Index: compiler-rt/trunk/lib/asan/asan_flags.inc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_flags.inc
+++ compiler-rt/trunk/lib/asan/asan_flags.inc
@@ -46,6 +46,8 @@
           "If set, uses custom wrappers for memset/memcpy/memmove intrinsics.")
 ASAN_FLAG(bool, detect_stack_use_after_return, false,
           "Enables stack-use-after-return checking at run-time.")
+ASAN_FLAG(bool, detect_stack_use_after_scope, true,
+          "Enables stack-use-after-scope checking at run-time.")
 ASAN_FLAG(int, min_uar_stack_size_log, 16, // We can't do smaller anyway.
           "Minimum fake stack size log.")
 ASAN_FLAG(int, max_uar_stack_size_log,
Index: compiler-rt/trunk/lib/asan/asan_interface_internal.h
===================================================================
--- compiler-rt/trunk/lib/asan/asan_interface_internal.h
+++ compiler-rt/trunk/lib/asan/asan_interface_internal.h
@@ -160,6 +160,10 @@
   SANITIZER_INTERFACE_ATTRIBUTE
   extern int __asan_option_detect_stack_use_after_return;
 
+// Global flag, copy of ASAN_OPTIONS=detect_stack_use_after_scope
+  SANITIZER_INTERFACE_ATTRIBUTE
+  extern int __asan_option_detect_stack_use_after_scope;
+
   SANITIZER_INTERFACE_ATTRIBUTE
   extern uptr *__asan_test_only_reported_buggy_pointer;
 
Index: compiler-rt/trunk/lib/asan/asan_poisoning.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_poisoning.cc
+++ compiler-rt/trunk/lib/asan/asan_poisoning.cc
@@ -315,11 +315,13 @@
 }
 
 void __asan_poison_stack_memory(uptr addr, uptr size) {
+  if (!__asan_option_detect_stack_use_after_scope) return;
   VReport(1, "poisoning: %p %zx\n", (void *)addr, size);
   PoisonAlignedStackMemory(addr, size, true);
 }
 
 void __asan_unpoison_stack_memory(uptr addr, uptr size) {
+  if (!__asan_option_detect_stack_use_after_scope) return;
   VReport(1, "unpoisoning: %p %zx\n", (void *)addr, size);
   PoisonAlignedStackMemory(addr, size, false);
 }
Index: compiler-rt/trunk/lib/asan/asan_rtl.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_rtl.cc
+++ compiler-rt/trunk/lib/asan/asan_rtl.cc
@@ -33,6 +33,7 @@
 #include "ubsan/ubsan_platform.h"
 
 int __asan_option_detect_stack_use_after_return;  // Global interface symbol.
+int __asan_option_detect_stack_use_after_scope;  // Global interface symbol.
 uptr *__asan_test_only_reported_buggy_pointer;  // Used only for testing asan.
 
 namespace __asan {
@@ -434,10 +435,12 @@
 
   __sanitizer_set_report_path(common_flags()->log_path);
 
-  // Enable UAR detection, if required.
   __asan_option_detect_stack_use_after_return =
       flags()->detect_stack_use_after_return;
 
+  __asan_option_detect_stack_use_after_scope =
+      flags()->detect_stack_use_after_scope;
+
   // Re-exec ourselves if we need to set additional env or command line args.
   MaybeReexec();
 
Index: compiler-rt/trunk/lib/asan/asan_win.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_win.cc
+++ compiler-rt/trunk/lib/asan/asan_win.cc
@@ -37,6 +37,12 @@
   return __asan_option_detect_stack_use_after_return;
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE
+int __asan_should_detect_stack_use_after_scope() {
+  __asan_init();
+  return __asan_option_detect_stack_use_after_scope;
+}
+
 // -------------------- A workaround for the abscence of weak symbols ----- {{{
 // We don't have a direct equivalent of weak symbols when using MSVC, but we can
 // use the /alternatename directive to tell the linker to default a specific
Index: compiler-rt/trunk/lib/asan/asan_win_dll_thunk.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_win_dll_thunk.cc
+++ compiler-rt/trunk/lib/asan/asan_win_dll_thunk.cc
@@ -198,9 +198,11 @@
 // Don't use the INTERFACE_FUNCTION machinery for this function as we actually
 // want to call it in the __asan_init interceptor.
 WRAP_W_V(__asan_should_detect_stack_use_after_return)
+WRAP_W_V(__asan_should_detect_stack_use_after_scope)
 
 extern "C" {
   int __asan_option_detect_stack_use_after_return;
+  int __asan_option_detect_stack_use_after_scope;
 
