
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.
@@ -5707,7 +5937,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 extern int d[100]; f(50, d + 50, d); // valid f(50, d + 1, d); // undefined behavior - } + } +
EXAMPLE 3 The function parameter declarations @@ -5717,7 +5948,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -5727,7 +5959,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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;
@@ -5739,7 +5970,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -5751,10 +5984,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 t.n = n; t.v = malloc(n * sizeof (float)); return t; - } + } + -
Footnotes
119) 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 @@ -5762,12 +5996,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
function-specifier:
- inline
-Constraints
Function specifiers shall be used only in the declaration of an identifier for a function.
@@ -5777,7 +6012,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
In a hosted environment, the inline function specifier shall not appear in a declaration of main. -
Semantics
A function declared with an inline function specifier is an inline function. The function specifier may appear more than once; the behavior is the same as if it appeared @@ -5800,7 +6035,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 EXAMPLE 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)
{
@@ -5815,7 +6049,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{
/* 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 @@ -5826,7 +6062,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
120) 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 @@ -5844,23 +6080,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -5872,11 +6108,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -5891,23 +6128,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 incomplete type, either @@ -5915,11 +6155,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: array declarators (6.7.5.2), type definitions (6.7.7).
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. @@ -5932,7 +6173,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -5942,12 +6184,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -5960,14 +6203,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 An ordinary identifier (as defined in 6.2.3) that has a variably modified type shall have either block scope and no linkage or function prototype scope. If an identifier is declared to be an object with static 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 ''.123)
(See 6.7.5.3 for the meaning of the optional type qualifiers and the keyword static.)
@@ -5997,14 +6241,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -6022,7 +6268,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
p = a; // invalid: not compatible because 4 != 6
r = c; // compatible, but defined behavior only if
// n == 6 and m == n+1
- }
+ }
+
@@ -6053,19 +6300,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 (6.7.5.3), function definitions (6.9.1), initialization (6.7.8). -
Footnotes
123) When several ''array of'' specifications are adjacent, a multidimensional array is declared.
124) Thus, * can be used only in function declarations that are not definitions (see 6.7.5.3).
Constraints
A function declarator shall not specify a return type that is a function type or an array type. @@ -6077,15 +6325,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 ''. @@ -6147,7 +6397,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -6164,7 +6415,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -6172,7 +6424,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -6196,7 +6449,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -6204,20 +6458,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (6.7.6). -
Footnotes
125) The macros defined in the <stdarg.h> header (7.15) may be used to access arguments that correspond to the ellipsis. @@ -6227,25 +6483,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -6260,7 +6517,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (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 @@ -6273,21 +6531,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
128) 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 @@ -6297,7 +6556,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -6307,13 +6567,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -6322,7 +6584,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -6335,7 +6598,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -6346,7 +6610,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -6359,7 +6624,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -6374,10 +6640,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 int b[n]; // a and b are different sizes for (int i = 1; i < n; i++) a[i-1] = b[i]; - } + } +
Syntax
initializer:
@@ -6385,8 +6652,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{ initializer-list }
{ initializer-list , }
initializer-list:
- designationopt initializer
- initializer-list , designationopt initializer
+ designationopt initializer
+ initializer-list , designationopt initializer
designation:
designator-list =
designator-list:
@@ -6394,8 +6661,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -6411,18 +6679,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -6515,13 +6785,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -6532,7 +6804,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{ 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
@@ -6540,7 +6813,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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].
@@ -6549,13 +6823,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
int z[4][3] = {
{ 1 }, { 2 }, { 3 }, { 4 }
- };
+ };
+
initializes the first column of z as specified and initializes the rest with zeros.
EXAMPLE 5 The declaration
- struct { int a[3], b; } w[] = { { 1 }, 2 };
+ struct { int a[3], b; } w[] = { { 1 }, 2 };
+
is a definition with an inconsistently bracketed initialization. It defines an array with two element
structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
@@ -6570,7 +6846,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{ 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
@@ -6584,7 +6861,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
1, 0, 0, 0, 0, 0,
2, 3, 0, 0, 0, 0,
4, 5, 6
- };
+ };
+
or by:
short q[4][3][2] = {
@@ -6598,7 +6876,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
{ 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 @@ -6608,27 +6887,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -6641,39 +6926,44 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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> (7.17). -
Footnotes
129) 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. @@ -6691,7 +6981,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
statement:
@@ -6700,8 +6990,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -6723,21 +7014,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (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 @@ -6745,28 +7037,30 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.134) @@ -6779,7 +7073,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
int p(int);
/* ... */
- (void)p(0);
+ (void)p(0);
+
@@ -6790,7 +7085,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
char *s;
/* ... */
while (*s++ != '\0')
- ;
+ ;
+
a null statement is used to supply an empty loop body to the iteration statement.
@@ -6807,23 +7103,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 } /* ... */ end_loop1: ; - } + } +
Forward references: iteration statements (6.8.5). -
Footnotes
134) 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. @@ -6833,10 +7131,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -6848,7 +7146,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 syntax.
Constraints
The controlling expression of a switch statement shall have integer type.
@@ -6862,7 +7160,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (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 @@ -6876,7 +7174,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -6897,33 +7195,35 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 /* 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
135) 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 @@ -6938,7 +7238,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
136) 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. @@ -6957,7 +7257,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -6969,7 +7270,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a nonzero constant. -
Footnotes
137) 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 @@ -6977,15 +7278,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
jump-statement:
goto identifier ;
continue ;
break ;
- return expressionopt ;
-Semantics
A jump statement causes an unconditional jump to another place. @@ -6995,12 +7297,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -7012,10 +7314,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
/* ... */
goto first_time;
for (;;) {
-
// determine next operation
/* ... */
if (need to reinitialize) {
@@ -7027,8 +7329,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
continue;
}
// handle other operations
- /* ... */
+ /* ... */
}
+
@@ -7046,37 +7349,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 of the statements - while (/* ... */) { do { for (/* ... */) {
+ while (/* ... */) { do { for (/* ... */) {
/* ... */ /* ... */ /* ... */
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;.138)
-Footnotes
138) 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. @@ -7086,12 +7391,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -7119,7 +7424,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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). @@ -7128,7 +7434,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
139) 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 and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra @@ -7136,7 +7442,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Syntax
translation-unit:
@@ -7144,8 +7450,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -7155,7 +7462,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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'' @@ -7175,21 +7482,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
140) 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.141) @@ -7215,7 +7523,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
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 @@ -7249,11 +7557,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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:
@@ -7266,7 +7576,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -7276,24 +7587,27 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
141) The intent is that the type category in a function definition cannot be inherited from a typedef:
@@ -7307,13 +7621,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
142) See ''future language directions'' (6.11.7).
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. @@ -7346,23 +7661,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -7372,47 +7689,48 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -7431,14 +7749,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -7450,20 +7768,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
143) 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: it shall not contain a cast; identifiers (including those lexically identical to @@ -7475,10 +7794,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- defined identifier+ defined identifier + or
- defined ( identifier )+ defined ( identifier ) + which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is predefined or if it has been the subject of a #define preprocessing directive without an intervening #undef directive with the same subject identifier), 0 if it is not. @@ -7486,12 +7807,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -7519,8 +7841,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- # 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. @@ -7536,7 +7859,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: macro replacement (6.10.3), source file inclusion (6.10.2), largest integer types (7.18.1.5). -
Footnotes
144) 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. @@ -7546,8 +7869,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
146) Thus, the constant expression in the following #if directive and if statement is not guaranteed to
evaluate to the same value in these two contexts.
+
#if 'z' - 'a' == 25
if ('z' - 'a' == 25)
+
147) As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive @@ -7556,15 +7881,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -7576,19 +7902,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- # include "q-char-sequence" new-line+ # include "q-char-sequence" new-line + causes the replacement of that directive by the entire contents of the source file identified by the specified sequence between the " delimiters. The named source file is searched for in an implementation-defined manner. If this search is not supported, or if the search fails, the directive is reprocessed as if it read
- # include <h-char-sequence> new-line+ # include <h-char-sequence> new-line + with the identical contained sequence (including > characters, if any) from the original directive.
A preprocessing directive of the form
- # include pp-tokens new-line+ # include pp-tokens new-line + (that does not match one of the two previous forms) is permitted. The preprocessing tokens after include in the directive are processed just as in normal text. (Each identifier currently defined as a macro name is replaced by its replacement list of @@ -7610,7 +7939,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
#include <stdio.h>
- #include "myprog.h"
+ #include "myprog.h"
+
EXAMPLE 2 This illustrates macro-replaced #include directives: @@ -7627,17 +7957,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #else #define INCFILE "versN.h" #endif - #include INCFILE + #include INCFILE +
Forward references: macro replacement (6.10.3). -
Footnotes
148) 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 @@ -7666,7 +7997,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -7679,7 +8010,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 name149) 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 @@ -7687,9 +8019,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -7718,7 +8051,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
merger, the number of arguments is one more than the number of parameters in the macro
definition (excluding the ...).
-Footnotes
149) 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.
@@ -7741,11 +8074,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
replace it.
6.10.3.2 The # operator
-Constraints
+
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 @@ -7765,11 +8098,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -7795,21 +8128,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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
151) Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that exist only within translation phase 4. @@ -7840,14 +8175,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -7856,7 +8193,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -7880,13 +8218,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -7906,7 +8246,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 == 0) str(: @\n), s); #include xstr(INCFILE(2).h) glue(HIGH, LOW); - xglue(HIGH, LOW) + xglue(HIGH, LOW) + results in
@@ -7916,7 +8257,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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);
@@ -7925,7 +8267,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -7933,11 +8276,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
#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. @@ -7947,13 +8292,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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: @@ -7966,21 +8313,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -7988,7 +8337,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -7996,13 +8346,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -8011,20 +8363,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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)152) causes the implementation to behave in an implementation-defined manner. The behavior might cause translation to fail or cause the @@ -8040,7 +8394,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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). @@ -8049,7 +8404,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
152) 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 @@ -8060,64 +8415,60 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Semantics
A preprocessing directive of the form
- # new-line+ # new-line + has no effect.
The following macro names154) shall be defined by the implementation: - __DATE__ The date of translation of the preprocessing translation unit: a character -
+
- source line (an integer constant).155)- __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.- __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in -
+ shall be supplied. +
+ integer character constant. +
The following macro names are conditionally defined by the implementation: - __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the -
- specifications in annex F (IEC 60559 floating-point arithmetic).- __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate -
+
-
+ compatible complex arithmetic). +
The values of the predefined macros (except for __FILE__ and __LINE__) remain constant throughout the translation unit.
@@ -8130,7 +8481,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 in any standard header.
