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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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