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libstdc++: Use formatting locale for std::time_put formats

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When using std::time_put to format a chrono value, we should imbue the
formatting locale into the stream. This ensures that when
std::time_put::do_put uses a ctype or __timepunct facet from the locale,
it gets the correct facets.

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (__formatter_chrono::_M_locale_fmt):
	Imbue locale into ostringstream.
	* testsuite/std/time/format/localized.cc: Check that correct
	locale is used for call to time_put::put.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
This commit is contained in:
Jonathan Wakely 2025-03-19 19:38:15 +00:00 • committed by Jonathan Wakely
parent 3e1d760bf4
commit 3c7f2fd8c4
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2 changed files with 34 additions and 0 deletions
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1
libstdc++-v3/include/bits/chrono_io.h
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@ -1697,6 +1697,7 @@ namespace __format
char __fmt, char __mod) const
{
basic_ostringstream<_CharT> __os;
__os.imbue(__loc);
const auto& __tp = use_facet<time_put<_CharT>>(__loc);
__tp.put(__os, __os, _S_space, &__tm, __fmt, __mod);
if (__os)

33
libstdc++-v3/testsuite/std/time/format/localized.cc
View file

@ -13,6 +13,7 @@
#include <chrono>
#include <format>
#include <locale>
#include <stdio.h>
#include <testsuite_hooks.h>
@ -81,10 +82,42 @@ test_en()
}
}
void
test_locale_imbued()
{
// Custom time_put facet which returns %b string for %Om.
// The %b string will come from io.getloc() which should be
// the formatting locale using by std::format.
struct TimePut : 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
{
if (format == 'm' && modifier == 'O')
format = 'b';
return std::time_put<char>::do_put(out, io, fill, t, format, 0);
}
};
auto m = std::chrono::March;
std::locale fr(ISO_8859(1,fr_FR));
std::locale fr2(fr, new TimePut);
auto s1 = std::format(fr2, "{:L%Om}", m); // should be %b in fr_FR locale
VERIFY( s1 == std::format(fr, "{:L}", m) );
std::locale es(ISO_8859(1,es_ES));
std::locale es2(es, new TimePut);
auto s2 = std::format(es2, "{:L%Om}", m); // should be %b in es_ES locale
VERIFY( s2 == std::format(es, "{:L}", m) );
}
int main()
{
test_ru();
test_es();
test_fr();
test_en();
test_locale_imbued();
}