Write to NULL will trigger a Clang compile warning and the compiler may

third_party/tcmalloc/chromium/src/base/abort.h

 // 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.
 //
 // ---
 // On some platforms abort() is implemented in a way that Chrome's crash
 // reporter treats it as a normal exit. See issue:
 // http://code.google.com/p/chromium/issues/detail?id=118665
 // So we replace abort with a
 // segmentation fault, that crash reporter can always detect.
 
 #ifndef BASE_ABORT_H_
 #define BASE_ABORT_H_
 
 #if defined(TCMALLOC_USE_SYSTEM_ABORT)
 #include <stdlib.h>
 
 namespace tcmalloc {
 inline void Abort() {
   abort();
 }
 } // namespace tcmalloc
 
 #else
 namespace tcmalloc {
 inline void Abort() {
   // Make a segmentation fault to force abort.
-  *reinterpret_cast<int*>(NULL) = 0x2001;
+  *reinterpret_cast<volatile int*>(NULL) = 0x2001;
 }
 } // namespace tcmalloc
 
 #endif
 
 #endif  // BASE_ABORT_H_