Re: [Vala] Unregister a GType

[Igor Azevedo <igor azevedo neticle pt>]

Hi, I worked around this issue by modifying valac to change the code
generated for the <class>_get_type() function.

Originally it outputed something like this:

static volatile gsize test_module_type_id__volatile = 0;
if (g_once_init_enter (&test_module_type_id__volatile)) {
                (...)
GType test_module_type_id;
test_module_type_id = g_type_register_fundamental (g_type_fundamental_next
(), "TestModule", &g_define_type_info, &g_define_type_fundamental_info, 0);
g_once_init_leave (&test_module_type_id__volatile, test_module_type_id);
}
return test_module_type_id__volatile;


I added a check before attempting to register the type:

static volatile gsize test_module_type_id__volatile = 0;
if (g_once_init_enter (&test_module_type_id__volatile)) {
                (...)
GType test_module_type_id;

test_module_type_id = g_type_from_name ("TestModule");
if (test_module_type_id) {
g_once_init_leave (&test_module_type_id__volatile, test_module_type_id);
return test_module_type_id__volatile;
}

test_module_type_id = g_type_register_fundamental (g_type_fundamental_next
(), "TestModule", &g_define_type_info, &g_define_type_fundamental_info, 0);
g_once_init_leave (&test_module_type_id__volatile, test_module_type_id);
}
return test_module_type_id__volatile;

Are there any problems that can be caused due to this "workaround"?


Com os melhores cumprimentos,
Igor Azevedo

Neticle, serviços de webdesign e programação
Telm: 968 323 131
www.neticle.pt


2013/5/7 Igor Azevedo <igor azevedo neticle pt>

> 2013/5/5 PCMan <pcman tw gmail com>
>
> > On Sun, May 5, 2013 at 2:15 AM, Igor Azevedo <igor azevedo neticle pt>
> > wrote:
> > > 2013/5/4 Luca Bruno <lethalman88 gmail com>
> > >
> > > > On Sat, May 4, 2013 at 6:29 PM, Igor Azevedo <igor azevedo neticle pt
> > > wrote:
> > > > > Hello,
> > > > >
> > > > > I'm developing an application that dynamically loads plugins using
> > > > > GModule.
> > > > > Each of the plugins registers it's own GTypes but if I load, unload,
> > and
> > > > > finally reload them I get some errors and the modules don't load
> > properly.
> > > > > Errors are:
> > > > >
> > > > > (process:21259): GLib-GObject-WARNING **: cannot register existing
> > type
> > > > > `NeticleInfinityModulesBaseBaseModule'
> > > > >
> > > > > I understand why this happens, I'm registering a GType that was
> > already
> > > > > registered previously when I first loaded the plugin and even after
> > > > > unloading the module, the types remained registered, so it obviously
> > > > > fails.
> > > > >
> > > > > My question is if there is any way to unregister a GType so I can
> > reload
> > > > > the plugin successfully?
> > > > Are you doing this way?
> > > > https://live.gnome.org/Vala/TypeModules
> > > > https://live.gnome.org/Vala/TypeModuleSample
> > >
> > > My implementation was based on the first example you mentioned. Should I
> > > use TypeModule (like in the second example)?
> > >
> > > Thanks,
> > > Igor Azevedo
> >
> > You're not able to unregister a GType no matter it's a dynamic one or not.
> > Once registered, it should persist until the program terminates.
> > If you use type module, the type module objects and the types they
> > registered should not be freed until program termination.
> >
> > The underlying modules used inside your type module implementation can
> > be unloaded when they're not needed, but the GType registered persist.
> > When someone referenced that GType again and GObject type system finds
> > that the module is not loaded, it tries to load your type module.
> > So the module can be unloaded, but the GType it registered cannot.
> >
> > Unfortunately, this is hard to do correctly, and GTypeModule will be
> > deprecated later.
> > I talked with a gtk+ developer in #gtk+ channel last time and I'm
> > informed that GTypeModule will be moved.
> >
> > So, don't waste your time trying to do that. Once you register a new
> > GType inside the module, you'd better make it persist and never unload
> > it.
>
> What I'm really trying to accomplish here is reloading a certain external
> plugin (as there might have been changes to it) without having to restart
> my application. I don't really mind if the GTypes stay registered, as long
> as it doesn't bother me when I'm reloading the lib. Is there absolutely no
> way to do this?
>
> TypeModule seems to be able to reload the library without having issues
> regarding the registration of GTypes, how is this being done?