1 //===--- UnnecessaryCopyInitialization.h - clang-tidy------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H 10 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H 11 12 #include "../ClangTidyCheck.h" 13 #include "clang/AST/Decl.h" 14 15 namespace clang::tidy::performance { 16 17 // The check detects local variable declarations that are copy initialized with 18 // the const reference of a function call or the const reference of a method 19 // call whose object is guaranteed to outlive the variable's scope and suggests 20 // to use a const reference. 21 // 22 // The check currently only understands a subset of variables that are 23 // guaranteed to outlive the const reference returned, namely: const variables, 24 // const references, and const pointers to const. 25 class UnnecessaryCopyInitialization : public ClangTidyCheck { 26 public: 27 UnnecessaryCopyInitialization(StringRef Name, ClangTidyContext *Context); isLanguageVersionSupported(const LangOptions & LangOpts)28 bool isLanguageVersionSupported(const LangOptions &LangOpts) const override{ 29 return LangOpts.CPlusPlus; 30 } 31 void registerMatchers(ast_matchers::MatchFinder *Finder) override; 32 void check(const ast_matchers::MatchFinder::MatchResult &Result) override; 33 void storeOptions(ClangTidyOptions::OptionMap &Opts) override; 34 35 protected: 36 // A helper to manipulate the state common to 37 // `CopyFromMethodReturn` and `CopyFromLocalVar`. 38 struct CheckContext { 39 const VarDecl &Var; 40 const Stmt &BlockStmt; 41 const DeclStmt &VarDeclStmt; 42 clang::ASTContext &ASTCtx; 43 const bool IssueFix; 44 const bool IsVarUnused; 45 const bool IsVarOnlyUsedAsConst; 46 }; 47 48 // Create diagnostics. These are virtual so that derived classes can change 49 // behaviour. 50 virtual void diagnoseCopyFromMethodReturn(const CheckContext &Ctx); 51 virtual void diagnoseCopyFromLocalVar(const CheckContext &Ctx, 52 const VarDecl &OldVar); 53 54 private: 55 void handleCopyFromMethodReturn(const CheckContext &Ctx, 56 const VarDecl *ObjectArg); 57 void handleCopyFromLocalVar(const CheckContext &Ctx, const VarDecl &OldVar); 58 59 void maybeIssueFixes(const CheckContext &Ctx, DiagnosticBuilder &Diagnostic); 60 61 const std::vector<StringRef> AllowedTypes; 62 const std::vector<StringRef> ExcludedContainerTypes; 63 }; 64 65 } // namespace clang::tidy::performance 66 67 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H 68