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SubjectRe: __attribute__((unused))
On Thu, Oct 14, 2004 at 11:04:56PM +0100, David Woodhouse wrote:
> On Thu, 2004-10-14 at 22:02 +0100, Russell King wrote:
> > Hi,
> >
> > I notice that module.h contains stuff like:
> >
> > #define MODULE_GENERIC_TABLE(gtype,name) \
> > extern const struct gtype##_id __mod_##gtype##_table \
> > __attribute__ ((unused, alias(__stringify(name))))
> >
> > and even:
> >
> > #define __MODULE_INFO(tag, name, info) \
> > static const char __module_cat(name,__LINE__)[] \
> > __attribute_used__ \
> > __attribute__((section(".modinfo"),unused)) = __stringify(tag) "=" info
> >
> > My understanding is that we shouldn't be using __attribute__((unused))
> > in either of these - can someone confirm.
>
> Since the structure in question isn't explicitly referenced from
> elsewhere, the compiler may feel free to omit it. Since we want the
> compiler to emit it, not omit it, we use "unused" to say "yes, I know it
> looks unused; please emit it anyway". Later compilers use "used" to say
> "I use it really; please emit it anyway", meaning much the same thing.

It's the "later compilers" which I'm worried about here - I think they
defined "unused" to mean "this really really isn't used and you can
discard it". Hence my concern with the above.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core
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