Add ALIGNAS and ALIGNOF macros to ensure proper alignment of StaticMemorySingletonTraits

base/memory/singleton_unittest.cc

 // Copyright (c) 2011 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.
 
 #include "base/at_exit.h"
 #include "base/file_util.h"
 #include "base/memory/singleton.h"
 #include "base/path_service.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 92 matching lines @@
 struct CallbackSingletonWithStaticTrait::Trait
     : public StaticMemorySingletonTraits<CallbackSingletonWithStaticTrait> {
   static void Delete(CallbackSingletonWithStaticTrait* instance) {
     if (instance->callback_)
       (instance->callback_)();
     StaticMemorySingletonTraits<CallbackSingletonWithStaticTrait>::Delete(
         instance);
   }
 };
 
+template <class Type>
+class AlignedTestSingleton {
+ public:
+  AlignedTestSingleton() {}
+  ~AlignedTestSingleton() {}
+  static AlignedTestSingleton* GetInstance() {
+    return Singleton<AlignedTestSingleton,
+        StaticMemorySingletonTraits<AlignedTestSingleton> >::get();
+  }
+
+  Type type_;
+};
+
 
 void SingletonNoLeak(CallbackFunc CallOnQuit) {
   CallbackSingletonWithNoLeakTrait::GetInstance()->callback_ = CallOnQuit;
 }
 
 void SingletonLeak(CallbackFunc CallOnQuit) {
   CallbackSingletonWithLeakTrait::GetInstance()->callback_ = CallOnQuit;
 }
 
 CallbackFunc* GetLeakySingleton() {
@@ skipping 120 matching lines @@
     {
       // Resurrect the static singleton, and assert that it
       // still points to the same (static) memory.
       CallbackSingletonWithStaticTrait::Trait::Resurrect();
       EXPECT_EQ(GetStaticSingleton(), static_singleton);
     }
   }
   // The leaky singleton shouldn't leak since SingletonLeak has not been called.
   VerifiesCallbacksNotCalled();
 }
+
+#define EXPECT_ALIGNED(ptr, align) \
+    EXPECT_EQ(0u, reinterpret_cast<uintptr_t>(ptr) & (align - 1))
+
+TEST_F(SingletonTest, Alignment) {
+  using base::AlignedMemory;
+
+  // Create some static singletons with increasing sizes and alignment
+  // requirements. By ordering this way, the linker will need to do some work to
+  // ensure proper alignment of the static data.
+  AlignedTestSingleton<int32>* align4 =
+      AlignedTestSingleton<int32>::GetInstance();
+  AlignedTestSingleton<AlignedMemory<32, 32> >* align32 =
+      AlignedTestSingleton<AlignedMemory<32, 32> >::GetInstance();
+  AlignedTestSingleton<AlignedMemory<128, 128> >* align128 =
+      AlignedTestSingleton<AlignedMemory<128, 128> >::GetInstance();
+  AlignedTestSingleton<AlignedMemory<4096, 4096> >* align4096 =
+      AlignedTestSingleton<AlignedMemory<4096, 4096> >::GetInstance();
+
+  EXPECT_ALIGNED(align4, 4);
+  EXPECT_ALIGNED(align32, 32);
+  EXPECT_ALIGNED(align128, 128);
+  EXPECT_ALIGNED(align4096, 4096);
+}