Replace OFFSET_OF with offsetof as far as possible.

src/base/macros.h

 // Copyright 2014 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.
 
 #ifndef V8_BASE_MACROS_H_
 #define V8_BASE_MACROS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <cstring>
 
 #include "src/base/build_config.h"
 #include "src/base/compiler-specific.h"
 #include "src/base/logging.h"
 
 
-// The expression OFFSET_OF(type, field) computes the byte-offset
-// of the specified field relative to the containing type. This
-// corresponds to 'offsetof' (in stddef.h), except that it doesn't
-// use 0 or NULL, which causes a problem with the compiler warnings
-// we have enabled (which is also why 'offsetof' doesn't seem to work).
-// Here we simply use the aligned, non-zero value 16.
+// TODO(all) Replace all uses of this macro with C++'s offsetof. To do that, we
+// have to make sure that only standard-layout types and simple field
+// designators are used.
 #define OFFSET_OF(type, field) \
   (reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(16)->field)) - 16)
 
 
 #if V8_OS_NACL
 
 // ARRAYSIZE_UNSAFE performs essentially the same calculation as arraysize,
 // but can be used on anonymous types or types defined inside
 // functions.  It's less safe than arraysize as it accepts some
 // (although not all) pointers.  Therefore, you should use arraysize
@@ skipping 383 matching lines @@
 }
 
 template <>
 inline bool is_fundamental<uint8_t>() {
   return true;
 }
 }
 }  // namespace v8::base
 
 #endif   // V8_BASE_MACROS_H_