Forward references: the asctime function (7.23.3.1), standard headers (7.1.2). -
Footnotes
154) See ''future language directions'' (6.11.9).
155) The presumed source file name and line number can be changed by the #line directive. @@ -8141,11 +8492,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -8156,18 +8508,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 )
+
Footnotes
157) The functions that make use of the decimal-point character are the numeric conversion functions (7.20.1, 7.24.4.1) and the formatted input/output functions (7.19.6, 7.24.2). @@ -8273,14 +8628,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 include type qualifiers, unless explicitly stated otherwise.
The standard headers are -
<assert.h> <inttypes.h> <signal.h> <stdlib.h>
<complex.h> <iso646.h> <stdarg.h> <string.h>
<ctype.h> <limits.h> <stdbool.h> <tgmath.h>
<errno.h> <locale.h> <stddef.h> <time.h>
<fenv.h> <math.h> <stdint.h> <wchar.h>
- <float.h> <setjmp.h> <stdio.h> <wctype.h>
+ <float.h> <setjmp.h> <stdio.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. @@ -8310,7 +8666,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
159) A header is not necessarily a source file, nor are the < and > delimited sequences in header names necessarily valid source file names. @@ -8344,7 +8700,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 If the program removes (with #undef) any macro definition of an identifier in the first group listed above, the behavior is undefined. -
Footnotes
160) The list of reserved identifiers with external linkage includes errno, math_errhandling, setjmp, and va_end. @@ -8399,30 +8755,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #include <stdlib.h> const char *str; /* ... */ - i = atoi(str); + i = atoi(str); +
#include <stdlib.h>
#undef atoi
const char *str;
/* ... */
- i = atoi(str);
+ i = atoi(str);
+
or
#include <stdlib.h>
const char *str;
/* ... */
- i = (atoi)(str);
+ i = (atoi)(str);
+
extern int atoi(const char *);
const char *str;
/* ... */
- i = atoi(str);
+ i = atoi(str);
+
-Footnotes
161) This means that an implementation shall provide an actual function for each library function, even if it also provides a macro for that function. @@ -8434,13 +8794,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -8448,16 +8810,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
164) Thus, a signal handler cannot, in general, call standard library functions. -
The header <assert.h> defines the assert macro 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.
@@ -8468,12 +8832,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -8483,7 +8848,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 the preprocessing macros __FILE__ and __LINE__ and of the identifier __func__) on the standard error stream in an implementation-defined format.165) It then calls the abort function. -
Returns
The assert macro returns no value.
Forward references: the abort function (7.20.4.1). @@ -8493,12 +8858,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
165) The message written might be of the form: Assertion failed: expression, function abc, file xyz, line nnn. -
@@ -8511,26 +8876,31 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.167)
The macros
- imaginary+ imaginary + and
- _Imaginary_I+ _Imaginary_I + are defined if and only if the implementation supports imaginary types;168) 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.
@@ -8542,10 +8912,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
166) See ''future library directions'' (7.26.1). -
167) The imaginary unit is a number i such that i 2 = -1. +
167) The imaginary unit is a number i such that i2 = -1.
168) A specification for imaginary types is in informative annex G. @@ -8575,12 +8945,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -8599,50 +8970,52 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 compound statement. If this pragma is used in any other context, the behavior is undefined. The default state for the pragma is ''off''. -
Footnotes
169) 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
- ???????????????
+ (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v2)
+ | x + iy | = (sqrt)(x2 + y2)
+
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] @@ -8650,203 +9023,215 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 non-negative 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 @@ -8855,52 +9240,55 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
#include <complex.h>
double complex cpow(double complex x, double complex y);
float complex cpowf(float complex x, float complex y);
long double complex cpowl(long double complex x,
- long double complex y);
-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). @@ -8908,74 +9296,79 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.170) -
Returns
The cimag functions return the imaginary part value (as a real). -
Footnotes
170) For a variable z of complex type, z == creal(z) + cimag(z)*I.
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. @@ -8985,17 +9378,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.171) -
Returns
The creal functions return the real part value. @@ -9004,11 +9398,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
171) For a variable z of complex type, z == creal(z) + cimag(z)*I. -
The header <ctype.h> declares several functions useful for classifying and mapping characters.172) In all cases the argument is an int, the value of which shall be @@ -9024,7 +9418,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 characters.173) All letters and digits are printing characters.
Forward references: EOF (7.19.1), localization (7.11). -
Footnotes
172) See ''future library directions'' (7.26.2).
173) In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
@@ -9038,22 +9432,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
argument c conforms to that in the description of the function.
7.4.1.1 The isalnum function
-Synopsis
+
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 @@ -9064,18 +9460,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 none of iscntrl, isdigit, ispunct, or isspace is true.174) In the "C" locale, isalpha returns true only for the characters for which isupper or islower is true. -
Footnotes
174) 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 @@ -9084,47 +9481,51 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -9132,22 +9533,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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" @@ -9155,12 +9558,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -9170,12 +9574,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 "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 @@ -9183,27 +9588,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -9212,15 +9619,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -9228,7 +9636,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 for any given locale); otherwise, the argument is returned unchanged. -
The header <errno.h> defines several macros, all relating to the reporting of error conditions. @@ -9237,11 +9645,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 lvalue175) that has type int, the value of which is set to a positive error number by several library functions. It is unspecified whether errno is a macro or an identifier declared with external linkage. If a macro definition is suppressed @@ -9261,7 +9671,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
175) 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()). @@ -9273,7 +9683,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
177) See ''future library directions'' (7.26.3). -
The header <fenv.h> declares two types and several macros and functions to provide access to the floating-point environment. The floating-point environment refers @@ -9298,12 +9708,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -9318,7 +9730,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 7.6.2.181) Additional implementation-defined floating-point exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also @@ -9329,7 +9742,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -9338,7 +9752,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -9352,18 +9767,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- FE_DFL_ENV+ FE_DFL_ENV + represents the default floating-point environment -- the one installed at program startup -
Additional implementation-defined environments, with macro definitions beginning with FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may also be specified by the implementation. -
Footnotes
178) 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. Also it is designed to facilitate code portability among all systems. @@ -9385,12 +9799,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -9417,7 +9832,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
EXAMPLE -
#include <fenv.h>
void f(double x)
@@ -9429,13 +9843,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.185) -
Footnotes
184) 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
@@ -9454,7 +9870,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
functions is undefined.
-footnotes
+
Footnotes
186) 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- @@ -9463,16 +9879,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -9481,36 +9898,38 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.187) The order in which these floating-point exceptions are raised is unspecified, except as stated in F.7.6. 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. @@ -9520,20 +9939,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
187) 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.7.6 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 @@ -9541,24 +9961,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.188) -
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 @@ -9582,10 +10003,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 if (set_excepts & FE_INVALID) f(); if (set_excepts & FE_OVERFLOW) g(); /* ... */ - } + } + -
Footnotes
188) This mechanism allows testing several floating-point exceptions with just one function call. @@ -9595,32 +10017,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -9642,7 +10066,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 /* ... */ fesetround(save_round); /* ... */ - } + } +
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.189) -
Returns
The feholdexcept function returns zero if and only if non-stop floating-point exception handling was successfully installed. -
Footnotes
189) 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 @@ -9691,37 +10118,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -9749,9 +10178,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 if (feupdateenv(&save_env)) return /* indication of an environmental problem */; return result; - } + } + -
The header <float.h> defines several macros that expand to various limits and parameters of the standard floating-point types. @@ -9760,7 +10190,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 in 5.2.4.2.2. -
The header <inttypes.h> includes the header <stdint.h> and extends it with additional facilities provided by hosted implementations. @@ -9768,14 +10198,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.190)
Forward references: integer types <stdint.h> (7.18), formatted input/output functions (7.19.6), formatted wide character input/output functions (7.24.2). -
Footnotes
190) See ''future library directions'' (7.26.4). @@ -9794,7 +10225,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The fprintf macros for signed integers are:
PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
- PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
+ PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
+
@@ -9802,23 +10234,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -9834,10 +10269,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 wprintf(L"The largest integer value is %020" PRIxMAX "\n", i); return 0; - } + } + -
Footnotes
191) C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined before <inttypes.h> is included. @@ -9849,12 +10285,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.193) @@ -9862,25 +10299,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Returns
The imaxabs function returns the absolute value. -
Footnotes
193) 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 @@ -9888,20 +10326,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -9913,7 +10352,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <stddef.h> // for wchar_t
@@ -9921,13 +10360,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -9938,7 +10378,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (7.24.4.1.2). -
The header <iso646.h> defines the following eleven macros (on the left) that expand to the corresponding tokens (on the right): @@ -9954,9 +10394,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 or || or_eq |= xor ^ - xor_eq ^= + xor_eq ^= + -
The header <limits.h> defines several macros that expand to various limits and parameters of the standard integer types. @@ -9965,19 +10406,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 in 5.2.4.2.1. -
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; // ""
@@ -10002,7 +10443,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 7.17); and
LC_ALL
@@ -10010,13 +10453,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.194) Additional macro definitions, beginning
with the characters LC_ and an uppercase letter,195) may also be specified by the
implementation.
-Footnotes
194) ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
195) See ''future library directions'' (7.26.5).
@@ -10025,12 +10469,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
7.11.1 Locale control
7.11.1.1 The setlocale function
-Synopsis
+
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 @@ -10053,11 +10498,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
At program startup, the equivalent of
- setlocale(LC_ALL, "C");+ setlocale(LC_ALL, "C"); + is executed.
