win32: replace the check for _MSC_VER by a more generic __has_include check

[jcelerier]

The check has the same effect since support for stdbool.h and __has_include were
both introduced in the same MSVC version, but at least now it also works with MinGW

[gpakosz]

According to this page https://learn.microsoft.com/en-us/cpp/overview/visual-cpp-language-conformance:

• boolean type in <stdbool.h> support landed in VS 2015
• __has_include support landed VS 2017 15.3

However this page https://devblogs.microsoft.com/cppblog/c99-library-support-in-visual-studio-2013/ says the stdbool.h header landed in VS 2013.

This page gives the corresponding values for _MSC_VER: https://learn.microsoft.com/en-us/cpp/overview/compiler-versions.

All in all, it seems that we want

#if (_MSC_VER >= 1800)
#include <stdbool.h>
#elif #defined (__has_include)
#if __has_include (<stdbool.h>)
#include <stdbool.h>
#endif
#else
#define bool int
#define false 0
#define true 1
#endif

[gpakosz]

Or more conservatively

#if (_MSC_VER >= 1900)
#include <stdbool.h>
#elif #defined (__has_include)
#if __has_include (<stdbool.h>)
#include <stdbool.h>
#endif
#else
#define bool int
#define false 0
#define true 1
#endif

If we can't confirm that VS 2013 provides a working stdbool.h header.

[gpakosz]

Hello @jcelerier 👋

Still around?

[jcelerier]

wops, completely forgot about this sorry !

[jcelerier]

#if (_MSC_VER >= 1900)
  #include <stdbool.h>
#elif #defined (__has_include)
  #if __has_include (<stdbool.h>)
    #include <stdbool.h>
  #endif
  //here a hypothetical case of a windows compiler with __has_include and without stdbool.h would fail. Though maybe none exist? I'm not enough on windows to know but I feel that current MinGW wouldn't have any issue with that
#else
  #define bool int
  #define false 0
  #define true 1
#endif

I think there's a missing branch here. I don't think it's too problematic though in practice