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From: ado@elsie.UUCP (Arthur David Olson)
Newsgroups: net.bugs.4bsd
Subject: bug in 4.?bsd libnm version of sqrt (with fix)
Message-ID: <6003@elsie.UUCP>
Date: Thu, 2-Jan-86 20:29:58 EST
Article-I.D.: elsie.6003
Posted: Thu Jan  2 20:29:58 1986
Date-Received: Sat, 4-Jan-86 05:34:04 EST
Organization: NIH-LEC, Bethesda, MD
Lines: 47
Keywords: libnm sqrt

Index:		libnm/sqrt.s Fix

Description:
	The 4.?bsd "libnm" version of "sqrt" handles negative arguments
	differently than the way documented in the exp(3m) manual page.

Repeat-By:
	Feeding these lines to your favorite shell:
		cat > try.c << EOF
		main()
		{
			extern double	sqrt();
			extern int	errno;
			double		d;

			d = sqrt(-4.);
			printf("%d\n", errno);
			printf("%g\n", d);

		}
		EOF
		cc try.c -lnm
		a.out
	and noting the output:
		98
		-2
	which differs from the documented:
		33
		0

Fix:
	As usual, the trade secret status of the code involved precludes a
	clearer posting.  The change comes near the end of "libnm/sqrt.s":
		negarg:
		# Next few lines added by ado, January 1986
			.set	EDOM,33
			movl	$EDOM,_errno
			clrd	r0
			ret
		# Last few lines added by ado, January 1986
	Note also that the lines that originally followed the "negarg:" label
	may be removed.
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