https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80564
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <[email protected]>: https://gcc.gnu.org/g:83aab2f73661ac8aa1643d58d2fbfed87d5c1601 commit r16-5930-g83aab2f73661ac8aa1643d58d2fbfed87d5c1601 Author: Patrick Palka <[email protected]> Date: Fri Dec 5 21:09:34 2025 -0500 libstdc++: Use deducing this in std::bind when available [PR80564] Implement the forwarding performed by std::bind via deducing this when available, instead of needing 4 operator() overloads. Using deducing this here is more complicated than in other standard call wrappers because std::bind is not really "perfect forwarding": it doesn't consider value category, and along with const-ness it also forwards volatile-ness (until C++20). The old implementation suffers from the same problem that other pre-C++23 SFINAE-friendly call wrappers have which is solved by using deducing this (see p5.5 of the deducing this paper P0847R7). PR libstdc++/80564 libstdc++-v3/ChangeLog: * include/std/functional (__cv_like): New. (_Bind::_Res_type): Don't define when not needed. (_Bind::__dependent): Likewise. (_Bind::_Res_type_cv): Likewise. (_Bind::operator()) [_GLIBCXX_EXPLICIT_THIS_PARAMETER]: Define as two instead of four overloads using deducing this. * testsuite/20_util/bind/cv_quals_2.cc: Ignore SFINAE diagnostics inside headers. * testsuite/20_util/bind/ref_neg.cc: Likewise. * testsuite/20_util/bind/80564.cc: New test. Reviewed-by: Tomasz KamiÅski <[email protected]> Reviewed-by: Jonathan Wakely <[email protected]>
