Re: [boost] [move][unique_ptr] c++14 unique_ptr comes to town

Ion Gaztañaga wrote:

On the other hand, with the default_deleter it could be safe to convert (maybe if N >= M):

4) unique_ptr -> unique_ptr

I don't support this conversion in shared_ptr and have no plans to. reinterpret_pointer_cast should work though.

A problem might occure if a user-provided deleter is be convertible to deleter but it does not properly handle unknown-length arrays.

In general, if deleter<X> is convertible to deleter<Y> but does not handle Y properly, it might cause problems. So I'm not sure that this case is extraordinary in this sense. It's true that these cases are a bit convoluted because, esp. in the presence of a user-defined pointer type, we need to decide how much to trust the deleter and how much to override whatever it says WRT conversions. For instance, let's say unique_ptr wants to convert to unique_ptr and D1::pointer is convertible to D2::pointer and D1 is convertible to D2 _but_ X2 does not have a virtual destructor. Do we disallow the conversion as we do in the ordinary X1* -> X2* case when using the default deleter, or do we go ahead? The array case is similar, unique_ptr -> unique_ptr, X(*)[] is not convertible to Y(*)[] but both D1::pointer and D1 are convertible to D2::pointer and D2. Legal or not?