Date: Thu, 11 Jan 2001 22:12:00 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender: halo1 AT zahav DOT net DOT il
To: "Tanes Sriviroolchai" <Tanes DOT Sriviroolchai AT Thailand DOT NCR DOT COM>
Message-Id: <2593-Thu11Jan2001221159+0200-eliz@is.elta.co.il>
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CC: djgpp AT delorie DOT com
In-reply-to: <3a5d81c9@rpc1284.daytonoh.ncr.com>
	(Tanes DOT Sriviroolchai AT Thailand DOT NCR DOT COM)
Subject: Re: Weird results of log( -1.0 ) with libm.a and without libm.a
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> From: "Tanes Sriviroolchai" <Tanes DOT Sriviroolchai AT Thailand DOT NCR DOT COM>
> Newsgroups: comp.os.msdos.djgpp
> Date: Thu, 11 Jan 2001 16:49:21 +0700
> 
> gcc -o test1.exe test1.c
> when running you will get
> 
> NaN
> 
> This is expected result. However if I compile using
> gcc -o test1.exe test1.c -lm
> and then running, you will get
> 
> -Inf

In addition to what I already wrote in this thread, you can request
that the libm version returns the same NaN as the libc version by
forcing libm into the IEEE mode, like this:

     #include <libm/math.h>

     _LIB_VERSION_TYPE _LIB_VERSION = _IEEE_;

This turns on the IEEE compatibility, but you lose the matherr
feature, and also the value of errno will not be set to EDOM/ERANGE.