re PR boehm-gc/48514 ([4.6] boehm gc incorrectly compile using…

re PR boehm-gc/48514 ([4.6] boehm gc incorrectly compile using __declspec(dllexport) on i686-w64-mingw32 target)

        PR boehm-gc/48514
        * include/gc_config_macros.h (GC_DLL): Define it for mingw-targets
        only, if we are actual in boehm-gc's build and DLL_EXPORT
        is defined.

From-SVN: r184100

boehm-gc/ChangeLog

+2012-02-10  Kai Tietz  <ktietz@redhat.com>
+
+	PR boehm-gc/48514
+	* include/gc_config_macros.h (GC_DLL): Define it for mingw-targets
+	only, if we are actual in boehm-gc's build and DLL_EXPORT
+	is defined.
+	
 2011-11-21  Andreas Tobler  <andreast@fgznet.ch>
 
 	* configure: Regenerate.

boehm-gc/include/gc_config_macros.h

@@ -81,7 +81,9 @@
     typedef long ptrdiff_t;	/* ptrdiff_t is not defined */
 # endif
 
-#if defined(_DLL) && !defined(GC_NOT_DLL) && !defined(GC_DLL)
+#if ((defined(_DLL) && !defined (__MINGW32__)) \
+     || (defined (DLL_EXPORT) && defined (GC_BUILD))) \
+    && !defined(GC_DLL)
 # define GC_DLL
 #endif