[PATCH] [clang-tidy] Add a checker that warns on const string & members.

[Benjamin Kramer]

Hi alexfh, djasper,

Those are considered unsafe and should be replaced with simple pointers or
full copies. It recognizes both std::string and ::string.

http://reviews.llvm.org/D4522

Files:
  clang-tidy/google/CMakeLists.txt
  clang-tidy/google/GoogleTidyModule.cpp
  clang-tidy/google/MemberStringReferencesCheck.cpp
  clang-tidy/google/MemberStringReferencesCheck.h

Index: clang-tidy/google/CMakeLists.txt
===================================================================
--- clang-tidy/google/CMakeLists.txt
+++ clang-tidy/google/CMakeLists.txt
@@ -5,6 +5,7 @@
   ExplicitConstructorCheck.cpp
   ExplicitMakePairCheck.cpp
   GoogleTidyModule.cpp
+  MemberStringReferencesCheck.cpp
   NamedParameterCheck.cpp
   OverloadedUnaryAndCheck.cpp
 
Index: clang-tidy/google/GoogleTidyModule.cpp
===================================================================
--- clang-tidy/google/GoogleTidyModule.cpp
+++ clang-tidy/google/GoogleTidyModule.cpp
@@ -13,6 +13,7 @@
 #include "AvoidCStyleCastsCheck.h"
 #include "ExplicitConstructorCheck.h"
 #include "ExplicitMakePairCheck.h"
+#include "MemberStringReferencesCheck.h"
 #include "NamedParameterCheck.h"
 #include "OverloadedUnaryAndCheck.h"
 
@@ -31,6 +32,9 @@
         "google-explicit-constructor",
         new ClangTidyCheckFactory<ExplicitConstructorCheck>());
     CheckFactories.addCheckFactory(
+        "google-runtime-member-string-references",
+        new ClangTidyCheckFactory<runtime::MemberStringReferencesCheck>());
+    CheckFactories.addCheckFactory(
         "google-runtime-operator",
         new ClangTidyCheckFactory<runtime::OverloadedUnaryAndCheck>());
     CheckFactories.addCheckFactory(
Index: clang-tidy/google/MemberStringReferencesCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/google/MemberStringReferencesCheck.cpp
@@ -0,0 +1,48 @@
+//===--- MemberStringReferenceCheck.cpp - clang-tidy ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MemberStringReferencesCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/AST/ASTContext.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace runtime {
+
+void MemberStringReferencesCheck::registerMatchers(
+    ast_matchers::MatchFinder *Finder) {
+  // Look for const references to std::string or ::string.
+  auto String = anyOf(recordDecl(hasName("::std::basic_string")),
+                      recordDecl(hasName("::string")));
+  auto ConstString = qualType(isConstQualified(), hasDeclaration(String));
+
+  // Ignore members in templates.
+  auto InTemplate = hasAncestor(
+      decl(anyOf(recordDecl(ast_matchers::isTemplateInstantiation()),
+                 functionDecl(ast_matchers::isTemplateInstantiation()))));
+
+  Finder->addMatcher(fieldDecl(hasType(references(ConstString)),
+                               unless(InTemplate)).bind("member"),
+                     this);
+}
+
+void
+MemberStringReferencesCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Member = Result.Nodes.getNodeAs<FieldDecl>("member");
+  diag(Member->getLocStart(), "const string& members are dangerous. It is much "
+                              "better to use alternatives, such as pointers or "
+                              "simple constants.");
+}
+
+} // namespace runtime
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/google/MemberStringReferencesCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/google/MemberStringReferencesCheck.h
@@ -0,0 +1,36 @@
+//===--- MemberStringReferenceCheck.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_GOOGLE_MEMBER_STRING_REF_CHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_MEMBER_STRING_REF_CHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace runtime {
+
+/// \brief Finds members of type 'const string&'.
+///
+/// const string reference members are generally considered unsafe. This check
+/// emit warnings for both std::string and ::string const reference members.
+///
+/// http://www.corp.google.com/eng/doc/devguide/cpp/primer.html#reference_members
+/// Corresponding cpplint.py check name: 'runtime/member_string_reference'.
+class MemberStringReferencesCheck : public ClangTidyCheck {
+public:
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace runtime
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_MEMBER_STRING_REF_CHECK_H

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