1 files changed, 90 insertions, 0 deletions
diff --git a/compilerplugins/clang/typeidcomparison.cxx b/compilerplugins/clang/typeidcomparison.cxx
new file mode 100644
index 000000000000..359231f262e6
--- /dev/null
+++ b/compilerplugins/clang/typeidcomparison.cxx
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * 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/.
+ */
+
+// Find (in-)equality comparisons between typeid expressions that can never succeed.  For now, just
+// detects cases where the two involved types are structurally different, one a pointer type and the
+// other a non-pointer type.
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include "plugin.hxx"
+
+namespace
+{
+class TypeidComparison final : public loplugin::FilteringPlugin<TypeidComparison>
+{
+public:
+    explicit TypeidComparison(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    // For CXXRewrittenBinaryOperator `typeid(...) != typeid(...)`:
+    bool shouldVisitImplicitCode() const { return true; }
+
+    bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
+
+    void run() override
+    {
+        if (preRun())
+        {
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+        }
+    }
+
+    bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* expr)
+    {
+        if (ignoreLocation(expr))
+        {
+            return true;
+        }
+        auto const op = expr->getOperator();
+        if (op != OO_EqualEqual && op != OO_ExclaimEqual)
+        {
+            return true;
+        }
+        assert(expr->getNumArgs() == 2);
+        auto const e1 = dyn_cast<CXXTypeidExpr>(expr->getArg(0)->IgnoreParenImpCasts());
+        if (e1 == nullptr)
+        {
+            return true;
+        }
+        auto const e2 = dyn_cast<CXXTypeidExpr>(expr->getArg(1)->IgnoreParenImpCasts());
+        if (e2 == nullptr)
+        {
+            return true;
+        }
+        auto const t1 = getOperandType(e1);
+        auto const t2 = getOperandType(e2);
+        if (t1->isPointerType() == t2->isPointerType())
+        {
+            return true;
+        }
+        report(DiagnosticsEngine::Warning,
+               "comparison of type info of mixed pointer and non-pointer types %0 and %1 can never "
+               "succeed",
+               expr->getExprLoc())
+            << t1 << t2 << expr->getSourceRange();
+        return true;
+    }
+
+private:
+    QualType getOperandType(CXXTypeidExpr const* expr)
+    {
+        return expr->isTypeOperand() ? expr->getTypeOperand(compiler.getASTContext())
+                                     : expr->getExprOperand()->getType();
+    }
+};
+
+static loplugin::Plugin::Registration<TypeidComparison> typeidcomparison("typeidcomparison");
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */