https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121154
--- Comment #2 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:d31c76cb844154ccd638abc642b9bbb5fea519d4 commit r16-2349-gd31c76cb844154ccd638abc642b9bbb5fea519d4 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Fri Jul 18 11:30:22 2025 +0200 libstdc++: Fixed localized empty-spec formatting for months/weekdays [PR121154] Previously for localized output, if _M_debug option was set, the _M_check_ok completed succesfully and _M_locale_fmt was called for months/weekdays that are !ok(). This patch lifts debug checks from each conversion function into _M_check_ok, that in case of !ok() values return a string_view containing the kind of calendar data, to be included after "is not a valid" string. The localized output (_M_locale_fmt) is not used if string is non-empty. Emitting of this message is now handled in _M_format_to, further reducing each specifier function. To handle weekday (%a,%A) and month (%b,%B), _M_check_ok now accepts a mutable reference to conversion specifier, and updates it to corresponding numeric value (%w, %m). Extra care needs to be taken to handle a month(0) that needs to be printed as single digit in debug format. Finally, the _M_time_point is replaced with _M_needs_ok_check member, that indicates if input contains any user-suplied values that are checked for being ok() and these values are referenced in chrono-specs. PR libstdc++/121154 libstdc++-v3/ChangeLog: * include/bits/chrono_io.h (_ChronoSpec::_M_time_point): Remove. (_ChronoSpec::_M_needs_ok_check): Define (__formatter_chrono::_M_parse): Set _M_needs_ok_check. (__formatter_chrono::_M_check_ok): Check values also for debug mode, and return __string_view. (__formatter_chrono::_M_format_to): Handle results of _M_check_ok. (__formatter_chrono::_M_wi, __formatter_chrono::_M_a_A) (__formatter_chrono::_M_b_B, __formatter_chrono::_M_C_y_Y) (__formatter_chrono::_M_d_e, __formatter_chrono::_M_F): Removed handling of _M_debug. (__formatter_chrono::__M_m): Print zero unpadded in _M_debug mode. (__formatter_duration::_S_spec_for): Remove _M_time_point refernce. (__formatter_duration::_M_parse): Override _M_needs_ok_check. * testsuite/std/time/month/io.cc: Test for localized !ok() values. * testsuite/std/time/weekday/io.cc: Test for localized !ok() values.
