https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96416
--- Comment #21 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:b8018e5c5ec0e9b6948182f13fba47c67b758d8a commit r12-5532-gb8018e5c5ec0e9b6948182f13fba47c67b758d8a Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Nov 25 16:49:45 2021 +0000 libstdc++: Make std::pointer_traits SFINAE-friendly [PR96416] This implements the resolution I'm proposing for LWG 3545, to avoid hard errors when using std::to_address for types that make pointer_traits ill-formed. Consistent with std::iterator_traits, instantiating std::pointer_traits for a non-pointer type will be well-formed, but give an empty type with no member types. This avoids the problematic cases for std::to_address. Additionally, the pointer_to member is now only declared when the element type is not cv void (and for C++20, when the function body would be well-formed). The rebind member was already SFINAE-friendly in our implementation. libstdc++-v3/ChangeLog: PR libstdc++/96416 * include/bits/ptr_traits.h (pointer_traits): Reimplement to be SFINAE-friendly (LWG 3545). * testsuite/20_util/pointer_traits/lwg3545.cc: New test. * testsuite/20_util/to_address/1_neg.cc: Adjust dg-error line. * testsuite/20_util/to_address/lwg3545.cc: New test.
