Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -4183,6 +4183,20 @@
 #define INIT_TMPNAM_R
 #endif
 
+#if SANITIZER_INTERCEPT_TTYNAME_R
+INTERCEPTOR(int, ttyname_r, int fd, char *name, SIZE_T namesize) {
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, ttyname_r, fd, name, namesize);
+  int res = REAL(ttyname_r)(fd, name, namesize);
+  if (res == 0)
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, name, REAL(strlen)(name) + 1);
+  return res;
+}
+#define INIT_TTYNAME_R COMMON_INTERCEPT_FUNCTION(ttyname_r);
+#else
+#define INIT_TTYNAME_R
+#endif
+
 #if SANITIZER_INTERCEPT_TEMPNAM
 INTERCEPTOR(char *, tempnam, char *dir, char *pfx) {
   void *ctx;
@@ -6008,6 +6022,7 @@
   INIT_PTHREAD_BARRIERATTR_GETPSHARED;
   INIT_TMPNAM;
   INIT_TMPNAM_R;
+  INIT_TTYNAME_R;
   INIT_TEMPNAM;
   INIT_PTHREAD_SETNAME_NP;
   INIT_SINCOS;
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_platform_interceptors.h
@@ -235,6 +235,7 @@
 #define SANITIZER_INTERCEPT_PTHREAD_BARRIERATTR_GETPSHARED SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_TMPNAM SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_TMPNAM_R SI_LINUX_NOT_ANDROID
+#define SANITIZER_INTERCEPT_TTYNAME_R SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_TEMPNAM SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_SINCOS SI_LINUX
 #define SANITIZER_INTERCEPT_REMQUO SI_NOT_WINDOWS
Index: compiler-rt/trunk/test/msan/Linux/forkpty.cc
===================================================================
--- compiler-rt/trunk/test/msan/Linux/forkpty.cc
+++ compiler-rt/trunk/test/msan/Linux/forkpty.cc
@@ -2,6 +2,8 @@
 
 #include <assert.h>
 #include <pty.h>
+#include <unistd.h>
+#include <cstring>
 
 #include <sanitizer/msan_interface.h>
 
@@ -13,6 +15,10 @@
   assert(__msan_test_shadow(&master, sizeof(master)) == -1);
   assert(__msan_test_shadow(&slave, sizeof(slave)) == -1);
 
+  char ttyname[255];
+  ttyname_r(master, ttyname, sizeof(ttyname));
+  assert(__msan_test_shadow(ttyname, strlen(ttyname) + 1) == -1);
+
   int master2;
   forkpty(&master2, NULL, NULL, NULL);
   assert(__msan_test_shadow(&master2, sizeof(master2)) == -1);