This page describes the C99 support in mainline GCC, not in any
particular release. Information is also available on C99 support in GCC 4.7, C99 support in GCC 4.6, C99 support in GCC 4.5, C99 support in GCC 4.4,
+
+
+ This table is based on the list in the foreword to N1256
+(ISO/IEC 9899:1999 (E), consolidated with ISO/IEC 9899:1999/Cor.1:2001
+(E), ISO/IEC 9899:1999/Cor.2:2004 (E) and ISO/IEC 9899:1999/Cor.3:2007
+(E)). Where "Library Issue" is listed in conjunction with some other
+status, this means that some compiler support is needed for the
+library support, or desirable in conjunction with it. Note that the
+headers required of conforming freestanding implementations (clause 4
+paragraph 6) do not count as library issues. This page describes the C99 support in GCC 4.7. Information on C99 support in mainline GCC is also
+available. See below the table for further notes on some issues.Status of C99 features in GCC 4.7
+
+
| Feature | +Library Issue | +Done | +Broken | +Missing | +
|---|---|---|---|---|
restricted character set support via digraphs and
+ <iso646.h> (originally specified in AMD1) |
+ + | Done | + | |
wide character library support in
+ <wchar.h>and <wctype.h>
+ (originally specified in AMD1) |
+ Library Issue | +Missing | +||
| more precise aliasing rules via effective type | +Done | ++ | ||
| restricted pointers | +Done | ++ | ||
| variable-length arrays | +Done | + | + | |
| flexible array members | +Done | + | ||
static and type qualifiersin parameter array declarators |
+ Done | + | ||
complex (and imaginary) support in <complex.h> |
+ Done | + | ||
type-generic math macros in <tgmath.h> |
+ Library Issue | +Done | + | |
the long long int type and library functions |
+ Done | ++ | ||
| increased minimum translation limits | +Done | ++ | ||
| additional floating-point characteristics in <float.h> |
+ Done | ++ | ||
remove implicit int |
+ Done | ++ | ||
| reliable integer division | +Done | + | ||
universal character names (\u and \U) |
+ Done | + | ||
| extended identifiers | +Missing | +|||
hexadecimal floating-point constants and
+ %aand %A
+ printf/scanf conversion specifiers |
+ Library Issue | Done | ++ | |
| compound literals | +Done | + | + | |
| designated initializers | +Done | + | + | |
// comments |
+ Done | ++ | ||
library functions in <inttypes.h> |
+ Library Issue | ++ | ||
extended integer types in <stdint.h> |
+ + | Missing | +||
| remove implicit function declaration | +Done | ++ | ||
| preprocessor arithmetic done in intmax_t/uintmax_t |
+ Done | + | ||
| mixed declarations and code | +Done | + | ||
| new block scopes for selection and iteration statements |
+ Done | + | ||
| integer constant type rules | +Done | + | ||
| integer promotion rules | +Done | + | ||
| macros with a variable number of arguments | +Done | ++ | ||
the vscanf family of functions
+ in<stdio.h> and <wchar.h> |
+ Library Issue | +Done | + | |
additional math library functions in <math.h> |
+ Library Issue | ++ | ||
treatment of error conditions by math library functions (math_errhandling) |
+ Library Issue | +Missing | +||
| floating-point environment access in <fenv.h> |
+ Library Issue | ++ | ||
| IEC 60559 (also known as IEC 559 or IEEE arithmetic) support |
+ Broken | + | ||
trailing comma allowed in enum declaration |
+ Done | ++ | ||
%lf conversion specifierallowed in printf |
+ Library Issue | Done | + | |
| inline functions | +Done | + | + | |
the snprintf family of functions in <stdio.h> |
+ Library Issue | +Done | + | |
boolean type in <stdbool.h> |
+ + | Done | + | |
| idempotent type qualifiers | +Done | + | ||
| empty macro arguments | +Done | + | ||
| new struct type compatibility rules (tag compatibility) |
+ Done | + | ||
| additional predefined macro names | +Missing | +|||
_Pragma preprocessing operator |
+ Done | + | ||
| standard pragmas | +Missing | +|||
__func__ predefined identifier |
+ Done | ++ | ||
va_copy macro |
+ Done | + | ||
additional strftime conversion specifiers |
+ Library Issue | Done | + | |
deprecate ungetc at thebeginning of a binary file |
+ Library Issue | ++ | ||
| remove deprecation of aliased array parameters |
+ Done | ++ | ||
| conversion of array to pointer not limited to lvalues | +Done | ++ | ||
| relaxed constraints on aggregate and union initialization |
+ Done | ++ | ||
| relaxed restrictions on portable header names | +Done | ++ | ||
return without expression not permitted
+ infunction that returns a value (and vice versa) |
+ Done | ++ | ||
| Feature | +Library Issue | +Done | +Broken | +Missing | +
__STDC_IEC_559__ or implement the associated standard
+pragmas; nor do some options such as -frounding-math to
+enable the pragmas globally work in all cases (for example, required
+exceptions may not be generated) and contracting expressions (e.g.,
+using fused multiply-add) is not restricted to source-language
+expressions as required by C99.math_errhandling; see
+messages 1,
+2,
+3
+on this subject to libc-hacker. The compiler needs to mark its output
+from compilations using -fno-trapping-math
+or -fno-math-errno, possibly using
+the .gnu_attribute mechanism, to indicate that built-in
+function optimizations may have been applied that mean that not all
+calls report error status in a particular way; the static linker
+needs to put this information in executables and shared libraries and
+the C library needs to use it to set math_errhandling at
+startup to a conservatively correct value based on the information
+from the compiler. There is currently some limited GNU C Library
+support that only conforms as long as the above options are not used
+anywhere in the program.wprintf, wscanf and
+wcsftime format checking support.<stdint.h> is provided by GCC, or fixed where
+the system headers provide a nonconforming version, on some but not
+yet all systems. On systems where types in this header have been
+defined as char, GCC retains this definition although it
+is not permitted by C99.const-qualified compound literals could share storage
+with each other and with string literals, but currently don't.static in parameter array
+declarators is not used for optimization. It might make sense to use
+it in future in conjunction with work
+on prefetching.<stdint.h> and
+<inttypes.h> entries have been separated, but are a
+single entry in C99.