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<xloctime>: Fix time_put::do_put to correctly handle %c and %r formatting in "C" locale #6299

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<xloctime>: Fix time_put::do_put to correctly handle %c and %r formatting in "C" locale #6299

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e326b90
`<xloctime>`: Fix `time_put::do_put` to correctly handle %c and %r fo…
ferhatgec May 28, 2026
b520074
Update P0355R7 test assertions to match standard C locale %c output
ferhatgec May 29, 2026
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78 changes: 57 additions & 21 deletions stl/inc/xloctime
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Original file line number Diff line number Diff line change
Expand Up @@ -888,24 +888,36 @@ protected:

virtual _OutIt __CLR_OR_THIS_CALL do_put(_OutIt _Dest, ios_base& _Iosbase, _Elem, const tm* _Pt, char _Specifier,
char _Modifier = '\0') const { // put formatted time from _Pt to _Dest for [_Fmtfirst, _Fmtlast)
char _Fmt[5] = "!%x\0"; // '!' for nonzero count, null for modifier
const char* _Fmt_ptr = nullptr;
char _Fmt[5] = "!%x\0"; // '!' for nonzero count, null for modifier
size_t _Count;
size_t _Num;
string _Str;

if (_Modifier == '\0') {
_Fmt[2] = _Specifier;
} else { // add both modifier and specifier
_Fmt[2] = _Modifier;
_Fmt[3] = _Specifier;
if (_Iosbase.getloc() == locale::classic()) {
if (_Specifier == 'c') {
_Fmt_ptr = "!%a %b %e %T %Y";
} else if (_Specifier == 'r') {
_Fmt_ptr = "!%I:%M:%S %p";
}

@MattStephanson MattStephanson Jun 2, 2026

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The C Standard (N3685 7.31.3.6/7) and the informative "Application Usage" part of the POSIX spec both say that
"In the C [or POSIX] locale, the E and O modifiers are ignored". The UCRT is actually doing the opposite of this PR; it unconditionally replaces %r in the C locale but only replaces non-alternative %c (I don't have a link for this but you can find it in the UCRT expand_time source).

@ferhatgec ferhatgec Jun 2, 2026

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Thanks for the catch. I've made some changes, now in C locale, %r, %Er and %Or are treated in the same way.

}

if (!_Fmt_ptr) {
if (_Modifier == '\0') {
_Fmt[2] = _Specifier;
} else { // add both modifier and specifier
_Fmt[2] = _Modifier;
_Fmt[3] = _Specifier;
}
_Fmt_ptr = _Fmt;
}

int& _Errno_ref = errno; // Nonzero cost, pay it once
const int _Old_errno = _Errno_ref;

for (_Num = 16;; _Num *= 2) { // convert into ever larger string buffer until success
_Str.append(_Num, '\0');
_Count = _Strftime(&_Str[0], _Str.size(), _Fmt, _Pt, _Tnames._Getptr());
_Count = _Strftime(&_Str[0], _Str.size(), _Fmt_ptr, _Pt, _Tnames._Getptr());
if (0 < _Count) {
break;
} else if (_Errno_ref == EINVAL) {
Expand Down Expand Up @@ -1034,24 +1046,36 @@ protected:

virtual _OutIt __CLR_OR_THIS_CALL do_put(_OutIt _Dest, ios_base& _Iosbase, _Elem, const tm* _Pt, char _Specifier,
char _Modifier = '\0') const { // put formatted time from _Pt to _Dest for [_Fmtfirst, _Fmtlast)
wchar_t _Fmt[5] = L"!%x\0"; // ! for nonzero count, null for modifier
const wchar_t* _Fmt_ptr = nullptr;
wchar_t _Fmt[5] = L"!%x\0"; // ! for nonzero count, null for modifier
size_t _Count;
size_t _Num;
wstring _Str;

if (_Modifier == '\0') {
_Fmt[2] = static_cast<_Elem>(_Specifier); // conversion rule unspecified
} else { // add both modifier and specifier
_Fmt[2] = static_cast<_Elem>(_Modifier);
_Fmt[3] = static_cast<_Elem>(_Specifier);
if (_Iosbase.getloc() == locale::classic()) {
if (_Specifier == 'c') {
_Fmt_ptr = L"!%a %b %e %T %Y";
} else if (_Specifier == 'r') {
_Fmt_ptr = L"!%I:%M:%S %p";
}
}

if (!_Fmt_ptr) {
if (_Modifier == '\0') {
_Fmt[2] = static_cast<_Elem>(_Specifier);
} else {
_Fmt[2] = static_cast<_Elem>(_Modifier);
_Fmt[3] = static_cast<_Elem>(_Specifier);
}
_Fmt_ptr = _Fmt;
}

int& _Errno_ref = errno; // Nonzero cost, pay it once
const int _Old_errno = _Errno_ref;

for (_Num = 16;; _Num *= 2) { // convert into ever larger string buffer until success
_Str.append(_Num, '\0');
_Count = _Wcsftime(&_Str[0], _Str.size(), _Fmt, _Pt, _Tnames._Getptr());
_Count = _Wcsftime(&_Str[0], _Str.size(), _Fmt_ptr, _Pt, _Tnames._Getptr());
if (0 < _Count) {
break;
} else if (_Errno_ref == EINVAL) {
Expand Down Expand Up @@ -1183,24 +1207,36 @@ protected:

