https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95578
--- Comment #2 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:a73051a0ea9ce8281e748a74dd924a6eb8fb3723 commit r11-1186-ga73051a0ea9ce8281e748a74dd924a6eb8fb3723 Author: Patrick Palka <ppa...@redhat.com> Date: Wed Jun 10 17:37:53 2020 -0400 libstdc++: Fix some ranges algos optimizations [PR95578] ranges::copy and a number of other ranges algorithms have unwrapping optimizations for iterators of type __normal_iterator, move_iterator and reverse_iterator. But in the checks that guard these optimizations we currently only test that the iterator of the iterator/sentinel pair has the appropriate type before proceeding with the corresponding optimization, and do not also test the sentinel type. This breaks the testcase in this PR because this testcase constructs via range adaptors a range whose begin() is a __normal_iterator and whose end() is a custom sentinel type, and then performs ranges::copy on it. From there we bogusly perform the __normal_iterator unwrapping optimization on this iterator/sentinel pair, which immediately leads to a constraint failure since the custom sentinel type does not model sentinel_for<int*>. This patch fixes this issue by refining each of the problematic checks to also test that the iterator and sentinel types are the same before applying the corresponding unwrapping optimization. Along the way, some code simplifications are made. libstdc++-v3/ChangeLog: PR libstdc++/95578 * include/bits/ranges_algo.h (__lexicographical_compare_fn): Also check that the iterator and sentinel have the same type before applying the unwrapping optimization for __normal_iterator. Split the check into two, one for the first iterator/sentinel pair and another for second iterator/sentinel pair. Remove uses of __niter_base, and remove uses of std::move on a __normal_iterator. * include/bits/ranges_algobase.h (__equal_fn): Likewise. (__copy_or_move): Likewise. Perform similar adjustments for the reverse_iterator and move_iterator optimizations. Inline the checks into the if-constexprs, and use using-declarations to make them less visually noisy. Remove uses of __niter_wrap. (__copy_or_move_backward): Likewise. * testsuite/25_algorithms/copy/95578.cc: New test. * testsuite/25_algorithms/copy_backward/95578.cc: New test. * testsuite/25_algorithms/equal/95578.cc: New test. * testsuite/25_algorithms/lexicographical_compare/95578.cc: New test. * testsuite/25_algorithms/move/95578.cc: New test. * testsuite/25_algorithms/move_backward/95578.cc: New test.
