linux-kernel - Re: [PATCH] btrfs: tree-checker: use %zu format string for size

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Date:   Thu, 7 Dec 2017 10:06:50 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Qu Wenruo <quwenruo.btrfs@....com>
Cc:     Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>, Qu Wenruo <wqu@...e.com>,
        Su Yue <suy.fnst@...fujitsu.com>,
        Nikolay Borisov <nborisov@...e.com>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] btrfs: tree-checker: use %zu format string for size_t

On Thu, Dec 7, 2017 at 1:32 AM, Qu Wenruo <quwenruo.btrfs@....com> wrote:
>
>
> On 2017年12月06日 22:18, Arnd Bergmann wrote:
>> The return value of sizeof() is of type size_t, so we must print it
>> using the %z format modifier rather than %l to avoid this warning
>> on some architectures:
>>
>> fs/btrfs/tree-checker.c: In function 'check_dir_item':
>> fs/btrfs/tree-checker.c:273:50: error: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'u32' {aka 'unsigned int'} [-Werror=format=]
>
> Any idea about which architecture will cause such warning?
> On x86_64 I always fail to get such warning.

I think all 32-bit architectures:

#ifndef __kernel_size_t
#if __BITS_PER_LONG != 64
typedef unsigned int    __kernel_size_t;
typedef int             __kernel_ssize_t;
typedef int             __kernel_ptrdiff_t;
#else
typedef __kernel_ulong_t __kernel_size_t;
typedef __kernel_long_t __kernel_ssize_t;
typedef __kernel_long_t __kernel_ptrdiff_t;
#endif
#endif

      Arnd