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

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Message-ID: <alpine.DEB.2.22.394.2303121525270.2865@hadrien>
Date:   Sun, 12 Mar 2023 15:25:37 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Menna Mahmoud <eng.mennamahmoud.mm@...il.com>
cc:     Julia Lawall <julia.lawall@...ia.fr>, outreachy@...ts.linux.dev,
        lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
        gregkh@...uxfoundation.org, linux-iio@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: iio: meter: enclose Macros with complex values
 in parentheses



On Sun, 12 Mar 2023, Menna Mahmoud wrote:

>
> 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?

No, I don't think so.

julia

>
>
> > > 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@...il.com>
> > > ---
> > >   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
> > >
> > >
> > >
>