clang-tools 10.0.0

ForwardDeclarationNamespaceCheck.cpp
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1 //===--- ForwardDeclarationNamespaceCheck.cpp - 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 #include "ForwardDeclarationNamespaceCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/AST/Decl.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/ASTMatchers/ASTMatchers.h"
14 #include <stack>
15 #include <string>
16
17 using namespace clang::ast_matchers;
18
19 namespace clang {
20 namespace tidy {
21 namespace bugprone {
22
23 void ForwardDeclarationNamespaceCheck::registerMatchers(MatchFinder *Finder) {
24 // Match all class declarations/definitions *EXCEPT*
25 // 1. implicit classes, e.g. `class A {};` has implicit `class A` inside `A`.
26 // 2. nested classes declared/defined inside another class.
27 // 3. template class declaration, template instantiation or
28 // specialization (NOTE: extern specialization is filtered out by
29 // `unless(hasAncestor(cxxRecordDecl()))`).
30 auto IsInSpecialization = hasAncestor(
31 decl(anyOf(cxxRecordDecl(isExplicitTemplateSpecialization()),
32 functionDecl(isExplicitTemplateSpecialization()))));
33 Finder->addMatcher(
34 cxxRecordDecl(
35 hasParent(decl(anyOf(namespaceDecl(), translationUnitDecl()))),
36 unless(isImplicit()), unless(hasAncestor(cxxRecordDecl())),
37 unless(isInstantiated()), unless(IsInSpecialization),
38 unless(classTemplateSpecializationDecl()))
39 .bind("record_decl"),
40 this);
41
42 // Match all friend declarations. Classes used in friend declarations are not
43 // marked as referenced in AST. We need to record all record classes used in
44 // friend declarations.
45 Finder->addMatcher(friendDecl().bind("friend_decl"), this);
46 }
47
48 void ForwardDeclarationNamespaceCheck::check(
49 const MatchFinder::MatchResult &Result) {
50 if (const auto *RecordDecl =
51 Result.Nodes.getNodeAs<CXXRecordDecl>("record_decl")) {
52 StringRef DeclName = RecordDecl->getName();
53 if (RecordDecl->isThisDeclarationADefinition()) {
54 DeclNameToDefinitions[DeclName].push_back(RecordDecl);
55 } else {
56 // If a declaration has no definition, the definition could be in another
57 // namespace (a wrong namespace).
58 // NOTE: even a declaration does have definition, we still need it to
59 // compare with other declarations.
60 DeclNameToDeclarations[DeclName].push_back(RecordDecl);
61 }
62 } else {
63 const auto *Decl = Result.Nodes.getNodeAs<FriendDecl>("friend_decl");
64 assert(Decl && "Decl is neither record_decl nor friend decl!");
65
66 // Classes used in friend declarations are not marked referenced in AST,
67 // so we need to check classes used in friend declarations manually to
68 // reduce the rate of false positive.
69 // For example, in
70 // \code
71 // struct A;
72 // struct B { friend A; };
73 // \endcode
74 // `A` will not be marked as "referenced" in the AST.
75 if (const TypeSourceInfo *Tsi = Decl->getFriendType()) {
76 QualType Desugared = Tsi->getType().getDesugaredType(*Result.Context);
77 FriendTypes.insert(Desugared.getTypePtr());
78 }
79 }
80 }
81
82 static bool haveSameNamespaceOrTranslationUnit(const CXXRecordDecl *Decl1,
83 const CXXRecordDecl *Decl2) {
84 const DeclContext *ParentDecl1 = Decl1->getLexicalParent();
85 const DeclContext *ParentDecl2 = Decl2->getLexicalParent();
86
87 // Since we only matched declarations whose parent is Namespace or
88 // TranslationUnit declaration, the parent should be either a translation unit
89 // or namespace.
