I am writing a C++ wrapper around a legacy API. This API provides me with a pointer value to keep extra data, and I want to implement the Small Buffer Optimization with it.

I have implemented an is_small_pod metafunction that checks whether a given type is POD and it fits within a void*:

template< typename Type >
struct is_small_pod
  : std::integral_constant<
        bool
      , std::is_pod< Type >::type::value
        && sizeof( Type ) <= sizeof( void* )
    >
{};

and I'm setting the value like this:

// void*& param;
if( detail::is_small_pod< Type >() )
{
    *static_cast< Type* >( &param ) = value;
} else {
    param = new Type( value );
}

Am I implementing this optimization correctly? I believe this will fail when the value alignment is not compatible with the alignment of a pointer (odd corner case as it may be). Is that situation even possible, or am I just overthinking it? How should I extend my metafunction to check for compatible alignment as well?

c++ c++11
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