Date: Wed, 28 Feb 2007 18:02:04 GMT From: Denis Koreshkov<dynamic-wind@mail.ru> To: freebsd-gnats-submit@FreeBSD.org Subject: bin/109692: printing -NaN Message-ID: <200702281802.l1SI24Cb005332@www.freebsd.org> Resent-Message-ID: <200702281810.l1SIA3Mm035400@freefall.freebsd.org>
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>Number: 109692 >Category: bin >Synopsis: printing -NaN >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: Wed Feb 28 18:10:03 GMT 2007 >Closed-Date: >Last-Modified: >Originator: Denis Koreshkov >Release: freebsd 6.2-stable >Organization: BMSTU >Environment: >Description: The vfprintf() function correctly formats +Inf and -Inf but it has no provision for distinguishing between +NaN and -NaN. Hence all functions of printf(3) family output all -NaNs as NaNs. >How-To-Repeat: printf("%g %g\n", +0.0/0.0, -0.0/0.0); outputs: NaN NaN which should be: NaN -NaN >Fix: vfprintf(3) tests for a 'double' argument being an Inf or a NaN using isinf() and isinf(). Then, an Inf's signum is detected by a trivial arithmetic comparison to 0.0 But arithmetic comparisons fail when an argument is a NaN, so there is no corresponding code to set a negative NaN's signum to '-'. Consider using copysign(1.0, _double) which returns +1.0 and -1.0 for +NaN and -NaN. This is the case for the msun libm used in FreeBSD, though other implementations of copysign(3) may not derive a NaN's signum correctly, or raise an exception with signaling NaNs. >Release-Note: >Audit-Trail: >Unformatted:
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