1 files changed, 85 insertions, 0 deletions
diff --git a/compilerplugins/clang/rangedforcopy.cxx b/compilerplugins/clang/rangedforcopy.cxx
new file mode 100644
index 0000000000..2de4766dab
--- /dev/null
+++ b/compilerplugins/clang/rangedforcopy.cxx
@@ -0,0 +1,85 @@
+
+/* -*- 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/.
+ */
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include <string>
+#include <iostream>
+
+#include "check.hxx"
+#include "plugin.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 loplugin::FilteringPlugin<RangedForCopy>
+{
+public:
+    explicit RangedForCopy(loplugin::InstantiationData const & data):
+        FilteringPlugin(data) {}
+
+    virtual void run() override {
+        if (preRun())
+            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;
+    if (isa<DecompositionDecl>(varDecl))
+    {
+        // Assume that use of a non-reference structured binding is intentional:
+        return true;
+    }
+
+    const QualType type = varDecl->getType();
+    if (type->isRecordType() && !type->isReferenceType() && !type->isPointerType())
+    {
+        if (loplugin::TypeCheck(type).Class("__bit_const_reference").StdNamespace())
+        {
+            // With libc++ without _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL,
+            // iterating over a const std::vector<bool> non-compliantly uses a variable of some
+            // internal __bit_const_reference class type, rather than of type bool (see
+            // <https://reviews.llvm.org/D123851> "[libc++] Change
+            // vector<bool>::const_iterator::reference to bool in ABIv2"):
+            return true;
+        }
+        std::string name = type.getAsString();
+        report(
+               DiagnosticsEngine::Warning,
+               "Loop variable passed by value, pass by reference instead, e.g. 'const %0&'",
+               varDecl->getBeginLoc())
+               << name << varDecl->getSourceRange();
+    }
+
+    return true;
+}
+
+
+loplugin::Plugin::Registration< RangedForCopy > rangedforcopy("rangedforcopy");
+
+} // namespace
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */