libstdc++: Avoid -Wswitch warning from chrono formatters

Add a default case to the switch to suppress warnings about unhandled
enumeration values. This is a consteval function, so if the default case
is ever reached it will be an error not silent miscompilation.

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (__formatter_duration::_S_spec_for):
	Add default case to switch and use __builtin_unreachable.

diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index bcf9830fb9e23890c28e5c0b0e3358b5c17283bb..72cd569ccd65dcf68b98073366fa3924f2117a6b 100644 (file)
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -1841,6 +1841,8 @@ namespace __format
              break;
            case _None:
              break;
+           default:
+             __builtin_unreachable();
            }
          return __res;
        };