Fix some potential Mach port leaks from mach_host_self using a new ScopedMachPort class.

base/mac/scoped_mach_port.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MAC_SCOPED_MACH_PORT_H_
+#define BASE_MAC_SCOPED_MACH_PORT_H_
+
+#include <mach/mach.h>
+
+#include "base/basictypes.h"
+
+namespace base {
+namespace mac {
+
+// Templated class for managing the life of a Mach port, releasing via
+// mach_port_deallocate either its send and/or receive rights. The template
+// parameter allows for a specific kind of Mach port to be specified
+// for specialized Mach port types.

[Mark Mentovai, 2012/10/16 16:17:52]

But practically speaking, at least in userland, everything’s a mach_port_t, and
even routines like mach_host_self are declared as returning a mach_port_t and
not a host_name_port_t. Would we realize a code size savings if we did this as a
straight class with the implementation in a .cc file, rather than having to
instantiate template code all over the place?

[Robert Sesek, 2012/10/16 16:30:59]

Done.

+template <typename PortT>
+class ScopedMachPort {
+ public:
+  ScopedMachPort() : port_(MACH_PORT_NULL) {}
+
+  explicit ScopedMachPort(mach_port_t port) : port_(port) {}
+
+  ~ScopedMachPort() {
+    if (port_ != MACH_PORT_NULL) {
+      mach_port_deallocate(mach_task_self(), port_);
+      port_ = MACH_PORT_NULL;
+    }
+  }
+
+  operator PortT() const {
+    return port_;
+  }
+
+  PortT get() const {
+    return port_;
+  }
+
+ private:
+  PortT port_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedMachPort);
+};
+
+// A specialization of the base ScopedMachPort that is used for the generic
+// mach_port_t.
+class ScopedMachPortT : public ScopedMachPort<mach_port_t> {

[Mark Mentovai, 2012/10/16 16:17:52]

If you’re going to do the templated thing, why bother with this? It’s never
used. Every time you did use the template, you used it for host_name_port_t.

[Robert Sesek, 2012/10/16 16:30:59]

Removed.

+};
+
+}  // namespace mac
+}  // namespace base
+
+#endif  // BASE_MAC_SCOPED_MACH_PORT_H_