Re: [Swig-user] Callback problem

[Nitro <ni...@dr...>]

Am 05.10.2006, 01:58 Uhr, schrieb Günter Dannoritzer <dan...@we...>:

> Hi,
>
> I am trying to create a callback and follow chapter 5.4.9 "Pointers to
> functions and callbacks" on page 38 of the swig documentation.
>
> It shows the use of the %constant directive to define some call back
> functions like this:
>
>
> 	/* Function with a callback */
> 	int binary_op(int a, int b, int (*op)(int,int));
>
> 	/* Some callback functions */
> 	%constant int add(int,int);
> 	%constant int sub(int,int);
> 	%constant int mul(int,int);
>
> Now when I do that with my function, I am getting a compiler error, that
> the function I used instead of the add function is undeclared.
>
> Here is the code I am using in my .i file:
>
> 	typedef int (*brh_t) (handle_t, unsigned int generation);
>
> 	brh_t set_handler(handle_t, brh_t new_h);
>
> 	%constant brh_t my_handler(handle_t, unsigned int generation);
>
>
> The error message is:
>
> my_wraper.c: error: my_handler undeclared here (not in a function)
>
> What am I overlooking here? As in the documentation shown, I want to use
> myhandler() in my Python code. I am aware that this needs to be declared
> in the _wrap.c file first, but wouldn't that need to be a function done
> by swig?

You need to define my_handler in your C code yourself somewhere. It could  
look like this for example:

typedef int (*brh_t) (handle_t, unsigned int generation);
brh_t set_handler(handle_t, brh_t new_h);

%{
     brh_t my_handler(handle_t, unsigned int generation)
     {
         printf("I was called!");
         return 0;
     }
%}

%constant brh_t my_handler(handle_t, unsigned int generation);

Of course you can also just link to the library which exposes my_handler  
(if you have a library that exposes it).

-Matthias