linux-kernel - Re: [PATCH] FS-Cache: print hexadecimal value for special cookies type

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Message-ID: <28723.1493305425@warthog.procyon.org.uk>
Date:   Thu, 27 Apr 2017 16:03:45 +0100
From:   David Howells <dhowells@...hat.com>
To:     =?UTF-8?q?J=C3=A9r=C3=A9my=20Lefaure?= <jeremy.lefaure@....epita.fr>
Cc:     dhowells@...hat.com, linux-cachefs@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] FS-Cache: print hexadecimal value for special cookies type

Jérémy Lefaure <jeremy.lefaure@....epita.fr> wrote:

> When building object-list.o, gcc 6 raises a warning on the sprintf call
> in fscache_objlist_show:
> 
>   CC      fs/fscache/object-list.o
> fs/fscache/object-list.c: In function ‘fscache_objlist_show’:
> fs/fscache/object-list.c:265:19: warning: ‘sprintf’ may write a
> terminating nul past the end of the destination [-Wformat-overflow=]
>     sprintf(_type, "%02u", cookie->def->type);
>                    ^~~~~~
> fs/fscache/object-list.c:265:4: note: ‘sprintf’ output between 3 and 4
> bytes into a destination of size 3
>     sprintf(_type, "%02u", cookie->def->type);
>     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Moreover, the documentation says that we should have an hex value for
> special cookies (see Documentation/filesystems/caching/fscache.txt).
> 
> Printing hexadecimal value for special cookies fixes the overflow
> warning and complies with the documentation.

Fine by me.  We don't actually handle special type cookies at the moment, so
you're not going to see anything other than DT or IX for now anyway.

I'll push this in the next merge window if that's okay with you.

David