[d8] Do not try to verify zero-ness of failed virtual memory allocation.

src/d8.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 
 #include <algorithm>
@@ skipping 58 matching lines @@
 // array buffers storing the lengths as a SMI internally.
 #define TWO_GB (2u * 1024u * 1024u * 1024u)
 
 class ShellArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
  public:
   virtual void* Allocate(size_t length) {
 #if USE_VM
     if (RoundToPageSize(&length)) {
       void* data = VirtualMemoryAllocate(length);
 #if DEBUG
-      // In debug mode, check the memory is zero-initialized.
-      uint8_t* ptr = reinterpret_cast<uint8_t*>(data);
-      for (size_t i = 0; i < length; i++) {
-        DCHECK_EQ(0, ptr[i]);
+      if (data) {
+        // In debug mode, check the memory is zero-initialized.
+        size_t limit = length / sizeof(uint64_t);
+        uint64_t* ptr = reinterpret_cast<uint64_t*>(data);
+        for (size_t i = 0; i < limit; i++) {
+          DCHECK_EQ(0u, ptr[i]);
+        }
       }
 #endif
       return data;
     }
 #endif
     void* data = AllocateUninitialized(length);
     return data == NULL ? data : memset(data, 0, length);
   }
   virtual void* AllocateUninitialized(size_t length) {
 #if USE_VM
@@ skipping 2924 matching lines @@
 }
 
 }  // namespace v8
 
 
 #ifndef GOOGLE3
 int main(int argc, char* argv[]) {
   return v8::Shell::Main(argc, argv);
 }
 #endif