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//===--- ForwardDeclarationNamespaceCheck.cpp - clang-tidy ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "ForwardDeclarationNamespaceCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include <stack>
#include <string>
using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {
void ForwardDeclarationNamespaceCheck::registerMatchers(MatchFinder *Finder) {
// Match all class declarations/definitions *EXCEPT*
// 1. implicit classes, e.g. `class A {};` has implicit `class A` inside `A`.
// 2. nested classes declared/defined inside another class.
// 3. template class declaration, template instantiation or
// specialization (NOTE: extern specialization is filtered out by
// `unless(hasAncestor(cxxRecordDecl()))`).
auto IsInSpecialization = hasAncestor(
decl(anyOf(cxxRecordDecl(isExplicitTemplateSpecialization()),
functionDecl(isExplicitTemplateSpecialization()))));
Finder->addMatcher(
cxxRecordDecl(
hasParent(decl(anyOf(namespaceDecl(), translationUnitDecl()))),
unless(isImplicit()), unless(hasAncestor(cxxRecordDecl())),
unless(isInstantiated()), unless(IsInSpecialization),
unless(classTemplateSpecializationDecl()))
.bind("record_decl"),
this);
// Match all friend declarations. Classes used in friend declarations are not
// marked as referenced in AST. We need to record all record classes used in
// friend declarations.
Finder->addMatcher(friendDecl().bind("friend_decl"), this);
}
void ForwardDeclarationNamespaceCheck::check(
const MatchFinder::MatchResult &Result) {
if (const auto *RecordDecl =
Result.Nodes.getNodeAs<CXXRecordDecl>("record_decl")) {
StringRef DeclName = RecordDecl->getName();
if (RecordDecl->isThisDeclarationADefinition()) {
DeclNameToDefinitions[DeclName].push_back(RecordDecl);
} else {
// If a declaration has no definition, the definition could be in another
// namespace (a wrong namespace).
// NOTE: even a declaration does have definition, we still need it to
// compare with other declarations.
DeclNameToDeclarations[DeclName].push_back(RecordDecl);
}
} else {
const auto *Decl = Result.Nodes.getNodeAs<FriendDecl>("friend_decl");
assert(Decl && "Decl is neither record_decl nor friend decl!");
// Classes used in friend declarations are not marked referenced in AST,
// so we need to check classes used in friend declarations manually to
// reduce the rate of false positive.
// For example, in
// \code
// struct A;
// struct B { friend A; };
// \endcode
// `A` will not be marked as "referenced" in the AST.
if (const TypeSourceInfo *Tsi = Decl->getFriendType()) {
QualType Desugared = Tsi->getType().getDesugaredType(*Result.Context);
FriendTypes.insert(Desugared.getTypePtr());
}
}
}
static bool haveSameNamespaceOrTranslationUnit(const CXXRecordDecl *Decl1,
const CXXRecordDecl *Decl2) {
const DeclContext *ParentDecl1 = Decl1->getLexicalParent();
const DeclContext *ParentDecl2 = Decl2->getLexicalParent();
// Since we only matched declarations whose parent is Namespace or
// TranslationUnit declaration, the parent should be either a translation unit
// or namespace.
if (ParentDecl1->getDeclKind() == Decl::TranslationUnit ||
ParentDecl2->getDeclKind() == Decl::TranslationUnit) {
return ParentDecl1 == ParentDecl2;
}
assert(ParentDecl1->getDeclKind() == Decl::Namespace &&
"ParentDecl1 declaration must be a namespace");
assert(ParentDecl2->getDeclKind() == Decl::Namespace &&
"ParentDecl2 declaration must be a namespace");
auto *Ns1 = NamespaceDecl::castFromDeclContext(ParentDecl1);
auto *Ns2 = NamespaceDecl::castFromDeclContext(ParentDecl2);
return Ns1->getOriginalNamespace() == Ns2->getOriginalNamespace();
}
static std::string getNameOfNamespace(const CXXRecordDecl *Decl) {
const auto *ParentDecl = Decl->getLexicalParent();
if (ParentDecl->getDeclKind() == Decl::TranslationUnit) {
return "(global)";
}
const auto *NsDecl = cast<NamespaceDecl>(ParentDecl);
std::string Ns;
llvm::raw_string_ostream OStream(Ns);
NsDecl->printQualifiedName(OStream);
OStream.flush();
return Ns.empty() ? "(global)" : Ns;
}
void ForwardDeclarationNamespaceCheck::onEndOfTranslationUnit() {
// Iterate each group of declarations by name.
for (const auto &KeyValuePair : DeclNameToDeclarations) {
const auto &Declarations = KeyValuePair.second;
// If more than 1 declaration exists, we check if all are in the same
// namespace.
for (const auto *CurDecl : Declarations) {
if (CurDecl->hasDefinition() || CurDecl->isReferenced()) {
continue; // Skip forward declarations that are used/referenced.
}
if (FriendTypes.contains(CurDecl->getTypeForDecl())) {
continue; // Skip forward declarations referenced as friend.
}
if (CurDecl->getLocation().isMacroID() ||
CurDecl->getLocation().isInvalid()) {
continue;
}
// Compare with all other declarations with the same name.
for (const auto *Decl : Declarations) {
if (Decl == CurDecl) {
continue; // Don't compare with self.
}
if (!CurDecl->hasDefinition() &&
!haveSameNamespaceOrTranslationUnit(CurDecl, Decl)) {
diag(CurDecl->getLocation(),
"declaration %0 is never referenced, but a declaration with "
"the same name found in another namespace '%1'")
<< CurDecl << getNameOfNamespace(Decl);
diag(Decl->getLocation(), "a declaration of %0 is found here",
DiagnosticIDs::Note)
<< Decl;
break; // FIXME: We only generate one warning for each declaration.
}
}
// Check if a definition in another namespace exists.
const auto DeclName = CurDecl->getName();
if (!DeclNameToDefinitions.contains(DeclName)) {
continue; // No definition in this translation unit, we can skip it.
}
// Make a warning for each definition with the same name (in other
// namespaces).
const auto &Definitions = DeclNameToDefinitions[DeclName];
for (const auto *Def : Definitions) {
diag(CurDecl->getLocation(),
"no definition found for %0, but a definition with "
"the same name %1 found in another namespace '%2'")
<< CurDecl << Def << getNameOfNamespace(Def);
diag(Def->getLocation(), "a definition of %0 is found here",
DiagnosticIDs::Note)
<< Def;
}
}
}
}
} // namespace clang::tidy::bugprone
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