Re: [PATCH] string: Improve the generic strlcpy() implementation

[Ingo Molnar <mingo@kernel.org>]

* Ingo Molnar <mingo@kernel.org> wrote:

> 2)
> 
> Another problem is that strlcpy() will also happily do bad stuff if we pass
> it a negative size. Instead of that we will from now on print a (one time)
> warning and return safely.

Hm, so this check is buggy, as 'size_t' is unsigned - and for some reason GCC 
didn't warn about the never-met comparison and the resulting unreachable dead
code here:

> +	/* Overflow check: */
> +	if (unlikely(dest_size < 0)) {
> +		WARN_ONCE(1, "strlcpy(): dest_size < 0 underflow!");
> +		return strlen(src);
> +	}

which is annoying.

Would people object to something like:

> +	/* Overflow check: */
> +	if (unlikely((ssize_t)dest_size < 0)) {
> +		WARN_ONCE(1, "strlcpy(): dest_size < 0 underflow!");
> +		return strlen(src);
> +	}

?

As I doubt it's legit to have larger than 2GB strings.

Also, I'm wondering why GCC didn't warn.

Thanks,

	Ingo