Re: [PATCH] staging: iio: meter: enclose Macros with complex values in parentheses

[Menna Mahmoud]

On ١٢‏/٣‏/٢٠٢٣ ١٦:١٢, Julia Lawall wrote:
> On Sun, 12 Mar 2023, Menna Mahmoud wrote:
>
> > enclose Macros with complex values in parentheses is especially useful
> > in making macro definitions “safe” (so that they
> > evaluate each operand exactly once).
> enclose -> Enclose, and Macros -> macros
>
> I don't understand the above comment though.  How does adding parentheses
> around the body of a macro cause the operands to be evaluated only once?
> And the macros that you have changed don't have any operands.
>
> The value of adding parentheses is normally to ensure that the body of the
> macro doesn't interact with the context in a weird way.  For example, you
> could have
>
> #define ADD 3 + 4
>
> Then if you use your macro as 6 * ADD, you will end up evaluating
> 6 * 3 + 4, ie 18 + 4, when you might have expected 6 * 7.  The issue is
> that * has higher precedence than +.


yes, I mean that but i couldn't explain it well, thanks for your feedback.


> But I don't think that such a problem can arise with a cast expression, so
> parentheses around it should not be necessary.


So, no need for this patch?


> > this error reported by chechpatch.pl
> this error is reported by checkpatch.
>
> > "ERROR: Macros with complex values should be enclosed in parentheses"
> >
> > for ADE7854_SPI_SLOW, ADE7854_SPI_BURST and ADE7854_SPI_FAST
> > macros and this error fixed by enclose these macros in parentheses.
> The last two lines aren't needed.  One can easily see that from looking at
> the patch.


Got it, Thank you.

Menna

> julia
>
> > Signed-off-by: Menna Mahmoud <eng.mennamahmoud.mm@xxxxxxxxx>
> > ---
> >   drivers/staging/iio/meter/ade7854.h | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/staging/iio/meter/ade7854.h b/drivers/staging/iio/meter/ade7854.h
> > index 7a49f8f1016f..41eeedef569b 100644
> > --- a/drivers/staging/iio/meter/ade7854.h
> > +++ b/drivers/staging/iio/meter/ade7854.h
> > @@ -139,9 +139,9 @@
> >   #define ADE7854_MAX_RX    7
> >   #define ADE7854_STARTUP_DELAY 1000
> >
> > -#define ADE7854_SPI_SLOW	(u32)(300 * 1000)
> > -#define ADE7854_SPI_BURST	(u32)(1000 * 1000)
> > -#define ADE7854_SPI_FAST	(u32)(2000 * 1000)
> > +#define ADE7854_SPI_SLOW	((u32)(300 * 1000))
> > +#define ADE7854_SPI_BURST	((u32)(1000 * 1000))
> > +#define ADE7854_SPI_FAST	((u32)(2000 * 1000))
> >
> >   /**
> >    * struct ade7854_state - device instance specific data
> > --
> > 2.34.1
> >