clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h

   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);
  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