[PUSHED] libstdc++: Avoid '-Wunused-parameter' for '__what' in function 'void std::__throw_format_error(const char*)'

[Thomas Schwinge]

In a '-fno-exceptions' configuration:

    In file included from 
../../../../../source-gcc/libstdc++-v3/src/c++20/format.cc:29:
    [...]/build-gcc/[...]/libstdc++-v3/include/format: In function ‘void 
std::__throw_format_error(const char*)’:
    [...]/build-gcc/[...]/libstdc++-v3/include/format:200:36: error: unused 
parameter ‘__what’ [-Werror=unused-parameter]
      200 |   __throw_format_error(const char* __what)
          |                        ~~~~~~~~~~~~^~~~~~

        libstdc++-v3/
        * include/bits/c++config [!__cpp_exceptions]
        (_GLIBCXX_THROW_OR_ABORT): Reference '_EXC'.

Co-authored-by: Jonathan Wakely <jwak...@redhat.com>
---
 libstdc++-v3/include/bits/c++config | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/c++config 
b/libstdc++-v3/include/bits/c++config
index 6a73507d074..676f5eecbbb 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -261,7 +261,7 @@
 # if __cpp_exceptions
 #  define _GLIBCXX_THROW_OR_ABORT(_EXC) (throw (_EXC))
 # else
-#  define _GLIBCXX_THROW_OR_ABORT(_EXC) (__builtin_abort())
+#  define _GLIBCXX_THROW_OR_ABORT(_EXC) (__builtin_abort(), (void)(_EXC))
 # endif
 #endif
 
-- 
2.34.1