compilerplugins/clang/faileddyncast.cxx | 122 ++++++++++++++++++++++++++++++++
1 file changed, 122 insertions(+)
New commits:
commit 75f0f9d5538577e0d4923b4d46ba6f88b6199814
Author: Stephan Bergmann <sberg...@redhat.com>
Date: Tue Jan 12 15:00:33 2016 +0100
New loplugin:faileddyncast
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 in
548c43238d02b34cf73e7c2ca1a912ee4fe82544
"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 in
63b67ab5cab8cf7576a68cabe5fb1a42c6ad800c "Use public derivation, and remove
then-unnecessary downcasts")---but not so.
Change-Id: I962ee19820758f9c601f4a292da7f37fa9dff5ce
diff --git a/compilerplugins/clang/faileddyncast.cxx
b/compilerplugins/clang/faileddyncast.cxx
new file mode 100644
index 0000000..6fef227
--- /dev/null
+++ b/compilerplugins/clang/faileddyncast.cxx
@@ -0,0 +1,122 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <algorithm>
+
+#include "clang/AST/CXXInheritance.h"
+
+#include "plugin.hxx"
+
+namespace {
+
+// cf. Clang's clang::AST::CXXDynamicCastExpr::isAlwaysNull
+// (lib/AST/ExprCXX.cpp):
+bool isAlwaysNull(CXXDynamicCastExpr const * expr) {
+ QualType SrcType = expr->getSubExpr()->getType();
+ QualType DestType = expr->getType();
+
+ if (const PointerType *SrcPTy = SrcType->getAs<PointerType>()) {
+ SrcType = SrcPTy->getPointeeType();
+#if 0
+ DestType = DestType->castAs<PointerType>()->getPointeeType();
+#else
+ auto DstPTy = DestType->getAs<PointerType>();
+ if (!DstPTy)
+ return false;
+ DestType = DstPTy->getPointeeType();
+#endif
+ }
+
+ if (DestType->isVoidType())
+ return false;
+
+#if 0
+ const CXXRecordDecl *SrcRD =
+ cast<CXXRecordDecl>(SrcType->castAs<RecordType>()->getDecl());
+#else
+ auto SrcRT = SrcType->getAs<RecordType>();
+ if (!SrcRT)
+ return false;
+ const CXXRecordDecl *SrcRD = cast<CXXRecordDecl>(SrcRT->getDecl());
+#endif
+
+#if 0
+ if (!SrcRD->hasAttr<FinalAttr>())
+ return false;
+#endif
+
+#if 0
+ const CXXRecordDecl *DestRD =
+ cast<CXXRecordDecl>(DestType->castAs<RecordType>()->getDecl());
+#else
+ auto DestRT = DestType->getAs<RecordType>();
+ if (!DestRT)
+ return false;
+ const CXXRecordDecl *DestRD = cast<CXXRecordDecl>(DestRT->getDecl());
+#endif
+
+#if 1
+ if (!(SrcRD && DestRD))
+ return false;
+
+ if (DestRD->hasAttr<FinalAttr>()) {
+ CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true,
+ /*DetectVirtual=*/false);
+ if (DestRD->isDerivedFrom(SrcRD, Paths) &&
+ std::all_of(Paths.begin(), Paths.end(),
+ [](CXXBasePath const & Path) {
+ return Path.Access != AS_public; }))
+ return true;
+ }
+
+ if (!SrcRD->hasAttr<FinalAttr>())
+ return false;
+#endif
+
+ return !DestRD->isDerivedFrom(SrcRD);
+}
+
+class FailedDynCast:
+ public RecursiveASTVisitor<FailedDynCast>, public loplugin::Plugin
+{
+public:
+ explicit FailedDynCast(InstantiationData const & data): Plugin(data) {}
+
+ bool shouldVisitTemplateInstantiations() const { return true; }
+
+ void run() override;
+
+ bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr);
+};
+
+void FailedDynCast::run() {
+ if (compiler.getLangOpts().CPlusPlus) {
+ TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+ }
+}
+
+bool FailedDynCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
+ if (ignoreLocation(expr)) {
+ return true;
+ }
+ if (isAlwaysNull(expr)) {
+ report(
+ DiagnosticsEngine::Warning,
+ "dynamic_cast from %0 to %1 always fails", expr->getLocStart())
+ << expr->getSubExpr()->getType() << expr->getType()
+ << expr->getSourceRange();
+ }
+ return true;
+}
+
+loplugin::Plugin::Registration<FailedDynCast> X("faileddyncast");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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