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    SubjectRe: Fix empty macros in acpi.
    On Tuesday 12 June 2007 20:26, Al Viro wrote:
    > On Tue, Jun 12, 2007 at 08:21:15PM -0400, Dave Jones wrote:
    > > On Wed, Jun 13, 2007 at 01:00:29AM +0100, Al Viro wrote:
    > > > On Tue, Jun 12, 2007 at 07:33:09PM -0400, Dave Jones wrote:
    > > > > +#define DBG(x...) do { } while(0)
    > > >
    > > > Eh... Please, stop it - if you want a function-call-like no-op returning void,
    > > > use ((void)0). At least that way one can say DBG(....),foo(), etc.
    > >
    > > They both end up compiled to nothing anyway, so I'm not bothered
    > > either way.. I'm not sure I follow why the syntax of that last part
    > > is a good thing. It looks like something we'd want to avoid rather
    > > than promote?
    > If on one side of ifdef it's a void-valued expression, so it should be
    > on another; the reason is that we don't get surprise differences between
    > the builds...

    true, DBG() in this case would expand to printk(), which returns int.

    But in practice, DBG isn't used in any expressions -- and the other zillion
    places in the kernel where it is used, it is used as in dave's patch.

    Indeed, I don't see printk used in expressions either...

    While I know it is common Linux style, and by default it is okay with gcc,
    it seems somewhat half-baked to call functions and not check their return
    value by default. IMHO, if they return something, it should be checked,
    or explicitly ignored -- or it shouldn't return anything in the first place...

    > IOW, if it doesn't build in some context, it should consistently fail to
    > build in that context.

    whelp, it seems that the reason for this patch is this:

    #define DBG()


    which turns into
    if(...) ;

    But since there is an intervening ';', this code is still functionally correct
    and a decent compiler will delete the test altogether, yes?

    So is there some real problem here that I missed,
    or is this to make some code-checking tool that I don't have happy?

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