https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104098
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:5c8f58be95d666e08221447d43d84782e1e6fb95 commit r10-10578-g5c8f58be95d666e08221447d43d84782e1e6fb95 Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Jan 18 15:34:24 2022 +0000 libstdc++: Use __cpp_lib_concepts in std::reverse_iterator [PR104098] We should not assume that std::iter_value_t etc. are defined unconditionally for C++20 mode. libstdc++-v3/ChangeLog: PR libstdc++/104098 * include/bits/stl_iterator.h (reverse_iterator): Check __cpp_lib_concepts instead of __cplusplus. (cherry picked from commit e13e95bd274148a825bc9527efac49e99080dd64)