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 @@ -10077,7 +10523,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (7.20.8), numeric conversion functions (7.20.1), the strcoll function (7.21.4.3), the strftime function (7.23.3.5), the strxfrm function (7.21.4.5). -
Footnotes
196) The only functions in 7.4 whose behavior is not affected by the current locale are isdigit and isxdigit. @@ -10088,12 +10534,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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) @@ -10107,145 +10554,149 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 strings shall start and end in the initial shift state. The members with type char are nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not available in the current locale. The members include the following: - char *decimal_point -
- The decimal-point character used to format nonmonetary quantities.- char *thousands_sep -
+
+ character in formatted nonmonetary quantities. +
- The decimal-point used to format monetary quantities.- char *mon_thousands_sep -
+ formatted nonmonetary quantities. +
+ monetary quantities. +
+ formatted monetary quantities. +
- The string used to indicate a negative-valued formatted monetary quantity.- char *currency_symbol -
- The local currency symbol applicable to the current locale.- char frac_digits -
+ quantity. +
+ displayed in a locally formatted monetary quantity. +
+
+ succeeds the value for a negative locally formatted monetary quantity. +
+ quantity. +
+ quantity. +
+ nonnegative locally formatted monetary quantity. +
+ negative locally formatted monetary quantity. +
+ the international currency symbol from the monetary quantity. +
+ displayed in an internationally formatted monetary quantity. +
+ quantity. +
+
+ monetary quantity. +
+ quantity. +
-
+ nonnegative 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.- other The integer value is the number of digits that compose 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.- 2 If the currency symbol and sign string are adjacent, a space separates them; -
- otherwise, a space separates the sign string from the value.+
The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and int_n_sign_posn are interpreted according to the following: - 0 Parentheses surround the quantity and currency symbol. - 1 The sign string precedes the quantity and currency symbol. - 2 The sign string succeeds the quantity and currency symbol. - 3 The sign string immediately precedes the currency symbol. - 4 The sign string immediately succeeds the currency symbol. +
The implementation shall behave as if no library function calls the localeconv function. -
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 @@ -10256,19 +10707,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 + Country Positive Negative Positive Negative Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234 - Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56 + Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C +
For these four countries, the respective values for the monetary members of the structure returned by localeconv could be:
- Country1 Country2 Country3 Country4+ Country1 Country2 Country3 Country4 mon_decimal_point "," "" "," "." mon_thousands_sep "." "." "." "," @@ -10291,31 +10743,30 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 int_n_sep_by_space 2 1 2 1 int_p_sign_posn 1 1 1 1 int_n_sign_posn 4 1 4 2 +
EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members affect the formatted value.
- p_sep_by_space- - p_cs_precedes p_sign_posn 0 1 2 - -
- 0 0 (1.25$) (1.25 $) (1.25$) - 1 +1.25$ +1.25 $ + 1.25$ - 2 1.25$+ 1.25 $+ 1.25$ + - 3 1.25+$ 1.25 +$ 1.25+ $ - 4 1.25$+ 1.25 $+ 1.25$ +- - -
- 1 0 ($1.25) ($ 1.25) ($1.25) - 1 +$1.25 +$ 1.25 + $1.25 - 2 $1.25+ $ 1.25+ $1.25 + - 3 +$1.25 +$ 1.25 + $1.25 - 4 $+1.25 $+ 1.25 $ +1.25+ p_sep_by_space + p_cs_precedes p_sign_posn 0 1 2 -
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 @@ -10327,7 +10778,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -10337,17 +10789,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.200)
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 @@ -10358,7 +10813,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -10368,7 +10824,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -10376,20 +10833,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.202) 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.
@@ -10400,10 +10860,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -10414,7 +10876,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in <fenv.h>. -
Footnotes
198) 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. @@ -10476,7 +10938,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow'' floating-point exception is raised is implementation-defined. -
Footnotes
203) 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. @@ -10485,12 +10947,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -10516,18 +10979,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.205) -
Returns
The fpclassify macro returns the value of the number classification macro appropriate to the value of its argument. @@ -10537,22 +11001,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #define fpclassify(x) \ ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \ (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \ - __fpclassifyl(x)) + __fpclassifyl(x)) + -
Footnotes
205) 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 @@ -10563,84 +11029,88 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
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. Then determination is based on the type of the argument.206) -
Returns
The isnan macro returns a nonzero value if and only if its argument has a NaN value. -
Footnotes
206) 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);
+ 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.207) -
Returns
The signbit macro returns a nonzero value if and only if the sign of its argument value is negative. -
Footnotes
207) The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is unsigned, it is treated as positive. @@ -10648,18 +11118,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -10669,96 +11140,102 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -10766,184 +11243,195 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 range 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 . + 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 . + 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.208) -
Returns
- The expm1 functions return ex - 1. + The expm1 functions return ex - 1. -
Footnotes
208) 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, the results are unspecified. Otherwise, the frexp functions return the value x, such that x has a magnitude in the interval [1/2, 1) or - zero, and value equals x x 2*exp . If value is zero, both parts of the result are zero. + zero, and value equals x 2*exp . If value is zero, both parts of the result are zero.
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 @@ -10956,94 +11444,99 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
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 . + The ldexp functions return 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 range 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 range 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.209) A domain error occurs if the argument is less than -1. A range error may occur if the argument equals -1. -
Returns
The log1p functions return loge (1 + x). -
Footnotes
209) 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 range error may occur if the argument is zero. -
Returns
The log2 functions return log2 x. @@ -11053,45 +11546,48 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 FLT_RADIX-logb(x) < FLT_RADIX + A domain error or range 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>
@@ -11100,267 +11596,262 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 . + The scalbn and scalbln functions return 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 . + 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 . -
- ??? - ???????????????+ 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 range error may occur if x is zero and y is less than zero. -
Returns
- The pow functions return xy . + 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. -
- ??? - ???+ 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. -
- 2 x - (integral)- - The erf functions return erf x = e-t dt. -
- 2- - +
Returns +
+ The erf functions return
- (sqrt)pi - ??? - ??? 0- + 2 x + erf x = --- (integral) e-t2 dt . + (sqrt)(pi) 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. -
- 2 (inf) - (integral)- - The erfc functions return erfc x = 1 - erf x = e-t dt. +
Returns +
+ The erfc functions return
- 2- + 2 (inf) + erfc x = 1 - erf x = --- (integral) e-t2 dt . + (sqrt)(pi) x + -
- (sqrt)pi - ??? - ??? 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 range 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 range error may occur if x is a negative integer or zero. A range error may occur if the magnitude of x is too large or 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. + 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. + 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>
@@ -11369,37 +11860,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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>
@@ -11408,30 +11901,32 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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. @@ -11439,17 +11934,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -11457,17 +11953,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 60559.210) -
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. @@ -11477,7 +11974,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
210) ''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. Thus, the remainder is always exact. If r = 0, its sign shall be that of @@ -11485,21 +11982,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 + 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 @@ -11508,33 +12006,35 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -11542,28 +12042,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (7.20.1.3).
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.211) 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. @@ -11571,26 +12072,27 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
211) 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.212) -
Footnotes
212) 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. @@ -11598,87 +12100,92 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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+ {x - y 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.213) -
Returns
The fmax functions return the maximum numeric value of their arguments. -
Footnotes
213) 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.9.9.2.
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.214) -
Returns
The fmin functions return the minimum numeric value of their arguments. -
Footnotes
214) 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 fma functions compute (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. + The fma functions return (x y) + z, rounded as one ternary operation. @@ -11698,35 +12205,37 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 the synopses in this subclause, real-floating indicates that the argument shall be an expression of real floating type. -
Footnotes
215) 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.
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);
-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 @@ -11736,49 +12245,52 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
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 @@ -11786,32 +12298,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. -
The header <setjmp.h> defines the macro setjmp, and declares one function and one type, for bypassing the normal function call and return discipline.216)
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 @@ -11823,7 +12337,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
216) These functions are useful for dealing with unusual conditions encountered in a low-level function of a program. @@ -11831,21 +12345,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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:
Synopsis
#include <setjmp.h>
- 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 @@ -11886,7 +12402,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -11922,23 +12438,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 { int b[n]; // b may remain allocated longjmp(buf, 2); // might cause memory loss - } + } + -
Footnotes
217) 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.
218) This includes, but is not limited to, the floating-point status flags and the state of open files. -
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.
@@ -11946,13 +12464,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -11960,7 +12478,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -11973,7 +12493,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
219) See ''future library directions'' (7.26.9). The names of the signal numbers reflect the following terms
(respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
and termination.
@@ -11982,12 +12502,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
7.14.1 Specify signal handling
7.14.1.1 The signal function
-Synopsis
+
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 @@ -12021,18 +12542,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -12040,29 +12563,30 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: the abort function (7.20.4.1), the exit function (7.20.4.3), the _Exit function (7.20.4.4). -
Footnotes
220) 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. -
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 @@ -12075,7 +12599,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The type declared is
- va_list+ va_list + which is an 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 @@ -12084,7 +12609,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.221) -
Footnotes
221) 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. @@ -12100,12 +12625,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -12124,36 +12650,38 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -12163,17 +12691,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -12186,7 +12715,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -12202,17 +12731,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 va_list ap; char *array[MAXARGS]; int ptr_no = 0; - if (n_ptrs > MAXARGS) - n_ptrs = MAXARGS; - va_start(ap, n_ptrs); - while (ptr_no < n_ptrs) - array[ptr_no++] = va_arg(ap, char *); - va_end(ap); - f2(n_ptrs, array); - } + if (n_ptrs > MAXARGS) + n_ptrs = MAXARGS; + va_start(ap, n_ptrs); + while (ptr_no < n_ptrs) + 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 @@ -12244,27 +12775,32 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 array[ptr_no++] = va_arg(ap_save, char *); va_end(ap_save); f4(n_ptrs, array); - } + } + -
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 @@ -12275,24 +12811,27 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
222) See ''future library directions'' (7.26.7). -
The following types and macros are defined in the standard header <stddef.h>. 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; 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 @@ -12302,19 +12841,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -12322,7 +12864,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: localization (7.11). -
The header <stdint.h> declares sets of integer types having specified widths, and defines corresponding sets of macros.223) It also defines macros that specify limits of @@ -12348,7 +12890,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 shall provide those types described as ''required'', but need not provide any of the others (described as ''optional''). -
Footnotes
223) See ''future library directions'' (7.26.8).
224) Some of these types may denote implementation-defined extended integer types.
@@ -12397,7 +12939,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
7.18.1.3 Fastest minimum-width integer types
@@ -12419,10 +12962,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
Footnotes
225) 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.
@@ -12434,12 +12978,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
7.18.1.5 Greatest-width integer types
@@ -12447,11 +12993,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
7.18.2 Limits of specified-width integer types
@@ -12469,7 +13017,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
magnitude (absolute value) than the corresponding value given below, with the same sign,
except where stated to be exactly the given value.
