Why is __unix__ defined, and not __WINDOWS__ ?

[Mike Gran via cygwin]

On Sun, May 12, 2019 at 08:22:36PM +0200, Agner Fog wrote:
> I have noticed that the gcc and clang compilers have defined the
> preprocessing macro __unix__, but not __WINDOWS__, _WIN32, or _WIN64 when
> compiling a windows executable.
> 
> Why is this?

As I understand it, when using the cygwin compiler to compile for the
cygwin target, these defines are intentionally not defined, because
Cygwin is supposed to look and feel like a Posix platform, not a
windows one.

The various MinGW compilers do define these constants because the target
is native windows.

I think these days the canonical defines are (somebody correct me if
I'm wrong)

  __CYGWIN__ for Cygwin

  _WIN32 as 1 on MinGW when the compilation target is Windows 32-bit
  ARM, 64-bit ARM, x86, or x64. Otherwise, undefined.

  _WIN64 as 1 on MinGW when the compilation target is Windows 64-bit
  ARM or x64. Otherwise, undefined

I am not a maintainer.

-
Mike Gran
 

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