Re: Proposed Fix for GTK3 Crashes - dlopen flags

Scott Talbert wrote:
> On Tue, 24 Feb 2015, Scott Talbert wrote:
>
>> I've been working on investigating a couple of crashes that occur with
>> wxPython 3.0.2.0 with a GTK+3 backend:
>> http://trac.wxwidgets.org/ticket/16820
>>
>> There is a similar crash that occurs when using a wx.Printer.
>>
>> Anyway, I've spent considerable time investigating these and found
>> that the crash is because GTK performs some dlsym() calls to lookup
>> symbol names and fails in going so because its symbols were loaded in
>> the local namespace, not the global namespace (ie, RTLD_LOCAL vs
>> RTLD_GLOBAL). I've discussed this with the GTK devs and basically, GTK
>> expects its symbols to be loaded globally.
>>
>> Thus, I have a solution that I would like to propose for discussion:
>>
>> diff -up wxPython/src/__init__.py.dlopenflags wxPython/src/__init__.py
>> --- wxPython/src/__init__.py.dlopenflags 2013-02-27 15:14:01.000000000
>> -0500
>> +++ wxPython/src/__init__.py 2015-02-24 20:43:44.143492336 -0500
>> @@ -42,7 +42,11 @@ __all__ = [
>> ]
>>
>> # Load the package namespace with the core classes and such
>> +import dl, sys
>> +flags = sys.getdlopenflags()
>> +sys.setdlopenflags(flags|dl.RTLD_GLOBAL)
>> from wx._core import *
>> +sys.setdlopenflags(flags)
>> del wx
>>
>> if 'wxMSW' in PlatformInfo:
>>
>> ===
>>
>> 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?

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.

-- 
Robin Dunn
Software Craftsman
http://wxPython.org

-- 
You received this message because you are subscribed to the Google Groups "wxPython-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
For more options, visit https://groups.google.com/d/optout.