Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!decvax!ucbvax!hplabs!hpcea!hpfcdc!hpisla!wolpert
From: wolpert@hpisla.HP.COM (David Wolpert)
Newsgroups: comp.lang.c
Subject: Re: Re: machine specific languages (was: Re: C machine)
Message-ID: <5360001@hpisla.HP.COM>
Date: 20 Jan 88 16:33:27 GMT
References: <9907@mimsy.UUCP>
Organization: HP Instrument Systems Lab - Loveland, CO
Lines: 26


 pablo@polygen.uucp (Pablo Halpern) writes:"
"or better yet
"	typedef long		ptrdiff_t;
"	typedef unsigned	size_t;
"
"The reason for the long ptrdiff_t definition is that the difference
"between two unsigned, 16-bit pointers can excede the -32768 - +32767
"range of a 16-bit two's compliment signed integer.

... but the 32-bit case is the same: the difference between two unsigned
32-bit pointers can exceed the range of a 32-bit 2's complement number.
Maybe ptrdiff_t wasn't intended to handle the case of more than half of
the machine's address space allocated to one object?

More seriously, _is_ there a way to handle this?  Not that it'll ever
come up :-), but it looks as if I need to know the approximate expected
result of a pointer-subtraction to make the code foolproof (and check
for overflow myself).
                       _  _
                      / \/ \   wolpert@hpisla.HP.COM     David Wolpert
  /_  __   HEWLETT    \    /             Measurement Systems Operation
 / / /_/   PACKARD     \  /          P O Box 301 - Loveland, CO  80539
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