https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117214
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |14.3
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk so far.
This actually reveals a bigger problem, which is that we should really use
_M_locale_fmt for any format that is defined in terms of "the locale's ..."
My current implementation uses __timepunct to get the locale's info like D_FMT
etc., but that's for the C locale. The C++ formatting locale could have a
custom std::time_put that does something different:
#include <locale>
#include <format>
#include <chrono>
#include <iostream>
int main()
{
struct time_put : std::time_put<char>
{
iter_type
do_put(iter_type out, std::ios_base& io, char_type fill, const tm* t,
char format, char modifier) const override
{
using Base = std::time_put<char>;
if (format == 'a') // %a %b %e %H:%M:%S %Y
*out++ = '!';
return Base::do_put(out, io, fill, t, format, modifier);
}
};
std::locale loc(std::locale::classic(), new time_put);
std::cout << std::format(loc, "{:L%a}", std::chrono::Monday) << '\n';
}
I think this should print "!Mon" not "Mon".
So we should never use __timepunct directly (unless the formatting locale is
the classic locale, and profiling shows it's faster to format directly instead
of using _M_locale_fmt).
