Porting/Macros

Some projects have been ported to Apple ppc64. In that case, they may test macros like this:

#if defined(__ppc64__)
#endif

GCC does not define __ppc64__ (lowercase). It defines __PPC64__ (uppercase). To make the above code also build on Debian ppc64le or ppc64 (big endian) change the above code to:

#if defined(__ppc64__) || defined(__PPC64__)
#endif

Details discussed on #talos-workstation:

Apple's gcc (4.0.1) in MacOS 10.5, ppc32 headers define:

__POWERPC__ and __ppc__

with -m64, the following are defined:

__POWERPC__, __ppc__, and __ppc64__

GCC compiling for the Linux kernel defines, for ppc32:

__PPC__ and __powerpc__

gcc/config/rs6000/linux.h

and for ppc64:

__PPC__, __powerpc__, __PPC64__ and __powerpc64__

gcc/config/rs6000/linux64.h

Example from Debian ppc64le package: libtbb-dev, version 2020.3-1, /usr/include/tbb/machine/gcc_arm.h:

#if __powerpc64__ || __ppc64__
    // IBM XL documents __powerpc64__ (and __PPC64__).
    // Apple documents __ppc64__ (with __ppc__ only on 32-bit).
    #define __TBB_WORDSIZE 8
#else
    #define __TBB_WORDSIZE 4
#endif

Example from GCC/libstdc++-v3 source code: libstdc++-v3/src/c++17/fast_float/fast_float.h

[...] || (defined(__ppc64__) || defined(__PPC64__) || defined(__ppc64le__) || defined(__PPC64LE__)) )

libstdc++-v3 fast_float.h

That refers to "ppc64le" variants, but those are not canonical. It's better to check endianess separately.