Next: System-specific Predefined Macros, Previous: Standard Predefined Macros, Up: Predefined Macros
The common predefined macros are GNU C extensions. They are available with the same meanings regardless of the machine or operating system on which you are using GNU C or GNU Fortran. Their names all start with double underscores.
__COUNTER__## operator, this provides a convenient means to
generate unique identifiers. Care must be taken to ensure that
__COUNTER__ is not expanded prior to inclusion of precompiled headers
which use it. Otherwise, the precompiled headers will not be used.
__GFORTRAN____GNUC____GNUC_MINOR____GNUC_PATCHLEVEL____GNUC__ to 3,
__GNUC_MINOR__ to 2, and __GNUC_PATCHLEVEL__ to 1. These
macros are also defined if you invoke the preprocessor directly.
__GNUC_PATCHLEVEL__ is new to GCC 3.0; it is also present in the
widely-used development snapshots leading up to 3.0 (which identify
themselves as GCC 2.96 or 2.97, depending on which snapshot you have).
If all you need to know is whether or not your program is being compiled
by GCC, or a non-GCC compiler that claims to accept the GNU C dialects,
you can simply test __GNUC__. If you need to write code
which depends on a specific version, you must be more careful. Each
time the minor version is increased, the patch level is reset to zero;
each time the major version is increased (which happens rarely), the
minor version and patch level are reset. If you wish to use the
predefined macros directly in the conditional, you will need to write it
like this:
/* Test for GCC > 3.2.0 */
#if __GNUC__ > 3 || \
(__GNUC__ == 3 && (__GNUC_MINOR__ > 2 || \
(__GNUC_MINOR__ == 2 && \
__GNUC_PATCHLEVEL__ > 0))
Another approach is to use the predefined macros to calculate a single number, then compare that against a threshold:
#define GCC_VERSION (__GNUC__ * 10000 \
+ __GNUC_MINOR__ * 100 \
+ __GNUC_PATCHLEVEL__)
...
/* Test for GCC > 3.2.0 */
#if GCC_VERSION > 30200
Many people find this form easier to understand.
__GNUG__(__GNUC__ && __cplusplus).
__STRICT_ANSI____BASE_FILE____INCLUDE_LEVEL____ELF____VERSION____OPTIMIZE____OPTIMIZE_SIZE____NO_INLINE____OPTIMIZE__ is
defined in all optimizing compilations. __OPTIMIZE_SIZE__ is
defined if the compiler is optimizing for size, not speed.
__NO_INLINE__ is defined if no functions will be inlined into
their callers (when not optimizing, or when inlining has been
specifically disabled by -fno-inline).
These macros cause certain GNU header files to provide optimized
definitions, using macros or inline functions, of system library
functions. You should not use these macros in any way unless you make
sure that programs will execute with the same effect whether or not they
are defined. If they are defined, their value is 1.
__GNUC_GNU_INLINE__inline will be
handled in GCC's traditional gnu90 mode. Object files will contain
externally visible definitions of all functions declared inline
without extern or static. They will not contain any
definitions of any functions declared extern inline.
__GNUC_STDC_INLINE__inline will be
handled according to the ISO C99 standard. Object files will contain
externally visible definitions of all functions declared extern
inline. They will not contain definitions of any functions declared
inline without extern.
If this macro is defined, GCC supports the gnu_inline function
attribute as a way to always get the gnu90 behavior. Support for
this and __GNUC_GNU_INLINE__ was added in GCC 4.1.3. If
neither macro is defined, an older version of GCC is being used:
inline functions will be compiled in gnu90 mode, and the
gnu_inline function attribute will not be recognized.
__CHAR_UNSIGNED__char is
unsigned on the target machine. It exists to cause the standard header
file limits.h to work correctly. You should not use this macro
yourself; instead, refer to the standard macros defined in limits.h.
__WCHAR_UNSIGNED____CHAR_UNSIGNED__, this macro is defined if and only if the
data type wchar_t is unsigned and the front-end is in C++ mode.
__REGISTER_PREFIX__m68k-aout environment it
expands to nothing, but in the m68k-coff environment it expands
to a single ‘%’.
__USER_LABEL_PREFIX__m68k-aout environment it expands to an ‘_’, but in the
m68k-coff environment it expands to nothing.
