https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110739
--- Comment #7 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:e99040403f70cd4741f876bffa64259df8ab2199 commit r16-1739-ge99040403f70cd4741f876bffa64259df8ab2199 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Fri Jun 27 09:50:18 2025 +0200 libstdc++: Use runtime format for internal format calls in chrono [PR110739] This patch adjust all internal std::format call inside of __formatter_chrono, to use runtime format string and thus avoid compile time checking of validity of the format string. Majority of cases are covered by calling newly introduced _S_empty_fs() function that returns __Runtime_format_string containing _S_empty_spec, instead of passing later directly. In case of _M_j we use _S_str_d3 function (extracted from _S_str_d2), eliminating call to std::format outside of unlikely scenario in which day of year is greater than 1000 (this may happen for year_month_day with month greater than 12). In consequence, outside of handling subseconds, we no longer delegate to std::format or construct temporary strings, when formatting chrono types with ok() values. PR libstdc++/110739 libstdc++-v3/ChangeLog: * include/bits/chrono_io.h (__formatter_chrono::_S_empty_fs): Define. (__formatter_chrono::_S_str_d2): Use _S_str_d3 for 3+ digits and place allways_inline attribute after comment. (__formatter_chrono::_S_str_d3): Extracted from _S_str_d2. (__formatter_chrono::_M_H_I, __formatter_chrono::_M_R_X): Replace _S_empty_spec with _S_empty_fs(). (__formatter_chrono::_M_j): Likewise and use _S_str_d3 in common case. (__format::operator-(_ChronoParts, _ChronoParts)) (__format::operator-=(_ChronoParts, _ChronoParts)) (__formatter_chrono::_S_fill_two_digits) (__formatter_chrono::_S_str_d1): Place always_inline attribute after comment.
