[clang] [Clang] Support libstdc++ workarounds when using `-E` (PR #210802)

[Aaron Ballman via cfe-commits]

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@@ -2989,8 +2994,13 @@ class Preprocessor {
   void HandlePragmaIncludeAlias(Token &Tok);
   void HandlePragmaModuleBuild(Token &Tok);
   void HandlePragmaHdrstop(Token &Tok);
+  void HandlePragmaSetPPState(PragmaIntroducer Introducer, Token &Tok);
   IdentifierInfo *ParsePragmaPushOrPopMacro(Token &Tok);
 
+  /// Check whether this is a macro name that can be used as an argument to
+  /// '#pragma clang __set_pp_state'.
+  bool isPragmaSetPPStateMacro(IdentifierInfo *II);
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AaronBallman wrote:

Do we want to make this an inline function given that it's just doing pointer comparisons that should be fine in the header?

https://github.com/llvm/llvm-project/pull/210802