https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116529
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-14 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:4d88724c2d804e126d63aed77fa8c2c333e99396 commit r14-10708-g4d88724c2d804e126d63aed77fa8c2c333e99396 Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Aug 29 13:47:15 2024 +0100 libstdc++: Avoid forming T* in unique_ptr(auto_ptr<U>&&) constraints [PR116529] PR 116529 shows that std::unique_ptr<X&, D> is currently unusable because the constructor taking std::auto_ptr (which is a non-standard extension since C++17) tries to form the invalid type X&* during overload resolution. We can use the `pointer` type in the constructor constraints, instead of trying to form an invalid type. The std::auto_ptr constructor can never actually match for the case where element_type is a reference, so we just need it to produce a substitution failure instead of being ill-formed. LWG 4144 might make std::unique_ptr<X&, D> ill-formed, which would invalidate this new test. We would have to remove this test in that case. Using `pointer` in the constructor from std::auto_ptr would not be needed to support the std::unique_ptr<X&, D> case, but would not cause any harm either. libstdc++-v3/ChangeLog: PR libstdc++/116529 * include/bits/unique_ptr.h (unique_ptr(auto_ptr<U>&&)): Use pointer instead of T*. * testsuite/20_util/unique_ptr/creation/116529.cc: New test. (cherry picked from commit a001d515059ba4647169f8c17967d08bbe41cb7a)