-footnotes
+
Footnotes
226) C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined before <stdint.h> is included. @@ -12478,33 +13026,51 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
+ INTN_MIN exactly -(2N-1) +
+ INTN_MAX exactly 2N-1 - 1 +
+ UINTN_MAX exactly 2N - 1 +
+ INT_LEASTN_MIN -(2N-1 - 1) +
+ INT_LEASTN_MAX 2N-1 - 1 +
+ UINT_LEASTN_MAX 2N - 1 +
+ INT_FASTN_MIN -(2N-1 - 1) +
+ INT_FASTN_MAX 2N-1 - 1 +
+ UINT_FASTN_MAX 2N - 1 +
- INTPTR_MIN -(215 - 1)+ INTPTR_MIN -(215 - 1) +
- INTPTR_MAX 215 - 1+ INTPTR_MAX 215 - 1 +
+ UINTPTR_MAX 216 - 1 +
+ INTMAX_MIN -(263 - 1) +
+ INTMAX_MAX 263 - 1 +
+ UINTMAX_MAX 264 - 1 +
+ PTRDIFF_MIN -65535 + PTRDIFF_MAX +65535 +
+ SIG_ATOMIC_MIN see below + SIG_ATOMIC_MAX see below +
+ SIZE_MAX 65535 +
+ WCHAR_MIN see below + WCHAR_MAX see below +
+ WINT_MIN see below + WINT_MAX see below +
If sig_atomic_t (see 7.14) is defined as a signed integer type, the value of @@ -12581,7 +13165,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
227) C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined before <stdint.h> is included. @@ -12611,7 +13195,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
230) C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is defined before <stdint.h> is included. @@ -12629,14 +13213,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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) + -
@@ -12645,13 +13231,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The types declared are size_t (described in 7.17);
- 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 an object type other than an array type capable of recording all the information needed to specify uniquely every position within a file.
@@ -12659,47 +13247,56 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
_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;231)
- 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 maximum 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.
@@ -12731,7 +13328,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Forward references: files (7.19.3), the fseek function (7.19.9.2), streams (7.19.2), the tmpnam function (7.19.4.4), <wchar.h> (7.24). -
Footnotes
231) 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 @@ -12794,7 +13391,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -12808,7 +13405,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
232) 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. @@ -12863,9 +13460,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
At program startup, three text streams are predefined and need not be opened explicitly -
Environmental limits
The value of FOPEN_MAX shall be at least eight, including the three standard text streams. @@ -12922,7 +13517,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 fputwc function (7.24.3.3), conversion state (7.24.6), the mbrtowc function (7.24.6.3.2), the wcrtomb function (7.24.6.3.3). -
Footnotes
234) 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.
@@ -12931,75 +13526,79 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
7.19.4 Operations on files
7.19.4.1 The remove function
-Synopsis
+
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,235) in which case if the file existed previously it is still known by its original name. -
Footnotes
235) 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 (7.19.5.3).
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.236) The function is potentially capable of generating @@ -13012,7 +13611,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The tmpnam function generates a different string each time it is called.
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 @@ -13020,11 +13619,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
236) 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
@@ -13034,12 +13633,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
7.19.5 File access functions
7.19.5.1 The fclose function
-Synopsis
+
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 @@ -13047,19 +13647,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -13068,43 +13669,43 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 (7.19.5.3).
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.
The argument mode points to a string. If the string is one of the following, the file is open in the indicated mode. Otherwise, the behavior is undefined.237) - r open text file for reading - w truncate to zero length or create text file for writing - a append; open or create text file for writing at end-of-file - rb open binary file for reading - wb truncate to zero length or create binary file for writing - ab append; open or create binary file for writing at end-of-file - r+ open text file for update (reading and writing) - w+ truncate to zero length or create text file for update - a+ append; open or create text file for update, writing at end-of-file - - - +
Opening a file with read mode ('r' as the first character in the mode argument) fails if the file does not exist or cannot be read. @@ -13127,27 +13728,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 (7.19.9). -
Footnotes
237) 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 7.19.2).
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 @@ -13162,48 +13764,50 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
238) 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 is a null pointer), with the value _IONBF for mode. -
Returns
The setbuf function returns no value.
Forward references: the setvbuf function (7.19.5.6).
Synopsis
#include <stdio.h>
int setvbuf(FILE * restrict stream,
char * restrict buf,
- int mode, size_t size);
+ 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 @@ -13215,12 +13819,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. -
Footnotes
239) 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. @@ -13230,18 +13834,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The formatted input/output functions shall behave as if there is a sequence point after the actions associated with each specifier.240) -
Footnotes
240) 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 @@ -13289,25 +13894,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 precision were omitted.
The flag characters and their meanings are: - - The result of the conversion is left-justified within the field. (It is right-justified if -
- this flag is not specified.)- + 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.)242)- space If the first character of a signed conversion is not a sign, or if a signed conversion -
+ specified.)242) +
+ both appear, the space flag is ignored. +
-
+ result. For other 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 -
+
+ argument. +
+ int argument. +
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.
- ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
-+ specifier. +
+ argument. +
+ specifier applies to a pointer to an intmax_t argument. +
+ corresponding to size_t argument. +
- applies to a long double argument.- If a length modifier appears with any conversion specifier other than as specified above, + argument. +
The conversion specifiers and their meanings are: - d,i The int argument is converted to signed decimal in the style [-]dddd. The -
+
decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
letters abcdef are used for x conversion and the letters ABCDEF for X
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.
- f,F A double argument representing a floating-point number is converted to
-+ zero value with a precision of zero is no characters. +
+ respectively.243) +
+ of an f or F conversion specifier. +
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.
- a,A A double argument representing a floating-point number is converted in the
-+ of an f or F conversion specifier. +
+ of an f or F conversion specifier. +
- element of an array of character type.246) Characters from the array are- - + second a null wide character. +
written up to (but not including) the terminating null character. If the
precision is specified, no more than that many bytes are written. If the
precision is not specified or is greater than the size of the array, the array shall
@@ -13485,21 +14065,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
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.247)
- p The argument shall be a pointer to void. The value of the pointer is
-+ end of the array. In no case is a partial multibyte character written.247) +
+ manner. +
-
- conversion specification shall be %%.If a conversion specification is invalid, the behavior is undefined.248) If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined. @@ -13515,7 +14093,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -13530,11 +14108,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 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. @@ -13549,7 +14127,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -13563,7 +14142,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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");
@@ -13572,7 +14152,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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|
@@ -13581,11 +14162,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
| X Yabc Z|
| X Yabc Z W|
| abc Z W|
- | Z|
+ | Z|
+
Forward references: conversion state (7.24.6), the wcrtomb function (7.24.6.3.3). -
Footnotes
241) Note that 0 is taken as a flag, not as the beginning of a field width.
242) The results of all floating conversions of a negative zero, and of negative values that round to zero, @@ -13597,7 +14179,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
244) Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so that subsequent digits align to nibble (4-bit) boundaries. -
245) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is +
245) The precision p is sufficient to distinguish values of the source type if 16p-1 > b n where b is FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p might suffice depending on the implementation's scheme for determining the digit to the left of the decimal-point character. @@ -13614,13 +14196,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -13686,73 +14269,61 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 in the object, the behavior is undefined.
The length modifiers and their meanings are: - hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies -
- to an argument with type pointer to signed char or unsigned char.- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies -
+
+ int. +
+ conversion specifier applies to an argument with type pointer to wchar_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 -
+ long long int. +
+ integer type. +
- applies to an argument with type pointer to long double.+ unsigned integer type. +
The conversion specifiers and their meanings are: - d Matches an optionally signed decimal integer, whose format is the same as -
+
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.
- o Matches an optionally signed octal integer, whose format is the same as
-+ integer. +
+ unsigned integer. +
+ unsigned integer. +
+ unsigned integer. +
+ function. The corresponding argument shall be a pointer to floating. +
+ No null wide character is added. +
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
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.
- [ Matches a nonempty sequence of characters from a set of expected characters
-- (the scanset).252) + added automatically. +
same as the set of sequences that may be produced by the %p conversion of
the fprintf function. The corresponding argument shall be a pointer to a
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.
- n No input is consumed. The corresponding argument shall be a pointer to
-+ equal to that value; otherwise the behavior of the %p conversion is undefined. +
-
- complete conversion specification shall be %%.If a conversion specification is invalid, the behavior is undefined.253)
The conversion specifiers A, E, F, G, and X are also valid and behave the same as, @@ -13837,7 +14401,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 any conversion. Otherwise, the function returns the number of input items @@ -13849,10 +14413,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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. @@ -13862,20 +14428,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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>
/* ... */
@@ -13883,7 +14450,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
do {
count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
fscanf(stdin,"%*[^\n]");
- } while (!feof(stdin) && !ferror(stdin));
+ } while (!feof(stdin) && !ferror(stdin));
+
+If the stdin stream contains the following lines:
2 quarts of oil
@@ -13891,7 +14460,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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");
@@ -13902,7 +14472,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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: @@ -13910,7 +14481,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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. @@ -13927,10 +14499,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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.
@@ -13940,7 +14514,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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.
@@ -13950,7 +14525,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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.
@@ -13961,7 +14537,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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. @@ -13970,7 +14547,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 (7.24.6), the wcrtomb function (7.24.6.3.3). -
Footnotes
250) These white-space characters are not counted against a specified field width.
251) fscanf pushes back at most one input character onto the input stream. Therefore, some sequences @@ -13984,31 +14561,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 any conversion. Otherwise, the scanf function returns the number of input items @@ -14016,13 +14595,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -14031,7 +14611,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -14039,37 +14619,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 any conversion. Otherwise, the sscanf function returns the number of input @@ -14078,21 +14660,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.254) -
Returns
The vfprintf function returns the number of characters transmitted, or a negative value if an output or encoding error occurred. @@ -14110,34 +14693,36 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 // print out remainder of message vfprintf(stderr, format, args); va_end(args); - } + } + -
Footnotes
254) 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.254) -
Returns
The vfscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vfscanf function returns the number of input @@ -14145,40 +14730,42 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.254) -
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.254) -
Returns
The vscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vscanf function returns the number of input @@ -14186,22 +14773,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.254) If copying takes place between objects that overlap, the behavior is + va_end macro.254) 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 @@ -14210,42 +14798,44 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.254) If copying takes place between objects that overlap, the behavior is + va_end macro.254) 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.254) -
Returns
The vsscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vsscanf function returns the number of input @@ -14256,18 +14846,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14275,24 +14866,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 If a read error occurs, the error indicator for the stream is set and the fgetc function returns EOF.255) -
Footnotes
255) 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 @@ -14305,52 +14897,55 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14358,15 +14953,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -14374,18 +14970,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 getchar returns EOF.
Synopsis
#include <stdio.h>
- char *gets(char *s);
-Description
The gets function reads characters from the input stream pointed to by stdin, into the array pointed to by s, until end-of-file is encountered or a new-line character is read. Any new-line character is discarded, and a null character is written immediately after the last character read into the array. -
Returns
The gets 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 @@ -14395,59 +14992,63 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14471,7 +15072,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.256) -
Returns
The ungetc function returns the character pushed back after conversion, or EOF if the operation fails. @@ -14482,21 +15083,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
256) See ''future library directions'' (7.26.9).
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 @@ -14505,7 +15107,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -14513,14 +15115,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 unchanged.
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, @@ -14530,7 +15133,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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, @@ -14539,31 +15142,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 (7.19.9.3).
