linux-kernel - Re: [PATCH v2 11/24] stat.2: Cast to 'unsigned long' rather than 'long' when printing with "%lx"

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Date:   Fri, 11 Sep 2020 11:19:48 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Alejandro Colomar <colomar.6.4.3@...il.com>
Cc:     mtk.manpages@...il.com, linux-man@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/24] stat.2: Cast to 'unsigned long' rather than
 'long' when printing with "%lx"

On 9/11/20 11:16 AM, Alejandro Colomar wrote:
> Hi Michael,
> 
> On 2020-09-11 09:25, Michael Kerrisk (man-pages) wrote:
>> See my reply to patch 10/24.
> 
> As with 10/24, here's the new version.

Thanks, Alex. Applied.

Cheers,

Michael

> --------------------------------------------------------
>  From 911c791f0168851cdfdb30a65b6935011e4a161c Mon Sep 17 00:00:00 2001
> From: Alejandro Colomar <colomar.6.4.3@...il.com>
> Date: Fri, 11 Sep 2020 10:52:14 +0200
> Subject: [PATCH v2 11/24] stat.2: Cast to 'unsigned long' rather than 'long'
>   when printing with "%lx"
> 
>  From the email conversation:
> 
> On 2020-09-11 09:24, Michael Kerrisk (man-pages) wrote:
>  > Hi Alex,
>  >
>  > On 9/10/20 11:13 PM, Alejandro Colomar wrote:
>  >> Both major(3) and minor(3) return an 'unsigned int',
>  >> so there is no need to use a 'long' for printing.
>  >> Moreover, it should have been 'unsigned long',
>  >> as "%lx" expects an unsigned type.
>  >
>  > This may be true on Linux, but is not true on other systems.
>  > For example, on HP-UX, according to one header file I'm
>  > looking at, the return value is 'long'.
>  >
>  > These kinds of casts are intended to improve code portability
>  > across UNIX implementations, so I think they should stay
>  > (although, I do wonder if they would be even better as casts
>  > to 'unsigned long')
>  >
>  > Thanks,
>  >
>  > Michael
> 
> Signed-off-by: Alejandro Colomar <colomar.6.4.3@...il.com>
> ---
>   man2/stat.2 | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/man2/stat.2 b/man2/stat.2
> index b35e3c615..08af24c56 100644
> --- a/man2/stat.2
> +++ b/man2/stat.2
> @@ -665,7 +665,8 @@ main(int argc, char *argv[])
>       }
> 
>       printf("ID of containing device:  [%lx,%lx]\en",
> -	    (long) major(sb.st_dev), (long) minor(sb.st_dev));
> +	    (unsigned long) major(sb.st_dev),
> +            (unsigned long) minor(sb.st_dev));
> 
>       printf("File type:                ");
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/