https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110739
--- Comment #8 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:b2b7276a7e114d2e9f76e02b8567b6ce387a2234 commit r16-2251-gb2b7276a7e114d2e9f76e02b8567b6ce387a2234 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Fri Jun 27 15:04:19 2025 +0200 libstdc++: Format %a/%A/%b/%h/%B/%p without using locale::classic [PR110739] With changes r16-2063-g8ad5968a8dcb47 the _M_a_A, _M_b_B and _M_p functions are called only if the locale is equal to the locale::classic(), for which the behavior is know. This patch changes they implementation, so instead of reffering to __timepunct facet members, they use hardcoded list of English weekday, months names. Only one list is needed, as in case of locale::classic() abbreviated name corresponds to first tree letters of the full name. For _M_p, _M_r we use a new _M_fill_ampm helper, that fills provided buffer with "AM"/"PM" depending on the hours value. In _M_S we no longer guard querying of numpuct facet, with check that requires potentially equally expensive construction of locale::classic. We also mark localized path as unlikely. The _M_locale method is no longer used in __formatter_chrono, and thus was moved to __formatter_duration. PR libstdc++/110739 libstdc++-v3/ChangeLog: * include/bits/chrono_io.h (__formatter_chrono::_S_weekdays) (__formatter_chrono::_S_months, __formatter_chrono::_S_fill_ampm): Define. (__formatter_chrono::_M_format_to): Do not pass context parameter to functions listed below. (__formatter_chrono::_M_a_A, __formatter_chrono::_M_b_B): Implement using harcoded list of names, and remove format context parameter. (__formatter_chrono::_M_p, __formatter_chrono::_M_r): Implement using _S_fill_ampm. (__formatter_chrono::_M_c): Removed format context parameter. (__formatter_chrono::_M_subsecs): Call __ctx.locale() directly, instead of _M_locale and do not compare with locale::classic(). Add [[unlikely]] attributes. (__formatter_chrono::_M_locale): Move to __formatter_duration. (__formatter_duration::_M_locale): Moved from __formatter_chrono.
