New loplugin:charrightshift

Change-Id: Ib645fb11004bc0fe05c9c416ae72b0ae56c23a15

compilerplugins/clang/charrightshift.cxx

@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * 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 "check.hxx"
+#include "plugin.hxx"
+
+namespace {
+
+class CharRightShift:
+    public RecursiveASTVisitor<CharRightShift>, public loplugin::Plugin
+{
+public:
+    explicit CharRightShift(InstantiationData const & data): Plugin(data) {}
+
+    void run() override
+    { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitBinShr(BinaryOperator const * expr) {
+        if (ignoreLocation(expr)) {
+            return true;
+        }
+        auto t = expr->getLHS()->IgnoreParenImpCasts()->getType();
+        if (!loplugin::TypeCheck(t).Char()) {
+            return true;
+        }
+        if (!expr->getRHS()->getType()->isBuiltinType()) {
+            //TODO: in which case the expression should be an
+            // CXXOperatorCallExpr instead of a BinaryOperator? but at least
+            // recent Clang trunk reports
+            //
+            //  '(' >> orExpression
+            //
+            // (connectivity/source/commontools/RowFunctionParser.cxx, the RHS
+            // being of type boost::spirit::rule<ScannerT>) here
+            return true;
+        }
+        report(
+            DiagnosticsEngine::Warning,
+            ("right shift of %0 is implementation-defined when 'char' is signed"
+             " and value is negative"),
+            expr->getLHS()->getExprLoc())
+            << t << expr->getSourceRange();
+        return true;
+    }
+};
+
+loplugin::Plugin::Registration<CharRightShift> X("charrightshift");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */