Upgrade AlignedMemory to support dynamic allocations.

base/memory/aligned_memory.h

Index: base/memory/aligned_memory.h
diff --git a/base/memory/aligned_memory.h b/base/memory/aligned_memory.h
index 0a176347a6dd47768c20c9585870fcd9cef417f1..550dcdd5d8dc723a77c2cacfb8d6eb17b7f2bb5a 100644
--- a/base/memory/aligned_memory.h
+++ b/base/memory/aligned_memory.h
@@ -18,13 +18,30 @@
 //
 //   // ... later, to destruct my_class:
 //   my_class.data_as<MyClass>()->MyClass::~MyClass();
+//
+// Alternatively, a runtime sized aligned allocation can be created:
+//
+//   float* my_array = reinterpret_cast<float*>(AlignedAlloc(size, alignment));
+//
+//   // ... later, to release the memory:
+//   AlignedFree(my_array);
+//
+// Or using scoped_ptr_malloc:
+//
+//   scoped_ptr_malloc<float, ScopedAlignedFree> my_array(
+//       reinterpret_cast<float*>(AlignedAlloc(size, alignment)));
 
 #ifndef BASE_MEMORY_ALIGNED_MEMORY_H_
 #define BASE_MEMORY_ALIGNED_MEMORY_H_
 
+#if defined(COMPILER_MSVC) || defined(OS_ANDROID)
+#include <malloc.h>
+#endif
+#include <stdlib.h>
+
+#include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "base/logging.h"
 
 namespace base {
 
@@ -37,7 +54,6 @@ struct AlignedMemory {};
     template <size_t Size> \
     class AlignedMemory<Size, byte_alignment> { \
      public: \
-      ALIGNAS(byte_alignment) uint8 data_[Size]; \
       void* void_data() { return reinterpret_cast<void*>(data_); } \
       const void* void_data() const { \
         return reinterpret_cast<const void*>(data_); \
@@ -49,6 +65,7 @@ struct AlignedMemory {};
         return reinterpret_cast<const Type*>(void_data()); \
       } \
      private: \
+      ALIGNAS(byte_alignment) uint8 data_[Size]; \
       void* operator new(size_t); \
       void operator delete(void*); \
     }
@@ -71,6 +88,26 @@ BASE_DECL_ALIGNED_MEMORY(1024);
 BASE_DECL_ALIGNED_MEMORY(2048);
 BASE_DECL_ALIGNED_MEMORY(4096);
 
-}  // base
+#undef BASE_DECL_ALIGNED_MEMORY
+
+BASE_EXPORT void* AlignedAlloc(size_t size, size_t alignment);

[Jeffrey Yasskin, 2012/07/21 20:38:49]

Please make this signature match C11's aligned_alloc(), which is declared as
"void *aligned_alloc(size_t alignment, size_t size);"

[DaleCurtis, 2012/07/21 22:18:41]

I used this since it matches the original AlignedMemory order above, it seems
reasonable to keep them the same. Do you want to flip them both?

[Jeffrey Yasskin, 2012/07/21 22:42:07]

It does seem reasonable to keep them the same. Unfortunately, C++11's
aligned_storage<> and C11's aligned_alloc() picked opposite orders. Let's get a
third opinion from someone with more Chrome experience.

+
+inline void AlignedFree(void* ptr) {
+#if defined(COMPILER_MSVC)
+  _aligned_free(ptr);
+#else
+  free(ptr);
+#endif
+}
+
+// Helper class for use with scoped_ptr_malloc.
+class BASE_EXPORT ScopedAlignedFree {

[Jeffrey Yasskin, 2012/07/21 20:38:49]

This name seems awkward, but I don't have a concrete suggestion for a better
one.

[DaleCurtis, 2012/07/21 22:18:41]

AlignedFreeHelper, AlignedFreeScoper? The default one in scoped_ptr is called
ScopedPtrMallocFree, so this could be ScopedPtrAlignedFree.

[Jeffrey Yasskin, 2012/07/21 22:42:07]

ScopedPtrAlignedFree seems the least bad of those, but it is annoyingly long. No
strong opinions from me.

[DaleCurtis, 2012/07/22 00:45:40]

Changed to ScopedPtrAlignedFree for consistency with scoped_ptr.

+ public:
+  inline void operator()(void* x) const {
+    AlignedFree(x);
+  }
+};
+
+}  // namespace base
 
 #endif  // BASE_MEMORY_ALIGNED_MEMORY_H_