On Thu, Apr 06, 2023 at 03:32:20PM +0100, Mark Brown wrote:
> On Thu, Apr 06, 2023 at 04:20:29PM +0200, Willy Tarreau wrote:
> > On Thu, Apr 06, 2023 at 02:56:28PM +0100, Mark Brown wrote:
>
> > > At present the kselftest header can't be used with nolibc since it makes
> > > use of vprintf() which is not available in nolibc and seems like it would
> > > be inappropriate to implement given the minimal system requirements and
> > > environment intended for nolibc.
>
> > In fact we already have vfprintf(), and printf() is based on it, so
> > wouldn't it just be a matter of adding vprintf() that calls vfprintf()
> > for your case ? Maybe just something like this :
>
> > static int vprintf(const char *fmt, va_list args)
> > {
> > return vfprintf(stdout, fmt, args);
> > }
>
> > It's possible I'm missing something, but it's also possible you didn't
> > find vfprintf() which is why I prefer to raise my hand ;-)
>
> Oh, yes - I just didn't find that. Can't remember what I searched for
> but it didn't match.
No problem. I just remembered it existed because we just received a
new test for it a few days ago ;-)
> > > This has resulted in some open coded
> > > kselftests which use nolibc to test features that are supposed to be
> > > controlled via libc and therefore better exercised in an environment with
> > > no libc.
>
> > Yeah that's ugly. In nolibc-test we now have two build targets so that
> > we can more easily verify the compatibility between the default libc and
> > nolibc, so my recommendation would be to stick to a common subset of both
> > libcs, but not to rely on nolibc-specific stuff that could make tests
> > harder to debug.
>
> For these features we simply never want to run with a proper libc since
> if we use a libc which has support for the features then we can't
> meaningfully interact with them. We're trying to test interfaces that
> libc is supposed to use.
Indeed, this totally makes sense then! But I think you get the idea of
what I was suggesting which is to try to avoid getting trapped by a
single implementation in general, by using portable stuff as much as
possible.
Cheers,
Willy
