Re: structs called by reference only

[Maciej Stachowiak <mstachow@mit.edu>]

> While trying to wrap ncurses, I wonder if it is necessary to define
> the struct WINDOW as scheme object. The library functions themselves
> only call and return pointers to WINDOW -objects. My first approach
> is to hide that struct from the interface at all and just cast
> pointers into integers and back before applying libguile's
> conversion functions, or let g-wrap do that for me.

This is a bad idea, Scheme code would then be able to forge pointers
by passing made up ints instead of ints that represent struct WINDOW
objects. User scheme code should not cause a segfault when passing 0
instead of a window structure, just a tyoe error. Also, your suggested
wrapping would make it impossible to garbage-collect window
structs. You're not thinking of making scheme code free them
explicitly, are you?

> But I know that the SCM-ncurses-interface of J.Leveling creates
> windows as scheme objects. So is there a flaw in the former naive
> approach which hides structs that are called by reference only from
> the interface-file ?

It's not that hard to wrap C structs as Scheme objects, especially if
they are only ever accessed by reference. Do you want some sample
code?

 - Maciej Stachowiak