To the best of my knowledge:
* `_WIN32` and `_WIN64` are defined by the compiler,
* `WIN32` and `WIN64` are defined by the user, to indicate whatever
the user chooses them to indicate. They mean 32-bit and 64-bit Windows
compilation by convention only.
See:
https://accu.org/journals/overload/24/132/wilson_2223/
Windows compilers in general, and MSVC in particular, have been defining
`_WIN32` and `_WIN64` for a long time, provably at least since Visual Studio
2015, and in practice as early as in the days of 16-bit Windows.
See:
https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-140https://learn.microsoft.com/en-us/windows/win32/winprog64/the-tools
Tests used to be inconsistent, sometimes testing `_WIN32`, sometimes
`_WIN32` and `WIN32`. This brings consistency to Windows detection.
In zlib 1.2.12 the OF macro was changed to _Z_OF breaking any
project that used zlibWrapper. To fix this the OF has been
changed to _Z_OF everywhere and _Z_OF is defined as OF in the
case it is not yet defined for zlib 1.2.11 and older.
Fixes: https://github.com/facebook/zstd/issues/3216
