Re: CVS commit: src/share/mk

[Taylor R Campbell <campbell+netbsd-source-changes-d%mumble.net@localhost>]

> Date: Mon, 7 Aug 2023 23:58:50 +0200
> From: Tobias Nygren <tnn%NetBSD.org@localhost>
> 
> Is this sort of fix acceptable for the above cases?
> 
> +			ptrdiff_t offset = pos - buf;
>  			new_buf = realloc(buf, buf_size);
>  			if (!new_buf)
>  				err(2, "realloc of linebuf to %zu bytes failed",
>  					buf_size);
> -		
> +
>  			end = new_buf + buf_size;
> -			pos = new_buf + (pos - buf);
> +			pos = new_buf + offset;
>  			buf = new_buf;

Yes, this is a good approach.

Even if it's suboptimal in some cases, it is very easy to audit
mechanical changes, which is important if there are a lot of them.

Any further case-specific simplifications (like changing ptrdiff_t to
size_t, since it will always be nonnegative here; just using `size_t
offset = buf_size' before `buf_size *= 2', since since pos == end and
end == buf + buf_size) can be done afterward in a separate commit.