netdev - Re: [PATCH net-next] net: qualcomm: rmnet: fix two pointer math bugs

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Message-ID: <20210621071831.GB1901@kadam>
Date:   Mon, 21 Jun 2021 10:18:31 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     subashab@...eaurora.org
Cc:     Sean Tranchetti <stranche@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] net: qualcomm: rmnet: fix two pointer math bugs

On Mon, Jun 21, 2021 at 10:11:58AM +0300, Dan Carpenter wrote:
> On Sat, Jun 19, 2021 at 01:12:09PM -0600, subashab@...eaurora.org wrote:
> > On 2021-06-19 07:52, Dan Carpenter wrote:
> > 
> > Hi Dan
> > 
> > Thanks for fixing this. Could you cast the ip4h to char* instead of void*.
> > Looks like gcc might raise issues if -Wpointer-arith is used.
> > 
> > https://gcc.gnu.org/onlinedocs/gcc-4.5.0/gcc/Pointer-Arith.html#Pointer-Arith
> 
> The fix for that is to not enable -Wpointer-arith.  The warning is dumb.

Sorry, that was uncalled for and not correct.  The GCC warning would be
useful if we were trying to write portable userspace code.  But in the
kernel the kernel uses GCC extensions a lot.

The Clang compiler can also compile the kernel these days.  But it had
to add support for a bunch of GCC extensions to make that work.  Really
most of linux userspace is written with GCC in mind so Clang had to do
this anyway.

So we will never enable -Wpointer-arith in the kernel because there is
no need.

regards,
dan carpenter