Re: [PATCH 29/32] lib/string_helpers: string_get_size() now returns characters wrote

Kent Overstreet
2023-07-12T20:23:18Z

On Wed, Jul 12, 2023 at 12:58:54PM -0700, Kees Cook wrote:
> On Tue, May 09, 2023 at 12:56:54PM -0400, Kent Overstreet wrote:
> > From: Kent Overstreet <kent.overstreet@gmail.com>
> >
> > printbuf now needs to know the number of characters that would have been
> > written if the buffer was too small, like snprintf(); this changes
> > string_get_size() to return the the return value of snprintf().
>
> Unfortunately, snprintf doesn't return characters written, it return
> what it TRIED to write, and can cause a lot of problems[1]. This patch
> would be fine with me if the snprintf was also replaced by scnprintf,
> which will return the actual string length copied (or 0) *not* including
> the trailing %NUL.

Anyways, I can't use scnprintf here, printbufs/seq_buf both need the
number of characters that would have been written, but I'll update the