new loplugin:mapindex

Change-Id: I6b5f73b2187009e95d4d666e03e5803f522cee06
Reviewed-on: https://gerrit.libreoffice.org/76584
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 105 insertions, 0 deletions

diff --git a/compilerplugins/clang/mapindex.cxx b/compilerplugins/clang/mapindex.cxx
new file mode 100644
index 000000000000..bf8e38919552
--- /dev/null
+++ b/compilerplugins/clang/mapindex.cxx
@@ -0,0 +1,105 @@
+/* -*- 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 <memory>
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+
+#include "check.hxx"
+#include "plugin.hxx"
+
+/**
+  Look for places we are using map[idx] in a bool context, which allocates an entry in the map, which is sometimes a side-effect we don't want.
+*/
+
+namespace
+{
+class MapIndex : public loplugin::FilteringPlugin<MapIndex>
+{
+public:
+    explicit MapIndex(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual void run() override
+    {
+        if (preRun())
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitImplicitCastExpr(const ImplicitCastExpr*);
+    bool VisitMemberExpr(const MemberExpr*);
+};
+
+bool MapIndex::VisitMemberExpr(const MemberExpr* memberExpr)
+{
+    if (ignoreLocation(memberExpr))
+        return true;
+    // operator bool conversion
+    auto conversionDecl = dyn_cast<CXXConversionDecl>(memberExpr->getMemberDecl());
+    if (!conversionDecl || !conversionDecl->getConversionType()->isBooleanType())
+        return true;
+    auto operatorCall = dyn_cast<CXXOperatorCallExpr>(memberExpr->getBase()->IgnoreCasts());
+    if (!operatorCall)
+        return true;
+    if (operatorCall->getOperator() != OverloadedOperatorKind::OO_Subscript)
+        return true;
+    auto tc = loplugin::TypeCheck(operatorCall->getArg(0)->getType());
+    if (!tc.Class("map") && !tc.Class("unordered_map"))
+        return true;
+    report(DiagnosticsEngine::Warning,
+           "will create an empty entry in the map, you sure about that, rather use count()1",
+           operatorCall->getExprLoc());
+    return true;
+}
+
+bool MapIndex::VisitImplicitCastExpr(const ImplicitCastExpr* implicitCastExpr)
+{
+    if (ignoreLocation(implicitCastExpr))
+    {
+        return true;
+    }
+
+    // first cast is some kind of "ToBoolean" cast
+    auto ck = implicitCastExpr->getCastKind();
+    if (ck != CK_MemberPointerToBoolean && ck != CK_PointerToBoolean && ck != CK_IntegralToBoolean
+        && ck != CK_FloatingToBoolean && ck != CK_FloatingComplexToBoolean
+        && ck != CK_IntegralComplexToBoolean)
+        return true;
+
+    // second cast is LValueToRValue
+    implicitCastExpr = dyn_cast<ImplicitCastExpr>(implicitCastExpr->getSubExpr());
+    if (!implicitCastExpr)
+        return true;
+
+    if (implicitCastExpr->getCastKind() != CK_LValueToRValue)
+        return true;
+    auto operatorCall = dyn_cast<CXXOperatorCallExpr>(implicitCastExpr->getSubExpr());
+    if (!operatorCall)
+        return true;
+    if (operatorCall->getOperator() != OverloadedOperatorKind::OO_Subscript)
+        return true;
+    auto tc = loplugin::TypeCheck(operatorCall->getArg(0)->getType());
+    if (!tc.Class("map") && !tc.Class("unordered_map"))
+        return true;
+    report(DiagnosticsEngine::Warning,
+           "will create an empty entry in the map, you sure about that, rather use count()2",
+           implicitCastExpr->getExprLoc());
+    return true;
+}
+
+loplugin::Plugin::Registration<MapIndex> X("mapindex");
+
+} // namespace
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */