Re: [patch 01/10] compiler: define __attribute_unused__

Rusty Russell
2007-05-02T06:30:10Z

On Tue, 2007-05-01 at 23:06 -0700, David Rientjes wrote:
> On Wed, 2 May 2007, Rusty Russell wrote:
>
> > Adding this macro doesn't give us anything that simply saying
> > "__attribute__((unused))" doesn't give. But it does add a layer of
> > kernel-specific indirection.
> >
>
> That's obviously true since we're defining __attribute_unused__ to be
> __attribute__((unused)).

Hi David,

I'm horribly familiar with this issue, BTW, so we don't need so many
words 8)

> The patched version makes this:
>
> int type __attribute_unused__ = 0;
>
> which definitely tells you that you're using a compiler attribute that
> will be attached to that automatic. In your case:
>
> int type __unneeded = 0;
>
> doesn't say anything in this case. It doesn't resemble any attribute that
> a programmer might be familiar with and begs the question of why we've
> declared it if it's truly "unneeded"?

Your version makes one wonder why they didn't use
"__attribute__((unused))". Obviously the __attribute_unused__ macro
exists for a reason, so they wonder what's the difference between that
and the attribute? The answer: nothing.

OTOH, your point about "__unneeded" is well taken. "__needed" and
"__optional" perhaps? But their feature is *exactly* that the don't
look like the gcc attributes, hence avoid their semantic screwage.

> By the way, there are tons of these instances where __attribute__((used))
> needs to be added in driver code to suppress unreferenced warnings.

Sure; historically we refactor around it. But warnings are now so
commonplace few people care 8(

Cheers,
Rusty.