On Fri, 3 Jan 1997, Olaf Seibert wrote:

> Chris G Demetriou <Chris_G_Demetriou@ux2.sp.cs.cmu.edu> wrote:
> > The problem was that __syscall() was being used inconsistently --
> > sometimes it was being treated as if it returned an off_t, sometimes
> > it was being treated as if it returned a pointer, sometimes it was
> > being treated as if it returned an 'int'.
> >
> > That's actually _correct_.  It does, in fact, return those different
> > types, depending on the call, rather than returning an off_t.
> > however, it's impossible to prototype a function to have multiple
> > return types...
> 
> __syscall() could be prototyped to return a *union* of all these things.
> 
> At the locatation where the actual value is returned, it requires a cast
> of the value to this union, however, and this is not possible in
> Standard C. Gcc will allow it, though. For portability, a temporary
> union variable would be required.

Of course you can do this in standard C:

union intandlongandoff_t {
	int	i;
	long	l;
	off_t	o;
}

union intandlongandoff_t foo;

IntFunction(*((int*)(&foo)));

LongFunction(*((long*)(&foo)));

OffTFunction(*((off_t*)(&foo)));


This assumes that all the types align at the bottom address, but I assume
that's allowed...

Jules

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