Disable _Pragma during HTML macro rewriting to keep from crashing.

The preprocessor's handling of diagnostic push/pops is stateful, so
encountering pragmas during a re-parse causes problems. HTMLRewrite
already filters out normal # directives including #pragma, so it's
clear it's not expected to be interpreting pragmas in this mode.

This fix adds a flag to Preprocessor to explicitly disable pragmas.
The "right" fix might be to separate pragma lexing from pragma
parsing so that we can throw away pragmas like we do preprocessor
directives, but right now it's important to get the fix in.

Note that this has nothing to do with the "hack" of re-using the
input preprocessor in HTMLRewrite. Even if we someday copy the
preprocessor instead of re-using it, the copy would (and should) include
the diagnostic level tables and have the same problems.

llvm-svn: 158214

clang/include/clang/Lex/Preprocessor.h

@@ -131,6 +131,9 @@ class Preprocessor : public RefCountedBase<Preprocessor> {
   /// \brief Whether we have already loaded macros from the external source.
   mutable bool ReadMacrosFromExternalSource : 1;
 
+  /// \brief True if pragmas are enabled.
+  bool PragmasEnabled : 1;
+
   /// \brief True if we are pre-expanding macro arguments.
   bool InMacroArgPreExpansion;
 
@@ -416,6 +419,9 @@ public:
 
   bool getCommentRetentionState() const { return KeepComments; }
 
+  void setPragmasEnabled(bool Enabled) { PragmasEnabled = Enabled; }
+  bool getPragmasEnabled() const { return PragmasEnabled; }
+
   void SetSuppressIncludeNotFoundError(bool Suppress) {
     SuppressIncludeNotFoundError = Suppress;
   }

clang/lib/Lex/Pragma.cpp

@@ -103,6 +103,9 @@ void PragmaNamespace::HandlePragma(Preprocessor &PP,
 /// HandlePragmaDirective - The "#pragma" directive has been parsed.  Lex the
 /// rest of the pragma, passing it to the registered pragma handlers.
 void Preprocessor::HandlePragmaDirective(unsigned Introducer) {
+  if (!PragmasEnabled)
+    return;
+
   ++NumPragma;
 
   // Invoke the first level of pragma handlers which reads the namespace id.

clang/lib/Lex/Preprocessor.cpp

@@ -90,7 +90,8 @@ Preprocessor::Preprocessor(DiagnosticsEngine &diags, LangOptions &opts,
   InMacroArgs = false;
   InMacroArgPreExpansion = false;
   NumCachedTokenLexers = 0;
-  
+  PragmasEnabled = true;
+
   CachedLexPos = 0;
   
   // We haven't read anything from the external source.

clang/lib/Rewrite/HTMLRewrite.cpp

@@ -495,6 +495,11 @@ void html::HighlightMacros(Rewriter &R, FileID FID, const Preprocessor& PP) {
   // Inform the preprocessor that we don't want comments.
   TmpPP.SetCommentRetentionState(false, false);
 
+  // We don't want pragmas either. Although we filtered out #pragma, removing
+  // _Pragma and __pragma is much harder.
+  bool PragmasPreviouslyEnabled = TmpPP.getPragmasEnabled();
+  TmpPP.setPragmasEnabled(false);
+
   // Enter the tokens we just lexed.  This will cause them to be macro expanded
   // but won't enter sub-files (because we removed #'s).
   TmpPP.EnterTokenStream(&TokenStream[0], TokenStream.size(), false, false);
@@ -571,6 +576,7 @@ void html::HighlightMacros(Rewriter &R, FileID FID, const Preprocessor& PP) {
                    "<span class='macro'>", Expansion.c_str());
   }
 
-  // Restore diagnostics object back to its own thing.
+  // Restore the preprocessor's old state.
   TmpPP.setDiagnostics(*OldDiags);
+  TmpPP.setPragmasEnabled(PragmasPreviouslyEnabled);
 }

clang/test/Misc/emit-html.c

@@ -16,3 +16,11 @@ int main(int argc, char **argv) {
   FOR_ALL_FILES(f) { }
 #endif
 
+// <rdar://problem/11625964>
+// -emit-html filters out # directives, but not _Pragma (or MS __pragma)
+// Diagnostic push/pop is stateful, so re-lexing a file can cause problems
+// if these pragmas are interpreted normally.
+_Pragma("clang diagnostic push")
+_Pragma("clang diagnostic ignored \"-Wformat-extra-args\"")
+_Pragma("clang diagnostic pop")
+