[Coco] os9 intercept call from C

[Gene Heskett]

On Saturday 18 April 2020 12:44:08 Walter Zambotti wrote:

> Opps nine characters long!!!
>
> Which is exactly when the Ansi front end will start converting long
> variable names to hashes.

What ansi front end are you refering to?

> On 2020-04-19 00:41, Walter Zambotti wrote:
> > 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.


Cheers, Gene Heskett
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