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. @@ -14583,18 +15188,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (7.19.9.4).
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 @@ -14606,18 +15212,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 on the stream, clears the end-of-file indicator for the stream, and then establishes the new parse state and position. After a successful fsetpos call, the next operation on an update stream may be either input or output. -
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 @@ -14627,81 +15234,87 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -14709,43 +15322,50 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (7.21.6.2). -
The header <stdlib.h> declares five types and several functions of general utility, and defines several macros.257)
The types declared are size_t and wchar_t (both described in 7.17),
- 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 7.17);
- 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. @@ -14755,7 +15375,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
257) See ''future library directions'' (7.26.10). @@ -14766,31 +15386,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (7.20.1.3).
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. @@ -14798,8 +15421,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14807,7 +15431,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <stdlib.h>
@@ -14816,8 +15440,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -14836,13 +15461,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
@@ -14859,7 +15485,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
the subject sequence begins with a minus sign, the sequence is interpreted as negated.258)
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.259) A
pointer to the final string is stored in the object pointed to by endptr, provided that
@@ -14874,7 +15500,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14893,7 +15519,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 stipulation that the error with respect to D should have a correct sign for the current rounding direction.260) -
Returns
The functions return the converted value, if any. If no conversion could be performed, zero is returned. If the correct value is outside the range of representable values, plus or @@ -14903,7 +15529,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 than the smallest normalized positive number in the return type; whether errno acquires the value ERANGE is implementation-defined. -
Footnotes
258) 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, @@ -14917,7 +15543,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <stdlib.h>
@@ -14936,8 +15562,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -14982,7 +15609,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -14994,31 +15621,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
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.
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 @@ -15027,7 +15656,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -15043,7 +15672,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 void srand(unsigned int seed) { next = seed; - } + } +
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.261) -
Returns
The calloc function returns either a null pointer or a pointer to the allocated space. -
Footnotes
261) 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 @@ -15095,31 +15727,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 realloc 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. -
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 @@ -15132,7 +15766,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 calloc, malloc, or realloc 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 @@ -15142,12 +15776,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <stdlib.h>
- 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 @@ -15155,35 +15790,37 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 removed is implementation-defined. An implementation-defined form of the status unsuccessful termination is returned to the host environment by means of the function call raise(SIGABRT). -
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. - 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 exit function (7.20.4.3).
Synopsis
#include <stdlib.h>
- void exit(int status);
-Description
The exit function causes normal program termination to occur. If more than one call to the exit function is executed by a program, the behavior is undefined. @@ -15203,22 +15840,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
262) 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>
- 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 or @@ -15226,7 +15864,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 host environment is determined in the same way as for the exit function (7.20.4.3). 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. @@ -15236,19 +15874,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 and the method for altering the environment list are implementation-defined.
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 @@ -15256,19 +15895,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 be found, a null pointer is returned.
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 @@ -15303,24 +15943,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 comparison function, and also between any call to the comparison function and any movement of the objects passed as arguments to that call. -
Footnotes
263) 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 @@ -15335,24 +15977,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.264) -
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 matched is unspecified. -
Footnotes
264) 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. @@ -15364,7 +16007,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -15376,38 +16019,40 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.265) -
Returns
The abs, labs, and llabs, functions return the absolute value. -
Footnotes
265) 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 @@ -15431,27 +16076,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 otherwise.266) Changing the LC_CTYPE category causes the conversion state of these functions to be indeterminate. -
Footnotes
266) 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 mbtowc function is not affected, it is equivalent to -
- 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 @@ -15467,14 +16114,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -15485,7 +16133,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -15498,12 +16146,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -15515,7 +16164,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -15531,14 +16180,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -15550,7 +16200,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -15561,19 +16211,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
267) 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 @@ -15584,15 +16235,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.267) + any.267) -
@@ -15615,26 +16266,27 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 unsigned char (and therefore every possible object representation is valid and has a different value). -
Footnotes
268) See ''future library directions'' (7.26.11).
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. @@ -15644,47 +16296,50 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -15694,11 +16349,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
269) 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. @@ -15706,31 +16361,33 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -15739,12 +16396,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 takes place between objects that overlap, the behavior is undefined. -
Returns
The strncat function returns the value of s1.
Forward references: the strlen function (7.21.6.3). -
Footnotes
270) Thus, the maximum number of characters that can end up in the array pointed to by s1 is strlen(s1)+n+1. @@ -15757,38 +16414,40 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 s2.271) -
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
271) 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 @@ -15797,47 +16456,50 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -15848,7 +16510,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -15857,129 +16519,138 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. -
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 @@ -16004,7 +16675,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 searching from the saved pointer and behaves as described above.
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. @@ -16017,61 +16688,65 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 int to a message.
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. -
The header <tgmath.h> includes the headers <math.h> and <complex.h> and defines several type-generic macros. @@ -16106,6 +16781,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
<math.h> <complex.h> type-generic
function function macro
+
acos cacos acos
asin casin asin
atan catan atan
@@ -16122,7 +16798,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -16139,7 +16816,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -16149,7 +16827,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -16161,11 +16840,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 long double ld; float complex fc; double complex dc; - long double complex ldc; + long double complex ldc; + functions invoked by use of type-generic macros are shown in the following table:
- macro use invokes
+ macro use invokes
+
exp(n) exp(n), the function
acosh(f) acoshf(f)
sin(d) sin(d), the function
@@ -16186,9 +16867,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
cimag(ld) cimagl(ld)
fabs(fc) cabsf(fc)
carg(dc) carg(dc), the function
- cproj(ldc) cprojl(ldc)
+ cproj(ldc) cprojl(ldc)
+
-Footnotes
272) Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to make available the corresponding ordinary function. @@ -16196,7 +16878,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 the behavior is undefined. -
@@ -16209,19 +16891,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The macros defined are NULL (described in 7.17); 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 7.17);
- 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 @@ -16237,7 +16923,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 + @@ -16245,22 +16932,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
274) 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 @@ -16269,22 +16957,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 the processor time used is not available or its value cannot be represented, the function returns the value (clock_t)(-1).275) -
Footnotes
275) 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. @@ -16294,12 +16983,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -16310,7 +17000,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -16325,7 +17015,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 "Thursday", "Friday", "Saturday", "-unknown-" }; struct tm time_str; - /* ... */ + /* ... */ + @@ -16341,26 +17032,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
276) 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 @@ -16377,22 +17070,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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)
{
-
static const char wday_name[7][3] = {
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};
@@ -16407,25 +17102,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
timeptr->tm_mday, timeptr->tm_hour,
timeptr->tm_min, timeptr->tm_sec,
1900 + timeptr->tm_year);
- return result;
+ return result;
}
-Returns
+
+Returns
The asctime function returns a pointer to the string.
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))-
Returns
The ctime function returns the pointer returned by the asctime function with that broken-down time as argument. @@ -16433,45 +17131,48 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
#include <time.h>
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, @@ -16489,125 +17190,102 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 of the current locale and by the values of zero or more members of the broken-down time structure pointed to by timeptr, as specified in brackets in the description. If any of the specified values is outside the normal range, the characters stored are unspecified. - %a is replaced by the locale's abbreviated weekday name. [tm_wday] - %A is replaced by the locale's full weekday name. [tm_wday] - %b is replaced by the locale's abbreviated month name. [tm_mon] - %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 7.23.1]- %C is replaced by the year divided by 100 and truncated to an integer, as a decimal -
- 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]- %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon, -
- 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]- %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997). -
- [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] - %j is replaced by the day of the year as a decimal number (001-366). [tm_yday] - %m is replaced by the month as a decimal number (01-12). [tm_mon] - %M is replaced by the minute as a decimal number (00-59). [tm_min] - %n is replaced by a new-line character. - %p is replaced by the locale's equivalent of the AM/PM designations associated with a -
- 12-hour clock. [tm_hour]- %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]- %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday -
- 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]- %V is replaced by the ISO 8601 week number (see below) as a decimal number -
- (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]- %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]- %x is replaced by the locale's appropriate date representation. [all specified in 7.23.1] - %X is replaced by the locale's appropriate time representation. [all specified in 7.23.1] - %y is replaced by the last 2 digits of the year as a decimal number (00-99). -
- [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 -
+ tm_sec] +
- time zone is determinable. [tm_isdst]- %% is replaced by %. + zone is determinable. [tm_isdst] +
Some conversion specifiers can be modified by the inclusion of an E or O modifier character to indicate an alternative format or specification. If the alternative format or specification does not exist for the current locale, the modifier is ignored. - %Ec is replaced by the locale's alternative date and time representation. - %EC is replaced by the name of the base year (period) in the locale's alternative -
- representation.- %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.- %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 spaces).- %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric + symbol for zero). +
- symbols.- %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric -
- 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.- %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.- %Ow is replaced by the weekday as a number, using the locale's alternative numeric -
- symbols.- %OW is replaced by the week number of the year, using the locale's alternative numeric -
- 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 @@ -16622,18 +17300,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
In the "C" locale, the E and O modifiers are ignored and the replacement strings for the following specifiers are: - %a the first three characters of %A. - %A one of ''Sunday'', ''Monday'', ... , ''Saturday''. - %b the first three characters of %B. - %B one of ''January'', ''February'', ... , ''December''. - %c equivalent to ''%a %b %e %T %Y''. - %p one of ''AM'' or ''PM''. - %r equivalent to ''%I:%M:%S %p''. - %x equivalent to ''%m/%d/%y''. - %X equivalent to %T. - %Z implementation-defined. +
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 @@ -16641,7 +17321,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 zero is returned and the contents of the array are indeterminate. -
@@ -16650,24 +17330,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The types declared are wchar_t and size_t (both described in 7.17);
- mbstate_t+ mbstate_t + which is an 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);278) and
- struct tm+ struct tm + which is declared as an incomplete structure type (the contents are described in 7.23.1).
The macros defined are NULL (described in 7.17); WCHAR_MIN and WCHAR_MAX (described in 7.18.3); 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.279) It is accepted (and returned) by several functions in this subclause to indicate end-of-file, that is, no more input from a @@ -16692,7 +17376,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 subclause causes copying to take place between objects that overlap, the behavior is undefined. -
Footnotes
277) See ''future library directions'' (7.26.12).
278) wchar_t and wint_t can be the same integer type.
@@ -16705,19 +17389,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The formatted wide character input/output functions shall behave as if there is a sequence
point after the actions associated with each specifier.280)
-footnotes
+
Footnotes
280) 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 @@ -16766,105 +17451,93 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 precision were omitted.
