Re: Proposed Fix for GTK3 Crashes - dlopen flags

On Tue, 3 Mar 2015, Robin Dunn wrote:

>>> Basically, this would change the dlopen flags before importing the
>>> core module to RTLD_GLOBAL and then change them back afterwards. That
>>> way, the core module and its dependencies (to include GTK) are loaded
>>> into the global namespace.
>>> 
>>> Comments on this proposal?
>>> 
>>> It needs more work but I wanted to get feedback before finalizing a
>>> patch. (ie, it probably only needs to be done on when we're using a
>>> GTK+3 backend, needs to check whether the dl module is available, etc.)
>> 
>> Okay, here's an updated version of the patch. Unfortunately, it isn't
>> possible to check the backend (and only change the dlopen flags if on
>> GTK+3) because the backend isn't known until _core.so is imported. After
>> that point, it's too late.
>> 
>> It's possible that we could somehow have SWIG put this into the
>> generated _core.py only for GTK+3, but I'm not sure how to do that.
>> 
>> Comments?
>
> I'm curious how pygtk handles this. Have you checked there?

PyGTK is GTK2 only.  I don't think they started doing this dynamic UI
builder stuff until GTK3.  In PyGObject (the recommended GTK3 replacement
for PyGTK), they basically do exactly this - dlopen all the GTK libraries
into the global namespace.

> IIRC in the early days of OSX the default was the OSX equivalent of
> RTLD_GLOBAL, and it caused some hard to diagnose issues.  The alternative
> at the time was a 2 level namespace and using that meant that extension
> modules couldn't find the Python C API functions, so it was even worse.
> So setting RTLD_GLOBAL worries me a bit.

I too am a bit worried about the impacts of RTLD_GLOBAL.  Thus, I 
suggested a less risky workaround patch to wxWidgets for the Font Chooser 
crash - posted to the bug report.  It could probably be used in the 
wxPython C++ code if the wxWidgets guys won't take it.

Scott