https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109162
--- Comment #12 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tomasz Kaminski <tkami...@gcc.gnu.org>: https://gcc.gnu.org/g:473dde525248a694c0f4e62b31a7fc24b238c5b0 commit r15-9517-g473dde525248a694c0f4e62b31a7fc24b238c5b0 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Mon Apr 14 16:00:57 2025 +0200 libstdc++: Implement formatters for pair and tuple [PR109162] This patch implements formatter specializations for pair and tuple form P2286R8. In addition using 'm` and range_format::map (from P2585R1) for ranges are now supported. The formatters for pairs and tuples whose corresponding elements are the same (after applying remove_cvref_t) derive from the same __tuple_formatter class. This reduce the code duplication, as most of the parsing and formatting is the same in such cases. We use a custom reduced implementation of the tuple (__formatters_storage) to store the elements formatters. Handling of the padding (width and fill) options, is extracted to __format::__format_padded function, that is used both by __tuple_formatter and range_formatter. To reduce number of instantations range_formatter::format triggers, we cast incoming range to __format::__maybe_const_range<_Rg, _CharT>&, before formatting it. 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 last three of above as unconstrained types. Finally, test for tuple-like std::array and std::ranges::subrange, that illustrate that they remain formatted as ranges. PR libstdc++/109162 libstdc++-v3/ChangeLog: * include/std/format (__formatter_int::_M_format_character_escaped) (__formatter_str::format): Use __sink.out() to produce _Sink_iter. (__format::__const_formattable_range): Moved closer to range_formatter. (__format::__maybe_const_range): Use `__conditional_t` and moved closer to range_formatter. (__format::__format_padded, __format::maybe_const) (__format::__indexed_formatter_storage, __format::__tuple_formatter) (std::formatter<pair<_Fp, _Sp>, _CharT>>) (std::formatter<tuple<_Tps...>, _CharT): Define. (std::formatter<_Rg, _CharT>::format): Cast incoming range to __format::__maybe_const_range<_Rg, _CharT>&. (std::formatter<_Rg, _CharT>::_M_format): Extracted from format, and use __format_padded. (std::formatter<_Rg, _CharT>::_M_format_no_padding): Rename... (std::formatter<_Rg, _CharT>::_M_format_elems): ...to this. (std::formatter<_Rg, _CharT>::_M_format_with_padding): Extracted as __format_padded. * testsuite/util/testsuite_iterators.h (test_input_range_nocopy): Define. * testsuite/std/format/ranges/formatter.cc: Tests for `m` specifier. * testsuite/std/format/ranges/sequence.cc: Tests for array and subrange. * testsuite/std/format/ranges/map.cc: New test. * testsuite/std/format/tuple.cc: New test. Reviewed-by: Jonathan Wakely <jwak...@redhat.com> Signed-off-by: Tomasz KamiÅski <tkami...@redhat.com>
