https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109162
--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-15 branch has been updated by Tomasz Kaminski <tkami...@gcc.gnu.org>: https://gcc.gnu.org/g:5bd02daf8430ecce1d7fd847ef4fc9c369179542 commit r15-9588-g5bd02daf8430ecce1d7fd847ef4fc9c369179542 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Fri Apr 18 14:56:39 2025 +0200 libstdc++: Implement formatters for queue, priority_queue and stack [PR109162] This patch implements formatter specializations for standard container adaptors (queue, priority_queue and stack) from P2286R8. To be able to access the protected `c` member, the adaptors befriend corresponding formatter specializations. Note that such specialization may be disable if the container is formattable, in such case specializations are unharmful. As in the case of previous commits, the signatures of the user-facing parse and format methods of the provided formatters deviate from the standard by constraining types of parameters: * _CharT is constrained __formatter::__char * basic_format_parse_context<_CharT> for parse argument * basic_format_context<_Out, _CharT> for format second argument The standard specifies all above as unconstrained types. In particular _CharT constrain, allow us to befriend all allowed specializations. Furthermore the standard specifies these formatters as delegating to formatter<ranges::ref_view<const? _Container>, charT>, which in turn delegates to range_formatter. This patch avoids one level of indirection, and dependency of ranges::ref_view. This is technically observable if user specializes formatter<std::ref_view<PD>> where PD is program defined container, but I do not think this is the case worth extra indirection. This patch also moves the formattable and it's dependencies to the formatfwd.h, so it can be used in adapters formatters, without including format header. The definition of _Iter_for is changed from alias to denoting back_insert_iterator<basic_string<_CharT>>, to struct with type nested typedef that points to same type, that is forward declared. PR libstdc++/109162 libstdc++-v3/ChangeLog: * include/bits/formatfwd.h (__format::__parsable_with) (__format::__formattable_with, __format::__formattable_impl) (__format::__has_debug_format, __format::__const_formattable_range) (__format::__maybe_const_range, __format::__maybe_const) (std::formattable): Moved from std/format. (__format::Iter_for, std::range_formatter): Forward declare. * include/bits/stl_queue.h (std::formatter): Forward declare. (std::queue, std::priority_queue): Befriend formatter specializations. * include/bits/stl_stack.h (std::formatter): Forward declare. (std::stack): Befriend formatter specializations. * include/std/format (__format::_Iter_for): Define as struct with (__format::__parsable_with, __format::__formattable_with) (__format::__formattable_impl, __format::__has_debug_format) (_format::__const_formattable_range, __format::__maybe_const_range) (__format::__maybe_const, std::formattable): Moved to bits/formatfwd.h. (std::range_formatter): Remove default argument specified in declaration in bits/formatfwd.h. * include/std/queue: Include bits/version.h before bits/stl_queue.h. (formatter<queue<_Tp, _Container, _Compare>, _CharT>) (formatter<priority_queue<_Tp, _Container, _Compare>, _CharT>): Define. * include/std/stack: Include bits/version.h before bits/stl_stack.h (formatter<stack<_Tp, _Container, _Compare>, _CharT>): Define. * testsuite/std/format/ranges/adaptors.cc: New test. Reviewed-by: Jonathan Wakely <jwak...@redhat.com> Signed-off-by: Tomasz KamiÅski <tkami...@redhat.com> (cherry picked from commit 3d808ede38b959d283baaed1864434392eeb41e3)
