通过以下命令可以查看gcc的内置宏定义

gcc-E-dM-</dev/null

zhengwz@zqq-api-l3>gcc-E-dM-</dev/null#define__DBL_MIN_EXP__(-1021)#define__FLT_MIN__1.17549435e-38F#define__CHAR_BIT__8#define__WCHAR_MAX__2147483647#define__DBL_DENORM_MIN__4.9406564584124654e-324#define__FLT_EVAL_METHOD__0#define__DBL_MIN_10_EXP__(-307)#define__FINITE_MATH_ONLY__0#define__SHRT_MAX__32767#define__LDBL_MAX__1.18973149535723176502e+4932L#define__UINTMAX_TYPE__longunsignedint#define__linux1#define__unix1#define__linux__1#define__SCHAR_MAX__127#define__USER_LABEL_PREFIX__#define__STDC_HOSTED__1#define__DBL_DIG__15#define__FLT_EPSILON__1.19209290e-7F#define__LDBL_MIN__3.36210314311209350626e-4932L#define__unix__1#define__DECIMAL_DIG__21#define__gnu_linux__1#define__LDBL_HAS_QUIET_NAN__1#define__GNUC__4#define__MMX__1#define__DBL_MAX__1.7976931348623157e+308#define__DBL_HAS_INFINITY__1#define__DBL_MAX_EXP__1024#define__SSE2_MATH__1#define__amd641#define__LONG_LONG_MAX__9223372036854775807LL#define__GXX_ABI_VERSION1002#define__FLT_MIN_EXP__(-125)#define__x86_641#define__DBL_MIN__2.2250738585072014e-308#define__LP64__1#define__DBL_HAS_QUIET_NAN__1#define__REGISTER_PREFIX__#define__NO_INLINE__1#define__FLT_MANT_DIG__24#define__VERSION__"4.1.220080704(RedHat4.1.2-54)"#defineunix1#define__SIZE_TYPE__longunsignedint#define__ELF__1#define__FLT_RADIX__2#define__LDBL_EPSILON__1.08420217248550443401e-19L#define__GNUC_RH_RELEASE__54#define__SSE_MATH__1#define__k81#define__LDBL_DIG__18#define__x86_64__1#define__FLT_HAS_QUIET_NAN__1#define__FLT_MAX_10_EXP__38#define__LONG_MAX__9223372036854775807L#define__FLT_HAS_INFINITY__1#definelinux1#define__LDBL_MANT_DIG__64#define__k8__1#define__WCHAR_TYPE__int#define__FLT_DIG__6#define__INT_MAX__2147483647#define__FLT_MAX_EXP__128#define__DBL_MANT_DIG__53#define__WINT_TYPE__unsignedint#define__SSE__1#define__LDBL_MIN_EXP__(-16381)#define__amd64__1#define__LDBL_MAX_EXP__16384#define__LDBL_MAX_10_EXP__4932#define__DBL_EPSILON__2.2204460492503131e-16#define_LP641#define__GNUC_PATCHLEVEL__2#define__LDBL_HAS_INFINITY__1#define__INTMAX_MAX__9223372036854775807L#define__FLT_DENORM_MIN__1.40129846e-45F#define__FLT_MAX__3.40282347e+38F#define__SSE2__1#define__FLT_MIN_10_EXP__(-37)#define__INTMAX_TYPE__longint#define__GNUC_MINOR__1#define__DBL_MAX_10_EXP__308#define__LDBL_DENORM_MIN__3.64519953188247460253e-4951L#define__STDC__1#define__PTRDIFF_TYPE__longint#define__LDBL_MIN_10_EXP__(-4931)#define__GNUC_GNU_INLINE__1