Index: lib/asan/asan_flags.h
===================================================================
--- lib/asan/asan_flags.h
+++ lib/asan/asan_flags.h
@@ -52,7 +52,6 @@
   bool print_stats;
   bool print_legend;
   bool atexit;
-  bool allow_reexec;
   bool print_full_thread_history;
   bool poison_heap;
   bool poison_partial;
Index: lib/asan/asan_flags.cc
===================================================================
--- lib/asan/asan_flags.cc
+++ lib/asan/asan_flags.cc
@@ -113,10 +113,6 @@
       "If set, prints ASan exit stats even after program terminates "
       "successfully.");
 
-  ParseFlag(str, &f->allow_reexec, "allow_reexec",
-      "Allow the tool to re-exec the program. This may interfere badly with "
-      "the debugger.");
-
   ParseFlag(str, &f->print_full_thread_history,
       "print_full_thread_history",
       "If set, prints thread creation stacks for the threads involved in the "
@@ -209,7 +205,6 @@
   f->print_stats = false;
   f->print_legend = true;
   f->atexit = false;
-  f->allow_reexec = true;
   f->print_full_thread_history = true;
   f->poison_heap = true;
   f->poison_array_cookie = true;
Index: lib/asan/asan_mac.cc
===================================================================
--- lib/asan/asan_mac.cc
+++ lib/asan/asan_mac.cc
@@ -102,7 +102,6 @@
 }
 
 void MaybeReexec() {
-  if (!flags()->allow_reexec) return;
   // Make sure the dynamic ASan runtime library is preloaded so that the
   // wrappers work. If it is not, set DYLD_INSERT_LIBRARIES and re-exec
   // ourselves.
@@ -140,8 +139,15 @@
     VReport(1, "exec()-ing the program with\n");
     VReport(1, "%s=%s\n", kDyldInsertLibraries, new_env);
     VReport(1, "to enable ASan wrappers.\n");
-    VReport(1, "Set ASAN_OPTIONS=allow_reexec=0 to disable this.\n");
     execv(program_name, *_NSGetArgv());
+
+    // We get here only if execv() failed.
+    Report("ERROR: The process is launched without DYLD_INSERT_LIBRARIES, "
+           "which is required for ASan to work. ASan tried to set the "
+           "environment variable and re-execute itself, but execv() failed, "
+           "possibly because of sandbox restrictions. Make sure to launch the "
+           "executable with:\n%s=%s\n", kDyldInsertLibraries, new_env);
+    CHECK("execv failed" && 0);
   } else {
     // DYLD_INSERT_LIBRARIES is set and contains the runtime library.
     if (old_env_len == fname_len) {
Index: lib/asan/tests/asan_noinst_test.cc
===================================================================
--- lib/asan/tests/asan_noinst_test.cc
+++ lib/asan/tests/asan_noinst_test.cc
@@ -31,15 +31,6 @@
 // in this test. The static runtime library is linked explicitly (without
 // -fsanitize=address), thus the interceptors do not work correctly on OS X.
 
-#if !defined(_WIN32)
-extern "C" {
-// Set specific ASan options for uninstrumented unittest.
-const char* __asan_default_options() {
-  return "allow_reexec=0";
-}
-}  // extern "C"
-#endif
-
 // Make sure __asan_init is called before any test case is run.
 struct AsanInitCaller {
   AsanInitCaller() { __asan_init(); }