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Newsgroups: comp.lang.ada
Date: Tue, 16 Oct 2018 22:16:17 -0700 (PDT)
In-Reply-To: <pq2toa$j4s$1@franka.jacob-sparre.dk>
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Subject: Re: Least Dangerous Way to Do This ?
From: Petter Fryklund <petter.fryklund@atero.se>
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Xref: reader02.eternal-september.org comp.lang.ada:54611
Date: 2018-10-16T22:16:17-07:00
List-Id: <comp.lang.ada>

> > Hi Everyone
> >
> > Okay, don't laugh(or laugh too hard)
> >
> > I need to interface with automatically generated C. function pointers a=
re=20
> > represented as a pointer to a pointer to a char. This is weird but done=
=20
> > for pointer arithmetic purposes.
>=20
> It's not certain (in the real world, at least) if a function pointer and =
an=20
> object pointer have the same representation. We treat them as completely=
=20
> different things in our code generator, because some weird machines (in=
=20
> particular the U2200) have very large representations for function pointe=
rs=20
> (one version was 8 36-bit words!). Similarly, on the 16-bit 8086 compiler=
s,=20
> function pointers carried a segment (thus a 32-bit address), and object=
=20
> pointers usually didn't (thus a 16-bit address).
>=20
> So if you want this code to work in different environments, I'd try to av=
oid=20
> mixing the two (as Simon suggested).
>=20
>                                                   Randy.

I don't think the U2200 is weird, it is or was actually a very nice machine=
. Unfortunately most of the Unisys Link=C3=B6ping people where kicked out b=
efore we could try Ada, but we where very interested in it then. I for a wh=
ile maintained the local releases of COBOL before going in to performance a=
nalysis and cache-disk simulations.

Is there any U2200 out there? comp.sys.unisys talks a lot about virtual one=
s.

Regards,
Petter