netdev - Re: [PATCH] net/macmace: Replace zero-length array with DECLARE_FLEX

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Date: Tue, 1 Aug 2023 16:09:37 +0200
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Atul Raut <rauji.raut@...il.com>
CC: Larysa Zaremba <larysa.zaremba@...el.com>, Atul Raut
	<rauji.raut@...il.com>, <avem@...emloft.net>, <netdev@...r.kernel.org>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <rafal@...ecki.pl>,
	<linux-kernel-mentees@...ts.linuxfoundation.org>
Subject: Re: [PATCH] net/macmace: Replace zero-length array with
 DECLARE_FLEX_ARRAY() helper

On Mon, Jul 31, 2023 at 10:38:01AM +0300, Leon Romanovsky wrote:
> On Sun, Jul 30, 2023 at 04:14:42PM -0700, Atul Raut wrote:
> > Since zero-length arrays are deprecated, we are replacing
> > them with C99 flexible-array members. As a result, instead
> > of declaring a zero-length array, use the new
> > DECLARE_FLEX_ARRAY() helper macro.
> > 
> > This fixes warnings such as:
> > ./drivers/net/ethernet/apple/macmace.c:80:4-8: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)
> > 
> > Signed-off-by: Atul Raut <rauji.raut@...il.com>
> > ---
> >  drivers/net/ethernet/apple/macmace.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/apple/macmace.c b/drivers/net/ethernet/apple/macmace.c
> > index 8fcaf1639920..8775c3234e91 100644
> > --- a/drivers/net/ethernet/apple/macmace.c
> > +++ b/drivers/net/ethernet/apple/macmace.c
> > @@ -77,7 +77,7 @@ struct mace_frame {
> >  	u8	pad4;
> >  	u32	pad5;
> >  	u32	pad6;
> > -	u8	data[1];
> > +	DECLARE_FLEX_ARRAY(u8, data);
> 
> But data[1] is not zero-length array.
> 

So, please, if you are certain that data should be a flexible array,
send v2 without calling data a zero-length array. Also, with such change, I 
think driver code could be improved in many places in the same patchset.

> >  	/* And frame continues.. */
> >  };
> >  
> > -- 
> > 2.34.1
> > 
> > 
>