Path: utzoo!attcan!uunet!munnari.oz.au!metro!ipso!runxtsa!edward
From: edward@runxtsa.runx.oz.au (Edward Birch)
Newsgroups: comp.lang.c++
Subject: MININT problem with C++ streams
Keywords: c++,C++,MININT,streams
Message-ID: <1959@runxtsa.runx.oz.au>
Date: 12 Jul 90 01:32:32 GMT
Organization: RUNX Unix Timeshare.  Sydney, Australia.
Lines: 48

MININT is not printed out correctly by some Glockenspiel and AT&T
C++ compilers.

The below program produced the following output:

	assuming 2's complement arithmatic &
	     sizeof(long) = 4 & 8 bits per byte

	then using `C' we get MININT =  80000000 or -2147483648
	and using  C++ we get         = 80000000 or -(

------------------------------------------------------------------------

#include	<stream.h>
main()
{
	long	x = 0x80000000; /* minint, -2147483648 */

	printf("assuming 2's complement arithmatic &\n");
	printf("     sizeof(long) = 4 & 8 bits per byte\n");
	printf("\n");
	printf("then using `C' we get MININT =  %08lx or %ld\n", x, x);

	cout << "and using  C++ we get         = " << hex(x, 8);
	cout << " or " << x << "\n";

	return 0;		// exit(0);
}

------------------------------------------------------------------------

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