Re: [PATCH RFC v3 1/6] exterr: Introduce extended syscall error reporting

[Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>]

> I think that anything other than the errno "grab it now or lose it"
> behavior will prove confusing.  I don't think there is any other way to
> know that a given error report corresponds to a specific system call.
> Library calls can mess it up.  Kernel changes adding extended reporting to
> new system calls can mess it up.  Applications cannot possibly be expected
> to know which system calls might change the error-reporting status, they
> *have* to assume all of them will.
> 

Yeah I was about to say something similar - an application that expects
a certain syscall to have extended errors will get confused if running
on an older kernel where that syscall in fact does *not* have extended
errors (and thus also doesn't clear extended errors) and therefore the
extended error from a previous syscall could still be lingering on (for
example because the application didn't care to fetch it for that previo
us syscall.)

johannes