Re: [Swig-devel] octave support and boost_shared_ptr.i (octave crashes etc)

[William S F. <ws...@fu...>]

On 10/12/12 11:13, Kris Thielemans wrote:
>> From: William Fulton
>> Sent: 06 December 2012 20:57
>>
>> On 05/11/12 05:02, Kris Thielemans wrote:
>>> Hi
>>>
>>> I'm trying to use SWIG to wrap our C++ library. This has worked great
> for
>>> Python (work in progress of course) and I've now had a look at Octave
>> (using
>>> the same .i file).
>>>
>>> I first had to modify swig/Source/Modules/octave.cxx to add a line
>>>        Preprocessor_define((DOH *) "SWIG_CPLUSPLUS_CAST", 0);
>>> Otherwise, the generated code didn't compile. I'll submit this as a bug
> with
>>> an easy patch.
>>>
>>> More serious however are the problems I encounter when I use
>>> boost_shared_ptr.i. In summary, the way that the wrapped code works has
>>> problems with accessing the members of a shared_ptr, see below. I seem
>> to be
>>> able to fix this by modifying boost_shared_ptr.i as attached, i.e.
>>> replacing all occurrences of
>>> 	$descriptor(SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< TYPE >
>> *)
>>> by
>>> 	$descriptor(TYPE *)
>>>
>>> That seems rather scary though. Anyone any experience with this?
>> I really have no idea how good the octave support for shared_ptr is. The
>> initial commit of Lib/octave/boost_shared_ptr.i mentions that partial
>> support was added for boost::shared_ptr by Xavier. I developed the
>> Python/Java/C# versions and it is time consuming getting it right. I
>> would diff the file with the python version which is good because I'd
>> imagine the typemaps would be identical and any other problems will be
>> in the runtime system which I'm afraid probably requires a volunteer
>> like yourself to debug and fix.
>>
>
> Thanks William
>
> I haven't encountered any problems with this yet, but haven't done any
> extensive testing at all. In fact, I'm not 100% sure how I would test it
> (aside from not seeing any run-time errors). Maybe I could use valgrind to
> see if there's any memory leaks? I have done that now but unfortunately
> there development octave version that I'm running has memory leaks itself so
> it's not entirely straightforward to test this. I do see a few small leaks
> in the swig-octave run-time (which I don't have time to look into), and a
> few from calling my code (which surprised me). No major leaks with any of
> the shared_ptr though.
>
> In any case, without my suggested fix, the code doesn't run at all, which is
> arguably worse than having a memory leak :-)
>
> So, I'll submit a bug report with the patch then.
There is some testing mechanism in the test-suite for this. See 
SHARED_PTR_WRAPPER in li_boost_shared_ptr.i. You can check and compare 
with Java / Python for which this was originally developed. I strongly 
recommend porting the Java or Python version to Octave as it took quite 
some effort to put this test in place and it'll be a lot easier to port 
it to Octave than to re-invent something similar.

William