Proposed resolution:

This wording is relative to N4910.

1. Modify [out.ptr.t] as indicated:

   explicit out_ptr_t(Smart& smart, Args... args);
   

   -6- Effects: Initializes s with smart, a with std::forward<Args>(args)..., and value-initializes p. Then, equivalent to:

   • (6.1) —

     s.reset();

     if the expression s.reset() is well-formed;

   • (6.2) — otherwise,

     s = Smart();
     

     if is_constructible_v<Smart> is true;

   • (6.3) — otherwise, the program is ill-formed.

   -7- [Note 2: The constructor is not noexcept to allow for a variety of non-terminating and safe implementation strategies. For example, an implementation can allocate a shared_ptr's internal node in the constructor and let implementation-defined exceptions escape safely. The destructor can then move the allocated control block in directly and avoid any other exceptions. — end note]