linux-kernel - Re: [PATCH 1/2] linux/kernel.h: use 'short' to define USHRT_MAX, SHRT_MAX, SHRT

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Date:   Sat, 2 Feb 2019 19:31:05 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Zhang Yanmin <yanmin.zhang@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] linux/kernel.h: use 'short' to define USHRT_MAX,
 SHRT_MAX, SHRT_MIN

On Sun, Feb 03, 2019 at 01:06:24AM +0900, Masahiro Yamada wrote:
> The log of commit 44f564a4bf6a ("ipc: add definitions of USHORT_MAX
> and others") did not explain why it used (s16) and (u16) instead of
> (short) and (unsigned short).
> 
> Let's use (short) and (unsigned short), which is more sensible, and
> more consistent with the other MAX/MIN defines.
> 
> As you see in include/uapi/asm-generic/int-ll64.h, s16/u16 are
> typedef'ed as signed/unsigned short. So, this commit does not have
> a functional change.

> -#define USHRT_MAX	((u16)(~0U))
> -#define SHRT_MAX	((s16)(USHRT_MAX>>1))
> -#define SHRT_MIN	((s16)(-SHRT_MAX - 1))
> +#define USHRT_MAX	((unsigned short)(~0U))
					 ^   ^
					 +---+
					   unnecessary ()
> +#define SHRT_MAX	((short)(USHRT_MAX>>1))
> +#define SHRT_MIN	((short)(-SHRT_MAX - 1))

"short" and "unsigned short" are probably the most useless C types.
I doubt their usage should be promoted.