Message 328341 - Python tracker

The relevant macro seems to be "__MINGW64__". I have neither a Windows environment nor MinGW-64 for testing, but the logic should be the same as for the "_WIN64" macro, i.e.

#if defined(_WIN64) || defined(__MINGW64__)
#define MS_WIN64
#endif

And then there's probably also something to do to record the compiler version in the long CPython version string, etc. I also can't say if MinGW-64 sets the "MS_WIN32" macro. Having "MS_WIN64" without "MS_WIN32" might be unexpected for some code.