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Don't require std::locale in chrono.h when FMT_USE_LOCALE is 0 #4921

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Don't require std::locale in chrono.h when FMT_USE_LOCALE is 0 #4921

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107 changes: 62 additions & 45 deletions include/fmt/chrono.h
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Original file line number Diff line number Diff line change
Expand Up @@ -407,6 +407,48 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
return write_encoded_tm_str(out, string_view(buf.data(), buf.size()), loc);
}

#if FMT_USE_LOCALE
// The locale used for localized formatting: the one passed to the formatting
// function or the global locale if none was passed.
inline auto get_locale(locale_ref loc, bool localized) -> std::locale {
if (!localized) return get_classic_locale();
return loc.get<std::locale>();
}

inline auto is_classic_locale(locale_ref loc, bool localized) -> bool {
return !localized || loc.get<std::locale>() == get_classic_locale();
}

template <typename Char, typename OutputIt>
auto write_localized_time(OutputIt out, const std::tm& time, locale_ref loc,
bool localized, char format, char modifier)
-> OutputIt {
return write<Char>(out, time, get_locale(loc, localized), format, modifier);
}

template <typename Char, typename OutputIt>
auto write_localized_str(OutputIt out, string_view sv, locale_ref loc,
bool localized) -> OutputIt {
return write_tm_str<Char>(out, sv, get_locale(loc, localized));
}
#else
constexpr auto is_classic_locale(locale_ref, bool) -> bool { return true; }

// Never called because is_classic_locale() is always true.
template <typename Char, typename OutputIt>
auto write_localized_time(OutputIt out, const std::tm&, locale_ref, bool, char,
char) -> OutputIt {
return out;
}

// Zone names are ASCII, so there is nothing to transcode.
template <typename Char, typename OutputIt>
auto write_localized_str(OutputIt out, string_view sv, locale_ref, bool)
-> OutputIt {
return copy<Char>(sv.data(), sv.data() + sv.size(), out);
}
#endif // FMT_USE_LOCALE

template <typename T, typename U>
using is_similar_arithmetic_type =
bool_constant<(std::is_integral<T>::value && std::is_integral<U>::value) ||
Expand Down Expand Up @@ -1045,7 +1087,8 @@ class tm_writer {
private:
static constexpr int days_per_week = 7;

const std::locale& loc_;
locale_ref loc_;
bool localized_;
bool is_classic_;
OutputIt out_;
const Duration* subsecs_;
Expand Down Expand Up @@ -1192,22 +1235,24 @@ class tm_writer {
template <typename T, FMT_ENABLE_IF(has_tm_zone<T>::value)>
void format_tz_name(const T& tm) {
if (!tm.tm_zone) FMT_THROW(format_error("no timezone"));
out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
out_ = write_localized_str<Char>(out_, tm.tm_zone, loc_, localized_);
}
template <typename T, FMT_ENABLE_IF(!has_tm_zone<T>::value)>
void format_tz_name(const T&) {
out_ = std::copy_n(utc(), 3, out_);
}

void format_localized(char format, char modifier = 0) {
out_ = write<Char>(out_, tm_, loc_, format, modifier);
out_ = write_localized_time<Char>(out_, tm_, loc_, localized_, format,
modifier);
}

public:
tm_writer(const std::locale& loc, OutputIt out, const std::tm& tm,
tm_writer(locale_ref loc, bool localized, OutputIt out, const std::tm& tm,
const Duration* subsecs = nullptr)
: loc_(loc),
is_classic_(loc_ == get_classic_locale()),
localized_(localized),
is_classic_(is_classic_locale(loc, localized)),
out_(out),
subsecs_(subsecs),
tm_(tm) {}
Expand Down Expand Up @@ -1583,31 +1628,6 @@ auto format_duration_unit(OutputIt out) -> OutputIt {
return out;
}

class get_locale {
private:
union {
std::locale locale_;
};
bool has_locale_ = false;

public:
inline get_locale(bool localized, locale_ref loc) : has_locale_(localized) {
if (!localized) return;
ignore_unused(loc);
::new (&locale_) std::locale(
#if FMT_USE_LOCALE
loc.template get<std::locale>()
#endif
);
}
inline ~get_locale() {
if (has_locale_) locale_.~locale();
}
inline operator const std::locale&() const {
return has_locale_ ? locale_ : get_classic_locale();
}
};

