Re: [PATCH 2/2] patch-id: replace `atoi()` with `strtol_i2()`

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 22, 2024, 19:32 UTC
Message-ID: <xmqq8r4htb8r.fsf@gitster.g>
In-Reply-To: <1ece724b1ca7f71542bfef42795fce798563ecde.1705913519.git.gitgitgadget@gmail.com>

"Mohit Marathe via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 16 quoted lines

>  	static const char digits[] = "0123456789";
>  	const char *q, *r;
> +	char *endp;
>  	int n;
>  
>  	q = p + 4;
>  	n = strspn(q, digits);
>  	if (q[n] == ',') {
>  		q += n + 1;
> -		*p_before = atoi(q);
> +		if (strtol_i2(q, 10, p_before, &endp) != 0)
> +			return 0;
>  		n = strspn(q, digits);
>  	} else {
>  		*p_before = 1;
>  	}

Looking at this code again, because we upfront run strspn() to make sure q[] begins with a run of digits *and* followed by a comma (which is not a digit), I think it is safe to use atoi() and assume it would slurp all the digits. So the lack of another check the use of new helper allows us to do, namely

		if (endp != q + n)
			return 0;

is probably OK, but that is one of the two reasons why you would favor the use of new helper over atoi(), so the upside of this change is not all that great as I originally hoped for X-<.

Not your fault, of course. We would still catch when the digit string that starts q[] is too large to fit in an int, which is an upside.

> -	if (n == 0 || q[n] != ' ' || q[n+1] != '+')
> +	if (q[n] != ' ' || q[n+1] != '+')
>  		return 0;

When we saw q[] that begins with ',' upon entry to this function, we used to say *p_before = 1 and then saw n==0 and realized it is not a good input and returned 0 from the function.

Now we instead peek q[0] and the check says q[0] is not SP so we will return 0 the same way so there is no behaviour change from the upper hunk? The conversion may be correct, but it wasn't explained in the proposed commit log message.

How are the change to stop caring about n==0 here ...

Show 13 quoted lines

>  	r = q + n + 2;
>  	n = strspn(r, digits);
>  	if (r[n] == ',') {
>  		r += n + 1;
> -		*p_after = atoi(r);
> -		n = strspn(r, digits);
> +		if (strtol_i2(r, 10, p_after, &endp) != 0)
> +			return 0;
>  	} else {
>  		*p_after = 1;
>  	}
> -	if (n == 0)
> -		return 0;

... and this change here, linked to the switch from atoi() to strtul_i2()[*]?

It looks like an unrelated behaviour change that is left unexplained.

>  	return 1;
>  }

Thanks for working on this one.

[Footnote]

 * by the way, what a horrible name for a public function.  Yuck.