Useful GCC Macros

You should always prefer to use more general tests than less general ones, since that way your program is more likely to work on future hardware and other operating systems. Most of these defines are specific to GCC. Check for them with #if defined(macro).

Compiler
__GNUC__	You're compiling with GCC
__APPLE_CC__	You're compiling with Apple's own GCC
Operating System
__APPLE__	You're compiling for Apple hardware
linux	You're compiling for Linux
_WIN32	You're compiling for 32-bit Windows
Hardware (General)
__LP64__	(Apple-only) You're compiling for a 64-bit machine (Longs and Pointers are 64-bit)
__BIG_ENDIAN__	You're compiling for a big-endian machine
__LITTLE_ENDIAN__	You're compiling for a little-endian machine
Hardware (Specific)
__ppc__	You're compiling for a 32-bit PowerPC
__i386__	You're compiling for a 32-bit Intel
__ppc64__	You're compiling for a 64-bit PowerPC
__x86_64__	You're compiling for a 64-bit Intel