Date: Tue, 20 Aug 2002 10:32:55 -0700 (PDT)
From: GOTO Kentaro <gotoken@notwork.org>
To: freebsd-gnats-submit@FreeBSD.org
Subject: bin/41823: printf("%+f\n", -0.0) generates +0.000000
Message-ID: <200208201732.g7KHWtKV034152@www.freebsd.org>
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>Number: 41823
>Category: bin
>Synopsis: printf("%+f\n", -0.0) generates +0.000000
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Aug 20 10:40:28 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: GOTO Kentaro
>Release: STABLE and CURRENT
>Organization:
>Environment:
FreeBSD 5.0-CURRENT i386
>Description:
vfprintf() generates a wrong "+" sign for a floating point number
minus zero, i.e., -0.0, when +[eEfgG] is specified in the format.
>How-To-Repeat:
% echo 'main(){printf("%+f\\n", -0.0);}' | /usr/bin/cc -xc - && ./a.out
+0.000000
>Fix:
How about Checking sign bit instead of `< 0'.
For example, NetBSD's /usr/src/lib/libc/stdio/vfprintf.c:cvt() does
digits = __dtoa(value, mode, ndigits, decpt, &dsgn, &rve);
if (dsgn) {
value = -value;
*sign = '-';
} else
*sign = '\000';
But FreeBSD's does
if (value < 0) {
value = -value;
*sign = '-';
} else
*sign = '\000';
This test does not work in this case because IEEE754 defines the
truth value of -ZERO < ZERO as FALSE.
>Release-Note:
>Audit-Trail:
>Unformatted:
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