Re: GCC 3.4 Heads-up

[H. Peter Anvin]

Followup to:  <20031226005840.A30827@xxxxxxxxxxxxx>
By author:    Andy Isaacson <adi@xxxxxxxxxxxxx>
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
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