[PATCH 4/4] libstdc++: Avoid '-Wunused-parameter' for 'out' in member function 'std::codecvt_base::result std::__format::{anonymous}::__encoding::conv(std::string_view, std::string&) const'

[Thomas Schwinge]

In a newlib configuration:

    ../../../../../source-gcc/libstdc++-v3/src/c++20/format.cc: In member function ‘std::codecvt_base::result std::__format::{anonymous}::__encoding::conv(std::string_view, std::string&) const’:
    ../../../../../source-gcc/libstdc++-v3/src/c++20/format.cc:100:35: error: unused parameter ‘out’ [-Werror=unused-parameter]
      100 |   conv(string_view input, string& out) const
          |                           ~~~~~~~~^~~

	libstdc++-v3/
	* src/c++20/format.cc (conv): Tag 'out' as '[[maybe_unused]]'.
---
 libstdc++-v3/src/c++20/format.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/src/c++20/format.cc b/libstdc++-v3/src/c++20/format.cc
index 1a24fcab7f7..6967d53259d 100644
--- a/libstdc++-v3/src/c++20/format.cc
+++ b/libstdc++-v3/src/c++20/format.cc
@@ -97,7 +97,7 @@ struct __encoding : locale::facet
 
   // Convert `input` to UTF-8, using `out` to hold the result.
   codecvt_base::result
-  conv(string_view input, string& out) const
+  conv(string_view input, [[maybe_unused]] string& out) const
   {
     if (input.empty()) [[unlikely]]
       return codecvt_base::noconv;
-- 
2.34.1