[C++-sig] Re: Calling a python function from C++ (from Jeff Holle)
Jeffrey Holle
jeff.holle at verizon.net
Wed Jun 30 08:39:46 CEST 2004
Given what the name of this exception, I assume there is a source of
information to obtain useful information about it.
To this end, I've dug a bit into the Python C API and found the added
the following to my code example:
catch (error_already_set& x) {
PyObject *err_type,*err_value,*err_traceback;
PyErr_Fetch(&err_type,&err_value,&err_traceback);
cout << "something bad happened" << endl;
}
While I see that err_type and error_value are not null pointers after
the call to PyErr_Fetch, I don't know what to do with either to get at a
useful message.
Can anybody provide any hints?
Jeffrey Holle wrote:
> I've explored whats actually going on some with my debugger and now see
> what is being thrown.
> It is "error_already_set". This is a trivial object (it has no
> attributes at all), and isn't much better than "catch (...)".
> However, its name implies something. Is there a meaningful error
> message set somewhere else that can be accessed within the catch clause
> of "error_already_set"?
>
> Jeff Holle wrote:
>
>>>
>>>
>>>> An underlining concern I have is error handling. When
>>>> PyImport_ImportModule fails, a NULL pointer is returned.
>>>> Seems like the underlining machinery in "handle<>" is intolerant of
>>>> this.
>>>
>>>
>>>
>>>
>>>
>>> What makes you say that?
>>>
>> You are correct about the success in compiling your much cleaner
>> example, and it works :-) , but has a flaw.
>>
>> When I hide the needed python script, the call to
>> PyImport_ImportModule returns NULL.
>> When this occurres, both your example and what I had created, but
>> commented out throws something because I can catch it with
>> "catch(...)". I don't however know how to be more specific. Any
>> hints? Whatever it is, it doesn't inherit from "exception".
>>
>> If I was operating on windows, I would anticipate it was a "structured
>> exception", or whatever Microsoft calls their propritary stuff. Don't
>> know of the equivalent on linux though. Without the "catch (...)",
>> the command line program exits with "Aborted".
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