90 if (ParentDecl1->getDeclKind() == Decl::TranslationUnit ||
91 ParentDecl2->getDeclKind() == Decl::TranslationUnit) {
92 return ParentDecl1 == ParentDecl2;
93 }
94 assert(ParentDecl1->getDeclKind() == Decl::Namespace &&
95 "ParentDecl1 declaration must be a namespace");
96 assert(ParentDecl2->getDeclKind() == Decl::Namespace &&
97 "ParentDecl2 declaration must be a namespace");
98 auto *Ns1 = NamespaceDecl::castFromDeclContext(ParentDecl1);
99 auto *Ns2 = NamespaceDecl::castFromDeclContext(ParentDecl2);
100 return Ns1->getOriginalNamespace() == Ns2->getOriginalNamespace();
101 }
102
103 static std::string getNameOfNamespace(const CXXRecordDecl *Decl) {
104 const auto *ParentDecl = Decl->getLexicalParent();
105 if (ParentDecl->getDeclKind() == Decl::TranslationUnit) {
106 return "(global)";
107 }
108 const auto *NsDecl = cast<NamespaceDecl>(ParentDecl);
109 std::string Ns;
110 llvm::raw_string_ostream OStream(Ns);
111 NsDecl->printQualifiedName(OStream);
112 OStream.flush();
113 return Ns.empty() ? "(global)" : Ns;
114 }
115
116 void ForwardDeclarationNamespaceCheck::onEndOfTranslationUnit() {
117 // Iterate each group of declarations by name.
118 for (const auto &KeyValuePair : DeclNameToDeclarations) {
119 const auto &Declarations = KeyValuePair.second;
120 // If more than 1 declaration exists, we check if all are in the same
121 // namespace.
122 for (const auto *CurDecl : Declarations) {
123 if (CurDecl->hasDefinition() || CurDecl->isReferenced()) {
124 continue; // Skip forward declarations that are used/referenced.
125 }
126 if (FriendTypes.count(CurDecl->getTypeForDecl()) != 0) {
127 continue; // Skip forward declarations referenced as friend.
128 }
129 if (CurDecl->getLocation().isMacroID() ||
130 CurDecl->getLocation().isInvalid()) {
131 continue;
132 }
133 // Compare with all other declarations with the same name.
134 for (const auto *Decl : Declarations) {
135 if (Decl == CurDecl) {
136 continue; // Don't compare with self.
137 }
138 if (!CurDecl->hasDefinition() &&
139 !haveSameNamespaceOrTranslationUnit(CurDecl, Decl)) {
140 diag(CurDecl->getLocation(),
141 "declaration %0 is never referenced, but a declaration with "
142 "the same name found in another namespace '%1'")
143 << CurDecl << getNameOfNamespace(Decl);
144 diag(Decl->getLocation(), "a declaration of %0 is found here",
145 DiagnosticIDs::Note)
146 << Decl;
147 break; // FIXME: We only generate one warning for each declaration.
148 }
149 }
150 // Check if a definition in another namespace exists.
151 const auto DeclName = CurDecl->getName();
152 if (DeclNameToDefinitions.find(DeclName) == DeclNameToDefinitions.end()) {
153 continue; // No definition in this translation unit, we can skip it.
154 }
155 // Make a warning for each definition with the same name (in other
156 // namespaces).
157 const auto &Definitions = DeclNameToDefinitions[DeclName];
158 for (const auto *Def : Definitions) {
159 diag(CurDecl->getLocation(),
160 "no definition found for %0, but a definition with "
161 "the same name %1 found in another namespace '%2'")
162 << CurDecl << Def << getNameOfNamespace(Def);
163 diag(Def->getLocation(), "a definition of %0 is found here",
164 DiagnosticIDs::Note)
165 << Def;
166 }
167 }
168 }
169 }
170
171 } // namespace bugprone
172 } // namespace tidy
173 } // namespace clang
clang::ast_matchers
Definition: AbseilMatcher.h:14
Decl
const FunctionDecl * Decl
Definition: AvoidBindCheck.cpp:93
clang::tidy::bugprone::haveSameNamespaceOrTranslationUnit
static bool haveSameNamespaceOrTranslationUnit(const CXXRecordDecl *Decl1, const CXXRecordDecl *Decl2)
Definition: ForwardDeclarationNamespaceCheck.cpp:82
clang::tidy::bugprone::getNameOfNamespace
static std::string getNameOfNamespace(const CXXRecordDecl *Decl)
Definition: ForwardDeclarationNamespaceCheck.cpp:103
clang::clangd::isExplicitTemplateSpecialization
bool isExplicitTemplateSpecialization(const NamedDecl *D)
Indicates if D is an explicit template specialization, e.g.
Definition: AST.cpp:153
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
ForwardDeclarationNamespaceCheck.h