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Re: gdb/500: math func sqrt(x) returns NaN for x>=0 in GDB, GNU/Linux i686
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: nobody at sources dot redhat dot com
- Cc: gdb-prs at sources dot redhat dot com,
- Date: 18 Apr 2002 17:08:02 -0000
- Subject: Re: gdb/500: math func sqrt(x) returns NaN for x>=0 in GDB, GNU/Linux i686
- Reply-to: Daniel Jacobowitz <drow at mvista dot com>
The following reply was made to PR gdb/500; it has been noted by GNATS.
From: Daniel Jacobowitz <drow@mvista.com>
To: falk@whoi.edu
Cc: gdb-gnats@sources.redhat.com
Subject: Re: gdb/500: math func sqrt(x) returns NaN for x>=0 in GDB, GNU/Linux i686
Date: Thu, 18 Apr 2002 12:59:58 -0400
On Thu, Apr 18, 2002 at 04:34:29PM -0000, falk@whoi.edu wrote:
>
> >Number: 500
> >Category: gdb
> >Synopsis: math func sqrt(x) returns NaN for x>=0 in GDB, GNU/Linux i686
> >Confidential: no
> >Severity: non-critical
> >Priority: low
> >Responsible: unassigned
> >State: open
> >Class: sw-bug
> >Submitter-Id: net
> >Arrival-Date: Thu Apr 18 09:38:01 PDT 2002
> >Closed-Date:
> >Last-Modified:
> >Originator: Falk Feddersen
> >Release: GDB 5.0rh (running Red Hat 7.2)
> >Organization:
> >Environment:
> Red Hat 7.2 Linux on i686
> >Description:
> program compiled in gcc w/ flags "-g -march=i686"
>
> double q,x=0;
> ....
> q=sqrt(x); /* returns q=NaN in GDB */
>
> if I don't compile w/ "-march=i686" flag it works fine in GDB
> w/ the -march=i686 flag, q=sqrt(x) works when run regularly.
Please try a current GDB snapshot from http://sources.redhat.com/gdb/current/.
A bug relating to floating point corruption was fixed recently, and
this may be the same bug.
(-march=i686 causes sqrt to be expanded inline via __builtin_sqrt,
instead of a function call; that's why there's a difference.)
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer