https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93884
--- Comment #4 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:85c143d002a31bebb675161315c8e62db240b636 commit r10-6819-g85c143d002a31bebb675161315c8e62db240b636 Author: Patrick Palka <ppa...@redhat.com> Date: Mon Feb 24 07:59:08 2020 -0500 libstdc++: Add missing bits of P0896R4 pertaining to [back|front]_insert_iterator This adds some missing pieces of the Ranges TS that make back_insert_iterator and front_insert_iterator conform to the new output_iterator requirements. It also fixes a bug in ranges::__copy_or_move and ranges::__copy_or_move_backward in which we were inspecting the iter_value_t of the output iterator, but output iterators such as back_insert_iterator and front_insert_iterator whose value_type = void do not have an iter_value_t according to [readable.traits] p4. The entire __use_memmove condition should probably be rewritten, but the simplest fix for now is to inspect the iterator_traits of the output iterator instead. libstdc++-v3/ChangeLog: PR libstdc++/93884 * include/bits/ranges_algobase.h (__copy_or_move, __copy_or_move_backward): Don't inspect the iter_value_t of the output iterator, instead inspect its iterator_traits directly. * include/bits/stl_iterator.h (back_insert_iterator::container): Conditionally initialize. (back_insert_iterator::difference_type): Conditionally define. (back_insert_iterator::back_insert_iterator): Conditionally define this default constructor. (front_insert_iterator::container): Conditionally initialize. (front_insert_iterator::difference_type): Conditionally define. (front_insert_iterator::front_insert_iterator): Conditionally define this default constructor. * 24_iterators/back_insert_iterator/pr93884.cc: New test. * 24_iterators/front_insert_iterator/pr93884.cc: New test.