   // Manually wrap __asan_init as we need to initialize
   // __asan_option_detect_stack_use_after_return afterwards.
@@ -214,6 +216,8 @@
     fn();
     __asan_option_detect_stack_use_after_return =
         (__asan_should_detect_stack_use_after_return() != 0);
+    __asan_option_detect_stack_use_after_scope =
+        (__asan_should_detect_stack_use_after_scope() != 0);
 
     InterceptHooks();
   }
Index: compiler-rt/trunk/lib/asan/asan_win_dynamic_runtime_thunk.cc
===================================================================
--- compiler-rt/trunk/lib/asan/asan_win_dynamic_runtime_thunk.cc
+++ compiler-rt/trunk/lib/asan/asan_win_dynamic_runtime_thunk.cc
@@ -15,6 +15,7 @@
 //
 // This includes:
 //  - forwarding the detect_stack_use_after_return runtime option
+//  - forwarding the detect_stack_use_after_scope runtime option
 //  - working around deficiencies of the MD runtime
 //  - installing a custom SEH handlerx
 //
@@ -51,6 +52,23 @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// Define a copy of __asan_option_detect_stack_use_after_scope that should be
+// used when linking an MD runtime with a set of object files on Windows.
+//
+// The ASan MD runtime dllexports '__asan_option_detect_stack_use_after_scope',
+// so normally we would just dllimport it.  Unfortunately, the dllimport
+// attribute adds __imp_ prefix to the symbol name of a variable.
+// Since in general we don't know if a given TU is going to be used
+// with a MT or MD runtime and we don't want to use ugly __imp_ names on Windows
+// just to work around this issue, let's clone the a variable that is
+// constant after initialization anyways.
+extern "C" {
+__declspec(dllimport) int __asan_should_detect_stack_use_after_scope();
+int __asan_option_detect_stack_use_after_scope =
+    __asan_should_detect_stack_use_after_scope();
+}
+
+////////////////////////////////////////////////////////////////////////////////
 // For some reason, the MD CRT doesn't call the C/C++ terminators during on DLL
 // unload or on exit.  ASan relies on LLVM global_dtors to call
 // __asan_unregister_globals on these events, which unfortunately doesn't work
Index: compiler-rt/trunk/test/asan/TestCases/use-after-scope.cc
===================================================================
--- compiler-rt/trunk/test/asan/TestCases/use-after-scope.cc
+++ compiler-rt/trunk/test/asan/TestCases/use-after-scope.cc
@@ -1,16 +1,19 @@
 // RUN: %clangxx_asan -O1 -fsanitize-address-use-after-scope %s -o %t && \
-// RUN:     not %run %t 2>&1 | FileCheck %s
+// RUN:     %env_asan_opts=detect_stack_use_after_scope=1 not %run %t 2>&1 | FileCheck %s
 
-int *p = 0;
+// RUN: %env_asan_opts=detect_stack_use_after_scope=0 %run %t
+
+volatile int *p = 0;
 
 int main() {
   {
     int x = 0;
     p = &x;
   }
-  return *p;  // BOOM
+  *p = 5;  // BOOM
   // CHECK: ERROR: AddressSanitizer: stack-use-after-scope
   // CHECK:  #0 0x{{.*}} in main {{.*}}use-after-scope.cc:[[@LINE-2]]
   // CHECK: Address 0x{{.*}} is located in stack of thread T{{.*}} at offset [[OFFSET:[^ ]+]] in frame
   // {{\[}}[[OFFSET]], {{[0-9]+}}) 'x'
+  return 0;
 }