[gcc r15-9551] libstdc++: Fixed signed comparision in _M_parse_fill_and_align [PR119840]

[Tomasz Kaminski]

https://gcc.gnu.org/g:930b504b598864ba1774eb209a748ed76b6fc7c1

commit r15-9551-g930b504b598864ba1774eb209a748ed76b6fc7c1
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date:   Thu Apr 17 10:33:10 2025 +0200

    libstdc++: Fixed signed comparision in _M_parse_fill_and_align [PR119840]
    
    Explicitly cast elements of __not_fill to _CharT. Only '{' and ':'
    are used as `__not_fill`, so they are never negative.
    
            PR libstdc++/119840
    
    libstdc++-v3/ChangeLog:
    
            * include/std/format (_M_parse_fill_and_align): Cast elements of
            __not_fill to _CharT.

Diff:
---
 libstdc++-v3/include/std/format | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index f3fd837897bd..e557e104d74d 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -555,8 +555,8 @@ namespace __format
       constexpr iterator
       _M_parse_fill_and_align(iterator __first, iterator __last, string_view __not_fill) noexcept
       {
-	for (char c : __not_fill)
-	  if (*__first == c)
+	for (char __c : __not_fill)
+	  if (*__first == static_cast<_CharT>(__c))
 	    return __first;
 
 	using namespace __unicode;