Re: portable way to get highest bit set?

Keith Thompson <[email protected]> Wed, 11 Oct 2023 14:30:55 -0700
Newsgroups comp.lang.c,alt.comp.lang.c
Organization None to speak of
Message-ID <[email protected]> 
Blue-Maned_Hawk <[email protected]> writes:
> candycanearter07 wrote:
>> What is the best/most portable way to get the highest bit set?
>> 
>> ie. 011010001 to  010000000
>
> #include <stdbit.h>
>
> unsigned char highest_bit_setc(unsigned char x)
> {
> 	return stdc_first_leading_one(x) ? (1 << stdc_first_leading_one(x) 
> - 1) : 0;
> }
>
> /* Repeat for all appropriate types and then probably make a generic macro 
> for all the subroutines. */

A solution that depends on a header that's introduced in C23, a standard
that hasn't been published yet, is hardly portable.

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-- 
Keith Thompson (The_Other_Keith) [email protected]
Will write code for food.
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