1 //===--- DeclRefExprUtils.cpp - clang-tidy---------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "DeclRefExprUtils.h" 11 #include "clang/AST/ASTContext.h" 12 #include "clang/AST/DeclCXX.h" 13 #include "clang/ASTMatchers/ASTMatchFinder.h" 14 #include "llvm/ADT/SmallPtrSet.h" 15 16 namespace clang { 17 namespace tidy { 18 namespace decl_ref_expr_utils { 19 20 using namespace ::clang::ast_matchers; 21 using llvm::SmallPtrSet; 22 23 namespace { 24 25 template <typename S> bool isSetDifferenceEmpty(const S &S1, const S &S2) { 26 for (const auto &E : S1) 27 if (S2.count(E) == 0) 28 return false; 29 return true; 30 } 31 32 // Extracts all Nodes keyed by ID from Matches and inserts them into Nodes. 33 template <typename Node> 34 void extractNodesByIdTo(ArrayRef<BoundNodes> Matches, StringRef ID, 35 SmallPtrSet<const Node *, 16> &Nodes) { 36 for (const auto &Match : Matches) 37 Nodes.insert(Match.getNodeAs<Node>(ID)); 38 } 39 40 // Finds all DeclRefExprs to VarDecl in Stmt. 41 SmallPtrSet<const DeclRefExpr *, 16> 42 declRefExprs(const VarDecl &VarDecl, const Stmt &Stmt, ASTContext &Context) { 43 auto Matches = match( 44 findAll(declRefExpr(to(varDecl(equalsNode(&VarDecl)))).bind("declRef")), 45 Stmt, Context); 46 SmallPtrSet<const DeclRefExpr *, 16> DeclRefs; 47 extractNodesByIdTo(Matches, "declRef", DeclRefs); 48 return DeclRefs; 49 } 50 51 // Finds all DeclRefExprs where a const method is called on VarDecl or VarDecl 52 // is the a const reference or value argument to a CallExpr or CXXConstructExpr. 53 SmallPtrSet<const DeclRefExpr *, 16> 54 constReferenceDeclRefExprs(const VarDecl &VarDecl, const Stmt &Stmt, 55 ASTContext &Context) { 56 auto DeclRefToVar = 57 declRefExpr(to(varDecl(equalsNode(&VarDecl)))).bind("declRef"); 58 auto ConstMethodCallee = callee(cxxMethodDecl(isConst())); 59 // Match method call expressions where the variable is referenced as the this 60 // implicit object argument and opertor call expression for member operators 61 // where the variable is the 0-th argument. 62 auto Matches = match( 63 findAll(expr(anyOf(cxxMemberCallExpr(ConstMethodCallee, on(DeclRefToVar)), 64 cxxOperatorCallExpr(ConstMethodCallee, 65 hasArgument(0, DeclRefToVar))))), 66 Stmt, Context); 67 SmallPtrSet<const DeclRefExpr *, 16> DeclRefs; 68 extractNodesByIdTo(Matches, "declRef", DeclRefs); 69 auto ConstReferenceOrValue = 70 qualType(anyOf(referenceType(pointee(qualType(isConstQualified()))), 71 unless(anyOf(referenceType(), pointerType())))); 72 auto UsedAsConstRefOrValueArg = forEachArgumentWithParam( 73 DeclRefToVar, parmVarDecl(hasType(ConstReferenceOrValue))); 74 Matches = match(findAll(callExpr(UsedAsConstRefOrValueArg)), Stmt, Context); 75 extractNodesByIdTo(Matches, "declRef", DeclRefs); 76 Matches = 77 match(findAll(cxxConstructExpr(UsedAsConstRefOrValueArg)), Stmt, Context); 78 extractNodesByIdTo(Matches, "declRef", DeclRefs); 79 return DeclRefs; 80 } 81 82 } // namespace 83 84 bool isOnlyUsedAsConst(const VarDecl &Var, const Stmt &Stmt, 85 ASTContext &Context) { 86 // Collect all DeclRefExprs to the loop variable and all CallExprs and 87 // CXXConstructExprs where the loop variable is used as argument to a const 88 // reference parameter. 89 // If the difference is empty it is safe for the loop variable to be a const 90 // reference. 91 auto AllDeclRefs = declRefExprs(Var, Stmt, Context); 92 auto ConstReferenceDeclRefs = constReferenceDeclRefExprs(Var, Stmt, Context); 93 return isSetDifferenceEmpty(AllDeclRefs, ConstReferenceDeclRefs); 94 } 95 96 } // namespace decl_ref_expr_utils 97 } // namespace tidy 98 } // namespace clang 99