Re: [PATCH] [net-next] socket: fix unused-function warning

[Al Viro <viro@zeniv.linux.org.uk>]

On Tue, Jan 07, 2020 at 10:35:59PM +0100, Arnd Bergmann wrote:
> When procfs is disabled, the fdinfo code causes a harmless
> warning:
> 
> net/socket.c:1000:13: error: 'sock_show_fdinfo' defined but not used [-Werror=unused-function]
>  static void sock_show_fdinfo(struct seq_file *m, struct file *f)
> 
> Change the preprocessor conditional to a compiler conditional
> to avoid the warning and let the compiler throw away the
> function itself.
> 
> Fixes: b4653342b151 ("net: Allow to show socket-specific information in /proc/[pid]/fdinfo/[fd]")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  net/socket.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/net/socket.c b/net/socket.c
> index 5230c9e1bdec..444a617819f0 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -151,9 +151,7 @@ static const struct file_operations socket_file_ops = {
>  	.sendpage =	sock_sendpage,
>  	.splice_write = generic_splice_sendpage,
>  	.splice_read =	sock_splice_read,
> -#ifdef CONFIG_PROC_FS
> -	.show_fdinfo =	sock_show_fdinfo,
> -#endif
> +	.show_fdinfo =	IS_ENABLED(CONFIG_PROC_FS) ? sock_show_fdinfo : NULL,
>  };

Ugh...  So put that ifdef around the definition of sock_show_fdinfo,
with #define sock_show_fdinfo NULL on the other side...