Re: [9fans] float overflow

["Federico G. Benavento" <benavento@gmail.com>]

garbage in, garbage out

lotte% echo 1.75e308+1.75e308 | hoc
hoc 730809: suicide: sys: fp: numeric overflow fppc=0x3004
status=0xb988 pc=0x3a75
lotte%

if you want to keep feeding garbage to your program disable the exceptions

see getfcr(2)

or http://plan9.bell-labs.com/magic/man2html/2/getfcr

setfcr(getfcr()&~(FPINVAL));

feel free to turn division by 0 trap too

On Fri, Mar 26, 2010 at 8:58 AM, hugo rivera <uair00@gmail.com> wrote:
> Hello,
> float operations are causing me some headaches on plan 9 (9vx).
> I have a program that crashes badly when I feed it with near-the-top
> doubles ~1.1e308. This causes an overflow in a function that needs to
> square this values and acid points the line where the first call to
> pow(2) occurs when I debug it. The problem is that this doesn't happen
> at all when the program is compiled with gcc (9c) on linux. Obviously
> my results aren't useful, but I get '+Inf' on my output and the
> program doesn't crash. I thought of using isInf(2) to avoid Infs in my
> operations, but this would make the code really ugly and probably
> slow.
> I've seen that hoc also suffers from this. On 9vx
>
> % echo 1.75e308+1.75e308 | hoc
> hoc 851: suicide: sys: trap: 19 (reserved) pc=0x00003a75
>
> but on linux
>
> echo 1.75e308+1.75e308 | hoc
> +Inf
>
> is there something I can do to remedy this situation? maybe this
> doesn't happen on a native plan 9 installation, but I don't have
> access to any.
> Saludos,
>
> --
> Hugo
>
>



--
Federico G. Benavento