https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107572
--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:3df9760d56662bdf38dd45f7398f003bbd64fdfe commit r13-6558-g3df9760d56662bdf38dd45f7398f003bbd64fdfe Author: Patrick Palka <ppa...@redhat.com> Date: Thu Mar 9 13:25:44 2023 -0500 libstdc++: extraneous begin in cartesian_product_view::end [PR107572] ranges::begin() isn't guaranteed to be equality-preserving for non-forward ranges, so in cartesian_product_view::end we need to avoid needlessly calling begin() on the first range (which could be non-forward) in the case where __empty_tail is false as per its specification. Since we're already using a variadic lambda to compute __empty_tail, we might as well use that same lambda to build up the tuple of iterators instead of building it separately via e.g. std::apply or __tuple_transform. PR libstdc++/107572 libstdc++-v3/ChangeLog: * include/std/ranges (cartesian_product_view::end): When building the tuple of iterators, avoid calling ranges::begin on the first range if __empty_tail is false. * testsuite/std/ranges/cartesian_product/1.cc (test07): New test.
