Re: [Chicken-users] ffi - the right way to return a list holding integers and strings

[felix winkelmann]

On 7/4/07, foobar <address@hidden> wrote:
> hi,
>
> as the title allready suggests i'm looking for a way to return a list
> from within
> a c-function. I know how to return a list, but what i don't know is how
> to fill
> some of the elements with strings. More importantly how does the
> allocation-deallocation-
> scheme look like in this situation?
>
> Here is a minimal example of what i want to do
>
> C_word return_a_list(){
>      int a = 1;
>      char *str = "just a test";
>      /* now i need to make the string an object that can be carried
>         around by the list. But how? C_string or C_string2? */
>
>     /* finally return the list with the ??? actually being something
> reasonable*/
>      C_return(C_h_list(2,C_fix(a),???);
> }
>
>
> How can this be done in a safe way?

You have to use storage that can be garbage collected, which means stack
storage. I recommend "foreign-primitive" and use "C_alloc" to allocate the
storage and "C_string2" to allocate the string.


cheers,
felix