Index: compiler-rt/trunk/include/sanitizer/common_interface_defs.h
===================================================================
--- compiler-rt/trunk/include/sanitizer/common_interface_defs.h
+++ compiler-rt/trunk/include/sanitizer/common_interface_defs.h
@@ -105,6 +105,12 @@
   int __sanitizer_verify_contiguous_container(const void *beg, const void *mid,
                                               const void *end);
 
+  // Similar to __sanitizer_verify_contiguous_container but returns the address
+  // of the first improperly poisoned byte otherwise. Returns null if the area
+  // is poisoned properly.
+  const void *__sanitizer_contiguous_container_find_bad_address(
+      const void *beg, const void *mid, const void *end);
+
   // Print the stack trace leading to this call. Useful for debugging user code.
   void __sanitizer_print_stack_trace();
 
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
@@ -375,10 +375,10 @@
   }
 }
 
-int __sanitizer_verify_contiguous_container(const void *beg_p,
-                                            const void *mid_p,
-                                            const void *end_p) {
-  if (!flags()->detect_container_overflow) return 1;
+const void *__sanitizer_contiguous_container_find_bad_address(
+    const void *beg_p, const void *mid_p, const void *end_p) {
+  if (!flags()->detect_container_overflow)
+    return nullptr;
   uptr beg = reinterpret_cast<uptr>(beg_p);
   uptr end = reinterpret_cast<uptr>(end_p);
   uptr mid = reinterpret_cast<uptr>(mid_p);
@@ -395,17 +395,24 @@
   uptr r3_end = end;
   for (uptr i = r1_beg; i < r1_end; i++)
     if (AddressIsPoisoned(i))
-      return 0;
+      return reinterpret_cast<const void *>(i);
   for (uptr i = r2_beg; i < mid; i++)
     if (AddressIsPoisoned(i))
-      return 0;
+      return reinterpret_cast<const void *>(i);
   for (uptr i = mid; i < r2_end; i++)
     if (!AddressIsPoisoned(i))
-      return 0;
+      return reinterpret_cast<const void *>(i);
   for (uptr i = r3_beg; i < r3_end; i++)
     if (!AddressIsPoisoned(i))
-      return 0;
-  return 1;
+      return reinterpret_cast<const void *>(i);
+  return nullptr;
+}
+
+int __sanitizer_verify_contiguous_container(const void *beg_p,
+                                            const void *mid_p,
+                                            const void *end_p) {
+  return __sanitizer_contiguous_container_find_bad_address(beg_p, mid_p,
+                                                           end_p) == nullptr;
 }
 
 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_interface_internal.h
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_interface_internal.h
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_interface_internal.h
@@ -53,6 +53,9 @@
   SANITIZER_INTERFACE_ATTRIBUTE
   int __sanitizer_verify_contiguous_container(const void *beg, const void *mid,
                                               const void *end);
-}  // extern "C"
+  SANITIZER_INTERFACE_ATTRIBUTE
+  const void *__sanitizer_contiguous_container_find_bad_address(
+      const void *beg, const void *mid, const void *end);
+  } // extern "C"
 
 #endif  // SANITIZER_INTERFACE_INTERNAL_H
Index: compiler-rt/trunk/test/asan/TestCases/contiguous_container.cc
===================================================================
--- compiler-rt/trunk/test/asan/TestCases/contiguous_container.cc
+++ compiler-rt/trunk/test/asan/TestCases/contiguous_container.cc
@@ -26,10 +26,18 @@
     for (size_t idx = size; idx < capacity; idx++)
         assert(__asan_address_is_poisoned(beg + idx));
     assert(__sanitizer_verify_contiguous_container(beg, mid, end));
-    if (mid != beg)
+    assert(NULL ==
+           __sanitizer_contiguous_container_find_bad_address(beg, mid, end));
+    if (mid != beg) {
       assert(!__sanitizer_verify_contiguous_container(beg, mid - 1, end));
-    if (mid != end)
+      assert(mid - 1 == __sanitizer_contiguous_container_find_bad_address(
+                            beg, mid - 1, end));
+    }
+    if (mid != end) {
       assert(!__sanitizer_verify_contiguous_container(beg, mid + 1, end));
+      assert(mid == __sanitizer_contiguous_container_find_bad_address(
+                        beg, mid + 1, end));
+    }
   }
 
   // Don't forget to unpoison the whole thing before destroing/reallocating.