--- llvm/tools/clang/lib/Headers/stddef.h	2010-07-08 13:05:11.112124500 -0700
+++ llvm-hacks/tools/clang/lib/Headers/stddef.h	2010-07-09 19:35:02.310076000 -0700
@@ -23,8 +23,10 @@
  *===-----------------------------------------------------------------------===
  */
 
+#if (!defined(__STDDEF_H) || defined(__need_wint_t))
 #ifndef __STDDEF_H
 #define __STDDEF_H
+#endif
 
 typedef __typeof__(((int*)0)-((int*)0)) ptrdiff_t;
 #ifndef _SIZE_T
