On Dec 7, 2012, at 10:35 AM, Benjamin Kramer <[email protected]> wrote:
>> Two lookups would be noticeably slower. I also suspect the memory overhead >> is inconsequential. We are talking about a few kilobytes at most, on a very >> complicated file. We can bit-mangle the pointer, if you like, to provide a >> sentinel value. > > Maybe we should specialize Optional on types that have pointerLikeTypeTraits > and automatically enable bitmangling if it has a spare bit. I had the same thought. We'd need to be careful about alignment, but it seems completely doable. > > OTOH Optional on pointers doesn't seem to be very common in clang so it may > not be worth the effort. It might be more common if it was implemented more efficiently. It's a nice type-safe abstraction in the places where it is useful.
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