Re: [Opensync-devel] python wrapper and plugin

[Mark E. <ma...@mp...>]

On Mon, 2012-08-13 at 12:16 +0200, Mark Ellis wrote:
> On Fri, 2012-08-10 at 20:07 +0200, Chris Frey wrote:
> > On Fri, Aug 10, 2012 at 01:40:35PM -0400, Chris Frey wrote:
> > > Glad to hear you're having success!  I'm still working out small details
> > > in the actual sync part.  Data flows from file-sync -> python-sample, but
> > > not quiet in the other direction yet.
> > 
> > Ok, data flows in both directions now, and the slow_sync flag argument
> > in the get_changes callback has been implemented.
> > 
> > - Chris
> > 
> 
> You're doing a magnificent job on this, many thanks. I've got some old
> patches to extend the wrapper, i'll have a look through them and see
> what state they're in a some point.
> 
> I've hit a snag early on, i think this may be one for a python list, but
> see what you think.
> 
> The first thing the synce plugin does is import some more python
> modules. The first being dbus, which in turn imports most of it's
> functionality from a C shared object. Quite correctly as I understand
> it, this object is not linked to libpython, and results in a python
> import error from undefined symbols. I first tried passing -Xlinker
> -export-dynamic when linking the python plugin, which didn't help,
> annoying since this seems to be the accepted way of fixing this.
> LD_PRELOAD with libpython fixes it, confirming everything else is ok,
> but the python plugin is linked to libpython, so it should already be
> loaded.
> 
> And to add insult to injury, this never happened in the 0.22 plugin.
> 

Found the problem. In opensync/module/opensync_module.c, the call to
g_module_open() uses the BIND_LOCAL flag, restricting the symbols from
the global namespace, which is not used in opensync 0.22. Removing the
flag resolves my symbol problem.

However, was this flag added for a good reason ? It was added in svn
revision 4396, and the reasoning makes sense, but I don't know whether
that was actually a real problem at the time. If the flag is necessary,
that makes python embedding somewhat difficult.

Mark