https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100290
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:b81834eaf85d5c4e0df8e4fc2307cbdd083dea6c commit r10-9789-gb81834eaf85d5c4e0df8e4fc2307cbdd083dea6c Author: Patrick Palka <ppa...@redhat.com> Date: Tue Apr 27 14:07:46 2021 -0400 libstdc++: Fix up lambda in join_view::_Iterator::operator++ [PR100290] Currently, the return type of this lambda is decltype(auto), so the lambda ends up returning a copy of _M_parent->_M_inner rather than a reference to it when _S_ref_glvalue is false. This means _M_inner and ranges::end(__inner_range) are respectively an iterator and sentinel for different ranges, so comparing them is undefined. libstdc++-v3/ChangeLog: PR libstdc++/100290 * include/std/ranges (join_view::_Iterator::operator++): Correct the return type of the lambda to avoid returning a copy of _M_parent->_M_inner. * testsuite/std/ranges/adaptors/join.cc (test10): New test. (cherry picked from commit 85ef4b8d4eb3313a48b79c7e752891f9646bb246)
