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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: How to print Task_ID type? (GNAT SunOS)
Date: 1996/04/06
Message-ID: <dewar.828789454@schonberg>#1/1
X-Deja-AN: 146087701
references: <4xu3yzpoi7.fsf@leibniz.enst-bretagne.fr>
 <4k1ma9$brt@michp1.redstone.army.mil> <4k50tc$7ge@mulga.cs.mu.OZ.AU>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada
Date: 1996-04-06T00:00:00+00:00
List-Id: <comp.lang.ada>

Fergus says

"This is because the C standard allows implementations to represent different
pointer types differently."

That's true, but in practice very rarely taken advantage of.

The Ada standard permits this too of course, and GNAT does take advantage
of this (using double width pointers for pointers to unconstrained
arrays).

It is surprising how MUCH Ada code out there relies on the assumption
that all pointers are the same size as addresses. n fact we ran into this
so often in GNAT, that now GNAT allows you to specify the size of an
access type, and force this to be true if you want it, e.g.

    type g is access string;
    for g'size use address'size;

This representation is less time efficient but lots of existing Ada code
had this assumption deeply built in.