Index: lib/asan/asan_malloc_win.cc
===================================================================
--- lib/asan/asan_malloc_win.cc
+++ lib/asan/asan_malloc_win.cc
@@ -12,6 +12,16 @@
 // Windows-specific malloc interception.
 //===----------------------------------------------------------------------===//
 
+#ifdef __MINGW32__
+// mingw-w64 winnt.h pulls in x86intrin.h, which can pull in mm_malloc.h
+// if __STDC_HOSTED__ is defined. mm_malloc.h includes stdlib.h and malloc.h,
+// which include conflicting declarations of these functions. Having earlier
+// declarations with or without dllimport produces warnings, but if an
+// inline function in a header referenced one of the functions, we no longer
+// can redeclare them with dllexport below.
+#undef __STDC_HOSTED__
+#endif
+
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_WINDOWS
 #define WIN32_LEAN_AND_MEAN