75f0f9d553
Offline discussion about tdf#96067 "Crash on undo row inserts" brought up the idea to warn about cases where uses of dynamic_cast are statically knwon to always fail. Clang's clang::AST::CXXDynamicCastExpr::isAlwaysNull already implements such a check, reporting true if the casted-from class is final, but has two issues: For one, it does not work for template code, when one of the involved types is a template parameter type (so e.g., DestType->castAs<PointerType>() can crash). For another, it misses the opportunity to report true if the casted-to type is final and only derives from the casted-from type non-publicly. My hope was that this, after the "final" decorations in548c43238d"Mark some classes as final," might turn up the culprit of tdf#96067 (with a scenario similar to the failed dynamic_cast on private derivation in63b67ab5ca"Use public derivation, and remove then-unnecessary downcasts")---but not so. Change-Id: I962ee19820758f9c601f4a292da7f37fa9dff5ce
123 lines
3.2 KiB
C++
123 lines
3.2 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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#include <algorithm>
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#include "clang/AST/CXXInheritance.h"
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#include "plugin.hxx"
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namespace {
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// cf. Clang's clang::AST::CXXDynamicCastExpr::isAlwaysNull
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// (lib/AST/ExprCXX.cpp):
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bool isAlwaysNull(CXXDynamicCastExpr const * expr) {
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QualType SrcType = expr->getSubExpr()->getType();
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QualType DestType = expr->getType();
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if (const PointerType *SrcPTy = SrcType->getAs<PointerType>()) {
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SrcType = SrcPTy->getPointeeType();
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#if 0
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DestType = DestType->castAs<PointerType>()->getPointeeType();
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#else
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auto DstPTy = DestType->getAs<PointerType>();
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if (!DstPTy)
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return false;
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DestType = DstPTy->getPointeeType();
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#endif
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}
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if (DestType->isVoidType())
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return false;
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#if 0
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const CXXRecordDecl *SrcRD =
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cast<CXXRecordDecl>(SrcType->castAs<RecordType>()->getDecl());
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#else
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auto SrcRT = SrcType->getAs<RecordType>();
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if (!SrcRT)
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return false;
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const CXXRecordDecl *SrcRD = cast<CXXRecordDecl>(SrcRT->getDecl());
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#endif
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#if 0
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if (!SrcRD->hasAttr<FinalAttr>())
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return false;
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#endif
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#if 0
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const CXXRecordDecl *DestRD =
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cast<CXXRecordDecl>(DestType->castAs<RecordType>()->getDecl());
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#else
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auto DestRT = DestType->getAs<RecordType>();
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if (!DestRT)
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return false;
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const CXXRecordDecl *DestRD = cast<CXXRecordDecl>(DestRT->getDecl());
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#endif
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#if 1
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if (!(SrcRD && DestRD))
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return false;
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if (DestRD->hasAttr<FinalAttr>()) {
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CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true,
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/*DetectVirtual=*/false);
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if (DestRD->isDerivedFrom(SrcRD, Paths) &&
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std::all_of(Paths.begin(), Paths.end(),
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[](CXXBasePath const & Path) {
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return Path.Access != AS_public; }))
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return true;
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}
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if (!SrcRD->hasAttr<FinalAttr>())
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return false;
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#endif
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return !DestRD->isDerivedFrom(SrcRD);
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}
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class FailedDynCast:
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public RecursiveASTVisitor<FailedDynCast>, public loplugin::Plugin
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{
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public:
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explicit FailedDynCast(InstantiationData const & data): Plugin(data) {}
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bool shouldVisitTemplateInstantiations() const { return true; }
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void run() override;
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bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr);
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};
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void FailedDynCast::run() {
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if (compiler.getLangOpts().CPlusPlus) {
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TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
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}
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}
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bool FailedDynCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
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if (ignoreLocation(expr)) {
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return true;
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}
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if (isAlwaysNull(expr)) {
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report(
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DiagnosticsEngine::Warning,
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"dynamic_cast from %0 to %1 always fails", expr->getLocStart())
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<< expr->getSubExpr()->getType() << expr->getType()
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<< expr->getSourceRange();
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}
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return true;
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}
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loplugin::Plugin::Registration<FailedDynCast> X("faileddyncast");
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}
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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