Python callbacks & PyGILState_Release()

[Thomas Heller]

Randall Hopper <viznut at charter.net> writes:

>      What is the correct way to propagate exceptions from Python callbacks?
>
>      When I do this:
>
>      Python -> C++ -> Python Callback
>
> (example attached) an exception raised in the callback doesn't make it back
> across C++ to Python.
>
>      It appears that PyGILState_Release() at the bottom of the callback
> wrapper is resetting the error state (as I can set a global based on
> PyErr_Occurred() there, and can catch that up in the exception handler in
> Python).
>
>      This obviously isn't correct.  What should I be doing?
>
> Thanks,
>
> Randall
>
>
> ------------------------------------------------------------------------------
> void callback_wrapper( void *user_data )
> {
>   // Acquire interpreter lock
>   PyGILState_STATE gstate = PyGILState_Ensure();
>   ...
>   // Call Python
>   pyresult = PyEval_CallObject( pyfunc, pyargs );
>   ...
>   /*********** At this point, PyErr_Occurred() is true   **************/
>   /****** But it's not true when we return through C++ to Python  ******/

    if (pyresult == NULL)
        PyErr_Print();

>   // Free interpreter lock
>   PyGILState_Release(gstate);
> }

PyErr_Print() will do the 'right' thing´s.

Thomas