Re: [Qemu-devel] [PATCH 3/3] qtest: kill QEMU process on g_assert() failure

[Stefan Hajnoczi]

On Mon, Feb 17, 2014 at 05:49:31PM +0100, Markus Armbruster wrote:
> Stefan Hajnoczi <address@hidden> writes:
> > +    /* Catch SIGABRT to clean up on g_assert() failure */
> > +    sigact = (struct sigaction){
> > +        .sa_handler = sigabrt_handler,
> > +        .sa_flags = SA_RESETHAND,
> > +    };
> 
> Assumes zero-initialization has the same effect as
> sigemptyset(&sigact.sa_mask).  Quoting POSIX:
> 
>     The implementation of the sigemptyset() (or sigfillset()) function
>     could quite trivially clear (or set) all the bits in the signal set.
>     Alternatively, it would be reasonable to initialize part of the
>     structure, such as a version field, to permit binary-compatibility
>     between releases where the size of the set varies.  For such
>     reasons, either sigemptyset() or sigfillset() must be called prior
>     to any other use of the signal set, even if such use is read-only
>     (for example, as an argument to sigpending()).
> 
> Looks like you better sigemptyset() here, for maximum portability.

Okay, will do that.

> > +    sigaction(SIGABRT, &sigact, &s->sigact_old);
> >  
> >      socket_path = g_strdup_printf("/tmp/qtest-%d.sock", getpid());
> >      qmp_socket_path = g_strdup_printf("/tmp/qtest-%d.qmp", getpid());
> > @@ -150,13 +167,19 @@ void qtest_quit(QTestState *s)
> >  {
> >      int status;
> >  
> > +    sigaction(SIGABRT, &s->sigact_old, NULL);
> > +
> 
> Can this ever restore the action to anything but the default action?

This code is in a "library" so I don't want to make assumptions about
the callers.  Keeping sigact_old around is literally 1 line of code so I
think it's worth it.

> >      if (s->qemu_pid != -1) {
> >          kill(s->qemu_pid, SIGTERM);
> >          waitpid(s->qemu_pid, &status, 0);
> >      }
> >  
> > -    close(s->fd);
> > -    close(s->qmp_fd);
> > +    if (s->fd != -1) {
> > +        close(s->fd);
> > +    }
> > +    if (s->qmp_fd != -1) {
> > +        close(s->qmp_fd);
> > +    }
> 
> I generally don't bother to avoid close(-1).

When I drive on the highway I stay on the lanes but I guess I could just
slide along the side barriers :).  It's a style issue but close(-1)
annoys me in strace so I try to avoid doing it.