[clang] [Clang] Improve infrastructure for libstdc++ workarounds (PR #141977)

[Erich Keane via cfe-commits]

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@@ -979,3 +979,50 @@ Preprocessor::EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro,
   return EvaluateDirectiveExpression(IfNDefMacro, Tok, EvaluatedDefined,
                                      CheckForEoD);
 }
+
+static std::optional<CXXStandardLibraryVersionInfo>
+getCXXStandardLibraryVersion(Preprocessor &PP, StringRef MacroName,
+                             CXXStandardLibraryVersionInfo::Library Lib) {
+  MacroInfo *Macro = PP.getMacroInfo(PP.getIdentifierInfo(MacroName));
+
+  if (!Macro || Macro->getNumTokens() != 1)
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erichkeane wrote:

Should we also check `isObjectLike` here too?

https://github.com/llvm/llvm-project/pull/141977