[Libguestfs] Patchable build problems on OS X 10.10

[Pino Toscano]

On Monday 09 February 2015 10:27:21 Richard W.M. Jones wrote:
> On Mon, Feb 09, 2015 at 10:56:54AM +0100, Pino Toscano wrote:
> > On Friday 06 February 2015 10:03:37 Richard W.M. Jones wrote:
> > > On Thu, Feb 05, 2015 at 10:53:06PM +0000, Margaret Lewicka wrote:
> > > > +/* Fixes for Mac OS X */
> > > > +#if defined __APPLE__ && defined __MACH__
> > > > +#include <sys/un.h>
> > > > +#endif
> > > > +#ifndef SOCK_CLOEXEC
> > > > +# define SOCK_CLOEXEC O_CLOEXEC
> > > > +#endif
> > > > +#ifndef SOCK_NONBLOCK
> > > > +# define SOCK_NONBLOCK O_NONBLOCK
> > > > +#endif
> > > > +/* End of fixes for Mac OS X */
> > > > +
> > > >  /* Check minimum required version of libvirt.  The libvirt backend
> > > >   * is new and not the default, so we can get away with forcing
> > > >   * people who want to try it to have a reasonably new version of
> > 
> > This IMHO is clearly wrong: the O_* constants are for open() & friends,
> > not for socket & socket4.
> 
> I checked this out before committing it, and I accepted it because on
> Linux/glibc, SOCK_CLOEXEC == O_CLOEXEC and SOCK_NONBLOCK == O_NONBLOCK
> (see the definitions in bits/socket.h and bits/socket_type.h on a
> Linux system).
> 
> Of course this is not a law of nature and there could be systems where
> this is not true.
> 
> The macros as defined only affect systems that don't define SOCK_* at
> all.

Yes, I know SOCK_CLOEXEC == O_CLOEXEC on Linux, but on libc's without
such flags passing them might just cause accept/accept4 to fail
at runtime with EPROTOTYPE or EINVAL.

> > Theoretically, we could switch the socket() usages in launch-libvirt.c
> > to socket4(), which can be replaced by gnulib if missing (we already
> > use the "accept4" gnulib module). On the other hand, it seems that
> > such gnulib emulation does not provide SOCK_NONBLOCK, so either
> > a) fix that in gnulib
> > b) use the "nonblocking" gnulib module, using set_nonblocking_flag()
> >    instead of SOCK_NONBLOCK
> 
> (b) would not be atomic.

I'm not sure how it matters, since socket() just creates the socket
without doing anything further.

-- 
Pino Toscano