Re: Potential need for librsvg API breakage

[Tim Janik <timj imendio com>]

On Wed, 1 Nov 2006, Dominic Lachowicz wrote:

> Hi,
>
> So I'm currently faced with a dilemma that's hitting a lot of users,
> causing their applications to crash and otherwise behave badly. I'd
> appreciate if people might offer any insight they had on the issue.
>
> In the 2.16.x series, librsvg's fundamental "type", the RsvgHandle,
> became a subclass of GObject, and is registered via
> g_type_register_static(). AFAIK, this relationship isn't exposed in
> any way that the public ABI is concerned (i.e. RsvgHandle is just a
> anonymous typedef in the header file).
>
> The problem is that librsvg is a library that gets used by a lot of
> plugins - I can think of at least 3 places: AbiWord's image loader,
> GdkPixbuf's "loader" architecture, and GTK+'s theme engine. Some of
> these (GTK+'s theme engine bits come to mind) make heavy use of what
> GObject calls "dynamic types" that get loaded/unloaded as necessary,
> and the GModule that ultimately called
> g_type_register_static(RSVG_TYPE_HANDLE, ...) may get unloaded.

this is already broken and has to be fixed. 
if you want to be able to unload a type implementaiton, you MUST
use g_type_register_dynamic.
using g_type_register_static and unloading its implementaiton is as
good as dlopen(); atexit(dlsym()); dlclose();
the alternative is of course to make the module effectively unloadable
by means of g_module_make_resident or dlopen(self) once loaded.

> Since
> there is no way to signal that types need to be unregistered, this
> causes subsequent registration of the RsvgHandle type to fail, and
> lots of code to go belly-up. This is bad.
>
> Now, I don't intend to pass judgment on the type registration system.
> I just want to come up with the best way to fix the problem I'm
> encountering. I can think of a few solutions, but I welcome other
> ideas and suggestions for implementing my proposals.

> 3) Whatever you all come up with

i'm not sure what exactly your problem is here.
if it's just the combo of g_type_register_static + unloading,
simply prevent unloading or use g_type_register_dynamic.
if it's something else, i didn't manage to grasp it from your email ;)

> Thanks for your help and understanding,
> Dom

---
ciaoTJ