new loplugin: commaoperator

Change-Id: I03f24e61f696b7619855e3c7010aa0d874e5a4ff

compilerplugins/clang/commaoperator.cxx

@@ -0,0 +1,75 @@
+/* -*- 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"
+#include "compat.hxx"
+
+/**
+the comma operator is best used sparingly
+*/
+
+namespace {
+
+class CommaOperator:
+    public RecursiveASTVisitor<CommaOperator>, public loplugin::Plugin
+{
+public:
+    explicit CommaOperator(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitBinaryOperator(const BinaryOperator* );
+};
+
+bool CommaOperator::VisitBinaryOperator(const BinaryOperator* binaryOp)
+{
+    if (ignoreLocation(binaryOp)) {
+        return true;
+    }
+    if (binaryOp->getOpcode() != BO_Comma) {
+        return true;
+    }
+    const Stmt* parent = parentStmt(binaryOp);
+    if (isa<ParenExpr>(parent)) {
+        return true;
+    }
+    if (isa<BinaryOperator>(parent)) {
+        return true;
+    }
+    if (isa<ForStmt>(parent)) {
+        return true;
+    }
+    if (isa<ExprWithCleanups>(parent)) {
+        const Stmt* parent2 = parentStmt(parent);
+        if (isa<ForStmt>(parent2)) {
+            return true;
+        }
+    }
+//    parent->dump();
+    report(
+        DiagnosticsEngine::Warning, "comma operator hides code",
+        binaryOp->getSourceRange().getBegin())
+      << binaryOp->getSourceRange();
+    return true;
+}
+
+
+loplugin::Plugin::Registration< CommaOperator > X("commaoperator", true);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */