linux-kernel - Re: [PATCH] remove abs64()

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Message-ID: <20110413142703.GA1511@redhat.com>
Date:	Wed, 13 Apr 2011 16:27:03 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	behlendorf1@...l.gov
Subject: Re: [PATCH] remove abs64()

On 04/13, Alexey Dobriyan wrote:
>
> +#define abs(x)								\
> +({									\
> +	typeof(x) _x = (x);						\
> +									\
> +	__builtin_choose_expr(						\
> +		__builtin_types_compatible_p(typeof(_x), signed char),	\
> +		(unsigned char)({ _x < 0 ? -_x : _x; }),		\
> +	__builtin_choose_expr(						\
> +		__builtin_types_compatible_p(typeof(_x), short),	\
> +		(unsigned short)({ _x < 0 ? -_x : _x; }),		\
> +	__builtin_choose_expr(						\
> +		__builtin_types_compatible_p(typeof(_x), int),		\
> +		(unsigned int)({ _x < 0 ? -_x : _x; }),			\
> +	__builtin_choose_expr(						\
> +		__builtin_types_compatible_p(typeof(_x), long),		\
> +		(unsigned long)({ _x < 0 ? -_x : _x; }),		\
> +	__builtin_choose_expr(						\
> +		__builtin_types_compatible_p(typeof(_x), long long),	\
> +		(unsigned long long)({ _x < 0 ? -_x : _x; }),		\
> +	_x)))));							\
> +})

Personally I agree.

But, we have some stupid users which do something like abs(u32_value)
and expecting that abs() should treat this value as "signed".

Oleg.

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