Index: compiler-rt/trunk/lib/asan/asan_flags.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_flags.cc
+++ compiler-rt/trunk/lib/asan/asan_flags.cc
@@ -159,6 +159,10 @@
         (ASAN_LOW_MEMORY) ? 1UL << 6 : 1UL << 8;
     f->quarantine_size_mb = kDefaultQuarantineSizeMb;
   }
+  if (!f->replace_str && common_flags()->intercept_strlen) {
+    Report("WARNING: strlen interceptor is enabled even though replace_str=0. "
+           "Use intercept_strlen=0 to disable it.");
+  }
 }
 
 }  // namespace __asan
Index: compiler-rt/trunk/lib/asan/asan_interceptors.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_interceptors.cc
+++ compiler-rt/trunk/lib/asan/asan_interceptors.cc
@@ -580,23 +580,6 @@
 }
 #endif
 
-INTERCEPTOR(SIZE_T, strlen, const char *s) {
-  void *ctx;
-  ASAN_INTERCEPTOR_ENTER(ctx, strlen);
-  if (UNLIKELY(!asan_inited)) return internal_strlen(s);
-  // strlen is called from malloc_default_purgeable_zone()
-  // in __asan::ReplaceSystemAlloc() on Mac.
-  if (asan_init_is_running) {
-    return REAL(strlen)(s);
-  }
-  ENSURE_ASAN_INITED();
-  SIZE_T length = REAL(strlen)(s);
-  if (flags()->replace_str) {
-    ASAN_READ_RANGE(ctx, s, length + 1);
-  }
-  return length;
-}
-
 INTERCEPTOR(SIZE_T, wcslen, const wchar_t *s) {
   void *ctx;
   ASAN_INTERCEPTOR_ENTER(ctx, wcslen);
@@ -763,7 +746,6 @@
   ASAN_INTERCEPT_FUNC(strcat);  // NOLINT
   ASAN_INTERCEPT_FUNC(strchr);
   ASAN_INTERCEPT_FUNC(strcpy);  // NOLINT
-  ASAN_INTERCEPT_FUNC(strlen);
   ASAN_INTERCEPT_FUNC(wcslen);
   ASAN_INTERCEPT_FUNC(strncat);
   ASAN_INTERCEPT_FUNC(strncpy);
Index: compiler-rt/trunk/lib/msan/msan_interceptors.cc
===================================================================
--- compiler-rt/trunk/lib/msan/msan_interceptors.cc
+++ compiler-rt/trunk/lib/msan/msan_interceptors.cc
@@ -43,6 +43,8 @@
 using __sanitizer::atomic_store;
 using __sanitizer::atomic_uintptr_t;
 
+DECLARE_REAL(SIZE_T, strlen, const char *s)
+
 #if SANITIZER_FREEBSD
 #define __errno_location __error
 #endif
@@ -280,15 +282,6 @@
 #define MSAN_MAYBE_INTERCEPT_MALLOC_STATS
 #endif
 
-INTERCEPTOR(SIZE_T, strlen, const char *s) {
-  if (msan_init_is_running)
-    return REAL(strlen)(s);
-  ENSURE_MSAN_INITED();
-  SIZE_T res = REAL(strlen)(s);
-  CHECK_UNPOISONED(s, res + 1);
-  return res;
-}
-
 INTERCEPTOR(SIZE_T, strnlen, const char *s, SIZE_T n) {
   ENSURE_MSAN_INITED();
   SIZE_T res = REAL(strnlen)(s, n);
@@ -1562,7 +1555,6 @@
   INTERCEPT_FUNCTION(strndup);
   MSAN_MAYBE_INTERCEPT___STRNDUP;
   INTERCEPT_FUNCTION(strncpy);  // NOLINT
-  INTERCEPT_FUNCTION(strlen);
   INTERCEPT_FUNCTION(strnlen);
   INTERCEPT_FUNCTION(gcvt);
   INTERCEPT_FUNCTION(strcat);  // NOLINT
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
@@ -11,7 +11,7 @@
 // ThreadSanitizer, MemorySanitizer, etc.
 //
 // This file should be included into the tool's interceptor file,
-// which has to define it's own macros:
+// which has to define its own macros:
 //   COMMON_INTERCEPTOR_ENTER
 //   COMMON_INTERCEPTOR_ENTER_NOIGNORE
 //   COMMON_INTERCEPTOR_READ_RANGE
@@ -200,6 +200,20 @@
 }
 #endif  // SI_NOT_WINDOWS
 
+#if SANITIZER_INTERCEPT_STRLEN
+INTERCEPTOR(SIZE_T, strlen, const char *s) {
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, strlen, s);
+  SIZE_T result = REAL(strlen)(s);
+  if (common_flags()->intercept_strlen)
+    COMMON_INTERCEPTOR_READ_RANGE(ctx, s, result + 1);
+  return result;
+}
+#define INIT_STRLEN COMMON_INTERCEPT_FUNCTION(strlen)
+#else
+#define INIT_STRLEN
+#endif
+
 #if SANITIZER_INTERCEPT_TEXTDOMAIN
 INTERCEPTOR(char*, textdomain, const char *domainname) {
   void *ctx;
@@ -5376,6 +5390,7 @@
   interceptor_metadata_map = new((void *)&metadata_mem) MetadataHashMap();
 
   INIT_TEXTDOMAIN;
+  INIT_STRLEN;
   INIT_STRCMP;
   INIT_STRNCMP;
   INIT_STRCASECMP;
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_flags.inc
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_flags.inc
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_flags.inc
@@ -182,6 +182,9 @@
 COMMON_FLAG(bool, intercept_strpbrk, true,
             "If set, uses custom wrappers for strpbrk function "
             "to find more errors.")
+COMMON_FLAG(bool, intercept_strlen, true,
+            "If set, uses custom wrappers for strlen function "
+            "to find more errors.")
 COMMON_FLAG(bool, intercept_memcmp, true,
             "If set, uses custom wrappers for memcmp function "
             "to find more errors.")
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
@@ -53,6 +53,7 @@
 # define SI_IOS 0
 #endif
 
+#define SANITIZER_INTERCEPT_STRLEN 1
 #define SANITIZER_INTERCEPT_STRCMP 1
 #define SANITIZER_INTERCEPT_STRSTR 1
 #define SANITIZER_INTERCEPT_STRCASESTR SI_NOT_WINDOWS
Index: compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
===================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors.cc
@@ -668,13 +668,6 @@
 }
 #endif
 
-TSAN_INTERCEPTOR(uptr, strlen, const char *s) {
-  SCOPED_TSAN_INTERCEPTOR(strlen, s);
-  uptr len = internal_strlen(s);
-  MemoryAccessRange(thr, pc, (uptr)s, len + 1, false);
-  return len;
-}
-
 TSAN_INTERCEPTOR(void*, memset, void *dst, int v, uptr size) {
   // On FreeBSD we get here from libthr internals on thread initialization.
   if (!COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED) {
@@ -2618,7 +2611,6 @@
   TSAN_MAYBE_INTERCEPT_PVALLOC;
   TSAN_INTERCEPT(posix_memalign);
 
-  TSAN_INTERCEPT(strlen);
   TSAN_INTERCEPT(memset);
   TSAN_INTERCEPT(memcpy);
   TSAN_INTERCEPT(memmove);