[Coco] os9 intercept call from C

[Walter Zambotti]

That's what I have trying to say guys.

The intercept function is not in the standard library as expected.

At least for me if I comment out my intercept function then it fails to
link with unresolved reference to intercept.

Figured out what is going wrong with the missing intercept library function.

An rdump shows it is in the library.

The problem starts when compiling with Ansi front end.  It converts the
reference to _hexvalue which I can see on the _ntbl file.

Which it should not do.  Especially since 'intercept' is only 8
characters long.

I suppose that's another bug in the Ansi front end.

I reverted the code back to K&R and it compiles and links with no problem.

Thanks guys

Walter

On 2020-04-18 23:38, Alex Evans wrote:
> Largely ignoring the fact that the above code uses ANSI syntax and the
> only MW C Compiler I am aware of for the CoCo uses K&R. If you use the
> provided intercept function in the library, the function to be called
> is a normal C function which takes an integer as a parameter (no RTI).
> If you are going to finable about directly using F$Icpt to set you
> trap, it needs to return using RTI. In addition, you need to set the
> pointer to the routine's storage area in U, but in the case of the
> function you have provided, it does not appear to need any storage
> space, so the fact you didn't set U shouldn't be a problem.
>
> I would think (untested) the answer would be:
> int catchall();
>
> int intflag=0;
>
> main(argc, argv)
> int argc;
> char *argv[];
> {
>   intercept(catchall);
>   while (!intrlag) {
>     pause();
>     write(1, "*", 1);
>   }
> }
>
> catchall(sig)
> int sig;
> {
>   intfrag=sig==0x03;
> }
>
> If your really, really want to directly use the system call, you need
> to also pull the signal number from somewhere. The routine expexted by
> F$cpt is a machine code routine, and sig will probably not be passed
> on the stack in the manner that MW C expects, so you need to figure
> out where it would be.
>