Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwvax!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.questions
Subject: Re: void *a
Message-ID: <17794@mimsy.UUCP>
Date: 31 May 89 00:26:30 GMT
References: <5197@rpi.edu>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 29

In article <5197@rpi.edu> kyriazis@rpics (George Kyriazis) writes:
>	void	*pt;
>... The compiler complains that 'pt' is not defined, on ANY system I tried
>it except the SUN.  What's so special about suns and/or void *  ???

The systems you tried must be using a version of PCC (`Portable C
Compiler').  PCC, like many compilers for many languages, keeps track
not only of declared variables but also of undeclared variables, and
emits an error only on the first use:

	main() {
		i = 10;	/* gets an error */
		i++;	/* says nothing */
		j++;	/* gets an error */
		j = i;	/* says nothing */
	}

Through some oversight, when `void' was added to PCC, someone used a
type-code number that, combined with `pointer to', matched the special
value for `undeclared variable': `void *p' enters p into the symbol
table as a `complain about this undeclared variable' name.%

This bug is fixed in modern PCCs, including the ones on current Berkeley
tapes.
-----
% This is not exactly right, but is close enough for explanatory purposes....
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris