[ASan] [MinGW] Only try to export MSVC specific C++ symbols if building with a MSVC like compiler

[timurrrr]

I'm now working on ASan for Windows anymore, Reid (rnk) should be the reviewer instead.

[mstorsjo]

This patch in itself is rather straightforward. But should we do something similar for e.g. the itanium ABI's corresponding functions? Would we in that case need to know whether libcxx will be linked statically or dynamically?

In mingw setups, not even the compiler driver knows which one it will be, only the linker knows once it sees whether e.g. libc++.dll.a or libc++.a is available.

[mstorsjo]

Bump. This one in itself is straightforward, but I'm wondering if we need to export the corresponding itanium abi symbols.

I tested asan with c++ allocated memory with this patch as is though, and that seemed to work as it should.

[rnk]

lgtm

[mstorsjo]

In D51878#1245227, @mstorsjo wrote:

but I'm wondering if we need to export the corresponding itanium abi symbols.

Actually, looking closer at it, the #else case that this hits already sets dllexport attributes, which seem to work just fine on the new/delete operators in itanium ABI mode. So then there's indeed no need for anything else than this.

compiler-rt/trunk/lib/asan/asan_new_delete.cc

 #include "interception/interception.h"
 
 #include <stddef.h>
 
 // C++ operators can't have dllexport attributes on Windows. We export them
 // anyway by passing extra -export flags to the linker, which is exactly that
 // dllexport would normally do. We need to export them in order to make the
 // VS2015 dynamic CRT (MD) work.
-#if SANITIZER_WINDOWS
+#if SANITIZER_WINDOWS && defined(_MSC_VER)
 #define CXX_OPERATOR_ATTRIBUTE
 #define COMMENT_EXPORT(sym) __pragma(comment(linker, "/export:" sym))
 #ifdef _WIN64
 COMMENT_EXPORT("??2@YAPEAX_K@Z")                     // operator new
 COMMENT_EXPORT("??2@YAPEAX_KAEBUnothrow_t@std@@@Z")  // operator new nothrow
 COMMENT_EXPORT("??3@YAXPEAX@Z")                      // operator delete
 COMMENT_EXPORT("??3@YAXPEAX_K@Z")                    // sized operator delete
 COMMENT_EXPORT("??_U@YAPEAX_K@Z")                    // operator new[]