Re: [RFC v5 6/7] sprintf: Add [v]sprintf_array()

[Matthew Wilcox <willy@infradead.org>]

On Fri, Jul 11, 2025 at 10:58:56AM -0700, Linus Torvalds wrote:
> That kind of "string buffer" obviously isn't useful for things like
> the printf family, but we do have others. Like "struct seq_buf", which
> already has "seq_buf_printf()" helpers.
> 
> That's the one you probably should use for most kernel "print to
> buffer", but it has very few users despite not being complicated to
> use:
> 
>         struct seq_buf s;
>         seq_buf_init(&s, buf, szie);
> 
> and you're off to the races, and can do things like
> 
>         seq_buf_printf(&s, ....);
> 
> without ever having to worry about overflows etc.

I actually wanted to go one step further with this (that's why I took
readpos out of seq_buf in d0ed46b60396).  If you look at the guts of
vsprintf.c, it'd be much improved by using seq_buf internally instead
of passing around buf and end.

Once we've done that, maybe we can strip these annoying %pXYZ out
of vsprintf.c and use seq_buf routines like it's a StringBuilder (or
whatever other language/library convention you prefer).

Anyway, I ran out of time to work on it, but I still think it's
worthwhile.  And then there'd be a lot more commonality between regular
printing and trace printing, which would be nice.