Re: [Discuss-gnuradio] SWIG, current gr-howto structure and exception specifiers

[Tom Rondeau]

On Tue, Jun 5, 2012 at 2:58 PM, Martin Braun <address@hidden> wrote:
> On Sun, Jun 03, 2012 at 10:22:14AM -0400, Tom Rondeau wrote:
>> On the other hand, I thought all standard exceptions were passed
>> properly through SWIG to Python already. I was under the impression
>> that if you're header file declares that it throws, then you can catch
>> it in Python. If that's not the case, then we should try to figure out
>> an easy way to handle that.
>
> Hi Tom and rest,
>
> so, I didn't do my research properly (partly): Exceptions *are* caught by
> SWIG, *but* they always end up as RuntimeErrors, regardless of what the
> exception type was in C++.
>
> So, for future reference:
> If you throw a std::invalid_argument in a block constructor, it ends
> up as a RuntimeError in Python. If you hand-edit the SWIG file and add
> an exception specifier, it ends up as a ValueError, which I think is the
> better behaviour, and it would be great if SWIG did this automatically.
>
> But frankly, I don't think this is that big a deal, I'll just catch
> RuntimeErrors instead of ValueErrors. Or edit .i-files.
>
> There's just no "clean" way to do this, because you'd either have to
> specify the exceptions in the header (which is deprecated C++), write a
> .i (redundant) or lose the exception type.
>
> MB


Yeah, I remember looking at this a while ago (since there is still an
error where FreeBSD treats one particular exception incorrectly).
There are a few exceptions that are handled by SWIG, but mostly the
C++ ones just get smashed into one or maybe two different exceptions
in Python.

I'm of the opinion that I agree that it's not a big deal. An exception
might now be technically incorrect, but I think we can translate as
needed.

Tom