virtual _OutIt __CLR_OR_THIS_CALL do_put(_OutIt _Dest, ios_base& _Iosbase, _Elem, const tm* _Pt, char _Specifier,
char _Modifier = '\0') const { // put formatted time from _Pt to _Dest for [_Fmtfirst, _Fmtlast)
wchar_t _Fmt[5] = L"!%x\0"; // ! for nonzero count, null for modifier
const wchar_t* _Fmt_ptr = nullptr;
wchar_t _Fmt[5] = L"!%x\0"; // ! for nonzero count, null for modifier
size_t _Count;
size_t _Num;
wstring _Str;

if (_Modifier == '\0') {
_Fmt[2] = static_cast<_Elem>(_Specifier); // conversion rule unspecified
} else { // add both modifier and specifier
_Fmt[2] = static_cast<_Elem>(_Modifier);
_Fmt[3] = static_cast<_Elem>(_Specifier);
if (_Iosbase.getloc() == locale::classic()) {
if (_Specifier == 'c') {
_Fmt_ptr = L"!%a %b %e %T %Y";
} else if (_Specifier == 'r') {
_Fmt_ptr = L"!%I:%M:%S %p";
}
}

if (!_Fmt_ptr) {
if (_Modifier == '\0') {
_Fmt[2] = static_cast<_Elem>(_Specifier);
} else {
_Fmt[2] = static_cast<_Elem>(_Modifier);
_Fmt[3] = static_cast<_Elem>(_Specifier);
}
_Fmt_ptr = _Fmt;
}

int& _Errno_ref = errno; // Nonzero cost, pay it once
const int _Old_errno = _Errno_ref;

for (_Num = 16;; _Num *= 2) { // convert into ever larger string buffer until success
_Str.append(_Num, '\0');
_Count = _Wcsftime(&_Str[0], _Str.size(), _Fmt, _Pt, _Tnames._Getptr());
_Count = _Wcsftime(&_Str[0], _Str.size(), _Fmt_ptr, _Pt, _Tnames._Getptr());
if (0 < _Count) {
break;
} else if (_Errno_ref == EINVAL) {
Expand Down
3 changes: 0 additions & 3 deletions tests/libcxx/expected_results.txt
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Expand Up @@ -566,9 +566,6 @@ std/localization/locale.categories/category.time/locale.time.get/locale.time.get
std/localization/locale.categories/category.time/locale.time.get/locale.time.get.members/get_weekday.pass.cpp FAIL
std/localization/locale.categories/category.time/locale.time.get/locale.time.get.members/get_weekday_wide.pass.cpp FAIL

# GH-6134 <xloctime>: time_put::do_put does not match strftime for the %c and %r specifiers in the "C" locale
std/localization/locale.categories/category.time/locale.time.put/locale.time.put.members/put2.pass.cpp FAIL

# GH-6135 <xloctime>: time_put_byname doesn't encode the output in UTF-8 even if the locale name contains ".UTF-8"
std/localization/locale.categories/category.time/locale.time.put.byname/put1.pass.cpp FAIL

Expand Down
4 changes: 2 additions & 2 deletions tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1012,7 +1012,7 @@ void test_local_time_format_formatter() {
// Implements N4885 [time.zone.zonedtime.nonmembers]/2 for zoned_time.
empty_braces_helper(ltf, STR("2021-04-19 01:02:03 Meow"));

assert(format(STR("{:%c, %x, %X}"), ltf) == STR("04/19/21 01:02:03, 04/19/21, 01:02:03"));
assert(format(STR("{:%c, %x, %X}"), ltf) == STR("Mon Apr 19 01:02:03 2021, 04/19/21, 01:02:03"));
assert(format(STR("{:%D %F, %Y %C %y, %b %B %h %m, %d %e, %a %A %u %w}"), ltf)
== STR("04/19/21 2021-04-19, 2021 20 21, Apr April Apr 04, 19 19, Mon Monday 1 1"));
assert(format(STR("{:%H %I %M %S, %r, %R %T %p}"), ltf) == STR("01 01 02 03, 01:02:03 AM, 01:02 01:02:03 AM"));
Expand All @@ -1027,7 +1027,7 @@ void test_zoned_time_formatter() {

empty_braces_helper(zt, STR("2021-04-19 08:16:17 PDT"), STR("2021-04-19 08:16:17 GMT-7"));

assert(format(STR("{:%c, %x, %X}"), zt) == STR("04/19/21 08:16:17, 04/19/21, 08:16:17"));
assert(format(STR("{:%c, %x, %X}"), zt) == STR("Mon Apr 19 08:16:17 2021, 04/19/21, 08:16:17"));
assert(format(STR("{:%D %F, %Y %C %y, %b %B %h %m, %d %e, %a %A %u %w}"), zt)
== STR("04/19/21 2021-04-19, 2021 20 21, Apr April Apr 04, 19 19, Mon Monday 1 1"));
assert(format(STR("{:%H %I %M %S, %r, %R %T %p}"), zt) == STR("08 08 16 17, 08:16:17 AM, 08:16 08:16:17 AM"));
Expand Down