new loplugin unnecessary override

Change-Id: I88d3e33823d68745b98625050a8a274f9ef04bcb
Reviewed-on: https://gerrit.libreoffice.org/27135
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 114 insertions, 0 deletions

diff --git a/compilerplugins/clang/unnecessaryoverride.cxx b/compilerplugins/clang/unnecessaryoverride.cxx
new file mode 100644
index 000000000000..8a882af9c362
--- /dev/null
+++ b/compilerplugins/clang/unnecessaryoverride.cxx
@@ -0,0 +1,114 @@
+/* -*- 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 <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+#include "plugin.hxx"
+
+/**
+look for methods where all they do is call their superclass method
+*/
+
+namespace {
+
+class UnnecessaryOverride:
+    public RecursiveASTVisitor<UnnecessaryOverride>, public loplugin::Plugin
+{
+public:
+    explicit UnnecessaryOverride(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        // ignore some files with problematic macros
+        StringRef fn( compiler.getSourceManager().getFileEntryForID(
+                          compiler.getSourceManager().getMainFileID())->getName() );
+        if (fn == SRCDIR "/sd/source/ui/framework/factories/ChildWindowPane.cxx")
+             return;
+        if (fn == SRCDIR "/forms/source/component/Date.cxx")
+             return;
+        if (fn == SRCDIR "/forms/source/component/Time.cxx")
+            return;
+
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitCXXMethodDecl(const CXXMethodDecl *);
+};
+
+bool UnnecessaryOverride::VisitCXXMethodDecl(const CXXMethodDecl* methodDecl)
+{
+    if (ignoreLocation(methodDecl->getCanonicalDecl()) || !methodDecl->doesThisDeclarationHaveABody()) {
+        return true;
+    }
+    // if we are overriding more than one method, then this is a disambiguating override
+    if (!methodDecl->isVirtual() || methodDecl->size_overridden_methods() != 1
+        || (*methodDecl->begin_overridden_methods())->isPure()) {
+        return true;
+    }
+    if (dyn_cast<CXXDestructorDecl>(methodDecl)) {
+        return true;
+    }
+    // sometimes the disambiguation happens in a base class
+    StringRef aFileName = compiler.getSourceManager().getFilename(compiler.getSourceManager().getSpellingLoc(methodDecl->getLocStart()));
+    if (aFileName == SRCDIR "/comphelper/source/property/propertycontainer.cxx")
+        return true;
+    // not sure what is happening here
+    if (aFileName == SRCDIR "/extensions/source/bibliography/datman.cxx")
+        return true;
+
+    const CXXMethodDecl* overriddenMethodDecl = *methodDecl->begin_overridden_methods();
+
+    const CompoundStmt* compoundStmt = dyn_cast<CompoundStmt>(methodDecl->getBody());
+    if (!compoundStmt || compoundStmt->size() != 1)
+        return true;
+    const Stmt* firstStmt = compoundStmt->body_front();
+    if (const ReturnStmt* returnStmt = dyn_cast<ReturnStmt>(firstStmt)) {
+        firstStmt = returnStmt->getRetValue();
+    }
+    if (!firstStmt)
+        return true;
+    const CXXMemberCallExpr* callExpr = dyn_cast<CXXMemberCallExpr>(firstStmt);
+    if (!callExpr || callExpr->getMethodDecl() != overriddenMethodDecl)
+        return true;
+    const ImplicitCastExpr* expr1 = dyn_cast_or_null<ImplicitCastExpr>(callExpr->getImplicitObjectArgument());
+    if (!expr1)
+        return true;
+    const CXXThisExpr* expr2 = dyn_cast_or_null<CXXThisExpr>(expr1->getSubExpr());
+    if (!expr2)
+        return true;
+    for (unsigned i = 0; i<callExpr->getNumArgs(); ++i) {
+        const DeclRefExpr * declRefExpr = dyn_cast<DeclRefExpr>(callExpr->getArg(i));
+        if (!declRefExpr || declRefExpr->getDecl() != methodDecl->getParamDecl(i))
+            return true;
+    }
+
+    report(
+        DiagnosticsEngine::Warning, "method just calls parent method",
+        methodDecl->getSourceRange().getBegin())
+      << methodDecl->getSourceRange();
+    if (methodDecl->getCanonicalDecl()->getLocation() != methodDecl->getLocation()) {
+        const CXXMethodDecl* pOther = methodDecl->getCanonicalDecl();
+        report(
+            DiagnosticsEngine::Note,
+            "method declaration here",
+            pOther->getLocStart())
+          << pOther->getSourceRange();
+    }
+    return true;
+}
+
+
+loplugin::Plugin::Registration< UnnecessaryOverride > X("unnecessaryoverride", true);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */