Put back MemoryBarrier fallback implementation on MINGW32

This almost reverts 2761e8a632c14353f286708898be8df6ebad7407,
but only if under MINGW32, so it doesn't affect MSVC.

diff --git a/src/hb-atomic-private.hh b/src/hb-atomic-private.hh
index 7047e21..9cc3bc5 100644 (file)
--- a/src/hb-atomic-private.hh
+++ b/src/hb-atomic-private.hh
@@ -47,6 +47,14 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
+#if defined(__MINGW32__) && !defined(MemoryBarrier)
+static inline void _HBMemoryBarrier (void) {
+  long dummy = 0;
+  InterlockedExchange (&dummy, 1);
+}
+# define MemoryBarrier _HBMemoryBarrier
+#endif
+
 typedef LONG hb_atomic_int_t;
 #define hb_atomic_int_add(AI, V)       InterlockedExchangeAdd (&(AI), (V))