Index: lib/msan/tests/msan_test.cc
===================================================================
--- lib/msan/tests/msan_test.cc
+++ lib/msan/tests/msan_test.cc
@@ -1952,6 +1952,16 @@
   EXPECT_POISONED(buff[2]);
 }
 
+TEST(MemorySanitizer, wcrtomb) {
+  wchar_t x = L'a';
+  char buff[10];
+  mbstate_t mbs;
+  memset(&mbs, 0, sizeof(mbs));
+  size_t res = wcrtomb(buff, x, &mbs);
+  EXPECT_EQ(res, (size_t)1);
+  EXPECT_EQ(buff[0], 'a');
+}
+
 TEST(MemorySanitizer, wmemset) {
     wchar_t x[25];
     break_optimization(x);
Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -2729,6 +2729,28 @@
 #define INIT_WCSNRTOMBS
 #endif
 
+
+#if SANITIZER_INTERCEPT_WCRTOMB
+INTERCEPTOR(SIZE_T, wcrtomb, char *dest, wchar_t src, void *ps) {
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, wcrtomb, dest, src, ps);
+  if (ps) COMMON_INTERCEPTOR_READ_RANGE(ctx, ps, mbstate_t_sz);
+  // FIXME: under ASan the call below may write to freed memory and corrupt
+  // its metadata. See
+  // https://code.google.com/p/address-sanitizer/issues/detail?id=321.
+  SIZE_T res = REAL(wcrtomb)(dest, src, ps);
+  if (res != (SIZE_T) - 1 && dest) {
+    SIZE_T write_cnt = res;
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, dest, write_cnt);
+  }
+  return res;
+}
+
+#define INIT_WCRTOMB COMMON_INTERCEPT_FUNCTION(wcrtomb);
+#else
+#define INIT_WCRTOMB
+#endif
+
 #if SANITIZER_INTERCEPT_TCGETATTR
 INTERCEPTOR(int, tcgetattr, int fd, void *termios_p) {
   void *ctx;
@@ -5160,6 +5182,7 @@
   INIT_MBSNRTOWCS;
   INIT_WCSTOMBS;
   INIT_WCSNRTOMBS;
+  INIT_WCRTOMB;
   INIT_TCGETATTR;
   INIT_REALPATH;
   INIT_CANONICALIZE_FILE_NAME;
Index: lib/sanitizer_common/sanitizer_platform_interceptors.h
===================================================================
--- lib/sanitizer_common/sanitizer_platform_interceptors.h
+++ lib/sanitizer_common/sanitizer_platform_interceptors.h
@@ -143,6 +143,8 @@
 #define SANITIZER_INTERCEPT_WCSTOMBS SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_WCSNRTOMBS \
   SI_FREEBSD || SI_MAC || SI_LINUX_NOT_ANDROID
+#define SANITIZER_INTERCEPT_WCRTOMB \
+  SI_FREEBSD || SI_MAC || SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_TCGETATTR SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_REALPATH SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_CANONICALIZE_FILE_NAME SI_LINUX_NOT_ANDROID