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

[Martin Braun]

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

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