Upgrade AlignedMemory to support dynamic allocations.

base/memory/aligned_memory.cc

Index: base/memory/aligned_memory.cc
diff --git a/base/memory/aligned_memory.cc b/base/memory/aligned_memory.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2c0b043d6bbd6091e43119fcca41083d2e09f5c6
--- /dev/null
+++ b/base/memory/aligned_memory.cc
@@ -0,0 +1,38 @@
+// Copyright (c) 2012 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/memory/aligned_memory.h"
+
+#include "base/logging.h"
+
+// NaCl currently does not have posix_memalign in its headers, though the malloc
+// implementation (dlmalloc) does support it.
+// http://code.google.com/p/nativeclient/issues/detail?id=2505
+#if defined(OS_NACL)
+extern int posix_memalign(void **memptr, size_t alignment, size_t size);
+#endif
+
+namespace base {
+
+void* AlignedAlloc(size_t size, size_t alignment) {
+  DCHECK_GT(size, static_cast<size_t>(0));

[Jeffrey Yasskin, 2012/07/21 22:42:06]

FWIW, "0U" usually works instead of static_cast<size_t>, unless there's a
template being instantiated that wants the types to actually be the same.

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

Done.

+  DCHECK_EQ(alignment & (alignment - 1), static_cast<size_t>(0));
+  DCHECK_EQ(alignment % sizeof(void*), static_cast<size_t>(0));
+  void* ptr = NULL;
+#if defined(COMPILER_MSVC)
+  ptr = _aligned_malloc(size, alignment);
+#elif defined(OS_ANDROID)
+  ptr = memalign(alignment, size);

[Jeffrey Yasskin, 2012/07/21 22:42:06]

I do want to find some sort of link to documentation saying memalign->free is
fine within Android.

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

I suspect aside from the commit message I linked previously and the standard
"read the code", the only documentation we'll find is what we write here. :)

As such, I've added a nice comment for future travelers.

+#else
+  if (posix_memalign(&ptr, alignment, size))
+    ptr = NULL;
+#endif
+  // Since aligned allocations may fail for non-memory related reasons, force a
+  // crash if we encounter a failed allocation; maintaining consistent behavior
+  // with a normal allocation failure in Chrome.
+  CHECK(ptr) << "If you crashed here, your aligned allocation is incorrect.";

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

It might be helpful to include 'size' and 'alignment' in the error message here.

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

Done.

+  return ptr;
+}
+
+}  // namespace base