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>

3 files changed, 90 insertions, 15 deletions

diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index 72cd569..75ee7e8 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -280,8 +280,8 @@ namespace __format
       // in the format-spec, e.g. "{:L%a}" is localized and locale-specific,
       // but "{:L}" is only localized and "{:%a}" is only locale-specific.
       unsigned _M_locale_specific : 1;
-      // Indicates that we are handling duration.
-      unsigned _M_time_only : 1;
+      // Indicates that we are handling time_point.
+      unsigned _M_time_point : 1;
       // Indicates that duration should be treated as floating point.
       unsigned _M_floating_point_rep : 1;
       // Indicate that duration uses user-defined representation.
@@ -693,8 +693,11 @@ namespace __format
 		  __allowed_mods = _Mod_O;
 		  break;
 		case 'j':
-		  __needed = __spec._M_time_only ? _HoursMinutesSeconds
-						 : _DayOfYear;
+		  __needed = __parts & _DayOfYear;
+		  // If we do not know day-of-year then we must have a duration,
+		  // which is to be formatted as decimal number of days.
+		  if (__needed == _None)
+		    __needed = _HoursMinutesSeconds;
 		  break;
 		case 'm':
 		  __needed = _Month;
@@ -919,7 +922,13 @@ namespace __format
       {
 	switch (__conv)
 	  {
+	  case 'a':
+	  case 'A':
+	  case 'b':
+	  case 'B':
 	  case 'c':
+	  case 'h':
+	  case 'p':
 	  case 'r':
 	  case 'x':
 	  case 'X':
@@ -947,6 +956,32 @@ namespace __format
 	  return __out;
 	}
 
+      void
+      _M_check_ok(const _ChronoData<_CharT>& __t, _CharT __conv) const
+      {
+	// n.b. for time point all date parts are computed, so
+	// they are always ok.
+	if (_M_spec._M_time_point || _M_spec._M_debug)
+	  return;
+
+	switch (__conv)
+	{
+	case 'a':
+	case 'A':
+	  if (!__t._M_weekday.ok()) [[unlikely]]
+	    __throw_format_error("format error: invalid weekday");
+	  return;
+	case 'b':
+	case 'h':
+	case 'B':
+	  if (!__t._M_month.ok()) [[unlikely]]
+	    __throw_format_error("format error: invalid month");
+	  return;
+	default:
+	  return;
+	}
+      }
+
       template<typename _OutIter, typename _FormatContext>
 	_OutIter
 	_M_format_to(const _ChronoData<_CharT>& __t, _OutIter __out,
@@ -1003,6 +1038,8 @@ namespace __format
 	  do
 	    {
 	      _CharT __c = *__first++;
+	      _M_check_ok(__t, __c);
+
 	      if (__use_locale_fmt && _S_localized_spec(__c, __mod)) [[unlikely]]
 		__out = _M_locale_fmt(std::move(__out), __fc.locale(),
 				      __tm, __c, __mod);
@@ -1153,11 +1190,8 @@ namespace __format
 	{
 	  // %a Locale's abbreviated weekday name.
 	  // %A Locale's full weekday name.
-	  if (!__wd.ok())
+	  if (_M_spec._M_debug && !__wd.ok())
 	    {
-	      if (!_M_spec._M_debug)
-		__throw_format_error("format error: invalid weekday");
-
 	      _CharT __buf[3];
 	      __out = __format::__write(std::move(__out),
 					_S_str_d1(__buf, __wd.c_encoding()));
@@ -1183,11 +1217,8 @@ namespace __format
 	{
 	  // %b Locale's abbreviated month name.
 	  // %B Locale's full month name.
-	  if (!__m.ok())
+	  if (_M_spec._M_debug && !__m.ok())
 	    {
-	      if (!_M_spec._M_debug)
-		__throw_format_error("format error: invalid month");
-
 	      _CharT __buf[3];
 	      __out = __format::__write(std::move(__out),
 					_S_str_d1(__buf, (unsigned)__m));
@@ -1419,7 +1450,7 @@ namespace __format
 	_OutIter
 	_M_j(const _ChronoData<_CharT>& __t, _OutIter __out) const
 	{
-	  if (_M_spec._M_time_only)
+	  if (!_M_spec._M_needs(_ChronoParts::_DayOfYear))
 	  {
 	    // Decimal number of days, without padding.
 	    auto __d = chrono::floor<chrono::days>(__t._M_hours).count();
@@ -1766,7 +1797,7 @@ namespace __format
       {
 	if (__n < 100) [[likely]]
 	  return _S_two_digits(__n);
-        return _S_str_d3(__buf, __n);
+	return _S_str_d3(__buf, __n);
       }
 
       // Returns decimal representation of __n, padded to 3 digits.
@@ -1811,7 +1842,7 @@ namespace __format
 	  using enum _ChronoParts;
 
 	  _ChronoSpec<_CharT> __res{};
-	  __res._M_time_only = (__parts & _Date) == 0;
+	  __res._M_time_point = (__parts & _DateTime) == _DateTime;
 	  __res._M_floating_point_rep = chrono::treat_as_floating_point_v<_Rep>;
 	  __res._M_custom_rep = !is_arithmetic_v<_Rep>;
 	  __res._M_prec = chrono::hh_mm_ss<_Duration>::fractional_width;
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");
+}