https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110719
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:f4bce119f617dc4663fb43f55784908daf16b4b6 commit r14-2640-gf4bce119f617dc4663fb43f55784908daf16b4b6 Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Jul 18 12:46:07 2023 +0100 libstdc++: Implement correct locale-specific chrono formatting [PR110719] This fixes some TODOs in the C++20 <chrono> format support, where the locale-specific output was incorrect or unimplemented. The approach taken here is to either use the formatting locale's std::time_put facet to do the formatting, or to remove subsecond precision from time points so that locale-specific formats don't print fractional seconds. This ensures that we are consistent with what the std::time_put facet would print (which never includes fractional seconds) even if we actually reimplement the formatting by hand instead of using the facet. This also fixes a misplaced statement that allowed modifiers for %Z which should have been on %z instead. There was also some ill-formed code in an untested branch for formatting time zone names to wide characters. A new test for zoned_time I/O has been added to exercise that code properly. libstdc++-v3/ChangeLog: PR libstdc++/110719 * include/bits/chrono_io.h (__formatter_chrono::_M_parse): Fix allowed modifiers for %z and %Z. Fix -Wparentheses and -Wnarrowing warnings. (__formatter_chrono::_M_format): Call new functions for %d, %e, %H, %I, %m and %M. (__formatter_chrono::_M_c): Use _S_floor_seconds to remove subsecond precision. (__formatter_chrono::_M_C_y_Y): Use _M_locale_fmt to handle modifiers. (__formatter_chrono::_M_e): Replace with _M_d_e and use _M_locale_fmt. (__formatter_chrono::_M_I): Replace with _M_H_I and use _M_locale_fmt. (__formatter_chrono::_M_m): New function. (__formatter_chrono::_M_M): New function. (__formatter_chrono::_M_r): Use _M_locale_fmt. (__formatter_chrono::_M_S): Likewise. (__formatter_chrono::_M_u_w): Likewise. (__formatter_chrono::_M_U_V_W): Likewise. (__formatter_chrono::_M_X): Use _S_floor_seconds. (__formatter_chrono::_M_Z): Fix untested branch for wchar_t. (__formatter_chrono::_S_altnum): Remove function. (__formatter_chrono::_S_dd_zero_fill): Remove function. (__formatter_chrono::_S_floor_seconds): New function. (__formatter_chrono::_M_locale_fmt): New function. * testsuite/std/time/clock/system/io.cc: Adjust expected output for locale-specific formats and check modified formats. * testsuite/std/time/clock/utc/io.cc: Likewise. * testsuite/std/time/zoned_time/io.cc: New test.
