GtkSharp/Source/Libs/GLibSharp/InitiallyUnowned.cs
Sebastian Dröge 89cfd16c10 Ensure to sink floating references passed unowned to GetObject() and to not increase their reference count
The API contract between GObject-Introspection and bindings is that
functions returning transfer-none floating references pass a reference
to the bindings that should be taken ownership of by sinking it. Not
doing so is wrong and will lead to memory leaks or double frees.

Previously we would not distinguish this case and simply increment the
reference count. In addition we would then sink the floating reference
when the Object.Raw field is set later for InitiallyUnowned subclasses.

Remove that last part and instead check directly in Object.Raw.set if we
get a floating reference and if so simply sink it here and take
ownership of it. The general assumption of Object.Raw.set is that it
gets passed a reference that it should take ownership of.

So in summary:
1) GetObject() would only increase the reference count of unowned,
   non-floating references so that we own it. For unowned, floating
   references it assumes ownership of the reference.
2) Raw.set assumes ownership of the reference passed to it and if it
   happens to be a floating reference then it will first sink it.

Also warn if we get a floating, owned reference passed to GetObject() as
that case is not allowed by GObject-Introspection and would cause the
reference to be leaked.

This fixes a memory leak with functions returning unowned, floating
references and with functions returning owned, non-floating references
of InitiallyUnowned subclasses. And at the same time keeps constructors
for InitiallyUnowned subclasses working correctly without leaks.

See https://gitlab.freedesktop.org/gstreamer/gstreamer-sharp/issues/31
2021-01-24 19:55:17 +01:00

74 lines
2.8 KiB
C#

// InitiallyUnowned.cs - GInitiallyUnowned class wrapper implementation
//
// Authors: Mike Kestner <mkestner@novell.com>
//
// Copyright (c) 2004-2005 Novell, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of version 2 of the Lesser GNU General
// Public License as published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this program; if not, write to the
// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA 02111-1307, USA.
namespace GLib {
using System;
using System.Runtime.InteropServices;
public class InitiallyUnowned : Object {
protected InitiallyUnowned (IntPtr raw) : base (raw) {}
delegate IntPtr d_g_initially_unowned_get_type ();
static d_g_initially_unowned_get_type g_initially_unowned_get_type = FuncLoader.LoadFunction<d_g_initially_unowned_get_type>(FuncLoader.GetProcAddress(GLibrary.Load(Library.GObject), "g_initially_unowned_get_type"));
public new static GLib.GType GType {
get {
IntPtr raw_ret = g_initially_unowned_get_type();
GLib.GType ret = new GLib.GType(raw_ret);
return ret;
}
}
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
delegate void d_g_object_ref_sink(IntPtr raw);
static d_g_object_ref_sink g_object_ref_sink = FuncLoader.LoadFunction<d_g_object_ref_sink>(FuncLoader.GetProcAddress(GLibrary.Load(Library.GObject), "g_object_ref_sink"));
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
delegate bool d_g_object_is_floating(IntPtr raw);
static d_g_object_is_floating g_object_is_floating = FuncLoader.LoadFunction<d_g_object_is_floating>(FuncLoader.GetProcAddress(GLibrary.Load(Library.GObject), "g_object_is_floating"));
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
delegate void d_g_object_force_floating(IntPtr raw);
static d_g_object_force_floating g_object_force_floating = FuncLoader.LoadFunction<d_g_object_force_floating>(FuncLoader.GetProcAddress(GLibrary.Load(Library.GObject), "g_object_force_floating"));
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
delegate void d_g_object_unref(IntPtr raw);
static d_g_object_unref g_object_unref = FuncLoader.LoadFunction<d_g_object_unref>(FuncLoader.GetProcAddress(GLibrary.Load(Library.GObject), "g_object_unref"));
public bool IsFloating {
get {
return g_object_is_floating (Handle);
}
set {
if (value == true) {
if (!IsFloating)
g_object_force_floating (Handle);
} else {
g_object_ref_sink (Handle);
g_object_unref (Handle);
}
}
}
}
}