Re: [libvirt] [PATCH] configure: Check for MSG_NOSIGNAL availability

On Tue, Jul 19, 2016 at 04:00:25PM +0200, Andrea Bolognani wrote: >  > The symbol being missing has been reported as causing build > failures on OS X. Check for its availability before using it. > --- > See https://www.redhat.com/archives/libvir-list/2016-July/msg00613.html >  > configure.ac          | 4 ++++ > src/util/virsystemd.c | 4 ++-- > 2 files changed, 6 insertions(+), 2 deletions(-) >  > diff --git a/configure.ac b/configure.ac > index 2c81c95..af5d2f8 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -402,6 +402,10 @@ AC_CHECK_TYPE([struct sockpeercred], >   [], [[#include <sys/socket.h> >   ]]) >  > +AC_CHECK_DECLS([MSG_NOSIGNAL], > +  [], [], [[#include <sys/socket.h> > +  ]]) > + > AC_CHECK_DECLS([ETH_FLAG_TXVLAN, ETH_FLAG_NTUPLE, ETH_FLAG_RXHASH, ETH_FLAG_LRO, >                 ETHTOOL_GGSO, ETHTOOL_GGRO, ETHTOOL_GFLAGS, ETHTOOL_GFEATURES], >   [], [], [[#include <linux/ethtool.h> > diff --git a/src/util/virsystemd.c b/src/util/virsystemd.c > index 969cd68..d2f4bfb 100644 > --- a/src/util/virsystemd.c > +++ b/src/util/virsystemd.c > @@ -482,7 +482,7 @@ int virSystemdTerminateMachine(const char *name) > void > virSystemdNotifyStartup(void) > { > -#ifdef HAVE_SYS_UN_H > +#if defined(HAVE_SYS_UN_H) && defined(HAVE_MSG_NOSIGNAL)   What are the benefits of checking this at configure-time?   Seems to me we could just as well use defined(MSG_NOSIGNAL) without slowing configure down even more if we aren't going to base other configure-time decisions on it.