The flag wide characters and their meanings are: - - The result of the conversion is left-justified within the field. (It is right-justified if -
- this flag is not specified.)- + The result of a signed conversion always begins with a plus or minus sign. (It -
+
+ specified.)282) +
+ space and + flags both appear, the space flag is ignored. +
and G conversions, the result of converting a floating-point number always
contains a decimal-point wide character, even if no digits follow it. (Normally, a
decimal-point wide character appears in the result of these conversions only if a
digit follows it.) For g and G conversions, trailing zeros are not removed from the
- result. For other conversions, the behavior is undefined.
- 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
--
+ result. For other 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 -
+
+ argument. +
+ int argument. +
+ specifier. +
an intmax_t or uintmax_t argument; or that a following n conversion
- 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
-+ specifier applies to a pointer to an intmax_t argument. +
+ corresponding to size_t argument. +
- applies to a long double argument.+ argument. +
The conversion specifiers and their meanings are: - d,i The int argument is converted to signed decimal in the style [-]dddd. The -
+
+ value with a precision of zero is no wide characters. +
decimal notation in the style [-]ddd.ddd, where the number of digits after
the decimal-point wide character is equal to the precision specification. If the
precision is missing, it is taken as 6; if the precision is zero and the # flag is
@@ -16877,9 +17550,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
[-]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.283)
- e,E A double argument representing a floating-point number is converted in the
-+ nan, respectively.283) +
+ of an f or F conversion specifier. +
+ of an f or F conversion specifier. +
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
distinguish285) values of type double, except that trailing zeros may be
@@ -16927,14 +17596,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
- c If no l length modifier is present, the int argument is converted to a wide
-+ of an f or F conversion specifier. +
+ wchar_t and written. +
- converted to a sequence of printing wide characters, in an implementation-- + shall contain a null wide character. +
- defined manner.- n The argument shall be a pointer to signed integer into which is written the -
+ defined manner. +
-
- conversion specification shall be %%.If a conversion specification is invalid, the behavior is undefined.286) If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined. @@ -16977,7 +17640,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -16992,13 +17655,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -17014,12 +17677,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 (7.24.6.1.1), the mbrtowc function (7.24.6.3.2). -
Footnotes
281) Note that 0 is taken as a flag, not as the beginning of a field width.
282) The results of all floating conversions of a negative zero, and of negative values that round to zero, @@ -17031,7 +17695,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
284) Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide character so that subsequent digits align to nibble (4-bit) boundaries. -
285) The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is +
285) The precision p is sufficient to distinguish values of the source type if 16p-1 > b n where b is FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p might suffice depending on the implementation's scheme for determining the digit to the left of the decimal-point wide character. @@ -17044,14 +17708,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -17118,73 +17783,61 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 represented in the object, the behavior is undefined.
The length modifiers and their meanings are: - hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies -
- to an argument with type pointer to signed char or unsigned char.- h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies -
+
+ int. +
+ conversion specifier applies to an argument with type pointer to wchar_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 -
+ long long int. +
+ integer type. +
- applies to an argument with type pointer to long double.+ unsigned integer type. +
The conversion specifiers and their meanings are: - d Matches an optionally signed decimal integer, whose format is the same as -
+
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.
- o Matches an optionally signed octal integer, whose format is the same as
-+ integer. +
+ unsigned integer. +
+ unsigned integer. +
+ unsigned integer. +
+ function. The corresponding argument shall be a pointer to floating. +
If no l length modifier is present, characters from the input field are
converted as if by repeated calls to the wcrtomb function, with the
conversion state described by an mbstate_t object initialized to zero
@@ -17208,9 +17860,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
- [ Matches a nonempty sequence of wide characters from a set of expected
-+ automatically. +
+ last character, the behavior is implementation-defined. +
signed integer into which is to be written the number of wide characters read
from the input stream so far by this call to the fwscanf function. Execution
of a %n directive does not increment the assignment count returned at the
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.
- % Matches a single % wide character; no conversion or assignment occurs. The
+ undefined.
+-
- complete conversion specification shall be %%.If a conversion specification is invalid, the behavior is undefined.290)
The conversion specifiers A, E, F, G, and X are also valid and behave the same as, @@ -17265,7 +17914,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 any conversion. Otherwise, the function returns the number of input items @@ -17278,10 +17927,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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. @@ -17292,10 +17943,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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. @@ -17305,7 +17958,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 wcstol, wcstoll, wcstoul, and wcstoull functions (7.24.4.1.2), the wcrtomb function (7.24.6.3.3). -
Footnotes
288) These white-space wide characters are not counted against a specified field width.
289) fwscanf pushes back at most one input wide character onto the input stream. Therefore, some @@ -17315,39 +17968,41 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 any conversion. Otherwise, the swscanf function returns the number of input @@ -17356,7 +18011,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <stdarg.h>
@@ -17364,14 +18019,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
#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.291) -
Returns
The vfwprintf function returns the number of wide characters transmitted, or a negative value if an output or encoding error occurred. @@ -17391,20 +18047,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 // print out remainder of message vfwprintf(stderr, format, args); va_end(args); - } + } + -
Footnotes
291) 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>
@@ -17412,14 +18069,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
#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.291) -
Returns
The vfwscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vfwscanf function returns the number of input @@ -17427,7 +18085,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 early matching failure.
Synopsis
#include <stdarg.h>
@@ -17435,14 +18093,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.291) -
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 @@ -17450,21 +18109,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.291) -
Returns
The vswscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vswscanf function returns the number of input @@ -17472,40 +18132,42 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.291) -
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.291) -
Returns
The vwscanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the vwscanf function returns the number of input @@ -17513,32 +18175,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 any conversion. Otherwise, the wscanf function returns the number of input @@ -17548,19 +18212,20 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -17569,20 +18234,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.292) -
Footnotes
292) 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 @@ -17592,7 +18258,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -17600,139 +18266,147 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.293) 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
293) 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 @@ -17757,7 +18431,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -17781,7 +18455,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <wchar.h>
@@ -17790,8 +18464,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -17812,14 +18487,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
@@ -17838,7 +18514,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
sign, the sequence is interpreted as negated.294) 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.295) A pointer to the
final wide string is stored in the object pointed to by endptr, provided that endptr is
@@ -17853,7 +18529,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -17874,7 +18550,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.296) -
Returns
The functions return the converted value, if any. If no conversion could be performed, zero is returned. If the correct value is outside the range of representable values, plus or @@ -17889,7 +18565,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
294) 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, @@ -17903,7 +18579,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <wchar.h>
@@ -17922,8 +18598,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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, @@ -17968,7 +18645,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -17979,30 +18656,32 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18011,28 +18690,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
297) 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. @@ -18042,50 +18722,53 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18093,11 +18776,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.298) -
Returns
The wcsncat function returns the value of s1. -
Footnotes
298) Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is wcslen(s1)+n+1. @@ -18109,33 +18792,35 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18146,32 +18831,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18180,7 +18867,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18190,21 +18877,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18213,108 +18902,115 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18345,7 +19041,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -18360,21 +19056,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. @@ -18383,37 +19081,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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>
@@ -18421,8 +19121,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18473,7 +19174,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
299) 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.
@@ -18482,35 +19183,37 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
7.24.6.1 Single-byte/wide character conversion functions
7.24.6.1.1 The btowc function
-Synopsis
+
Synopsis
#include <stdio.h>
#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 <stdio.h>
#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 @@ -18519,17 +19222,18 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Synopsis
#include <wchar.h>
- int mbsinit(const mbstate_t *ps);
-Description
If ps is not a null pointer, the mbsinit function determines whether the pointed-to mbstate_t object describes an initial conversion state. -
Returns
The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object describes an initial conversion state; otherwise, it returns zero. @@ -18548,21 +19252,23 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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). @@ -18570,19 +19276,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18592,47 +19300,46 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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).- between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte -
+
+ of bytes that complete the multibyte character. +
+ stored).300) +
Footnotes
300) 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 @@ -18641,7 +19348,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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: @@ -18665,15 +19372,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18690,7 +19398,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18703,20 +19411,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
301) 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 @@ -18734,7 +19443,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -18747,12 +19456,12 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
302) 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. -
@@ -18760,14 +19469,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
The types declared are
- wint_t+ wint_t + described in 7.24.1;
- 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.
@@ -18793,7 +19505,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
303) See ''future library directions'' (7.26.13). @@ -18819,7 +19531,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 both printing and white-space wide characters.304)
Forward references: the wctob function (7.24.6.1.2). -
Footnotes
304) 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) @@ -18827,23 +19539,25 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -18852,18 +19566,19 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace is true.305) -
Footnotes
305) 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 @@ -18872,117 +19587,126 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.306) -
Footnotes
306) 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.306) + is true.306)
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). @@ -18994,12 +19718,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 subclause (7.25.2.1).
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 @@ -19020,27 +19745,29 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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.
Forward references: the wctype function (7.25.2.2.2).
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 @@ -19054,15 +19781,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -19071,15 +19799,16 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -19095,12 +19824,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -19110,26 +19840,28 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 mapping function (7.25.3.1) 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.
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 @@ -19141,47 +19873,48 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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. -
The function names
cerf cexpm1 clog2
cerfc clog10 clgamma
- cexp2 clog1p ctgamma
+ cexp2 clog1p ctgamma
+
and the same names suffixed with f or l may be added to the declarations in the
<complex.h> header.
