swig-user

Re: [Swig-user] Using classes/functions/etc from a dynamic/sharedlibrary

[David B. <da...@da...>]

Swig is not going to do anything unless you give it the actual definition of mylib::myclass.  The declaration you have below is just a forward class declaration (which Swig just ignores 
because it provides no useful information).

Cheers,
Dave


On Wed 07/01/09 11:12 AM , "Justin Bayer" bay...@go... sent:
> Hi group,
> 
> I have a dynamic library on OS X which has some classes/functions that
> I want to access from python. So far I have done the following:
> 
> mylib.i
> ---------------------------
> %module mylib
> %{
> #include "mylib.h"
> %}
> 
> class mylib::myclass;
> #define BLUBB 1
> ---------------------------
> 
> then I run the following commands:
> 
> $ swig -Wall -python -c++ src/swig/arac.i
> *snip*
> $ gcc -lmylib -Lpath/to/mylib -c -Wno-long-double
> src/swig/arac_wrap.cxx -I/path/to/mylib/headers
> -I/usr/local/include/python2.6 -I/usr/local/lib/python2.6/config -o
> mylib_wrap.o
> *snip*
> $ gcc -lmylib -Lpath/to/mylib -Wno-long-double -bundle -undefined
> suppress -flat_namespace mylib_wrap.o -o _mylib.so
> *snip*
> $ python -c "import mylib; dir(mylib._mylib)"
> ['BLUBB', '__doc__', '__file__', '__name__', '__package__']
> 
> So myclass does not appear. What am I doing wrong?
> 
> 
> Regards,
> -Justin
> 
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Re: [Swig-user] Using classes/functions/etc from adynamic/sharedlibrary

[John W. <jwh...@ta...>]

Note also that this doesn't have to be a complete class definition.  You
can provide a subset of the class declaration in your interface file
(mylib.i) to control which functionality you want to expose into the
target language (Python, in your example).  If you want all code in
mylib.h wrapped, then just use:

	%include "mylib.h"

instead of your forward declaration.

-- John

Re: [Swig-user] Using classes/functions/etc from adynamic/sharedlibrary

[Justin B. <bay...@go...>]

>        %include "mylib.h"
>
> instead of your forward declaration.

I did that - one problem though. I have an abstract base class of
which the header file I do not %include. This leads to the derived
classes to miss the base classes methods. I cannot %include the ABC
though, because SWIG complains in that case.

How do I get the methods of the ABC?

Re: [Swig-user] Using classes/functions/etc from adynamic/sharedlibrary

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

Justin Bayer wrote:
> >        %include "mylib.h"
> >
> > instead of your forward declaration.
>
> I did that - one problem though. I have an abstract base class of
> which the header file I do not %include. This leads to the derived
> classes to miss the base classes methods. I cannot %include the ABC
> though, because SWIG complains in that case.
>
> How do I get the methods of the ABC?
Define the minimal amount of the ABC for SWIG to be useful, eg 
constructors, destructors virtual methods. Why is SWIG complaining 
about... that could be fixable if you explain the issue.

William

Re: [Swig-user] Using classes/functions/etc from adynamic/sharedlibrary

[Justin B. <bay...@go...>]

> Define the minimal amount of the ABC for SWIG to be useful, eg constructors,
> destructors virtual methods.

I was hoping I would not have to do that, but okay.

> Why is SWIG complaining about... that could be
> fixable if you explain the issue.

It's actually gcc that complains:
error: cannot allocate an object of abstract type 'MyABC' myabc.h:21:
note:   since type 'MyABC' has pure virtual functions

Re: [Swig-user] Using classes/functions/etc from adynamic/sharedlibrary

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

Justin Bayer wrote:
>> Define the minimal amount of the ABC for SWIG to be useful, eg constructors,
>> destructors virtual methods.
> 
> I was hoping I would not have to do that, but okay.
> 
>> Why is SWIG complaining about... that could be
>> fixable if you explain the issue.
> 
> It's actually gcc that complains:
> error: cannot allocate an object of abstract type 'MyABC' myabc.h:21:
> note:   since type 'MyABC' has pure virtual functions
> 

Since SWIG has not parsed MyABC, it cannot determine that it is an ABC. 
You need to give it some more type information. It can get away with not 
having much type information, unlike the C++ compiler, but there are 
limits as to what you can hide as it will have to make assumptions which 
can lead to uncompileable code.

William