new loplugin rangedforcopy - use reference in range based for

Inspired by 6e6ae9803796b120e95f6e89575e03c5fd0ed3c2

Change-Id: Ia0f264d3a6bbf076aa5080e3398683e50bc6ef01
Reviewed-on: https://gerrit.libreoffice.org/20190
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/compilerplugins/clang/rangedforcopy.cxx b/compilerplugins/clang/rangedforcopy.cxx
new file mode 100644
index 000000000000..4c86fe34420e
--- /dev/null
+++ b/compilerplugins/clang/rangedforcopy.cxx
@@ -0,0 +1,66 @@
+
+/* -*- 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 <iostream>
+
+#include "plugin.hxx"
+#include "compat.hxx"
+#include "clang/AST/CXXInheritance.h"
+
+// Check that we're not unnecessarily copying variables in a range based for loop
+// e.g. "for (OUString a: aList)" results in a copy of each string being made,
+// whereas "for (const OUString& a: aList)" does not.
+
+namespace
+{
+
+class RangedForCopy:
+    public RecursiveASTVisitor<RangedForCopy>, public loplugin::Plugin
+{
+public:
+    explicit RangedForCopy(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitCXXForRangeStmt( const CXXForRangeStmt* stmt );
+};
+
+bool RangedForCopy::VisitCXXForRangeStmt( const CXXForRangeStmt* stmt )
+{
+    if (ignoreLocation( stmt ))
+        return true;
+
+    const VarDecl* varDecl = stmt->getLoopVariable();
+    if (!varDecl)
+      return true;
+
+    const QualType type = varDecl->getType();
+    if (type->isRecordType() && !type->isReferenceType() && !type->isPointerType())
+    {
+        std::string name = type.getAsString();
+        report(
+               DiagnosticsEngine::Warning,
+               "Loop variable passed by value, pass by reference instead, e.g. 'const %0&'",
+               varDecl->getLocStart())
+               << name << varDecl->getSourceRange();
+    }
+
+    return true;
+}
+
+
+loplugin::Plugin::Registration< RangedForCopy > X("rangedforcopy");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */