Re: [PATCH] lib: Fix bug in int_sqrt() for 64 bit longs

[Eric Dumazet <dada1@cosmosbay.com>]

Peter Williams a écrit :
> The implementation of int_sqrt() assumes that longs have 32 bits.  On 
> systems that have 64 bit longs this will result in gross errors when the 
> argument to the function is greater than 2^32 - 1 on such systems. I 
> doubt whether any such use is currently made of int_sqrt() but the 
> attached patch fixes the problem anyway.
> 
> Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
> 
> 
> ------------------------------------------------------------------------
> 
> Index: GIT-warnings/lib/int_sqrt.c
> ===================================================================
> --- GIT-warnings.orig/lib/int_sqrt.c	2005-10-25 13:55:22.000000000 +1000
> +++ GIT-warnings/lib/int_sqrt.c	2006-01-06 14:29:19.000000000 +1100
> @@ -15,7 +15,7 @@ unsigned long int_sqrt(unsigned long x)
>  	op = x;
>  	res = 0;
>  
> -	one = 1 << 30;
> +	one = 1 << (BITS_PER_LONG - 2);
>  	while (one > op)
>  		one >>= 2;
>  

Are you sure it works ?

I would have writen :

one = 1L << (BITS_PER_LONG - 2);

Eric