__MACH__          973 gc/include/gc.h #  if defined(__APPLE__) && defined(__MACH__) || defined(GC_WIN32_THREADS)
__MACH__           86 gc/include/gc_config_macros.h # if defined(__APPLE__) && defined(__MACH__) && defined(__ppc__)
__MACH__          291 gc/include/private/gcconfig.h # if defined(__MWERKS__) && defined(__powerc) && !defined(__MACH__)
__MACH__          296 gc/include/private/gcconfig.h # if defined(macosx) || (defined(__APPLE__) && defined(__MACH__))