template <typename Char, typename Rep, typename Period>
struct duration_formatter {
using iterator = basic_appender<Char>;
Expand Down Expand Up @@ -1702,8 +1722,7 @@ struct duration_formatter {
template <typename Callback, typename... Args>
void format_tm(const tm& time, Callback cb, Args... args) {
if (isnan(val)) return write_nan();
get_locale loc(localized, locale);
auto w = tm_writer_type(loc, out, time);
auto w = tm_writer_type(locale, localized, out, time);
(w.*cb)(args...);
out = w.out();
}
Expand Down Expand Up @@ -1919,8 +1938,8 @@ struct formatter<weekday, Char> : private formatter<std::tm, Char> {
auto time = std::tm();
time.tm_wday = static_cast<int>(wd.c_encoding());
if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
detail::get_locale loc(false, ctx.locale());
auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
auto w = detail::tm_writer<decltype(ctx.out()), Char>(locale_ref(), false,
ctx.out(), time);
w.on_abbr_weekday();
return w.out();
}
Expand All @@ -1944,8 +1963,8 @@ struct formatter<day, Char> : private formatter<std::tm, Char> {
auto time = std::tm();
time.tm_mday = static_cast<int>(static_cast<unsigned>(d));
if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
detail::get_locale loc(false, ctx.locale());
auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
auto w = detail::tm_writer<decltype(ctx.out()), Char>(locale_ref(), false,
ctx.out(), time);
w.on_day_of_month(detail::numeric_system::standard, detail::pad_type::zero);
return w.out();
}
Expand All @@ -1969,8 +1988,8 @@ struct formatter<month, Char> : private formatter<std::tm, Char> {
auto time = std::tm();
time.tm_mon = static_cast<int>(static_cast<unsigned>(m)) - 1;
if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
detail::get_locale loc(false, ctx.locale());
auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
auto w = detail::tm_writer<decltype(ctx.out()), Char>(locale_ref(), false,
ctx.out(), time);
w.on_abbr_month();
return w.out();
}
Expand All @@ -1994,8 +2013,8 @@ struct formatter<year, Char> : private formatter<std::tm, Char> {
auto time = std::tm();
time.tm_year = static_cast<int>(y) - 1900;
if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
detail::get_locale loc(false, ctx.locale());
auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
auto w = detail::tm_writer<decltype(ctx.out()), Char>(locale_ref(), false,
ctx.out(), time);
w.on_year(detail::numeric_system::standard, detail::pad_type::zero);
return w.out();
}
Expand All @@ -2022,8 +2041,8 @@ struct formatter<year_month_day, Char> : private formatter<std::tm, Char> {
time.tm_mon = static_cast<int>(static_cast<unsigned>(val.month())) - 1;
time.tm_mday = static_cast<int>(static_cast<unsigned>(val.day()));
if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
detail::get_locale loc(true, ctx.locale());
auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
auto w = detail::tm_writer<decltype(ctx.out()), Char>(locale_ref(), false,
ctx.out(), time);
w.on_iso_date();
return w.out();
}
Expand Down Expand Up @@ -2140,10 +2159,8 @@ template <typename Char> struct formatter<std::tm, Char> {
detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
ctx);

auto loc_ref = specs.localized() ? ctx.locale() : locale_ref();
detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
auto w = detail::tm_writer<basic_appender<Char>, Char, Duration>(
loc, out, tm, subsecs);
ctx.locale(), specs.localized(), out, tm, subsecs);
detail::parse_chrono_format(fmt_.begin(), fmt_.end(), w);
return detail::write(
ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
Expand Down
4 changes: 4 additions & 0 deletions test/chrono-test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -717,6 +717,9 @@ TEST(chrono_test, weekday) {
EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L}", sat)));
EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L%a}", sat)));
EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L%a}", tm)));
// Without an explicit locale the global one is used.
EXPECT_THAT(saturdays, Contains(fmt::format("{:L}", sat)));
EXPECT_THAT(saturdays, Contains(fmt::format("{:L%a}", tm)));
}
}

Expand Down Expand Up @@ -1038,5 +1041,6 @@ TEST(chrono_test, year_month_day) {
auto months = std::vector<std::string>{"ene.", "ene"};
EXPECT_THAT(months, Contains(fmt::format(loc, "{:L}", month)));
EXPECT_THAT(months, Contains(fmt::format(loc, "{:L%b}", month)));
EXPECT_THAT(months, Contains(fmt::format("{:L}", month)));
}
}
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