VectorComparer should check null.

Source/wtf/Vector.h

 /*
  *  Copyright (C) 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 206 matching lines @@
     };
 
     template<bool canCompareWithMemcmp, typename T>
     struct VectorComparer;
 
     template<typename T>
     struct VectorComparer<false, T>
     {
         static bool compare(const T* a, const T* b, size_t size)
         {
+            if (!a || !b) {

[tkent, 2014/06/16 04:42:26]

I recommend to write popular case at first.  e.g.

if (LIKELY(a && b))
    return std::equal(...);
return !a && !b;

[yoichio, 2014/06/16 04:58:45]

Done.

+                if (!a && !b)
+                    return true;
+                return false;
+            }
             return std::equal(a, a + size, b);
         }
     };
 
     template<typename T>
     struct VectorComparer<true, T>
     {
         static bool compare(const T* a, const T* b, size_t size)
         {
             return memcmp(a, b, sizeof(T) * size) == 0;
@@ skipping 957 matching lines @@
         }
         if (this->hasOutOfLineBuffer())
             Allocator::markNoTracing(visitor, buffer());
     }
 
 } // namespace WTF
 
 using WTF::Vector;
 
 #endif // WTF_Vector_h