# SWIG 3.0.3 Issue

**URL:** <https://www.ruby-forum.com/t/swig-3-0-3-issue/233648>\
**Category:** GNU Radio\
**Created:** [December 31, 2014, 4:20am UTC](https://www.ruby-forum.com/t/swig-3-0-3-issue/233648 "2014-12-31T04:20:38Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [December 31, 2014, 4:20am UTC](https://www.ruby-forum.com/t/swig-3-0-3-issue/233648/1 "2014-12-31T04:20:38Z")

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SWIG 3.0.3 was released today (30 Dec 2014) \< [http://www.swig.org/](http://www.swig.org/) \>,  
and I maintain this port in MacPorts. So, I naturally was curious to see  
if it works with GNU Radio. Sadly, GNU Radio fails because some of the  
SWIG-generated Python scripts have errors in them. For example, in SWIG  
3.0.2 the vector\_source\_b::make is defined in blocks\_swig1.py as:  
{{{  
def make(\*args, \*\*kwargs):  
“”"  
make(std::vector\< unsigned char,std::allocator\< unsigned char \>  
\> const & data, bool repeat=False,  
int vlen=1, tags\_vector\_t tags=std::vector\< gr::tag\_t \>())  
 → vector\_source\_b\_sptr  
}}}  
while in 3.0.3 this code is:  
{{{  
def make(data, repeat=False, vlen=1, tags):  
“”"  
make(std::vector\< unsigned char,std::allocator\< unsigned char \>  
\> const & data, bool repeat=False, int vlen=1, tags\_vector\_t  
tags) → vector\_source\_b\_sptr  
}}}

The above are both generated using the current GIT HEAD (c67281b6), just  
changing which version of SWIG is used.

For now, I won’t upgrade SWIG to 3.0.3 since this is a pretty critical  
issue. I’ll also report it to the SWIG devs to see what they think – it  
might be that there were changes to how SWIG %-things are used; it also  
might be that there’s an actual error in the SWIG Python generator code.

- MLD

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**Author:** ![mdeering](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/278dde/32.png) [@mdeering](https://www.ruby-forum.com/u/mdeering)\
**Post date:** [January 4, 2015, 11:10am UTC](https://www.ruby-forum.com/t/swig-3-0-3-issue/233648/2 "2015-01-04T11:10:44Z")

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Yay, SWIG troubles. Until we’ve figured out what’s up, we should  
probably put in a version check \< 3.0.3 into our build setup.

From your example, I actually prefer the 3.0.3 code output and am  
curious why this would throw an error.

M

---

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**Author:** ![mdeering](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/278dde/32.png) [@mdeering](https://www.ruby-forum.com/u/mdeering)\
**Post date:** [January 4, 2015, 8:01pm UTC](https://www.ruby-forum.com/t/swig-3-0-3-issue/233648/3 "2015-01-04T20:01:44Z")

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On Sun, Jan 4, 2015 at 5:09 AM, Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Yay, SWIG troubles. Until we’ve figured out what’s up, we should  
> probably put in a version check \< 3.0.3 into our build setup.
> 
> From your example, I actually prefer the 3.0.3 code output and am  
> curious why this would throw an error.
> 
> M

Yes, this is supposedly a new feature of SWIGs. From their changelog:

2014-10-28: vadz  
[Python] Patch #201 The generated .py file no longer uses \*args for all  
Python parameters.  
Instead, the parameters are named using the C++ parameter names.

2014-10-21: wsfulton  
Fix issue #242 - Use of the “kwargs” feature no longer automatically  
turns  
on the  
“compactdefaultargs” feature if the target language does not support  
kwargs.  
Only Java and Python support kwargs, so this affects all the other  
languages.

\*\*\* POTENTIAL INCOMPATIBILITY \*\*\*

So either we need to change the syntax of something to point swig to set  
a  
proper default argument for std::vector arguments or they need to fix a  
bug.

Tom

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<div class="post-metadata">

**Author:** ![mdeering](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/278dde/32.png) [@mdeering](https://www.ruby-forum.com/u/mdeering)\
**Post date:** [January 4, 2015, 9:04pm UTC](https://www.ruby-forum.com/t/swig-3-0-3-issue/233648/4 "2015-01-04T21:04:12Z")

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I sent the primary SWIG maintainer (William S Fulton) an email, and got  
a prompt reply forwarding my email to the SWIG developer’s list. He  
primarily just verified and checked in the changes (that Tom found and  
quoted, below); he hopes that some of the SWIG developers can help him  
figure out what’s going on – is it a bug in their code, or the way GNU  
Radio is handling things. I don’t subscript to this list; maybe Tom or  
Martin does? I do see SWIG checkins, so if anything comes up there  
hopefully I’ll catch it.

On Sun, Jan 4, 2015, at 05:09 AM, Martin B. wrote:

> Yay, SWIG troubles. Until we’ve figured out what’s up, we should  
> probably put in a version check \< 3.0.3 into our build setup.

Agreed.

> From your example, I actually prefer the 3.0.3 code output and am  
> curious why this would throw an error.

Yes, I do to.

On Sun, Jan 4, 2015, at 01:59 PM, Tom R. wrote:

> Yes, this is supposedly a new feature of SWIGs. From their changelog:  
> {{{  
> 2014-10-28: vadz  
> [Python] Patch #201 The generated .py file no longer uses \*args for all  
> Python parameters.  
> Instead, the parameters are named using the C++ parameter names.

2014-10-21: wsfulton  
Fix issue #242 - Use of the “kwargs” feature no longer automatically  
turns on the  
“compactdefaultargs” feature if the target language does not support  
kwargs.  
Only Java and Python support kwargs, so this affects all the other  
languages.

\*\*\* POTENTIAL INCOMPATIBILITY \*\*\*  
}}}

> So either we need to change the syntax of something to point swig to set a  
> proper default argument for std::vector arguments or they need to fix a bug.

Also agreed. I think the hard part will be to keep compatibility for  
both the “new” and “old” ways at the same time, if this is not a bug. -  
MLD