Floating point problems with 68000 (no FPU)

[Doug Broadwell]

Thank you.

Including math.h did the trick.

Doug Broadwell


----- Original Message -----
From: "J. Johnston" <jjohnstn@redhat.com>
To: "Joel Sherrill" <joel.sherrill@OARcorp.com>
Cc: "Doug Broadwell" <dougb@value.net>; "Newlib Mail List"
<newlib@sources.redhat.com>
Sent: Monday, November 18, 2002 3:37 PM
Subject: Re: Floating point problems with 68000 (no FPU)


> Joel Sherrill wrote:
> >
> > Doug Broadwell wrote:
> > >
> > > I just started using the newlib floating point library with the
following
> > > results:
> > >
> > > sqrt(2) = 1.414213
> > > sqrt(10) = 10.000002
> > > sqrt(100) = 0.000000
> > > sqrt(10000) = 0.000000
> > >
> > > In one test sqrt(100)
> > >
= -7239...............................................................0,
> > > some 160 character long number.
> > >
> > > I'm using printf("%f", sqrt(n)) for these results.
> > >
> > > Any suggestions on how to debug?
> >
> > Did you include math.h?  Not getting a proper prototype would
> > be a simple and common problem.
> >
>
> Yes.  As well, make sure you have <stdio.h>.
>
> IIRC, you were manually specifying the libraries to link in.
> If it does not turn out to be as simple as a prototyping problem, you
> will want to ensure you got the correct libgcc for the float
> operations.  Also try looking in gdb at the input value passed to sqrt in
hex to ensure
> it is the correct IEEE floating point double value with the endianness you
are
> expecting.  This is fairly easy since you are passing integer values.
> Failing that, you might want to verify the return value of sqrt separate
> from printf - again looking at the hex return value (e.g. for sqrt(100.0)
it
> is fairly easy to confirm).
>
> -- Jeff J.
>