libstdc++: Format chrono %a/%A/%b/%h/%B/%p using locale's time_put [PR117214]

C++ formatting locale could have a custom time_put that performs
differently from the C locale, so do not use __timepunct directly,
instead all of above specifiers use _M_locale_fmt.

For %a/%A/%b/%h/%B, the code handling the exception is now moved
to the _M_check_ok function, that is invoked before handling of the
conversion specifier. For time_points the values of months/weekday
are computed, and thus are always ok(), this information is indicated
by new _M_time_point member of the _ChronoSpec.

The different behavior of j specifier for durations and time_points/calendar
types, is now handled using only _ChronoParts, and _M_time_only in _ChronoSpec
is no longer needed, thus it was removed.

	PR libstdc++/117214

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (_ChronoSpec::_M_time_only): Remove.
	(_ChronoSpec::_M_time_point): Define.
	(__formatter_chrono::_M_parse): Use __parts to determine
	interpretation of j.
	(__formatter_chrono::_M_check_ok): Define.
	(__formatter_chrono::_M_format_to): Invoke _M_check_ok.
	(__formatter_chrono::_M_a_A, __formatter_chrono::_M_b_B): Move
	exception throwing to _M_check_ok.
	(__formatter_chrono::_M_j): Use _M_needs to define interpretation.
	(__formatter_duration::_S_spec_for): Set _M_time_point.
	* testsuite/std/time/format/format.cc: Test for exception for !ok()
	months/weekday.
	* testsuite/std/time/format/pr117214_custom_timeput.cc: New
	test.

Co-authored-by: Tomasz Kaminski <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: XU Kailiang <xu2k3l4@outlook.com>
Signed-off-by: Tomasz Kaminski <tkaminsk@redhat.com>

2 files changed, 44 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/std/time/format/format.cc b/libstdc++-v3/testsuite/std/time/format/format.cc
index d6e3583..00affb9 100644
--- a/libstdc++-v3/testsuite/std/time/format/format.cc
+++ b/libstdc++-v3/testsuite/std/time/format/format.cc
@@ -78,6 +78,13 @@ test_bad_format_strings()
   VERIFY( not is_format_string_for("{:%OOy}", t) );
   VERIFY( not is_format_string_for("{:%OEy}", t) );
   VERIFY( not is_format_string_for("{:%EOy}", t) );
+
+  // weekday and month values for which ok() is false
+  VERIFY( not is_format_string_for("{:%a}", std::chrono::weekday(8)) );
+  VERIFY( not is_format_string_for("{:%A}", std::chrono::weekday(8)) );
+  VERIFY( not is_format_string_for("{:%b}", std::chrono::month(13)) );
+  VERIFY( not is_format_string_for("{:%h}", std::chrono::month(13)) );
+  VERIFY( not is_format_string_for("{:%B}", std::chrono::month(13)) );
 }
 
 template<typename I>
diff --git a/libstdc++-v3/testsuite/std/time/format/pr117214_custom_timeput.cc b/libstdc++-v3/testsuite/std/time/format/pr117214_custom_timeput.cc
new file mode 100644
index 0000000..03b9496
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/format/pr117214_custom_timeput.cc
@@ -0,0 +1,37 @@
+// { dg-do run { target c++20 } }
+
+#include <chrono>
+#include <format>
+#include <locale>
+#include <testsuite_hooks.h>
+
+struct custom_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>;
+
+    switch (format) {
+	case 'a': case 'A': case 'b': case 'h': case 'B': case 'p':
+	*out++ = '[';
+	*out++ = format;
+	*out++ = ']';
+    }
+    return Base::do_put(out, io, fill, t, format, modifier);
+  }
+};
+
+int main()
+{
+  using namespace std::chrono;
+  std::locale loc(std::locale::classic(), new custom_time_put);
+#define test(t, fmt, exp) VERIFY( std::format(loc, fmt, t) == exp )
+  test(Monday,  "{:L%a}", "[a]Mon");
+  test(Monday,  "{:L%A}", "[A]Monday");
+  test(January, "{:L%b}", "[b]Jan");
+  test(January, "{:L%h}", "[h]Jan");
+  test(January, "{:L%B}", "[B]January");
+  test(1h,      "{:L%p}", "[p]AM");
+}