lkml.org 
[lkml]   [2003]   [Dec]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: GCC 3.4 Heads-up
Date
Followup to:  <20031226005840.A30827@hexapodia.org>
By author: Andy Isaacson <adi@hexapodia.org>
In newsgroup: linux.dev.kernel
>
> On Thu, Dec 25, 2003 at 08:34:33PM -0800, Linus Torvalds wrote:
> > The cast/conditional expression as lvalue are _particularly_ ugly
> > extensions, since there is absolutely zero point to them. They are very
> > much against what C is all about, and writing something like this:
> >
> > a ? b : c = d;
> >
> > is something that only a high-level language person could have come up
> > with. The _real_ way to do this in C is to just do
> >
> > *(a ? &b : &c) = d;
> >
> > which is portable C, does the same thing, and has no strange semantics.
>
> But doesn't the first one potentially let the compiler avoid spilling to
> memory, if b and c are both in registers?
>
> Not that I'm fond of gccisms, but this one at least seems to have a
> potential value. And I'm sure I came up with an instance of it making
> my head ache, a while back, but I can't come up with a bad example now.
> Care to elaborate on your "strange semantics"?
>

A decent compiler should be able to avoid spills in either case.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
If you send me mail in HTML format I will assume it's spam.
"Unix gives you enough rope to shoot yourself in the foot."
Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:59    [W:1.911 / U:0.616 seconds]
©2003-2014 Jasper Spaans. Advertise on this site