Add V8_ALIGNAS() and V8_ALIGNOF() and use that in lazy-instance.h.

src/lazy-instance.h

 // 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 73 matching lines @@
 // - "Dynamic mode". In this mode, the instance is dynamically allocated and
 //   constructed (using new) by default. This mode is useful if you have to
 //   deal with some code already allocating the instance for you (e.g.
 //   OS::Mutex() which returns a new private OS-dependent subclass of Mutex).
 //   The macro LAZY_DYNAMIC_INSTANCE_INITIALIZER must be used to initialize
 //   dynamic lazy instances.
 
 #ifndef V8_LAZY_INSTANCE_H_
 #define V8_LAZY_INSTANCE_H_
 
+#include "checks.h"
 #include "once.h"
 
 namespace v8 {
 namespace internal {
 
-#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, {} }
+#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, { {} } }
 #define LAZY_DYNAMIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, 0 }
 
 // Default to static mode.
 #define LAZY_INSTANCE_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER
 
 
 template <typename T>
 struct LeakyInstanceTrait {
   static void Destroy(T* /* instance */) {}
 };
 
 
 // Traits that define how an instance is allocated and accessed.
 
-// TODO(kalmard): __alignof__ is only defined for GCC > 4.2. Fix alignment issue
-// on MIPS with other compilers.
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))
-#define LAZY_ALIGN(x) __attribute__((aligned(__alignof__(x))))
-#else
-#define LAZY_ALIGN(x)
-#endif
 
 template <typename T>
 struct StaticallyAllocatedInstanceTrait {
-  typedef char StorageType[sizeof(T)] LAZY_ALIGN(T);
+  // 16-byte alignment fallback to be on the safe side here.
+  struct V8_ALIGNAS(T, 16) StorageType {
+    char x[sizeof(T)];
+  };
+
+  STATIC_ASSERT(V8_ALIGNOF(StorageType) >= V8_ALIGNOF(T));
 
   static T* MutableInstance(StorageType* storage) {
     return reinterpret_cast<T*>(storage);
   }
 
   template <typename ConstructTrait>
   static void InitStorageUsingTrait(StorageType* storage) {
     ConstructTrait::Construct(MutableInstance(storage));
   }
 };
 
-#undef LAZY_ALIGN
-
 
 template <typename T>
 struct DynamicallyAllocatedInstanceTrait {
   typedef T* StorageType;
 
   static T* MutableInstance(StorageType* storage) {
     return *storage;
   }
 
   template <typename CreateTrait>
@@ skipping 106 matching lines @@
           typename InitOnceTrait = SingleThreadInitOnceTrait,
           typename DestroyTrait = LeakyInstanceTrait<T> >
 struct LazyDynamicInstance {
   typedef LazyInstanceImpl<T, DynamicallyAllocatedInstanceTrait<T>,
       CreateTrait, InitOnceTrait, DestroyTrait> type;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_LAZY_INSTANCE_H_