Add ALIGNAS and ALIGNOF macros to ensure proper alignment of StaticMemorySingletonTraits

base/compiler_specific.h

Index: base/compiler_specific.h
diff --git a/base/compiler_specific.h b/base/compiler_specific.h
index 0a6e05a6c67988b64b416b612d47ec41c457a78f..c47362a4e55c6932acfefa3277a19244b648afed 100644
--- a/base/compiler_specific.h
+++ b/base/compiler_specific.h
@@ -96,6 +96,25 @@
 #define NOINLINE
 #endif
 
+// Specify memory alignment for structs, classes or data.
+// Use like:
+//   class ALIGNED(16) MyClass { ... }
+//   int array[4] ALIGNED(16);
+#if defined(COMPILER_MSVC)
+#define ALIGNED(byte_alignment) __declspec(align(byte_alignment))

[Sigurður Ásgeirsson, 2012/01/13 14:32:18]

MSVS wants __declspec to precede the declarator, whereas it looks like GCC wants
__attribute__ to trail it.
I don't see how this macro could be used in a compiler-independent fashion.
Maybe you can do something with a two-argument function that takes a type and an
alignment, and would generally be used in a typedef.
#define ALIGNED_TYPE(type, alignment) __declspec(align(alignment)) type
#define ALIGNED_TYPE(type, alignment) type __attribute(...)

typedef ALIGNED_TYPE(char[sizeof(T)], ALIGNOF(T)) AlignedBuffer;
AlignedBuffer buffer_;

[jbates, 2012/01/13 17:29:18]

At least for struct and class, I think GCC allows either. So this seems to work
for both:
class ALIGNED(16) MyClass {...};

I haven't yet tested typedefs or the int array[4] example in MSVC though.

+#elif defined(COMPILER_GCC)
+#define ALIGNED(byte_alignment) __attribute__((aligned(byte_alignment)))
+#endif
+
+// Return the byte alignment of the given type (available at compile time).
+// Use like:
+//   ALIGNOF(int32)  // this would be 4
+#if defined(COMPILER_MSVC)
+#define ALIGNOF(type) __alignof(type)
+#elif defined(COMPILER_GCC)
+#define ALIGNOF(type) __alignof__(type)
+#endif
+
 // Annotate a virtual method indicating it must be overriding a virtual
 // method in the parent class.
 // Use like: