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From: Alexander Monakov <amonakov@ispras.ru>
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Subject: Re: [PATCH] simplify __procfdname by folding the 0 case
Date: Sun, 2 Sep 2018 14:14:52 +0300 (MSK)
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In 2016 I sent a more comprehensive cleanup, please review the thread
starting at http://openwall.com/lists/musl/2016/02/21/2

Some notes on the patch below.

On Sun, 2 Sep 2018, Fangrui Song wrote:
> --- a/src/internal/procfdname.c
> +++ b/src/internal/procfdname.c
> @@ -2,12 +2,7 @@ void __procfdname(char *buf, unsigned fd)
>  {
>  	unsigned i, j;
>  	for (i=0; (buf[i] = "/proc/self/fd/"[i]); i++);
> -	if (!fd) {
> -		buf[i] = '0';
> -		buf[i+1] = 0;
> -		return;
> -	}
> -	for (j=fd; j; j/=10, i++);
> -	buf[i] = 0;
> -	for (; fd; fd/=10) buf[--i] = '0' + fd%10;
> +	for (j=fd; i++, j /= 10; );

This is not correct as it only increments i once. A do-while loop would do the
job better here.

> +	buf[i] = '\0';
> +	while (buf[--i] = '0' + fd%10, fd /= 10);

Likewise, a do-while loop would be more suitable here.

>  }

Alexander