Re: Null reference

On Nov 25, 2003, at 11:05 AM, <renz@xxxxxxxxxxxxxxxx> wrote:

> Hello all,
>
> I ran into a problem, but not sure whether it is a SWIG or Python 
> problem.
>
> This is a simplest class with operator == defined:
>
> // v.h
> class v
> {
>    public:
>       v(const int a) : data(a) {}
>       bool operator==(const v& u) const {return data == u.data;}
>       int data;
> };
>
> % python
> Python 2.2.2 (#1, Feb 10 2003, 00:23:53)
> [GCC 3.2 20020903 (Red Hat Linux 8.0 3.2-7)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
> > > > import mod
> > > > None in (mod.v(1), None)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
>   File "mod.py", line 38, in __eq__
>     def __eq__(*args): return apply(_mod.v___eq__,args)
> TypeError: null reference
>
> This error does not occur if operator == is not defined.  Why == is 
> called here anyway?
>
> Could anyone help?  Thanks.

I don't know the whole flow of control here, but that error message 
about "null reference"
is definitely coming from SWIG.   It won't let you pass a NULL pointer 
to any function
taking a reference---since C++ doesn't allow references to be NULL.

-- Dave

_______________________________________________
Swig maillist  -  Swig@xxxxxxxxxxxxxxx
http://mailman.cs.uchicago.edu/mailman/listinfo/swig