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From: ggs@ulysses.att.com (Griff Smith)
Newsgroups: comp.lang.c++
Subject: Re: MININT problem with C++ streams
Summary: fixed in 2.0
Keywords: c++,C++,MININT,streams
Message-ID: <13407@ulysses.att.com>
Date: 12 Jul 90 21:24:33 GMT
References: <1959@runxtsa.runx.oz.au>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 29

In article <1959@runxtsa.runx.oz.au>, edward@runxtsa.runx.oz.au (Edward Birch) writes:
| MININT is not printed out correctly by some Glockenspiel and AT&T C++ compilers.

This may have been a problem with the AT&T 1.2 release, but it works on
my system with the 2.1 release.

| I think the bug is caused by an assumption in the C++ library
| going something like:
| 
| 	if (v < 0) {
| 		emit_char('-');
| 		v = -v;		// clearly wrong when v = MININT with
| 				// (2's complement arithmatic)
| 	}
| 
| Edward Birch
|                                         Phone:   (02) 958-2119
| 
| UUCP:   seismo!munnari!runx.oz!edward   ACSnet:  edward@runx.oz
| ARPA:   edward%runx.oz@seismo.css.gov   CSNET:   edward@runx.oz

Actually, it isn't wrong on a 2's complement machine if the `v = -v'
operation doesn't cause an overflow trap.  The trick is to cast the
resulting number to unsigned and then do the conversion.
-- 
Griff Smith	AT&T (Bell Laboratories), Murray Hill
Phone:		1-201-582-7736
UUCP:		{most AT&T sites}!ulysses!ggs
Internet:	ggs@ulysses.att.com