From GIMP Developer Wiki
Revision as of 20:07, 22 February 2014 by Scl
To make use of GCC specific features, use the __GNUC__ macro:
#ifdef __GNUC__ ... #endif
You can also grep the code for __GNU to find out existing samples to learn from.
To make use of LLVM/Clang specific features, use the Clang language extensions.