linux-kernel - Re: [PATCH] lib/vsprintf.c: remove %Z support

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Date:   Thu, 5 Jan 2017 16:07:48 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux@...musvillemoes.dk
Subject: Re: [PATCH] lib/vsprintf.c: remove %Z support

On Wed, 4 Jan 2017 02:01:27 +0300 Alexey Dobriyan <adobriyan@...il.com> wrote:

> Now that %z is standartised in C99 there is no reason to support %Z.
> Unlike %L it doesn't even make format strings smaller.
> 
> Use BUILD_BUG_ON in a couple ATM drivers.
> 
> In case anyone didn't notice lib/vsprintf.o is about half of SLUB
> which is in my opinion is quite an achievement. Hopefully this patch
> inspires someone else to trim vsprintf.c more.

There's a risk that more %Z uses will sneak into the tree during the
4.10 development cycle, and possibly even later.  So I added a
note-to-self to re-grep the tree before sending this upstream, but that
won't prevent people adding new instances later on: code which was
tested under earlier kernels which has %Z support.

The best suggestion I have is to add a checkpatch rule to try to catch
new %Z's being added.