[clang-tidy] Add a little checker for Twine locals in LLVM.

Those often cause use after free bugs and should be generally avoided.
Technically it is safe to have a Twine with >=2 components in a variable
but I don't think it is a good pattern to follow. The almost trivial checker
comes with elaborated fix-it hints that turn the Twine into a std::string
if necessary and otherwise fall back to the original type if the Twine
is created from a single value.

llvm-svn: 212535

1 files changed, 31 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h
new file mode 100644
index 00000000000..f538f81430c
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/llvm/TwineLocalCheck.h
@@ -0,0 +1,31 @@
+//===--- TwineLocalCheck.h - clang-tidy -------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H
+
+#include "../ClangTidy.h"
+#include "llvm/Support/Regex.h"
+
+namespace clang {
+namespace tidy {
+
+/// \brief Looks for local Twine variables which are prone to use after frees
+/// and should be generally avoided.
+class TwineLocalCheck : public ClangTidyCheck {
+public:
+  TwineLocalCheck();
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_LLVM_TWINE_LOCAL_CHECK_H