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copied!<p>You can use placement new. Like, set a maximal limit of size you want to allow <code>callback</code> to have, like <code>16</code> bytes. Then, put an <code>unsigned char</code> buffer into your <code>callback</code> class that's exactly that wide, and make sure it's aligned correctly (<code>GCC</code> has an attribute for that, and if you are lucky, microsoft has an attribute for that too). </p> <p>You may also go fairly safe if you use an union, and beside the char buffer put dummies of the types you want to stuff into it - that will ensure proper alignment too. </p> <p>Then, instead of using normal new, use placement new, like</p> <pre><code>if(placement_allocated< callable_from_object<C> >::value) { new ((void*)buffer.p) // union member p is the unsigned char buffer callable_from_object<C>(object, method); c = (callable*)buffer.p; } else { c = new callable_from_object<C>(object, method); } </code></pre> <p>Then, make the <code>c</code> member a pointer instead. You also need to set a flag so you remember whether you have to call delete in the destructor, or leave the placement buffer alone with explicitly calling the destructor. </p> <p>That's <em>basically</em> how <code>boost::function</code> does it. It, however, does a whole lot of other stuff to optimize allocation. It uses its own vtable mechanism to optimize space, and of course is very well tested. </p> <p>Of course, this is not exactly easy to do. But that seems to be the only thing to do about it. </p>

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