Don't set __GNUC__ and friends in microsoft mode, set _MSC_VER instead

[nico]

Bugzilla Link	11790
Resolution	FIXED
Resolved on	Aug 27, 2014 08:48
Version	unspecified
OS	Windows NT
Blocks	llvm/llvm-bugzilla-archive#13707
CC	@AaronBallman

Extended Description

Probably important for many projects.

Chromium for example uses this for compiler detection:

// Compiler detection.
#if defined(GNUC)
#define COMPILER_GCC 1
#elif defined(_MSC_VER)
#define COMPILER_MSVC 1
#else
#error Please add support for your compiler in build/build_config.h
#endif

...and uses that to decide whether to #include <hash_set> or <ext/hash_set.

[nico]

(chrome workaround: change build_config.h to always set COMPILER_MSVC)

[llvmbot]

For my information, can chromium be built with mingw-gcc?

[nico]

No, it can't. I haven't tried it myself, but a coworker tried once, and he says it doesn't work because chromium's string16 type assumes that short wchar_ts have the same type as shorts.

[AaronBallman]

Actually, it seems that _MSC_VER is defined. It's just that GNUC is also defined at the same time.

#if defined(_MSC_VER)
#error "MSVC defined"
#endif

#if defined(GNUC)
#error "GnuC defined"
#endif

#if defined(I_AM_NOT_DEFINED)
#error "The world is ending"
#endif

This gives two error messages: MSVC defined and GnuC defined

I think this may be a bug

[AaronBallman]

This is fixed in r152512

[tritao]

mentioned in issue llvm/llvm-bugzilla-archive#13707