From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12392 invoked by alias); 6 Feb 2014 16:38:54 -0000 Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: glibc-bugs-owner@sourceware.org Received: (qmail 12293 invoked by uid 55); 6 Feb 2014 16:38:51 -0000 From: "joseph at codesourcery dot com" To: glibc-bugs@sourceware.org Subject: [Bug math/16447] erfc (0x6.a8p+4) ldbl-128 throws underflow exception Date: Thu, 06 Feb 2014 16:38:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: math X-Bugzilla-Version: 2.19 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: joseph at codesourcery dot com X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-02/txt/msg00102.txt.bz2 http://sourceware.org/bugzilla/show_bug.cgi?id=16447 --- Comment #4 from joseph at codesourcery dot com --- On Thu, 6 Feb 2014, stli at linux dot vnet.ibm.com wrote: > unsafe = abs(n_i) >= -16363; Well, abs >= (negative value) doesn't seem right. To work out what's unsafe, you need to consider how small x22 can be in cases where ex2_u.d is small. The answer is roughly that x22, if not 0, is at least 1ulp of the input (not exactly, because of the way values from a table get subtracted from the input) - so, roughly, you could have problems up to n_i around -16382 + 113. Certainly saying unsafe = abs (n_i) >= 15000 should be safe, even allowing for the way x gets adjusted. > How to handle the unsafe-check? > Which platform uses this implementation of expl? > Can we simply change the unsafe-check in sysdeps/iee754 or is a new > platform-specific implementation required? The same correction should apply to all platforms using ldbl-128; no platform-specific implementation should be needed. -- You are receiving this mail because: You are on the CC list for the bug.