On Tue, Nov 12, 2024 at 12:15 PM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxx> wrote:
> On Mon, Nov 11, 2024 at 11:44:51AM +0200, Andy Shevchenko wrote:
> > On Sun, Nov 10, 2024 at 04:34:30PM -0500, Aren wrote:
> > > On Sun, Nov 10, 2024 at 09:52:32PM +0200, Andy Shevchenko wrote:
> > > > Sun, Nov 10, 2024 at 02:14:24PM -0500, Aren kirjoitti:
> >
> > You can do it differently
> >
> > #define STK3310_REGFIELD(name) \
> > do { \
> > data->reg_##name = \
> > devm_regmap_field_alloc(dev, regmap, stk3310_reg_field_##name); \
> > if (IS_ERR(data->reg_##name)) \
> > return dev_err_probe(dev, PTR_ERR(data->reg_##name), \
> > "reg field alloc failed.\n"); \
> > } while (0)
> >
> > > #define STK3310_REGFIELD(name) ({ \
> > > data->reg_##name = devm_regmap_field_alloc(dev, regmap, \
> > > stk3310_reg_field_##name); \
> > > if (IS_ERR(data->reg_##name)) \
> > > return dev_err_probe(dev, PTR_ERR(data->reg_##name), \
> > > "reg field alloc failed\n"); \
> > > })
> >
> > I am against unneeded use of GNU extensions.
> >
> > > > > replacing "do { } while (0)" with "({ })" and deindenting could make
> > > > > enough room to clean this up the formatting of this macro though.
> > > >
> > > > do {} while (0) is C standard, ({}) is not.
> > >
> > > ({ }) is used throughout the kernel, and is documented as such[1]. I
> > > don't see a reason to avoid it, if it helps readability.
> >
> > I don't see how it makes things better here, and not everybody is familiar with
> > the concept even if it's used in the kernel here and there. Also if a tool is
> > being used in one case it doesn't mean it's suitable for another.
>
> Just to throw in my subjective view here: I don't expect anyone with
> some base level knowledge of C will have doubts about the semantics of
> ({ ... }) and compared to that I find do { ... } while (0) less optimal,
> because it's more verbose and when spotting the "do {" part, the
> semantic only gets clear when you also see the "while (0)".
Seems we have to agree on a disagreement.
> Having said
> that I also dislike the "do" starting on column 0, IMHO the RHS of the
> #define should be intended.
This argument I kinda accept.
> So if you ask me, this is not an unneeded use of an extension. The
> extension is used to improve readabilty and I blame the C standard to
> not support this syntax.
Here I agree with you.
> While I'm in critics mode: I consider hiding a return in a macro bad
> style.
So, summarizing the discussion we have a split, hence Jonathan is our
arbiter here to judge.
--
With Best Regards,
Andy Shevchenko
