New loplugin:subtlezeroinit

Change-Id: I4530021d78f714d389833bd00ea87430d1d20f52

compilerplugins/clang/subtlezeroinit.cxx

+/* -*- 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 "plugin.hxx"
+
+// Find occurrences of 'new T()' where the instance is zero-initialized upfront
+// since C++11.  For one, in many cases this may be unnecessary and unintended,
+// as the code was written before C++11.  For another, the zero-initialization
+// would go away when T gets a user-provided default constructor, for example,
+// so better make any necessary initialization more explicit in the code.
+
+namespace {
+
+class Visitor final:
+    public RecursiveASTVisitor<Visitor>, public loplugin::Plugin
+{
+public:
+    explicit Visitor(InstantiationData const & data): Plugin(data) {}
+
+    bool VisitCXXNewExpr(CXXNewExpr const * expr) {
+        if (ignoreLocation(expr)) {
+            return true;
+        }
+        auto ce = expr->getConstructExpr();
+        if (ce == nullptr) {
+            return true;
+        }
+        if (!ce->requiresZeroInitialization()) {
+            return true;
+        }
+        report(
+            DiagnosticsEngine::Warning,
+            ("if zero-initialization of %0 is intentional here, better make"
+             " that more explicit (e.g., assigning to members, default"
+             " constructor, default member initializers, std::memset)"),
+            expr->getExprLoc())
+            << ce->getType() << expr->getSourceRange();
+        return true;
+    }
+
+private:
+    void run() override {
+        if (compiler.getLangOpts().CPlusPlus) {
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+        }
+    }
+};
+
+static loplugin::Plugin::Registration<Visitor> reg("subtlezeroinit");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */