[clang] [llvm] [Sema] Implement support for -Wformat-signedness (PR #74440)

[Karl-Johan Karlsson via llvm-commits]

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@@ -11881,6 +11896,8 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
           ICE->getType() == S.Context.UnsignedIntTy) {
         // All further checking is done on the subexpression
         ImplicitMatch = AT.matchesType(S.Context, ExprTy);
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karka228 wrote:

After more testing I have found out that this call to AT.matchesTypes (row 11898) can introduce new normal -Wformat warnings that should not occur. This happens if the above call to AT.matchesTypes (row 11875) return ArgType::NoMatchSignedness that is not returned at this call to AT.matchesTypes (row 11898) as we are looking through the promoted int type, but instead we get ArgType::NoMatch returned.
This mean that if the original AT.matchesTypes at row 11875 return a signedness match then this this call to AT.matchesTypes (row 11898) also must return a signedness match for us to report a new warning, otherwise we might introduce unwanted warnings. I will update the code to fix this ...

https://github.com/llvm/llvm-project/pull/74440