[sanitizer] if WINAPI is already defined, do not redefine it

[inglorion]

Summary

lib/sanitizer_common/sanitizer_win_defs.h defineds WINAPI, which is also defined by standard Windows headers. Redefining it causes warnings during compilation. This change causes us to only define WINAPI if it is not already defined, which avoids the warnings.

[zturner]

How about #include <minwindef.h>

[inglorion]

Instead of defining WINAPI ourselves? I would be happy with that. Would you like me to make that change?

[zturner]

Yea it seems like the more correct thing to do, at least to me. Not sure if someone disagrees though.

[mpividori]

Is minwindef.h provided by MSVC?

[zturner]

In D29683#670116, @mpividori wrote:

Is minwindef.h provided by MSVC?

Yes. Technically it's considered an implementation detail of the windows api, so yous houldn't include it directly. But the value of WINAPI is also an implementation detail.

[inglorion]

Including minwindef.h makes the compiler very unhappy, complaining about a lot of undefined types and identifiers. I guess if we wanted to include something, we would have to include something much larger. I think there is a good argument to be made to just define the one macro we care about here. Ok to ship as-is?

[rnk]

looks good as is

compiler-rt/trunk/lib/sanitizer_common/sanitizer_win_defs.h

 //
 //===----------------------------------------------------------------------===//
 #ifndef SANITIZER_WIN_DEFS_H
 #define SANITIZER_WIN_DEFS_H
 
 #include "sanitizer_platform.h"
 #if SANITIZER_WINDOWS
 
+#ifndef WINAPI
 #ifdef _M_IX86
 #define WINAPI __stdcall
 #else
 #define WINAPI
 #endif
+#endif
 
 #if defined(_WIN64)
 #define WIN_SYM_PREFIX
 #else
 #define WIN_SYM_PREFIX "_"
 #endif
 
 // Intermediate macro to ensure the parameter is expanded before stringified.