This macro will have the correct definition even if
-f(no-)underscores is in use, but it will not be correct if
target-specific options that adjust this prefix are used (e.g. the
OSF/rose -mno-underscores option).
__SIZE_TYPE____PTRDIFF_TYPE____WCHAR_TYPE____WINT_TYPE____INTMAX_TYPE____UINTMAX_TYPE____SIG_ATOMIC_TYPE____INT8_TYPE____INT16_TYPE____INT32_TYPE____INT64_TYPE____UINT8_TYPE____UINT16_TYPE____UINT32_TYPE____UINT64_TYPE____INT_LEAST8_TYPE____INT_LEAST16_TYPE____INT_LEAST32_TYPE____INT_LEAST64_TYPE____UINT_LEAST8_TYPE____UINT_LEAST16_TYPE____UINT_LEAST32_TYPE____UINT_LEAST64_TYPE____INT_FAST8_TYPE____INT_FAST16_TYPE____INT_FAST32_TYPE____INT_FAST64_TYPE____UINT_FAST8_TYPE____UINT_FAST16_TYPE____UINT_FAST32_TYPE____UINT_FAST64_TYPE____INTPTR_TYPE____UINTPTR_TYPE__size_t, ptrdiff_t, wchar_t, wint_t,
intmax_t, uintmax_t, sig_atomic_t, int8_t,
int16_t, int32_t, int64_t, uint8_t,
uint16_t, uint32_t, uint64_t,
int_least8_t, int_least16_t, int_least32_t,
int_least64_t, uint_least8_t, uint_least16_t,
uint_least32_t, uint_least64_t, int_fast8_t,
int_fast16_t, int_fast32_t, int_fast64_t,
uint_fast8_t, uint_fast16_t, uint_fast32_t,
uint_fast64_t, intptr_t, and uintptr_t typedefs,
respectively. They exist to make the standard header files
stddef.h, stdint.h, and wchar.h work correctly.
You should not use these macros directly; instead, include the
appropriate headers and use the typedefs. Some of these macros may
not be defined on particular systems if GCC does not provide a
stdint.h header on those systems.
__CHAR_BIT__char data type. It exists to make the standard header given
numerical limits work correctly. You should not use
this macro directly; instead, include the appropriate headers.
__SCHAR_MAX____WCHAR_MAX____SHRT_MAX____INT_MAX____LONG_MAX____LONG_LONG_MAX____WINT_MAX____SIZE_MAX____PTRDIFF_MAX____INTMAX_MAX____UINTMAX_MAX____SIG_ATOMIC_MAX____INT8_MAX____INT16_MAX____INT32_MAX____INT64_MAX____UINT8_MAX____UINT16_MAX____UINT32_MAX____UINT64_MAX____INT_LEAST8_MAX____INT_LEAST16_MAX____INT_LEAST32_MAX____INT_LEAST64_MAX____UINT_LEAST8_MAX____UINT_LEAST16_MAX____UINT_LEAST32_MAX____UINT_LEAST64_MAX____INT_FAST8_MAX____INT_FAST16_MAX____INT_FAST32_MAX____INT_FAST64_MAX____UINT_FAST8_MAX____UINT_FAST16_MAX____UINT_FAST32_MAX____UINT_FAST64_MAX____INTPTR_MAX____UINTPTR_MAX____WCHAR_MIN____WINT_MIN____SIG_ATOMIC_MIN__signed char, wchar_t,
signed short,
signed int, signed long, signed long long,
wint_t, size_t, ptrdiff_t,
intmax_t, uintmax_t, sig_atomic_t, int8_t,
int16_t, int32_t, int64_t, uint8_t,
uint16_t, uint32_t, uint64_t,
int_least8_t, int_least16_t, int_least32_t,
int_least64_t, uint_least8_t, uint_least16_t,
uint_least32_t, uint_least64_t, int_fast8_t,
int_fast16_t, int_fast32_t, int_fast64_t,
uint_fast8_t, uint_fast16_t, uint_fast32_t,
uint_fast64_t, intptr_t, and uintptr_t types and
to the minimum value of the wchar_t, wint_t, and
sig_atomic_t types respectively. They exist to make the
standard header given numerical limits work correctly. You should not
use these macros directly; instead, include the appropriate headers.
Some of these macros may not be defined on particular systems if GCC
does not provide a stdint.h header on those systems.
