[committed] libstdc++: Fix regression in std::format output of %Y for negative years

[Jonathan Wakely]

It seems that what I pushed didn't match what I tested, due to testing
on a different machine!

Tested x86_64-linux, on the right machine this time. Pushed to trunk.

-- >8 --

The change in r14-6468-ga01462ae8bafa8 was only supposed to apply to %C
formats, not %Y.

libstdc++-v3/ChangeLog:

        * include/bits/chrono_io.h (__formatter_chrono::_M_C_y_Y): Do
        not round century down for %Y formats.
---
 libstdc++-v3/include/bits/chrono_io.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/chrono_io.h 
b/libstdc++-v3/include/bits/chrono_io.h
index b63b8592eba..bcd76e4ab7b 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -825,7 +825,7 @@ namespace __format
                {
                  __s.assign(1, _S_plus_minus[1]);
                  // For floored division -123//100 is -2 and -100//100 is -1
-                 if ((__ci * 100) != __yi)
+                 if (__conv == 'C' && (__ci * 100) != __yi)
                    ++__ci;
                }
              if (__ci >= 100) [[unlikely]]
-- 
2.43.0