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.
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.
Can someone please describe for me how to keep two SIP applications running in two
threads of the same process from tangling? 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?
Thanks for any help,
Ric
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