Support formatting of std time_point with utc_clock (#3110)
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index ed7f5f1..1a8d8d0 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -22,6 +22,15 @@
FMT_BEGIN_NAMESPACE
+// Check if std::chrono::utc_timestamp is available.
+#ifndef FMT_USE_UTC_TIME
+# ifdef __cpp_lib_chrono
+# define FMT_USE_UTC_TIME (__cpp_lib_chrono >= 201907L)
+# else
+# define FMT_USE_UTC_TIME 0
+# endif
+#endif
+
// Enable tzset.
#ifndef FMT_USE_TZSET
// UWP doesn't provide _tzset.
@@ -2014,6 +2023,25 @@
}
};
+#if FMT_USE_UTC_TIME
+template <typename Char, typename Duration>
+struct formatter<std::chrono::time_point<std::chrono::utc_clock, Duration>,
+ Char> : formatter<std::tm, Char> {
+ FMT_CONSTEXPR formatter() {
+ basic_string_view<Char> default_specs =
+ detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>{};
+ this->do_parse(default_specs.begin(), default_specs.end());
+ }
+
+ template <typename FormatContext>
+ auto format(std::chrono::time_point<std::chrono::utc_clock> val,
+ FormatContext& ctx) const -> decltype(ctx.out()) {
+ return formatter<std::tm, Char>::format(
+ localtime(std::chrono::utc_clock::to_sys(val)), ctx);
+ }
+};
+#endif
+
template <typename Char> struct formatter<std::tm, Char> {
private:
enum class spec {
diff --git a/test/chrono-test.cc b/test/chrono-test.cc
index 0f2a249..bc474a4 100644
--- a/test/chrono-test.cc
+++ b/test/chrono-test.cc
@@ -641,3 +641,14 @@
}
#endif // FMT_STATIC_THOUSANDS_SEPARATOR
+
+// Disable the utc_clock test for windows, as the icu.dll used for tzdb
+// (time zone database) is not shipped with many windows versions.
+#if FMT_USE_UTC_TIME && !defined(_WIN32)
+TEST(chrono_test, utc_clock) {
+ auto t1 = std::chrono::system_clock::now();
+ auto t1_utc = std::chrono::utc_clock::from_sys(t1);
+ EXPECT_EQ(fmt::format("{:%Y-%m-%d %H:%M:%S}", t1),
+ fmt::format("{:%Y-%m-%d %H:%M:%S}", t1_utc));
+}
+#endif
