On 09/11/2013 15:05, John Emmas wrote:
On 08/11/2013 14:16, Kjell Ahlstedt wrote:
Before Gtk::Window::_destroy_c_instance() calls gtk_object_destroy(),
it calls Gtk::Object::disconnect_cpp_wrapper(), which removes
glibmm_Glib::quark_ and adds glibmm_Glib::quark_cpp_wrapper_deleted_.
Thanks Kjell, I'll test that on my system and see if I also get those
changes (I'm guessing I won't).
Hi Kjell, I got so bogged down with gtkmm problems that I forgot about
comparing my own execution path here - but yes, my code follows the very
same path. FWIW this is the interesting code from 'gtk/gtkmm/object.cc'
(function 'Object::disconnect_cpp_wrapper()')
if(gobj())
{
//Prevent gtk vfuncs and default signal handlers from calling our
instance methods:
g_object_steal_qdata((GObject*)gobj(), Glib::quark_); //It will
no longer be possible to get the C++ instance from the C instance.
//Allow us to prevent generation of a new C++ wrapper during
destruction:
g_object_set_qdata((GObject*)gobj(),
Glib::quark_cpp_wrapper_deleted_, (gpointer)true);
//Prevent C++ instance from using GTK+ object:
gobject_ = 0;
}
Pay particular attention to that last comment. This, I believe, is the
root of the problem. Setting 'gobject_' to zero DOES NOT prevent any
C++ wrapper from attempting to access it. Here's an example from
Gtk::Widget::on_unrealize() which can get called AFTER the call to
Object::disconnect_cpp_wrapper().
void Gtk::Widget::on_unrealize()
{
BaseClassType *const base = static_cast<BaseClassType*>(
g_type_class_peek_parent(G_OBJECT_GET_CLASS(gobject_)) // Get
the parent class of the object class (The original underlying C class).
);
if(base && base->unrealize)
(*base->unrealize)(gobj());
}
The commented line consistently crashes (for me) if 'gobject_' is zero.
I gave a very similar example here yesterday:-
https://mail.gnome.org/archives/gtkmm-list/2013-November/msg00034.html
The consensus of replies was that it's NOT safe to call these functions
if gObject_ == NULL. Does that give us any more help in tracking these
issues down??
John
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