-Function names that begin with either is or to, and a lowercase letter may be added to the declarations in the <ctype.h> header. -
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. -
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. -
Macros that begin with LC_ and an uppercase letter may be added to the definitions in the <locale.h> header. -
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. -
The ability to undefine and perhaps then redefine the macros bool, true, and false is an obsolescent feature. -
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 @@ -19189,7 +19922,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 <stdint.h> header. -
Lowercase letters may be added to the conversion specifiers and length modifiers in fprintf and fscanf. Other characters may be used in extensions. @@ -19199,17 +19932,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The use of ungetc on a binary stream where the file position indicator is zero prior to the call is an obsolescent feature. -
Function names that begin with str and a lowercase letter may be added to the declarations in the <stdlib.h> header. -
Function names that begin with str, mem, or wcs and a lowercase letter may be added to the declarations in the <string.h> header. -
Function names that begin with wcs and a lowercase letter may be added to the declarations in the <wchar.h> header. @@ -19225,10 +19958,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
(informative)
- Language syntax summary
+ Language syntax summary
+
+NOTE The notation is described in 6.1. @@ -19241,7 +19975,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 identifier constant string-literal - punctuator + punctuator + (6.4) preprocessing-token:
header-name
@@ -19250,7 +19985,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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
+
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
+
- 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 '
+ L' 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
+
- " s-char-sequenceopt " - L" s-char-sequenceopt "+ " s-char-sequenceopt " + L" s-char-sequenceopt " + (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 "
+
primary-expression
postfix-expression [ expression ]
- postfix-expression ( argument-expression-listopt )
+ postfix-expression ( argument-expression-listopt )
postfix-expression . identifier
postfix-expression -> identifier
postfix-expression ++
postfix-expression --
( type-name ) { initializer-list }
- ( type-name ) { initializer-list , }
+ ( type-name ) { initializer-list , }
+
(6.5.2) argument-expression-list:
assignment-expression
- argument-expression-list , assignment-expression
+ argument-expression-list , assignment-expression
+
(6.5.3) unary-expression:
postfix-expression
@@ -19529,101 +20317,123 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
-- unary-expression
unary-operator cast-expression
sizeof unary-expression
- sizeof ( type-name )
+ sizeof ( 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 ;+ declaration-specifiers init-declarator-listopt ; + (6.7) declaration-specifiers:
- storage-class-specifier declaration-specifiersopt - type-specifier declaration-specifiersopt - type-qualifier declaration-specifiersopt - function-specifier declaration-specifiersopt+ storage-class-specifier declaration-specifiersopt + type-specifier declaration-specifiersopt + type-qualifier declaration-specifiersopt + function-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:
@@ -19631,7 +20441,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
extern
static
auto
- register
+ register
+
(6.7.2) type-specifier:
void
@@ -19647,136 +20458,166 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
_Complex
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-list ;+ specifier-qualifier-list struct-declarator-list ; + (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
+
(6.7.3) type-qualifier:
const
restrict
- volatile
+ volatile
+
(6.7.4) function-specifier:
- inline+ inline + (6.7.5) declarator:
- pointeropt direct-declarator+ pointeropt direct-declarator + (6.7.5) 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 )
+
(6.7.5) pointer:
- * type-qualifier-listopt - * type-qualifier-listopt pointer+ * type-qualifier-listopt + * type-qualifier-listopt pointer + (6.7.5) type-qualifier-list:
type-qualifier
- type-qualifier-list type-qualifier
+ type-qualifier-list type-qualifier
+
(6.7.5) parameter-type-list:
parameter-list
- parameter-list , ...
+ parameter-list , ...
+
(6.7.5) parameter-list:
parameter-declaration
- parameter-list , parameter-declaration
+ parameter-list , parameter-declaration
+
(6.7.5) parameter-declaration:
declaration-specifiers declarator
- declaration-specifiers abstract-declaratoropt
+ declaration-specifiers abstract-declaratoropt
+
(6.7.5) identifier-list:
identifier
- identifier-list , identifier
+ identifier-list , identifier
+
(6.7.6) type-name:
- specifier-qualifier-list abstract-declaratoropt+ specifier-qualifier-list abstract-declaratoropt + (6.7.6) abstract-declarator:
pointer
- pointeropt direct-abstract-declarator
+ pointeropt direct-abstract-declarator
+
(6.7.6) 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 )
+
(6.7.7) typedef-name:
- identifier+ identifier + (6.7.8) initializer:
assignment-expression
{ initializer-list }
- { initializer-list , }
+ { initializer-list , }
+
(6.7.8) initializer-list:
- designationopt initializer - initializer-list , designationopt initializer+ designationopt initializer + initializer-list , designationopt initializer + (6.7.8) designation:
- designator-list =+ designator-list = + (6.7.8) designator-list:
designator
- designator-list designator
+ designator-list designator
+
(6.7.8) designator:
[ constant-expression ]
- . identifier
+ . identifier
+
identifier : statement
case constant-expression : statement
- default : statement
+ default : statement
+
(6.8.2) compound-statement:
- { block-item-listopt }
+ { block-item-listopt }
+
(6.8.2) block-item-list:
block-item
- block-item-list block-item
+ block-item-list block-item
+
(6.8.2) block-item:
declaration
- statement
+ statement
+
(6.8.3) expression-statement:
- expressionopt ;+ expressionopt ; + (6.8.4) selection-statement:
if ( expression ) statement
if ( expression ) statement else statement
- switch ( expression ) statement
+ switch ( expression ) statement
+
(6.8.5) iteration-statement:
while ( expression ) statement
do statement while ( expression ) ;
- for ( expressionopt ; expressionopt ; expressionopt ) statement
- for ( declaration expressionopt ; expressionopt ) statement
+ for ( expressionopt ; expressionopt ; expressionopt ) statement
+ for ( declaration expressionopt ; expressionopt ) statement
+
(6.8.6) jump-statement:
goto identifier ;
continue ;
break ;
- return expressionopt ;
+ return expressionopt ;
+
external-declaration
- translation-unit external-declaration
+ translation-unit external-declaration
+
(6.9) external-declaration:
function-definition
- declaration
+ declaration
+
(6.9.1) function-definition:
- declaration-specifiers declarator declaration-listopt compound-statement+ declaration-specifiers declarator declaration-listopt compound-statement + (6.9.1) declaration-list:
declaration
- declaration-list declaration
+ declaration-list declaration
+
- groupopt+ groupopt + (6.10) group:
group-part
- group group-part
+ group group-part
+
(6.10) group-part:
if-section
control-line
text-line
- # non-directive
+ # non-directive
+
(6.10) if-section:
- if-group elif-groupsopt else-groupopt endif-line+ if-group elif-groupsopt else-groupopt endif-line + (6.10) if-group:
- # if constant-expression new-line groupopt - # ifdef identifier new-line groupopt - # ifndef identifier new-line groupopt+ # if constant-expression new-line groupopt + # ifdef identifier new-line groupopt + # ifndef identifier new-line groupopt + (6.10) elif-groups:
elif-group
- elif-groups elif-group
+ elif-groups elif-group
+
(6.10) elif-group:
- # elif constant-expression new-line groupopt+ # elif constant-expression new-line groupopt + (6.10) else-group:
- # else new-line groupopt+ # else new-line groupopt + (6.10) endif-line:
- # endif new-line+ # endif new-line + (6.10) control-line:
# include pp-tokens new-line
# define identifier replacement-list new-line
- # define identifier lparen identifier-listopt )
+ # define identifier lparen identifier-listopt )
replacement-list new-line
# define identifier lparen ... ) replacement-list new-line
# define identifier lparen identifier-list , ... )
replacement-list new-line
# undef identifier new-line
# line pp-tokens new-line
- # error pp-tokensopt new-line
- # pragma pp-tokensopt new-line
- # new-line
+ # error pp-tokensopt new-line
+ # pragma pp-tokensopt new-line
+ # new-line
+
(6.10) text-line:
- pp-tokensopt new-line+ pp-tokensopt new-line + (6.10) non-directive:
- pp-tokens new-line+ pp-tokens new-line + (6.10) lparen:
- a ( character not immediately preceded by white-space+ a ( character not immediately preceded by white-space + (6.10) replacement-list:
- pp-tokensopt+ pp-tokensopt + (6.10) pp-tokens:
preprocessing-token
- pp-tokens preprocessing-token
+ pp-tokens preprocessing-token
+
(6.10) new-line:
- the new-line character+ the new-line character +
(informative)
- Library summary
+ Library summary
+
-
NDEBUG
- void assert(scalar expression);
+ void assert(scalar expression);
+
-
@@ -19997,9 +20869,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
long double complex cprojl(long double complex z);
double creal(double complex z);
float crealf(float complex z);
- long double creall(long double complex z);
+ long double creall(long double complex z);
+
-
int isalnum(int c);
int isalpha(int c);
@@ -20014,13 +20887,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
int isupper(int c);
int isxdigit(int c);
int tolower(int c);
- int toupper(int c);
+ int toupper(int c);
+
-- EDOM EILSEQ ERANGE errno+ EDOM EILSEQ ERANGE errno + -
fenv_t FE_OVERFLOW FE_TOWARDZERO
@@ -20040,9 +20915,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
int fegetenv(fenv_t *envp);
int feholdexcept(fenv_t *envp);
int fesetenv(const fenv_t *envp);
- int feupdateenv(const fenv_t *envp);
+ int feupdateenv(const fenv_t *envp);
+
-
FLT_ROUNDS DBL_MIN_EXP FLT_MAX
FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
@@ -20054,9 +20930,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
FLT_DIG LDBL_MAX_EXP DBL_MIN
DBL_DIG FLT_MAX_10_EXP LDBL_MIN
LDBL_DIG DBL_MAX_10_EXP
- FLT_MIN_EXP LDBL_MAX_10_EXP
+ FLT_MIN_EXP LDBL_MAX_10_EXP
+
-
imaxdiv_t
@@ -20080,30 +20957,34 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
intmax_t wcstoimax(const wchar_t * restrict nptr,
wchar_t ** restrict endptr, int base);
uintmax_t wcstoumax(const wchar_t * restrict nptr,
- wchar_t ** restrict endptr, int base);
+ wchar_t ** restrict endptr, int base);
+
-
and bitor not_eq xor
and_eq compl or xor_eq
- bitand not or_eq
+ bitand not or_eq
+
-
CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
- CHAR_MIN USHRT_MAX LONG_MAX
+ CHAR_MIN USHRT_MAX LONG_MAX
+
-
struct lconv LC_ALL LC_CTYPE LC_NUMERIC
NULL LC_COLLATE LC_MONETARY LC_TIME
char *setlocale(int category, const char *locale);
- struct lconv *localeconv(void);
+ struct lconv *localeconv(void);
+
-
jmp_buf
int setjmp(jmp_buf env);
- void longjmp(jmp_buf env, int val);
+ void longjmp(jmp_buf env, int val);
+
-
sig_atomic_t SIG_IGN SIGILL SIGTERM
SIG_DFL SIGABRT SIGINT
SIG_ERR SIGFPE SIGSEGV
void (*signal(int sig, void (*func)(int)))(int);
- int raise(int sig);
+ int raise(int sig);
+
-
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);
+
-
bool
true
false
- __bool_true_false_are_defined
+ __bool_true_false_are_defined
+
-
ptrdiff_t size_t wchar_t NULL
- offsetof(type, member-designator)
+ offsetof(type, member-designator)
+
-
intN_t INT_LEASTN_MIN PTRDIFF_MAX
uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
@@ -20353,9 +21240,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
uintmax_t INTMAX_MIN UINTN_C(value)
INTN_MIN INTMAX_MAX INTMAX_C(value)
INTN_MAX UINTMAX_MAX UINTMAX_C(value)
- UINTN_MAX PTRDIFF_MIN
+ UINTN_MAX PTRDIFF_MIN
+
-
@@ -20432,9 +21320,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
void clearerr(FILE *stream);
int feof(FILE *stream);
int ferror(FILE *stream);
- void perror(const char *s);
+ void perror(const char *s);
+
-
@@ -20492,9 +21381,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
size_t mbstowcs(wchar_t * restrict pwcs,
const char * restrict s, size_t n);
size_t wcstombs(char * restrict s,
- const wchar_t * restrict pwcs, size_t n);
+ const wchar_t * restrict pwcs, size_t n);
+
-
size_t
@@ -20527,9 +21417,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
const char * restrict s2);
void *memset(void *s, int c, size_t n);
char *strerror(int errnum);
- size_t strlen(const char *s);
+ size_t strlen(const char *s);
+
-
acos sqrt fmod nextafter
asin fabs frexp nexttoward
@@ -20545,9 +21436,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
tanh floor logb cimag
exp fma lrint conj
log fmax lround cproj
- pow fmin nearbyint creal
+ pow fmin nearbyint creal
+
-
NULL size_t time_t
@@ -20563,9 +21455,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
size_t strftime(char * restrict s,
size_t maxsize,
const char * restrict format,
- const struct tm * restrict timeptr);
+ const struct tm * restrict timeptr);
+
-
@@ -20671,9 +21564,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
mbstate_t * restrict ps);
size_t wcsrtombs(char * restrict dst,
const wchar_t ** restrict src, size_t len,
- mbstate_t * restrict ps);
+ mbstate_t * restrict ps);
+
-
@@ -20695,13 +21589,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
@@ -20735,65 +21632,80 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 sets. Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
- 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F+ 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F + Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
- 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
