[libunwind] [SjLj] Don't use __declspec(thread) in MinGW mode

[mstorsjo]

Summary

GCC and Clang in MinGW mode don't support __declspec(thread), which after expanding macros ends up as __attribute__((thread)). Use the GCC specific attribute __thread instead (the next one in the chain of alternatives).

[rnk]

lgtm

[mclow.lists]

Sigh. At least we've got a macro wrapping this; we only have to pore over this once.

libunwind/trunk/src/Unwind-sjlj.c

struct _Unwind_FunctionContext {
   void                           *jbuf[];
 };
 
 #if defined(_LIBUNWIND_HAS_NO_THREADS)
 # define _LIBUNWIND_THREAD_LOCAL
 #else
 # if __STDC_VERSION__ >= 201112L
 #  define _LIBUNWIND_THREAD_LOCAL _Thread_local
-# elif defined(_WIN32)
+# elif defined(_MSC_VER)
 #  define _LIBUNWIND_THREAD_LOCAL __declspec(thread)
 # elif defined(__GNUC__) || defined(__clang__)
 #  define _LIBUNWIND_THREAD_LOCAL __thread
 # else
 #  error Unable to create thread local storage
 # endif
 #endif