Cleanup pragma handlers after DoPrintPreprocessedInput

[teemperor]

Summary

The UnknownPragmaHandlers added by t`DoPrintPreprocessedInput` conflict with the real PragmaHandlers from clang::Parser because they try to handle the same #pragma directives. This makes it impossible to use a Preprocessor (that was previously passed to DoPrintPreprocessedInput), as an Preprocessor for a clang::Parser instance which is what we currently do in cling. This patch removes the added UnknownPragmaHandler to avoid conflicts these conflicts and leave the PragmaHandlers of the Preprocessors in a the same state as before calling DoPrintPreprocessedInput.

[yaron.keren]

Please move the =new out of the PP.AddPragmaHandler calls.
While at it, this code still (as the original) leaks the PragmaHandlers. These should be deleted after RemovePragmaHandler or instead, simply use std::unique_ptr.

[teemperor]

• Now using unique_ptr instead of raw pointers.

[yaron.keren]

LGTM

[yaron.keren]

Raphael , do you have commit access? should I commit this?

[v.g.vassilev]

Yaron, I can take care of this. Thanks for asking. Raphael and I are working together.

[yaron.keren]

OK

[v.g.vassilev]

Landed in r301563.

lib/Frontend/PrintPreprocessedOutput.cpp

void clang::DoPrintPreprocessedInput(Preprocessor &PP, raw_ostream *OS,
   PP.SetCommentRetentionState(Opts.ShowComments, Opts.ShowMacroComments);
 
   PrintPPOutputPPCallbacks *Callbacks = new PrintPPOutputPPCallbacks(
       PP, *OS, !Opts.ShowLineMarkers, Opts.ShowMacros,
       Opts.ShowIncludeDirectives, Opts.UseLineDirectives);
 
   // Expand macros in pragmas with -fms-extensions.  The assumption is that
   // the majority of pragmas in such a file will be Microsoft pragmas.
-  PP.AddPragmaHandler(new UnknownPragmaHandler(
+  // Remember the handlers we will add so that we can remove them later.
+  std::unique_ptr<UnknownPragmaHandler> MicrosoftExtHandler(
+      new UnknownPragmaHandler(
           "#pragma", Callbacks,
           /*RequireTokenExpansion=*/PP.getLangOpts().MicrosoftExt));
-  PP.AddPragmaHandler(
-      "GCC", new UnknownPragmaHandler(
-                 "#pragma GCC", Callbacks,
-                 /*RequireTokenExpansion=*/PP.getLangOpts().MicrosoftExt));
-  PP.AddPragmaHandler(
-      "clang", new UnknownPragmaHandler(
-                   "#pragma clang", Callbacks,
-                   /*RequireTokenExpansion=*/PP.getLangOpts().MicrosoftExt));
+
+  std::unique_ptr<UnknownPragmaHandler> GCCHandler(new UnknownPragmaHandler(
+
+  std::unique_ptr<UnknownPragmaHandler> ClangHandler(new UnknownPragmaHandler(
 
+  PP.AddPragmaHandler(MicrosoftExtHandler.get());
+  PP.AddPragmaHandler("GCC", GCCHandler.get());
+  PP.AddPragmaHandler("clang", ClangHandler.get());
+
   // The tokens after pragma omp need to be expanded.
   //
   //  OpenMP [2.1, Directive format]
   //  Preprocessing tokens following the #pragma omp are subject to macro
   //  replacement.
-  PP.AddPragmaHandler("omp",
-                      new UnknownPragmaHandler("#pragma omp", Callbacks,
-                                               /*RequireTokenExpansion=*/true));
+  std::unique_ptr<UnknownPragmaHandler> OpenMPHandler(
+  PP.AddPragmaHandler("omp", OpenMPHandler.get());
 
   PP.addPPCallbacks(std::unique_ptr<PPCallbacks>(Callbacks));
 
   // After we have configured the preprocessor, enter the main file.
   PP.EnterMainSourceFile();
 
   // Consume all of the tokens that come from the predefines buffer.  Those
   // should not be emitted into the output and are guaranteed to be at the
do {
 
     if (strcmp(PLoc.getFilename(), "<built-in>"))
       break;
   } while (true);
 
   // Read all the preprocessed tokens, printing them out to the stream.
   PrintPreprocessedTokens(PP, Tok, Callbacks, *OS);
   *OS << '\n';
+
+  // Remove the handlers we just added to leave the preprocessor in a sane state
+  // so that it can be reused (for example by a clang::Parser instance).
+  PP.RemovePragmaHandler(MicrosoftExtHandler.get());
+  PP.RemovePragmaHandler("GCC", GCCHandler.get());
+  PP.RemovePragmaHandler("clang", ClangHandler.get());
+  PP.RemovePragmaHandler("omp", OpenMPHandler.get());
 }