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 {
16 namespace tidy {
17 namespace bugprone {
18
UnhandledSelfAssignmentCheck(StringRef Name,ClangTidyContext * Context)19 UnhandledSelfAssignmentCheck::UnhandledSelfAssignmentCheck(
20 StringRef Name, ClangTidyContext *Context)
21 : ClangTidyCheck(Name, Context),
22 WarnOnlyIfThisHasSuspiciousField(
23 Options.get("WarnOnlyIfThisHasSuspiciousField", true)) {}
24
storeOptions(ClangTidyOptions::OptionMap & Opts)25 void UnhandledSelfAssignmentCheck::storeOptions(
26 ClangTidyOptions::OptionMap &Opts) {
27 Options.store(Opts, "WarnOnlyIfThisHasSuspiciousField",
28 WarnOnlyIfThisHasSuspiciousField);
29 }
30
registerMatchers(MatchFinder * Finder)31 void UnhandledSelfAssignmentCheck::registerMatchers(MatchFinder *Finder) {
32 // We don't care about deleted, default or implicit operator implementations.
33 const auto IsUserDefined = cxxMethodDecl(
34 isDefinition(), unless(anyOf(isDeleted(), isImplicit(), isDefaulted())));
35
36 // We don't need to worry when a copy assignment operator gets the other
37 // object by value.
38 const auto HasReferenceParam =
39 cxxMethodDecl(hasParameter(0, parmVarDecl(hasType(referenceType()))));
40
41 // Self-check: Code compares something with 'this' pointer. We don't check
42 // whether it is actually the parameter what we compare.
43 const auto HasNoSelfCheck = cxxMethodDecl(unless(anyOf(
44 hasDescendant(binaryOperator(hasAnyOperatorName("==", "!="),
45 has(ignoringParenCasts(cxxThisExpr())))),
46 hasDescendant(cxxOperatorCallExpr(
47 hasAnyOverloadedOperatorName("==", "!="), argumentCountIs(2),
48 has(ignoringParenCasts(cxxThisExpr())))))));
49
50 // Both copy-and-swap and copy-and-move method creates a copy first and
51 // assign it to 'this' with swap or move.
52 // In the non-template case, we can search for the copy constructor call.
53 const auto HasNonTemplateSelfCopy = cxxMethodDecl(
54 ofClass(cxxRecordDecl(unless(hasAncestor(classTemplateDecl())))),
55 traverse(ast_type_traits::TK_AsIs,
56 hasDescendant(cxxConstructExpr(hasDeclaration(cxxConstructorDecl(
57 isCopyConstructor(), ofClass(equalsBoundNode("class"))))))));
58
59 // In the template case, we need to handle two separate cases: 1) a local
60 // variable is created with the copy, 2) copy is created only as a temporary
61 // object.
62 const auto HasTemplateSelfCopy = cxxMethodDecl(
63 ofClass(cxxRecordDecl(hasAncestor(classTemplateDecl()))),
64 anyOf(hasDescendant(
65 varDecl(hasType(cxxRecordDecl(equalsBoundNode("class"))),
66 hasDescendant(parenListExpr()))),
67 hasDescendant(cxxUnresolvedConstructExpr(hasDescendant(declRefExpr(
68 hasType(cxxRecordDecl(equalsBoundNode("class")))))))));
69
70 // If inside the copy assignment operator another assignment operator is
71 // called on 'this' we assume that self-check might be handled inside
72 // this nested operator.
73 const auto HasNoNestedSelfAssign =
74 cxxMethodDecl(unless(hasDescendant(cxxMemberCallExpr(callee(cxxMethodDecl(
75 hasName("operator="), ofClass(equalsBoundNode("class"))))))));
76
77 DeclarationMatcher AdditionalMatcher = cxxMethodDecl();
78 if (WarnOnlyIfThisHasSuspiciousField) {
79 // Matcher for standard smart pointers.
80 const auto SmartPointerType = qualType(hasUnqualifiedDesugaredType(
81 recordType(hasDeclaration(classTemplateSpecializationDecl(
82 hasAnyName("::std::shared_ptr", "::std::unique_ptr",
83 "::std::weak_ptr", "::std::auto_ptr"),
84 templateArgumentCountIs(1))))));
85
86 // We will warn only if the class has a pointer or a C array field which
87 // probably causes a problem during self-assignment (e.g. first resetting
88 // the pointer member, then trying to access the object pointed by the
89 // pointer, or memcpy overlapping arrays).
90 AdditionalMatcher = cxxMethodDecl(ofClass(cxxRecordDecl(
91 has(fieldDecl(anyOf(hasType(pointerType()), hasType(SmartPointerType),
92 hasType(arrayType())))))));
93 }
94
95 Finder->addMatcher(cxxMethodDecl(ofClass(cxxRecordDecl().bind("class")),
96 isCopyAssignmentOperator(), IsUserDefined,
97 HasReferenceParam, HasNoSelfCheck,
98 unless(HasNonTemplateSelfCopy),
99 unless(HasTemplateSelfCopy),
100 HasNoNestedSelfAssign, AdditionalMatcher)
101 .bind("copyAssignmentOperator"),
102 this);
103 }
104
check(const MatchFinder::MatchResult & Result)105 void UnhandledSelfAssignmentCheck::check(
106 const MatchFinder::MatchResult &Result) {
107 const auto *MatchedDecl =
108 Result.Nodes.getNodeAs<CXXMethodDecl>("copyAssignmentOperator");
109 diag(MatchedDecl->getLocation(),
110 "operator=() does not handle self-assignment properly");
111 }
112
113 } // namespace bugprone
114 } // namespace tidy
115 } // namespace clang
116