Re: Installing a C function into the IDT

On May 8, 4:47=A0pm, The Prisoner <nos...@[EMAIL PROTECTED]
> wrote:
> Hey-
>
> I was reading about interrupts, and I got to thinking it would be a real
> neat thing to use interrupts for program-wide exception handling. What I
> haven't been able to find is a clear guide or example program for how to
> install a C function into the IDT. And what happens about passing
argument=
s?
>
> I'd like to have something like this:
>
> void malloc_failure();
>
> Say I install this as interrupt slot 42, then I can do:
>
> if(!(p=3D(int*)malloc(1000*4))) // array of 1000 ints
> =A0 =A0__asm__ ("int $0x42");

I'm impressed that nobody else has mentioned that casting the result
of malloc is a good way to hide bugs and a bad way to use malloc yet.
Or on your odd choice of int sizes.  These are fairly serious problems
with your code that you should understand and solve before trying
anything as tricky, hazardous, and arcane as writing your own ISRs.

The cast is dangerous because it hides a missing include; with the
missing include, the "implicit" declaration of malloc will have the
wrong signature.  This can and will lead to crashes.  See
http://c-faq.com/malloc/mallocnocast.html
.

The correct size of an int is sizeof (int), not 4.  Even better would
be

  p =3D malloc (1000 * sizeof (*p));

as it will stay in synch if you change the type of 'p' (say, to long)
in the future.

-o