On 4/9/2010 2:39 PM, Daniel Walker wrote:
So, yeah, in general, if some signature requires a type to be complete, then the function can't be used in context where the type is incomplete... But I can think of one counterexample. If SFINAE drops the signature during template substitution, then overload resolution could still succeed. So the following, I believe, is valid even though S is incomplete. g++ accepts it.
template<class T> int f(typename T::foo, T x = T());
template<class T> int f(...);
struct S; typedef decltype(f<S>(0)) type;
Whoa, that's wacky. I tried comeau in strict C++03 mode, removed the use of decltype from this example, and confirmed that whether the type is complete or not actually changes which overload gets selected. I didn't think type completeness was a SFINAE case. This has ODR written all over it -- I don't know if it's valid code or not. -- Eric Niebler BoostPro Computing http://www.boostpro.com