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From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.lang.c
Subject: portably printing pointers (was Novice MicroSoft C5.1 question)
Message-ID: <25995@mimsy.umd.edu>
Date: 12 Aug 90 21:31:50 GMT
References: <440@demott.COM> <165@srchtec.UUCP> <1906@tkou02.enet.dec.com> <171@srchtec.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 31

In article <171@srchtec.UUCP> johnb@srchtec.UUCP (John Baldwin) writes:
>[%p] solves a lot of problems for portability, and I for one am very glad
>I was wrong (I've been grumbling all this time about not being able to
>portably print pointers).

Although ANSI says that `%p' prints a pointer (of type `void *') and thus
this is in a sense `portable', it also goes on to say `in an implementation-
defined manner', so in another sense this is not anywhere near portable.
One possible manner for printing a pointer would be to print a mailing
address for one house/apartment/whatever somewhere in the world, with
a different (and unique) address for each possible pointer value.

	printf("%p %p %p", (void *)ptr1, (void *)ptr2, (void *)ptr3);

might produce

	9191 Farrel Avenue
	Columbus, OH

	12500 Lakeshore Drive
	Chicago, IL

	17 Ashburn Pl
	Avenue, MD

(Yes, there is a town in MD called `Avenue'.  I made up the other parts
though.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris
	(New campus phone system, active sometime soon: +1 301 405 2750)