From: Robert Dewar <dewar@gnat.com>
To: "Thomas R. Truscott" <trt@cs.duke.edu>
Cc: gcc@gcc.gnu.org
Subject: Re: Warning flags for unsigned operations (unsafe)
Date: Wed, 22 Sep 2004 16:18:00 -0000 [thread overview]
Message-ID: <41519C17.10804@gnat.com> (raw)
In-Reply-To: <200409221435.i8MEZYX0009371@minie.cs.duke.edu>
Thomas R. Truscott wrote:
> > I couldn't find out if gcc had a
> > warning flag for unsigned operation. For example, even the linear
> > interpolation on [a,b] can be tricky to code:
> >
> > c = a + t * (b - a); //unsafe
>
> Not for this situation. I think a warning would be appropriate
> when an unsigned quantity involving subtraction
> is widened or converted to double.
Why? The semantics are reasonable, well defined, and expected.
One assumes that in this case either the code expects the wrap
semantics (less likely) or, more likely, knows that the quantity
b-a will be non-negative.
I see nothing special about being widened or converted to double.
next prev parent reply other threads:[~2004-09-22 15:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-22 15:38 Thomas R. Truscott
2004-09-22 16:18 ` Robert Dewar [this message]
2004-09-22 16:31 ` Robert Dewar
2004-09-22 16:53 ` Dave Korn
-- strict thread matches above, loose matches on Subject: below --
2004-09-22 5:33 Mathieu Malaterre
2004-09-22 14:57 ` Dave Korn
2004-09-22 15:12 ` Robert Dewar
2004-09-22 20:50 ` Luca Masini
2004-09-23 1:37 ` Mathieu Malaterre
2004-09-24 6:20 ` Giovanni Bajo
2004-09-24 6:31 ` Mathieu Malaterre
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