new loplugin: VCL widget reference checker

First stage of new VCL widget reference checker

Change-Id: I63a2108a26b3c0e0a896d13672b1daa6f8e60b3a
Reviewed-on: https://gerrit.libreoffice.org/10427Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>

compilerplugins/clang/vclwidgets.cxx

+/* -*- 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 <string>
+
+#include "plugin.hxx"
+#include "compat.hxx"
+#include "clang/AST/CXXInheritance.h"
+
+// Final goal: Checker for VCL widget references. Makes sure that VCL Window subclasses are properly referenced counted and dispose()'ed.
+//
+// But at the moment it just finds subclasses of Window which are not heap-allocated
+//
+// TODO do I need to check for local and static variables, too ?
+// TODO when we have a dispose() method, verify that the dispose() methods releases all of the Window references
+// TODO when we have a dispose() method, verify that it calls the super-class dispose() method at some point.
+
+namespace {
+
+class VCLWidgets:
+    public RecursiveASTVisitor<VCLWidgets>, public loplugin::Plugin
+{
+public:
+    explicit VCLWidgets(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitFieldDecl(const FieldDecl * decl);
+
+    bool mbFoundWindow;
+};
+
+bool forallBasesCallback(const CXXBaseSpecifier *Specifier, CXXBasePath &, void *UserData) {
+    VCLWidgets* ro = (VCLWidgets*) UserData;
+    QualType qt = Specifier->getType();
+    std::string name = qt.getUnqualifiedType().getCanonicalType().getAsString();
+    if (name == "class Window") {
+          ro->mbFoundWindow = true;
+          return true;
+    }
+    return false;
+}
+
+bool VCLWidgets::VisitFieldDecl(const FieldDecl * fieldDecl) {
+    if (ignoreLocation(fieldDecl)) {
+        return true;
+    }
+    if (fieldDecl->isBitField()) {
+        return true;
+    }
+    const RecordType *recordType = fieldDecl->getType()->getAs<RecordType>();
+    if (recordType == nullptr) {
+        return true;
+    }
+    const CXXRecordDecl *recordDecl = dyn_cast<CXXRecordDecl>(recordType->getDecl());
+    if (recordDecl == nullptr) {
+        return true;
+    }
+    // check if this field is derived from Window
+    mbFoundWindow = false;
+    CXXBasePaths paths;
+    recordDecl->lookupInBases(forallBasesCallback, this, paths);
+    if (!mbFoundWindow) {
+        return true;
+    }
+
+    report(
+        DiagnosticsEngine::Warning,
+        "vcl::Window subclass not heap allocated",
+        fieldDecl->getLocation())
+      << fieldDecl->getSourceRange();
+    return true;
+}
+
+
+loplugin::Plugin::Registration< VCLWidgets > X("vclwidgets");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */