Re: [Chicken-users] a couple of questions about foreign functions

[Felix Winkelmann]

Am Wed, 21 Jan 2004 23:52:38 -0800 hat Valentyn Kamyshenko 
<address@hidden> geschrieben:

> > When this function returns, `buf' will point into a dead stack area,
> > so the data is likely to be corrupted after the return.
>
> I suspected it!.
>
> What makes the following code correct, then (have found it in runtime.c):
>
> [...]
>
> it looks like the vector is created on the stack, and then 'returned' to 
> the continuation...

Indeed. But the invocation of the continuation (via `C_kontinue') does
*never* return, the data will remain on the stack and be collected
when a certain stack-limit is reached. C-code wrapped with ##core#primitive
invokes it's continuation (and thus the stack is not popped), but code
wrapped with foreign-[callback-]lambda will return normally, in C fashion.

> > If you mean error-routines that eventually invoke Scheme, then
> > you should use foreign-callback-lambda*. If you handle the
> > error in C (for example to display a message and exit), then
> > I see no problem.
> I actually meant smth similar to ##sys#signal-hook (the hope was that 
> there is C function that do the same).

Not directly. You will have to invoke a Scheme callback for this
(for example defined with `define-external'). But actually it would be
helpful to have a simple C API for raising errors. Thanks for the
suggestion!


cheers,
felix