Xref: utzoo comp.lang.c:16753 comp.lang.fortran:1803
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!oliveb!sun!fatcity!khb
From: khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering)
Newsgroups: comp.lang.c,comp.lang.fortran
Subject: Re: Sun FPU question
Message-ID: <92698@sun.uucp>
Date: 7 Mar 89 01:42:27 GMT
References: <10660@pasteur.Berkeley.EDU> <331@kvasir.esosun.UUCP>
Sender: news@sun.uucp
Reply-To: khb@sun.UUCP (Keith Bierman Sun Tactical Engineering)
Organization: Sun Microsystems, Mountain View
Lines: 45

In article <331@kvasir.esosun.UUCP> ethan@esosun.UUCP (Ethan Brown) writes:
>
>In article <10660@pasteur.Berkeley.EDU> faustus@dogwood.Berkeley.EDU (Wayne A. Christopher) writes:
>
>   Path: esosun!seismo!uunet!lll-winken!ncis.llnl.gov!helios.ee.lbl.gov!pasteur!dogwood.Berkeley.EDU!faustus
>   From: faustus@dogwood.Berkeley.EDU (Wayne A. Christopher)
>   Newsgroups: comp.lang.c
>   Date: 3 Mar 89 22:58:15 GMT
>   Sender: news@pasteur.Berkeley.EDU
>   Lines: 6
>
>   It seems that on some Suns, the FPU by default doesn't signal
>   divide-by-zero errors, but makes the result Inf or NaN.  Is there a way
>   to make it give a floating point error?  Does gcc have a flag for
>   this?  How about the MIPS compiler, which has the same behavior?
>
>	   Wayne
>
>Wayne:
>  I found similar problems on a Sun 4 when testing a FORTRAN program I'm
>currently working on.  After the program terminated (normally, by the...


I suspect that dgh will post something (or has, the net acts as a time
warp of sorts) the fact of the matter is that this is what SHOULD
happen. IEEE arithmetic sez so.

To get the behavior you desire (if you have SunOS 4.+), add the following
line of code to your main program.

	i = ieee_handler("set","common",SIGFPE_ABORT)

Now your sun will act like a pre-ieee machine, and dump core when
anything nasty happens.

Of course, you can get much better results by being clever and letting
nature take its course, and check in key places....

Cheers.

khb


Keith H. Bierman
It's Not My Fault ---- I Voted for Bill & Opus