Compiler internal symbols

Each compiler will have its own set of compiler specific symbols which may be used to write code that is only compiled by a specific toolchain, or even version of a toolchain.

The compiler specific predefined symbols for the GNU compiler (GCC) are listed below along with the equivalent/counterpart symbols for the IAR C/C++ Compiler.

Symbols

GCC	IAR	Description
__CHAR_BIT__	__CHAR_BITS__	Size of char in bits
__SCHAR_MAX__	__CHAR_MAX__	Maximum value a signed char can receive
__INT_MAX__	__SIGNED_INT_MAX__	2147483647 (32-bit target)
__INT8_MAX__	__INT8_T_MAX__	127
__INT8_TYPE__	__INT8_T_TYPE__	signed char
__INT16_MAX__	__INT16_T_MAX__	32767
__INT16_TYPE__	__INT16_T_TYPE__	signed short int
__INT32_MAX__	__INT32_T_MAX__	2147483647
__INT32_TYPE__	__INT32_T_TYPE__	signed int
__INT64_MAX__	__INT64_T_MAX__	9223372036854775807LL
__INT64_TYPE__	__INT64_T_TYPE__	signed long long int
__UINT_MAX__	__UNSIGNED_INT_MAX__	0xffffffffU (32-bit target)
__UINT8_MAX__	__UINT8_T_MAX__	0xff
__UINT8_TYPE__	__UINT8_T_TYPE__	unsigned char
__UINT16_MAX__	__UINT16_T_MAX__	0xffff
__UINT16_TYPE__	__UINT16_T_TYPE__	unsigned short int
__UINT32_MAX__	__UINT32_T_MAX__	0xffffffffU
__UINT32_TYPE__	__UINT32_T_TYPE__	unsigned int
__UINT64_MAX__	__UINT64_T_MAX__	0xffffffffffffffffU
__UINT64_TYPE__	__UINT64_T_TYPE__	unsigned long long int
__SIZEOF_SHORT__	#define __SIZEOF_SHORT__ N	Size of short in bytes
__SIZEOF_INT__	#define __SIZEOF_INT__ N	Size of int in bytes
__SIZEOF_LONG}__	#define __SIZEOF_LONG__ N	Size of long in bytes
__INTPTR_MAX__	__INTPTR_T_MAX__
__INTPTR_TYPE__	__INTPTR_T_TYPE__
__INTPTR_WIDTH__	#define __INTPTR_WIDTH__ N	Size of a int * in bits
__SIZEOF_POINTER__	__DEF_PTR_SIZE__	Size of int * in bytes
__DIFFPTR_MAX__	__INTPTR_T_MAX__
__DIFFPTR_WIDTH__	#define __DIFFPTR_WIDTH__ N	Size of ptrdiff_t * in bits
__SIZEOF_PTRDIFF_T__	__DEF_PTR_SIZE__	Size of ptrdiff_t * in bytes
__SIZE_TYPE__	__SIZE_T_TYPE__	Type of size_t
__SIZE_MAX__	__SIZE_T_MAX__	Size of size_t in bytes
__GNUC_MINOR__, __GNUC_PATCHLEVEL__	__BUILD_NUMBER__	IAR provides a single symbol which lumps all necessary data
ARM_ARCH_*__	__CORE__	Architecture variant based on target selection (*Arm only)
__VFP_FP__	__ARMVFP__	VFP usage (*Arm only)
__GNUC__	__IAR_SYSTEMS_ICC__	Can be used to detect the compiler toolchain
__arm__	__ICCARM__	Denotes "build for Arm target" (*Arm only)
__IEEE_LITTLE_ENDIAN__ __IEEE_BIG_ENDIAN__	__LITTLE_ENDIAN__	Endian setting
__VERSION__	__VER__	String representation of compiler version "MAJOR.MINOR.PATCH"