[clang-tidy ObjC] [2/3] Support non-C++ files in ClangTidyTest

[benhamilton]

Summary

This is part 2 of 3 of a series of changes to improve
Objective-C linting in clang-tidy.

Currently, clang::tidy::test::runCheckOnCode() assumes all files
are C++ and unconditionally adds -std=c++11 to the list of
clang-tidy options.

This updates the logic to check the extension of the source file
and only add -std=c++11 if the extension indicates C++ or
Objective-C++.

Depends On D39188

Test Plan:

ninja ClangTidyTests && \
./tools/clang/tools/extra/unittests/clang-tidy/ClangTidyTests

[hokein]

LGTM.

unittests/clang-tidy/ClangTidyTest.h

90

nit: how about

std::string FilenameStr = Filename.str();
auto extension = llvm::sys::path::extension(FilenameStr);

?

[benhamilton]

• @hokein: Tidy up llvm::sys::path::extension call

[benhamilton]

unittests/clang-tidy/ClangTidyTest.h

90

I was trying to avoid a copy:

Twine -> StringRef -> llvm::sys::path::extension()

vs.

Twine -> StringRef -> std::string -> StringRef -> llvm::sys::path::extension()

but I guess readability is more important here. :)

Changed to:

auto extension = llvm::sys::path::extension(Filename.str());

[hokein]

unittests/clang-tidy/ClangTidyTest.h

90

The new change auto extension = llvm::sys::path::extension(Filename.str()); will have use-after-scope problem.

The std::string constructed from Filename.str() will be destructed after this statement, however, extension is a StringRef, which points to the std::string, bad things can happen when accessing the extension variable.

The original version is fine, because we hold the string memory in the SmallVector<char, 10> FilenameChars.

[benhamilton]

• @hokein: Fix use-after-free

unittests/clang-tidy/ClangTidyTest.h

90

Thank you for noticing, fixed.

[hokein]

Still LGTM.

unittests/clang-tidy/ClangTidyTest.h

 #include "ClangTidy.h"
 #include "ClangTidyDiagnosticConsumer.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Tooling/Refactoring.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/Support/Path.h"
 #include <map>
 #include <memory>
 
 namespace clang {
 namespace tidy {
 namespace test {
 
 class TestClangTidyAction : public ASTFrontendAction {
runCheckOnCode(StringRef Code, std::vector<ClangTidyError> *Errors = nullptr,
                std::map<StringRef, StringRef> PathsToContent =
                    std::map<StringRef, StringRef>()) {
   ClangTidyOptions Options = ExtraOptions;
   Options.Checks = "*";
   ClangTidyContext Context(llvm::make_unique<DefaultOptionsProvider>(
       ClangTidyGlobalOptions(), Options));
   ClangTidyDiagnosticConsumer DiagConsumer(Context);
 
-  std::vector<std::string> ArgCXX11(1, "clang-tidy");
-  ArgCXX11.push_back("-fsyntax-only");
-  ArgCXX11.push_back("-std=c++11");
-  ArgCXX11.push_back("-Iinclude");
-  ArgCXX11.insert(ArgCXX11.end(), ExtraArgs.begin(), ExtraArgs.end());
-  ArgCXX11.push_back(Filename.str());
+  std::vector<std::string> Args(1, "clang-tidy");
+  Args.push_back("-fsyntax-only");
+  auto extension = llvm::sys::path::extension(Filename.str());
+  if (extension == ".m" || extension == ".mm") {
+    Args.push_back("-fobjc-abi-version=2");
+    Args.push_back("-fobjc-arc");
+  }
+  if (extension == ".cc" || extension == ".cpp" || extension == ".mm") {
+    Args.push_back("-std=c++11");
+  }
+  Args.push_back("-Iinclude");
+  Args.insert(Args.end(), ExtraArgs.begin(), ExtraArgs.end());
+  Args.push_back(Filename.str());
 
   ast_matchers::MatchFinder Finder;
   llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
       new vfs::InMemoryFileSystem);
   llvm::IntrusiveRefCntPtr<FileManager> Files(
       new FileManager(FileSystemOptions(), InMemoryFileSystem));
 
   SmallVector<std::unique_ptr<ClangTidyCheck>, 1> Checks;
   CheckFactory<CheckList...>::createChecks(&Context, Checks);
   tooling::ToolInvocation Invocation(
-      ArgCXX11, new TestClangTidyAction(Checks, Finder, Context), Files.get());
+      Args, new TestClangTidyAction(Checks, Finder, Context), Files.get());
   InMemoryFileSystem->addFile(Filename, 0,
                               llvm::MemoryBuffer::getMemBuffer(Code));
   for (const auto &FileContent : PathsToContent) {
     InMemoryFileSystem->addFile(
         Twine("include/") + FileContent.first, 0,
         llvm::MemoryBuffer::getMemBuffer(FileContent.second));
   }
   Invocation.setDiagnosticConsumer(&DiagConsumer);