+ 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC
+
Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
- 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9+ 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9 + Armenian: 0531-0556, 0561-0587 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
- 05F0-05F2+ 05F0-05F2 + Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
- 06D0-06DC, 06E5-06E8, 06EA-06ED+ 06D0-06DC, 06E5-06E8, 06EA-06ED + Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
- 09DC-09DD, 09DF-09E3, 09F0-09F1
+ 09DC-09DD, 09DF-09E3, 09F0-09F1
+
Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
- 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
+ 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74
+
Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
- 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
+ 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0
+
Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
- 0B5C-0B5D, 0B5F-0B61
+ 0B5C-0B5D, 0B5F-0B61
+
Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
- 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
+ 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD
+
Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
- 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61+ 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61 + Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
- 0CE0-0CE1
+ 0CE0-0CE1
+
Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
- 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61+ 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61 + Thai: 0E01-0E3A, 0E40-0E5B Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
- 0EC8-0ECD, 0EDC-0EDD
+ 0EC8-0ECD, 0EDC-0EDD
+
Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
- 0FB1-0FB7, 0FB9
+ 0FB1-0FB7, 0FB9
+
Georgian: 10A0-10C5, 10D0-10F6
Hiragana: 3041-3093, 309B-309C
Katakana: 30A1-30F6, 30FB-30FC
@@ -20803,24 +21715,26 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
- 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
+ 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33
+
Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
- 2133-2138, 2160-2182, 3005-3007, 3021-3029
+ 2133-2138, 2160-2182, 3005-3007, 3021-3029
+
(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
@@ -20840,7 +21754,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
#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 @@ -20848,15 +21764,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 DBL_DIG 10
#define DBL_MANT_DIG
@@ -20877,14 +21793,17 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
#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: @@ -20894,12 +21813,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 #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
+
@@ -20926,7 +21847,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 Any non-IEC 60559 extended format used for the long double type shall have more precision than IEC 60559 double and at least the range of IEC 60559 double.308) - Recommended practice +
Recommended practice
The long double type should match an IEC 60559 extended format. @@ -20935,7 +21856,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
307) ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit and quadruple 128-bit IEC 60559 formats. @@ -20949,7 +21870,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
309) Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are sufficient for closure of the arithmetic. @@ -21040,7 +21961,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 integral part is within the range of the integer type raises the ''inexact'' floating-point exception is unspecified.310) -
Footnotes
310) 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
@@ -21069,7 +21990,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
-footnotes
+
Footnotes
311) 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 @@ -21081,7 +22002,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 A contracted expression 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. A contracted expression should deliver @@ -21094,7 +22015,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 IEC 60559 dynamic rounding precision and trap enablement modes, if the implementation supports them.312) -
Footnotes
312) This specification does not require dynamic rounding precision nor trap enablement modes. @@ -21106,7 +22027,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 <fenv.h>) is ''on'', these changes to the floating-point state are treated as side effects which respect sequence points.313) -
Footnotes
313) 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.8).
@@ -21120,7 +22041,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Recommended practice
The implementation should produce a diagnostic message for each translation-time
@@ -21131,7 +22052,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
floating-point exception, other than ''inexact'';314) the implementation should then
proceed with the translation of the program.
- Footnotes
314) 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
@@ -21159,7 +22080,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
is ''on'').315)
EXAMPLE
-
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
@@ -21179,14 +22101,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
execution time.
- Footnotes
315) 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
EXAMPLE
-
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
@@ -21226,12 +22150,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
- Footnotes
316) Use of float_t and double_t variables increases the likelihood of translation-time computation.
For example, the automatic initialization
@@ -21292,47 +22219,58 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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.
+ and others that round perfectly.
+
1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
Footnotes
317) Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
other transformations that remove arithmetic operators.
@@ -21340,11 +22278,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Examples include:
footnotes
+
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -21170,7 +22090,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
float y = 0.0/0.0; // raises an exception
double z = 0.0/0.0; // raises an exception
/* ... */
- }
+ }
+
+footnotes
+
- const static double one_third = 1.0/3.0;
+ const static double one_third = 1.0/3.0;
+
F.7.5 Initialization
@@ -21198,7 +22121,6 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
time.
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
@@ -21211,7 +22133,9 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
float y = 1.1e75f; // may raise exceptions
long double z = 1.1e75; // does not raise exceptions
/* ... */
- }
+ }
+
+footnotes
+
- double_t x = 1.1e75;
+ double_t x = 1.1e75;
+
could be done at translation time, regardless of the expression evaluation method.
@@ -21270,7 +22195,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
/* ... */
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
@@ -21283,7 +22209,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
the preceding loop could be treated as
- if (0 < n) x + 1;
+ if (0 < n) x + 1;
+
F.8.2 Expression transformations
- (on IEC 60559 machines, among others).317)
+ (on IEC 60559 machines, among others).317)
+
x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
- can be zero, infinite, or NaN.
+ can be zero, infinite, or NaN.
+
x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
- are equivalent (on IEC 60559 machines, among others).
+ are equivalent (on 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).318)
+ default rounding direction).318)
+
x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
- x is a NaN or infinite.
+ x is a NaN or infinite.
+
0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
- x is a NaN, infinite, or -0.
+ x is a NaN, 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.
+ 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
+ implementation can replace x - 0 by x, even if x
+
- might be zero.
+ 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).
+ (unless rounding is downward).
+
-footnotes
+
- 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.
@@ -21370,21 +22311,24 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -21392,13 +22336,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
if (isless(a,b))
f();
else
- g();
+ g();
+
but is equivalent to
if (!(a < b))
g();
else
- f();
+ f();
+
Footnotes
319) 0 - 0 yields -0 instead of +0 just when the rounding direction is downward. -
This subclause contains specifications of <math.h> facilities that are particularly suited for IEC 60559 implementations. @@ -21465,13 +22411,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
320) IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on when the floating-point exception is raised. @@ -21525,7 +22471,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
Footnotes
322) atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise the ''divide-by-zero'' floating-point exception. @@ -21647,7 +22593,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 { *exp = (value == 0) ? 0 : (int)(1 + logb(value)); return scalbn(value, -(*exp)); - } + } +
@@ -21727,7 +22674,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 return copysign( isinf(value) ? 0.0 : value - (*iptr), value); - } + } +
@@ -21853,7 +22801,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 result = rint(x); // or nearbyint instead of rint fesetround(save_round); return result; - } + } +
@@ -21913,7 +22862,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 } feupdateenv(&save_env); return result; - } + } + The round functions may, but are not required to, raise the ''inexact'' floating-point exception for non-integer numeric arguments, as this implementation does. @@ -21956,7 +22906,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 result = remainder(fabs(x), (y = fabs(y))); if (signbit(result)) result += y; return copysign(result, x); - } + } +
@@ -22006,9 +22957,10 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The body of the fmax function might be323)
{ return (isgreaterequal(x, y) ||
- isnan(y)) ? x : y; }
+ isnan(y)) ? x : y; }
+
-Footnotes
323) 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. @@ -22039,7 +22991,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
(informative)
- IEC 60559-compatible complex arithmetic
+ IEC 60559-compatible complex arithmetic
+
@@ -22092,7 +23045,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 When a value of real type is converted to an imaginary type, the result is a positive imaginary zero. -
Footnotes
324) See 6.3.1.2. @@ -22124,7 +23077,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -22133,31 +23086,39 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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:325)
#include <math.h>
#include <complex.h>
@@ -22231,14 +23191,15 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
}
}
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>
@@ -22282,20 +23243,22 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
}
}
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
325) 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 @@ -22304,29 +23267,36 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 In all cases the result and floating-point exception behavior of a + or - operator is defined by the usual mathematical formula:
- + or - u iv u + iv+ + or - u iv u + iv +
- x x(+-)u x (+-) iv (x (+-) u) (+-) iv+ x x(+-)u x (+-) iv (x (+-) u) (+-) iv +
- iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)+ iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v) +
- x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)+ x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v) + -
The macros
- imaginary+ imaginary + and
- _Imaginary_I+ _Imaginary_I + are defined, respectively, as _Imaginary and a constant expression of type const float _Imaginary with the value of the imaginary unit. The macro
- I+ I + is defined to be _Imaginary_I (not _Complex_I as stated in 7.3). Notwithstanding the provisions of 7.1.3, a program may undefine and then perhaps redefine the macro imaginary. @@ -22352,19 +23322,21 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
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 @@ -22380,7 +23352,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
Footnotes
326) 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. @@ -22601,7 +23573,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 The cpow functions raise floating-point exceptions if appropriate for the calculation of the parts of the result, and may raise spurious exceptions.327) -
Footnotes
327) This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding implementations that treat special cases more carefully. @@ -22629,7 +23601,7 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 -
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, @@ -22652,12 +23624,14 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
+
@@ -22689,7 +23663,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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'' @@ -22750,7 +23725,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 @@ -22781,11 +23757,13 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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
@@ -22883,10 +23861,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
(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. @@ -22927,10 +23906,11 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007
(informative)
- Portability issues
+ Portability issues
+
+This annex collects some information about portability that appears in this International Standard. @@ -23882,7 +24862,8 @@ WG14/N1256 Committee Draft -- Septermber 7, 2007 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 ); +