Add ALIGNAS and ALIGNOF macros to ensure proper alignment of StaticMemorySingletonTraits

base/stack_container.h

 // Copyright (c) 2010 The Chromium 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 BASE_STACK_CONTAINER_H_
 #define BASE_STACK_CONTAINER_H_
 #pragma once
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/memory/aligned_memory.h"
 
 // This allocator can be used with STL containers to provide a stack buffer
 // from which to allocate memory and overflows onto the heap. This stack buffer
 // would be allocated on the stack and allows us to avoid heap operations in
 // some situations.
 //
 // STL likes to make copies of allocators, so the allocator itself can't hold
 // the data. Instead, we make the creator responsible for creating a
 // StackAllocator::Source which contains the data. Copying the allocator
 // merely copies the pointer to this shared source, so all allocators created
@@ skipping 13 matching lines @@
   typedef typename std::allocator<T>::size_type size_type;
 
   // Backing store for the allocator. The container owner is responsible for
   // maintaining this for as long as any containers using this allocator are
   // live.
   struct Source {
     Source() : used_stack_buffer_(false) {
     }
 
     // Casts the buffer in its right type.
-    T* stack_buffer() { return reinterpret_cast<T*>(stack_buffer_); }
+    T* stack_buffer() { return stack_buffer_.template data_as<T>(); }
     const T* stack_buffer() const {
-      return reinterpret_cast<const T*>(stack_buffer_);
+      return stack_buffer_.template data_as<T>();
     }
 
-    //
-    // IMPORTANT: Take care to ensure that stack_buffer_ is aligned
-    // since it is used to mimic an array of T.
-    // Be careful while declaring any unaligned types (like bool)
-    // before stack_buffer_.
-    //
-
     // The buffer itself. It is not of type T because we don't want the
     // constructors and destructors to be automatically called. Define a POD
     // buffer of the right size instead.
-    char stack_buffer_[sizeof(T[stack_capacity])];
+    base::AlignedMemory<sizeof(T[stack_capacity]), ALIGNOF(T)> stack_buffer_;
 
     // Set when the stack buffer is used for an allocation. We do not track
     // how much of the buffer is used, only that somebody is using it.
     bool used_stack_buffer_;
   };
 
   // Used by containers when they want to refer to an allocator of type U.
   template<typename U>
   struct rebind {
     typedef StackAllocator<U, stack_capacity> other;
@@ skipping 173 matching lines @@
 
   // Vectors are commonly indexed, which isn't very convenient even with
   // operator-> (using "->at()" does exception stuff we don't want).
   T& operator[](size_t i) { return this->container().operator[](i); }
   const T& operator[](size_t i) const {
     return this->container().operator[](i);
   }
 };
 
 #endif  // BASE_STACK_CONTAINER_H_