Re: [PATCH next] netfilter: nf_conntrack_h323: Correct indentation when H323_TRACE defined

David Laight
2026-03-27T09:52:01Z

On Fri, 27 Mar 2026 11:24:50 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Thu, Mar 26, 2026 at 10:18:09PM +0000, David Laight wrote:
> > On Thu, 26 Mar 2026 21:24:39 +0100
> > Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > > On Thu, Mar 26, 2026 at 08:18:19PM +0000, david.laight.linux@gmail.com wrote:
> > > >
> > > > The trace lines are indented using PRINT("%*.s", xx, " ").
> > > > Userspace will treat this as "%*.0s" and will output no characters
> > > > when 'xx' is zero, the kernel treats it as "%*s" and will output
> > > > a single ' ' - which is probably what is intended.
> > > >
> > > > Change all the formats to "%*s" removing the default precision.
> > > > This gives a single space indent when level is zero.
> > >
> > > Do you have a setup using this helper? Or you just found this via
> > > visual inspection?
> >
> > Found with grep looking for places which might be affected by 'fixing'
> > the kernel printf code to be POSIX compliant.
>
> Do we have the respective test case in printf_kunit?
>

There are definitely related ones and this comment:

static void
test_string(struct kunit *kunittest)
{
[...]
/*
* POSIX and C99 say that a negative precision (which is only
* possible to pass via a * argument) should be treated as if
* the precision wasn't present, and that if the precision is
* omitted (as in %.s), the precision should be taken to be
* 0. However, the kernel's printf behave exactly opposite,
* treating a negative precision as 0 and treating an omitted
* precision specifier as if no precision was given.
*
* These test cases document the current behaviour; should
* anyone ever feel the need to follow the standards more
* closely, this can be revisited.
*/
test(" ", "%4.*s", -5, "123456");
[...]
}

I suspect whoever wrote the tests found the code was non-conformant.
But there isn't a comment in the snprintf() code itself.
I've not checked what the kernel code does (I've just written/fixed all
this for nolibc - the kernel will fail the nolibc tests).

David