1 //===--- UnhandledSelfAssignmentCheck.cpp - clang-tidy --------------------===// 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 #include "UnhandledSelfAssignmentCheck.h" 10 #include "clang/AST/ASTContext.h" 11 #include "clang/ASTMatchers/ASTMatchFinder.h" 12 13 using namespace clang::ast_matchers; 14 15 namespace clang::tidy::bugprone { 16 17 UnhandledSelfAssignmentCheck::UnhandledSelfAssignmentCheck( 18 StringRef Name, ClangTidyContext *Context) 19 : ClangTidyCheck(Name, Context), 20 WarnOnlyIfThisHasSuspiciousField( 21 Options.get("WarnOnlyIfThisHasSuspiciousField", true)) {} 22 23 void UnhandledSelfAssignmentCheck::storeOptions( 24 ClangTidyOptions::OptionMap &Opts) { 25 Options.store(Opts, "WarnOnlyIfThisHasSuspiciousField", 26 WarnOnlyIfThisHasSuspiciousField); 27 } 28 29 void UnhandledSelfAssignmentCheck::registerMatchers(MatchFinder *Finder) { 30 // We don't care about deleted, default or implicit operator implementations. 31 const auto IsUserDefined = cxxMethodDecl( 32 isDefinition(), unless(anyOf(isDeleted(), isImplicit(), isDefaulted()))); 33 34 // We don't need to worry when a copy assignment operator gets the other 35 // object by value. 36 const auto HasReferenceParam = 37 cxxMethodDecl(hasParameter(0, parmVarDecl(hasType(referenceType())))); 38 39 // Self-check: Code compares something with 'this' pointer. We don't check 40 // whether it is actually the parameter what we compare. 41 const auto HasNoSelfCheck = cxxMethodDecl(unless(hasDescendant( 42 binaryOperation(hasAnyOperatorName("==", "!="), 43 hasEitherOperand(ignoringParenCasts(cxxThisExpr())))))); 44 45 // Both copy-and-swap and copy-and-move method creates a copy first and 46 // assign it to 'this' with swap or move. 47 // In the non-template case, we can search for the copy constructor call. 48 const auto HasNonTemplateSelfCopy = cxxMethodDecl( 49 ofClass(cxxRecordDecl(unless(hasAncestor(classTemplateDecl())))), 50 traverse(TK_AsIs, 51 hasDescendant(cxxConstructExpr(hasDeclaration(cxxConstructorDecl( 52 isCopyConstructor(), ofClass(equalsBoundNode("class")))))))); 53 54 // In the template case, we need to handle two separate cases: 1) a local 55 // variable is created with the copy, 2) copy is created only as a temporary 56 // object. 57 const auto HasTemplateSelfCopy = cxxMethodDecl( 58 ofClass(cxxRecordDecl(hasAncestor(classTemplateDecl()))), 59 anyOf(hasDescendant( 60 varDecl(hasType(cxxRecordDecl(equalsBoundNode("class"))), 61 hasDescendant(parenListExpr()))), 62 hasDescendant(cxxUnresolvedConstructExpr(hasDescendant(declRefExpr( 63 hasType(cxxRecordDecl(equalsBoundNode("class"))))))))); 64 65 // If inside the copy assignment operator another assignment operator is 66 // called on 'this' we assume that self-check might be handled inside 67 // this nested operator. 68 const auto HasNoNestedSelfAssign = 69 cxxMethodDecl(unless(hasDescendant(cxxMemberCallExpr(callee(cxxMethodDecl( 70 hasName("operator="), ofClass(equalsBoundNode("class")))))))); 71 72 DeclarationMatcher AdditionalMatcher = cxxMethodDecl(); 73 if (WarnOnlyIfThisHasSuspiciousField) { 74 // Matcher for standard smart pointers. 75 const auto SmartPointerType = qualType(hasUnqualifiedDesugaredType( 76 recordType(hasDeclaration(classTemplateSpecializationDecl( 77 anyOf(allOf(hasAnyName("::std::shared_ptr", "::std::weak_ptr", 78 "::std::auto_ptr"), 79 templateArgumentCountIs(1)), 80 allOf(hasName("::std::unique_ptr"), 81 templateArgumentCountIs(2)))))))); 82 83 // We will warn only if the class has a pointer or a C array field which 84 // probably causes a problem during self-assignment (e.g. first resetting 85 // the pointer member, then trying to access the object pointed by the 86 // pointer, or memcpy overlapping arrays). 87 AdditionalMatcher = cxxMethodDecl(ofClass(cxxRecordDecl( 88 has(fieldDecl(anyOf(hasType(pointerType()), hasType(SmartPointerType), 89 hasType(arrayType()))))))); 90 } 91 92 Finder->addMatcher(cxxMethodDecl(ofClass(cxxRecordDecl().bind("class")), 93 isCopyAssignmentOperator(), IsUserDefined, 94 HasReferenceParam, HasNoSelfCheck, 95 unless(HasNonTemplateSelfCopy), 96 unless(HasTemplateSelfCopy), 97 HasNoNestedSelfAssign, AdditionalMatcher) 98 .bind("copyAssignmentOperator"), 99 this); 100 } 101 102 void UnhandledSelfAssignmentCheck::check( 103 const MatchFinder::MatchResult &Result) { 104 const auto *MatchedDecl = 105 Result.Nodes.getNodeAs<CXXMethodDecl>("copyAssignmentOperator"); 106 diag(MatchedDecl->getLocation(), 107 "operator=() does not handle self-assignment properly"); 108 } 109 110 } // namespace clang::tidy::bugprone 111