[PyKDE] Threading, PyQt and SIP
claus at slac.stanford.edu
Thu Mar 25 05:48:00 GMT 2004
SIP 4 solves the problem! Thanks!
A nit: When I added %ModuleCode, #line 44 "c:\Online\Ebf\sip\EBF.sip" was generated in sipEBFcmodule.cpp. The compiler warns about "unrecognized character escape sequences"...
> -----Original Message-----
> From: Phil Thompson [mailto:phil at riverbankcomputing.co.uk]
> Sent: Sunday, March 21, 2004 10:30 PM
> To: pykde at mats.imk.fraunhofer.de
> Cc: Claus, Richard
> Subject: Re: [PyKDE] Threading, PyQt and SIP
> On Monday 22 March 2004 02:19, Claus, Richard wrote:
> > I've written a library in C++ that takes a buffer of data
> and calls
> > back application resolved virtual methods based on the
> contents of the buffer.
> > All the work is done in place, so there is no memory
> management other
> > than temporaries created on the stack. It would be very
> useful for us
> > if this library were also available from Python, so I've used SIP
> > 3.10.1 (snapshot
> > 20040313-194) to expose its interface. I haven't tried to
> do anything
> > tricky with %MethodCode or anything like that.
> > The results on Windows XP (Python 2.3.3, MSVS .Net 7.1) so far:
> > - With a pure C++ application dynamically linked against
> this library,
> > I have seen no problems and everything works as expected. - With
> > single and multi-threaded, non-PyQt applications, I have seen no
> > problems and everything works as expected. - With PyQt
> applications, I
> > see no problems when I use the library from the Qt GUI
> thread (the one
> > running QApplication.exec_loop()).
> > - With PyQt applications, there are problems when I use the library
> > from a non-GUI thread. Often Python crashes with "Fatal
> Python error:
> > GC object already tracked". With Python 2.2, the message was
> > something like "...GC object already on linked list".
> Other crashes
> > are access violations in seemingly random locations. Once, I saw a
> > Python traceback involving libqtc.sipCallCtor(204,self,args) ->
> > AttributeError: sipThis before getting the GC error
> (sorry, I can't
> > paste it in right now). This appeared to happen when the
> GUI thread
> > decided to update the screen. The amount of time things
> appear to run
> > correctly before crashing seems to be random.
> How are the threads being created?
> > There are no intentional interactions between the usage of
> my library
> > and the rest of the PyQt application, e.g., the library's methods
> > aren't trying to update the screen.
> Problems like this are usually related to unintentional
> interactions :)
> > Can someone please describe for me how to keep two SIP applications
> > running in two threads of the same process from tangling?
> The first thing I'd try is SIP v4. The thread handling is
> much more forgiving because it uses Python's new thread API.
> > Or is the rule of the game that there can be only one
> thread using SIP
> > generated code? If so, can I solve this by going to one of
> the other
> > C/C++ to Python interface packages, e.g., SWIG or Boost? Can these
> > coexist with SIP?
> I don't know about SWIG. Boost ignored threads and the GIL
> completely, I don't know if this has changed recently.
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