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

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

Reviewers: alexfh, djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4522

llvm-svn: 213133

clang-tools-extra/clang-tidy/google/CMakeLists.txt

@@ -7,6 +7,7 @@ add_clang_library(clangTidyGoogleModule
   GoogleTidyModule.cpp
   NamedParameterCheck.cpp
   OverloadedUnaryAndCheck.cpp
+  StringReferenceMemberCheck.cpp
 
   LINK_LIBS
   clangAST

clang-tools-extra/clang-tidy/google/GoogleTidyModule.cpp

@@ -15,6 +15,7 @@
 #include "ExplicitMakePairCheck.h"
 #include "NamedParameterCheck.h"
 #include "OverloadedUnaryAndCheck.h"
+#include "StringReferenceMemberCheck.h"
 
 using namespace clang::ast_matchers;
 
@@ -33,6 +34,9 @@ public:
     CheckFactories.addCheckFactory(
         "google-runtime-operator",
         new ClangTidyCheckFactory<runtime::OverloadedUnaryAndCheck>());
+    CheckFactories.addCheckFactory(
+        "google-runtime-member-string-references",
+        new ClangTidyCheckFactory<runtime::StringReferenceMemberCheck>());
     CheckFactories.addCheckFactory(
         "google-readability-casting",
         new ClangTidyCheckFactory<readability::AvoidCStyleCastsCheck>());

clang-tools-extra/clang-tidy/google/StringReferenceMemberCheck.cpp

@@ -0,0 +1,48 @@
+//===--- StringReferenceMemberCheck.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 "StringReferenceMemberCheck.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 StringReferenceMemberCheck::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 template instantiations.
+  auto InTemplateInstantiation = hasAncestor(
+      decl(anyOf(recordDecl(ast_matchers::isTemplateInstantiation()),
+                 functionDecl(ast_matchers::isTemplateInstantiation()))));
+
+  Finder->addMatcher(fieldDecl(hasType(references(ConstString)),
+                               unless(InTemplateInstantiation)).bind("member"),
+                     this);
+}
+
+void
+StringReferenceMemberCheck::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

clang-tools-extra/clang-tidy/google/StringReferenceMemberCheck.h

@@ -0,0 +1,50 @@
+//===--- StringReferenceMemberCheck.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_STRING_REF_MEMBER_CHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_GOOGLE_STRING_REF_MEMBER_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 as they can
+/// be created from a temporary quite easily.
+///
+/// \code
+/// struct S {
+///  S(const string &Str) : Str(Str) {}
+///  const string &Str;
+/// };
+/// S instance("string");
+/// \endcode
+///
+/// In the constructor call a string temporary is created from const char * and
+/// destroyed immediately after the call. This leaves around a dangling
+/// reference.
+///
+/// This check emit warnings for both std::string and ::string const reference
+/// members.
+///
+/// Corresponding cpplint.py check name: 'runtime/member_string_reference'.
+class StringReferenceMemberCheck : 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_STRING_REF_MEMBER_CHECK_H

clang-tools-extra/test/clang-tidy/google-member-string-references.cpp

@@ -0,0 +1,49 @@
+// RUN: clang-tidy %s -checks='-*,google-runtime-member-string-references' -- | FileCheck %s -implicit-check-not="{{warning|error}}:"
+
+namespace std {
+template<typename T>
+  class basic_string {};
+
+typedef basic_string<char> string;
+}
+
+class string {};
+
+
+struct A {
+  const std::string &s;
+// CHECK: :[[@LINE-1]]:3: warning: const string& members are dangerous. It is much better to use alternatives, such as pointers or simple constants.
+};
+
+struct B {
+  std::string &s;
+};
+
+struct C {
+  const std::string s;
+};
+
+template <typename T>
+struct D {
+  D();
+  const T &s;
+  const std::string &s2;
+// CHECK: :[[@LINE-1]]:3: warning: const string& members are dangerous. It is much better to use alternatives, such as pointers or simple constants.
+};
+
+D<std::string> d;
+
+struct AA {
+  const string &s;
+// CHECK: :[[@LINE-1]]:3: warning: const string& members are dangerous. It is much better to use alternatives, such as pointers or simple constants.
+};
+
+struct BB {
+  string &s;
+};
+
+struct CC {
+  const string s;
+};
+
+D<string> dd;