__INT8_C__INT16_C__INT32_C__INT64_C__UINT8_C__UINT16_C__UINT32_C__UINT64_C__INTMAX_C__UINTMAX_C__. They exist the make the
implementation of that header work correctly. You should not use
these macros directly; instead, include the appropriate headers. Some
of these macros may not be defined on particular systems if GCC does
not provide a stdint.h header on those systems.
__SIZEOF_INT____SIZEOF_LONG____SIZEOF_LONG_LONG____SIZEOF_SHORT____SIZEOF_POINTER____SIZEOF_FLOAT____SIZEOF_DOUBLE____SIZEOF_LONG_DOUBLE____SIZEOF_SIZE_T____SIZEOF_WCHAR_T____SIZEOF_WINT_T____SIZEOF_PTRDIFF_T__int,
long, long long, short, void *, float,
double, long double, size_t, wchar_t, wint_t
and ptrdiff_t.
__BYTE_ORDER____ORDER_LITTLE_ENDIAN____ORDER_BIG_ENDIAN____ORDER_PDP_ENDIAN____BYTE_ORDER__ is defined to one of the values
__ORDER_LITTLE_ENDIAN__, __ORDER_BIG_ENDIAN__, or
__ORDER_PDP_ENDIAN__ to reflect the layout of multi-byte and
multi-word quantities in memory. If __BYTE_ORDER__ is equal to
__ORDER_LITTLE_ENDIAN__ or __ORDER_BIG_ENDIAN__, then
multi-byte and multi-word quantities are laid out identically: the
byte (word) at the lowest address is the least significant or most
significant byte (word) of the quantity, respectively. If
__BYTE_ORDER__ is equal to __ORDER_PDP_ENDIAN__, then
bytes in 16-bit words are laid out in a little-endian fashion, whereas
the 16-bit subwords of a 32-bit quantity are laid out in big-endian
fashion.
You should use these macros for testing like this:
/* Test for a little-endian machine */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
__FLOAT_WORD_ORDER____FLOAT_WORD_ORDER__ is defined to one of the values
__ORDER_LITTLE_ENDIAN__ or __ORDER_BIG_ENDIAN__ to reflect
the layout of the words of multi-word floating-point quantities.
__DEPRECATED__EXCEPTIONS__GXX_RTTI__USING_SJLJ_EXCEPTIONS__setjmp and longjmp for exception
handling.
__GXX_EXPERIMENTAL_CXX0X____GXX_WEAK____NEXT_RUNTIME____LP64___LP64long int and pointer both use 64-bits and
int uses 32-bit.
__SSP____SSP_ALL____SSP_STRONG____SANITIZE_ADDRESS____TIMESTAMP__"Sun Sep 16 01:03:52 1973".
If the day of the month is less than 10, it is padded with a space on the left.
If GCC cannot determine the current date, it will emit a warning message
(once per compilation) and __TIMESTAMP__ will expand to
"??? ??? ?? ??:??:?? ????".
__GCC_HAVE_SYNC_COMPARE_AND_SWAP_1__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8__GCC_HAVE_SYNC_COMPARE_AND_SWAP_16__GCC_HAVE_DWARF2_CFI_ASM__FP_FAST_FMA__FP_FAST_FMAF__FP_FAST_FMALfma, fmaf, and fmal builtin functions, so that
the include file math.h can define the macros
FP_FAST_FMA, FP_FAST_FMAF, and FP_FAST_FMAL
for compatibility with the 1999 C standard.
__GCC_IEC_559float and
double as defined in C99 and C11 Annex F (for example, that the
standard rounding modes and exceptions are not supported, or that
optimizations are enabled that conflict with IEEE 754 semantics). If
1, it indicates that IEEE 754 arithmetic is intended to be supported;
this does not mean that all relevant language features are supported
by GCC. If 2 or more, it additionally indicates support for IEEE
754-2008 (in particular, that the binary encodings for quiet and
signaling NaNs are as specified in IEEE 754-2008).
This macro does not indicate the default state of command-line options
that control optimizations that C99 and C11 permit to be controlled by
standard pragmas, where those standards do not require a particular
default state. It does not indicate whether optimizations respect
signaling NaN semantics (the macro for that is
__SUPPORT_SNAN__). It does not indicate support for decimal
floating point or the IEEE 754 binary16 and binary128 types.
__GCC_IEC_559_COMPLEX