linux-kernel - Re: [PATCH] seq_buf: avoid type mismatch for seq_buf

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Date:   Mon, 26 Oct 2020 13:23:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
        Petr Mladek <pmladek@...e.cz>, Arnd Bergmann <arnd@...db.de>,
        Piotr Maziarz <piotrx.maziarz@...ux.intel.com>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] seq_buf: avoid type mismatch for seq_buf_init

On Mon, 26 Oct 2020 17:10:58 +0100
Arnd Bergmann <arnd@...nel.org> wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> Building with W=2 prints a number of warnings for one function that
> has a pointer type mismatch:
> 
> linux/seq_buf.h: In function 'seq_buf_init':
> linux/seq_buf.h:35:12: warning: pointer targets in assignment from 'unsigned char *' to 'char *' differ in signedness [-Wpointer-sign]

I've always hated the warning about char * and unsigned char *, as they are
mostly meaningless. Yes, bugs happen with int to unsigned int conversions,
but this is dealing with strings, where unsigned char * and char * are
basically equivalent, except when it comes to one thing, which is why I
prefer unsigned char * over char *, and that is printing out the numerical
values of a buffer, if they go above 177, the char * prints the negative
value, but unsigned char * keeps printing what you would expect.

As this is just an annoyance (extra warnings), and not really a "fix", I'll
queue it up for the next merge window.

-- Steve

> 
> Change the type in the function prototype according to the type in
> the structure.
> 
> Fixes: 9a7777935c34 ("tracing: Convert seq_buf fields to be like seq_file fields")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---