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SubjectRe: [PATCH 1/4] dynamic_debug: consolidate repetitive struct _ddebug descriptor definitions
On Thu, 08 Sep 2011 19:13:16 -0700 Joe Perches <joe@perches.com> wrote:

> On Thu, 2011-09-08 at 16:52 -0700, Andrew Morton wrote:
> > On Tue, 30 Aug 2011 14:28:41 -0400
> > Jason Baron <jbaron@redhat.com> wrote:
> > > Replace the repetitive struct _ddebug descriptor definitions with
> > > a new DECLARE_DYNAMIC_DEBUG_META_DATA(name, fmt) macro.
> > > +#define DECLARE_DYNAMIC_DEBUG_METADATA(name, fmt) \
> > > + static struct _ddebug __used __aligned(8) \
> > > + __attribute__((section("__verbose"))) name = { \
> > > + .modname = KBUILD_MODNAME, \
> > > + .function = __func__, \
> > > + .filename = __FILE__, \
> > > + .format = (fmt), \
> > > + .lineno = __LINE__, \
> > > + .flags = _DPRINTK_FLAGS_DEFAULT, \
> > > + .enabled = false, \
> > > + }
> > <anal>That macro implements a definition, not a declaration</anal>
>
> Andrew, that's not quite true

It's precisely true.

: Exercise 2.8
:
: A declaration introduces a name and a type for something. It does not
: necessarily reserve any storage.
:
: Exercise 2.9
:
: A definition is a declaration that also reserves storage.

(http://publications.gbdirect.co.uk/c_book/answers/chapter_2.html)

> and that's how
> DECLARE is normally used in linux.

It's how it's sometimes used, when we screwed up.

> DECLARE_BITMAP, DECLARE_COMPLETION, DECLARE_RWSEM, etc.

Mistakes.


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