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From: tm <thomas.mertes@gmx.at>
Newsgroups: comp.lang.java.programmer,comp.lang.c
Subject: Re: Arithmetic overflow checking
Date: Tue, 12 Jul 2011 10:13:33 -0700 (PDT)
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On 12 Jul., 18:26, markspace <-@.> wrote:
> On 7/12/2011 6:16 AM, Stefan Ram wrote:
>
> > "BartC"<b...@freeuk.com> =A0writes:
> >> a+b overflows, but then what?
>
> > =A0 =A0This can only be answered given the requirements
> > =A0 =A0specification of a specific project.
>
> What I think he's saying is there's no way physically detect the
> overflow in a language like C which has no exceptions.

But there are signals, which can be used for that purpose.
Signals are also used for other exceptional things, like
a division by zero.

> You'd have to at
> least introduce some sort of global flag.
>
> =A0 =A0int c =3D a + b;
> =A0 =A0if( GLOBAL_OVERFLOW_FLAG ) {
> =A0 =A0 =A0printf( "bugger..." );
> =A0 =A0}

Checking a global flag is a bad idea, since it does not
allow zero overhead arithmethic overflow detection (by
CPUs which are able to trigger an interrupt on overflow).


Greetings Thomas Mertes

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