[PATCH] Expose AST language options to checkers

[aaron.ballman]

Summary

Some of the checkers need to know what language options are enabled in order to behave sensibly. For instance, the modernize-use-nullptr checker should not suggest use of nullptr when the file being checked is a C file, not a C++ file.

This patch exposes the language options to checkers, and corrects the bug with modernize-use-nullptr by only registering the matcher if C++11 language features are enabled.

~Aaron

[alexfh]

Looks good .Thanks for fixing this!

BTW, there are other checks that use LangOpts in the check() method. IIRC, misc-use-override, google-readabiity-casting and maybe something else. We need to fix those as well.

[aaron.ballman]

Thanks! I've commit in r246209.

I plan to do a more thorough search of clang-tidy to see what else can make use of this feature, this just happened to be low-hanging fruit that I found today by accident.

~Aaron

clang-tidy/ClangTidy.h

   OptionsView Options;
   /// \brief Returns the main file name of the current translation unit.
   StringRef getCurrentMainFile() const { return Context->getCurrentFile(); }
+  /// \brief Returns the language options from the context.
+  LangOptions getLangOpts() const { return Context->getLangOpts(); }
 };
 
 class ClangTidyCheckFactories;

clang-tidy/ClangTidyDiagnosticConsumer.h

   /// \brief Sets ASTContext for the current translation unit.
   void setASTContext(ASTContext *Context);
 
+  /// \brief Gets the language options from the AST context
+  LangOptions getLangOpts() const { return LangOpts; }
+
   /// \brief Returns the name of the clang-tidy check which produced this
   /// diagnostic ID.
   StringRef getCheckName(unsigned DiagnosticID) const;

   ClangTidyOptions CurrentOptions;
   std::unique_ptr<GlobList> CheckFilter;
 
+  LangOptions LangOpts;
+
   ClangTidyStats Stats;
 
   llvm::DenseMap<unsigned, std::string> CheckNamesByDiagnosticID;

clang-tidy/ClangTidyDiagnosticConsumer.cpp

 
 void ClangTidyContext::setASTContext(ASTContext *Context) {
   DiagEngine->SetArgToStringFn(&FormatASTNodeDiagnosticArgument, Context);
+  LangOpts = Context->getLangOpts();
 }
 
 const ClangTidyGlobalOptions &ClangTidyContext::getGlobalOptions() const {

clang-tidy/modernize/UseNullptrCheck.cpp

 }
 
 void UseNullptrCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(makeCastSequenceMatcher(), this);
+  // Only register the matcher for C++11.
+  if (getLangOpts().CPlusPlus11)
+    Finder->addMatcher(makeCastSequenceMatcher(), this);
 }
 
 void UseNullptrCheck::check(const MatchFinder::MatchResult &Result) {

test/clang-tidy/modernize-use-nullptr.c

+// RUN: clang-tidy %s -checks=-*,modernize-use-nullptr -- | count 0
+
+// Note: this test expects no diagnostics, but FileCheck cannot handle that,
+// hence the use of | count 0.
+
+#define NULL 0
+void f(void) {
+  char *str = NULL; // ok
+  (void)str;
+}