[gcc r15-9876] libstdc++: Report compilation error on formatting "%d" from month_last [PR120650]

[Tomasz Kaminski]

https://gcc.gnu.org/g:53d2ca1541b34bb2f840d5aede9b826025dd0bb7

commit r15-9876-g53d2ca1541b34bb2f840d5aede9b826025dd0bb7
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date:   Tue Jun 24 09:17:12 2025 +0200

    libstdc++: Report compilation error on formatting "%d" from month_last [PR120650]
    
    For month_day we incorrectly reported day information to be available, which lead
    to format_error being thrown from the call to formatter::format at runtime, instead
    of making call to format ill-formed.
    
            PR libstdc++/120650
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/chrono_io.h
            (formatter<chrono::month_day_last,_CharT>::parse): Call _M_parse with
            only Month being available.
    
    (cherry picked from commit 190aaaaf077fe5f318e168a7a1e1aa57058f377e)

Diff:
---
 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 32ef3533c720..e9e6a440efb2 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -1905,7 +1905,7 @@ namespace __format
     {
       constexpr typename basic_format_parse_context<_CharT>::iterator
       parse(basic_format_parse_context<_CharT>& __pc)
-      { return _M_f._M_parse(__pc, __format::_Month|__format::_Day); }
+      { return _M_f._M_parse(__pc, __format::_Month); }
 
       template<typename _Out>
 	typename basic_format_context<_Out, _CharT>::iterator