Tweak Memcheck sanity tests to avoid duplicate reports.

base/tools_sanity_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // This file contains intentional memory errors, some of which may lead to
 // crashes if the test is ran without special memory testing tools. We use these
 // errors to verify the sanity of the tools.
 
 #include "base/atomicops.h"
 #include "base/message_loop.h"
@@ skipping 10 matching lines @@
 // Helper for memory accesses that can potentially corrupt memory or cause a
 // crash during a native run.
 #ifdef ADDRESS_SANITIZER
 #define HARMFUL_ACCESS(action,error_regexp) EXPECT_DEATH(action,error_regexp)
 #else
 #define HARMFUL_ACCESS(action,error_regexp) \
 do { if (RunningOnValgrind()) { action; } } while (0)
 #endif
 
 void ReadUninitializedValue(char *ptr) {
-  // The || in the conditional is to prevent clang from optimizing away the
+  // Comparison with 64 is to prevent clang from optimizing away the
   // jump -- valgrind only catches jumps and conditional moves, but clang uses
   // the borrow flag if the condition is just `*ptr == '\0'`.
-  if (*ptr == '\0' || *ptr == 64) {
+  if (*ptr == 64) {
     (*ptr)++;
   } else {
     (*ptr)--;
   }
 }
 
 void ReadValueOutOfArrayBoundsLeft(char *ptr) {
   char c = ptr[-2];
   VLOG(1) << "Reading a byte out of bounds: " << c;
 }
@@ skipping 189 matching lines @@
 
 TEST(ToolsSanityTest, AtomicsAreIgnored) {
   base::subtle::Atomic32 shared = 0;
   ReleaseStoreThread thread1(&shared);
   AcquireLoadThread thread2(&shared);
   RunInParallel(&thread1, &thread2);
   EXPECT_EQ(kMagicValue, shared);
 }
 
 }  // namespace base