linux-kernel - Re: [PATCH] XArray tests: Compare pointers to NULL instead of 0

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Message-Id: <20240524130748.cdac446bb90f75fee5ffe47f@linux-foundation.org>
Date: Fri, 24 May 2024 13:07:48 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org, Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH] XArray tests: Compare pointers to NULL instead of 0

On Fri, 24 May 2024 15:16:55 +0800 Jiapeng Chong <jiapeng.chong@...ux.alibaba.com> wrote:

> Avoid pointer type value compared with 0 to make code clear.
> 
> ./lib/test_xarray.c:973:52-53: WARNING comparing pointer to 0
> 
> ...
>
> --- a/lib/test_xarray.c
> +++ b/lib/test_xarray.c
> @@ -975,7 +975,7 @@ static noinline void check_xa_alloc_1(struct xarray *xa, unsigned int base)
>  
>  	XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(10), XA_LIMIT(10, 5),
>  				GFP_KERNEL) != -EBUSY);
> -	XA_BUG_ON(xa, xa_store_index(xa, 3, GFP_KERNEL) != 0);
> +	XA_BUG_ON(xa, NULL != xa_store_index(xa, 3, GFP_KERNEL));
>  	XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_index(10), XA_LIMIT(10, 5),
>  				GFP_KERNEL) != -EBUSY);
>  	xa_erase_index(xa, 3);

Thanks, but we avoid the (0 != expression) trick in the kernel.

And as far as I understand, it's used to prevent people from
accidentally using = where they meant == so isn't applicable to !=
anyway.