Re: [PATCH] uapi: fix linux/btrfs.h userspace compilation error

[Joe Perches]

On Wed, 2017-02-15 at 23:02 +0300, Dmitry V. Levin wrote:
> Stop using NULL to fix the following linux/btrfs.h userspace compilation
> error:
> 
> /usr/include/linux/btrfs.h: In function 'btrfs_err_str':
> /usr/include/linux/btrfs.h:740:11: error: 'NULL' undeclared (first use in this function)
>     return NULL;
> 
> Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> ---
>  include/uapi/linux/btrfs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
[]
> @@ -737,7 +737,7 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
>  			return "add/delete/balance/replace/resize operation "\
>  				"in progress";
>  		default:
> -			return NULL;
> +			return 0;

Perhaps to avoid some other warnings this might be better

	return (void *)0;