Fix NULL-pointer arithmetic abuse in tests surfaced by clang

test/cctest/test-mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 35 matching lines @@
 static v8::Persistent<v8::Context> env;
 
 static void InitializeVM() {
   if (env.IsEmpty()) env = v8::Context::New();
   v8::HandleScope scope;
   env->Enter();
 }
 
 
 TEST(MarkingDeque) {
+  InitializeVM();
   int mem_size = 20 * kPointerSize;
   byte* mem = NewArray<byte>(20*kPointerSize);
   Address low = reinterpret_cast<Address>(mem);
   Address high = low + mem_size;
   MarkingDeque s;
   s.Initialize(low, high);
 
-  Address address = NULL;
+  Address original_address = reinterpret_cast<Address>(&s);
+  Address current_address = original_address;
   while (!s.IsFull()) {
-    s.PushBlack(HeapObject::FromAddress(address));
-    address += kPointerSize;
+    s.PushBlack(HeapObject::FromAddress(current_address));
+    current_address += kPointerSize;
   }
 
   while (!s.IsEmpty()) {
     Address value = s.Pop()->address();
-    address -= kPointerSize;
-    CHECK_EQ(address, value);
+    current_address -= kPointerSize;
+    CHECK_EQ(current_address, value);
   }
 
-  CHECK_EQ(NULL, address);
+  CHECK_EQ(original_address, current_address);
   DeleteArray(mem);
 }
 
 
 TEST(Promotion) {
   // This test requires compaction. If compaction is turned off, we
   // skip the entire test.
   if (FLAG_never_compact) return;
 
   // Ensure that we get a compacting collection so that objects are promoted
@@ skipping 478 matching lines @@
       if (v8::internal::Snapshot::IsEnabled()) {
         CHECK_LE(delta, 2600 * 1024);
       } else {
         CHECK_LE(delta, 3100 * 1024);
       }
     }
   }
 }
 
 #endif  // __linux__ and !USE_SIMULATOR