[libvirt] [PATCHv2 12/12] build: require Jansson if QEMU driver is enabled

[Peter Krempa]

On Thu, May 10, 2018 at 18:44:24 +0200, Ján Tomko wrote:
> If the QEMU driver was requested, require Jansson, since we need to use
> the JSON monitor to probe capabilities for all QEMU version supported
> by libvirt.
> 
> Switch the default from 'yes' to 'check', and enable the QEMU driver
> by default if the Jansson library is present.
> 
> Signed-off-by: Ján Tomko <jtomko at redhat.com>
> ---
>  m4/virt-driver-qemu.m4 | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/m4/virt-driver-qemu.m4 b/m4/virt-driver-qemu.m4
> index b9bafdab90..a0d34f1dca 100644
> --- a/m4/virt-driver-qemu.m4
> +++ b/m4/virt-driver-qemu.m4
> @@ -18,7 +18,7 @@ dnl <http://www.gnu.org/licenses/>.
>  dnl
>  
>  AC_DEFUN([LIBVIRT_DRIVER_ARG_QEMU], [
> -  LIBVIRT_ARG_WITH_FEATURE([QEMU], [QEMU/KVM], [yes])
> +  LIBVIRT_ARG_WITH_FEATURE([QEMU], [QEMU/KVM], [check])
>    LIBVIRT_ARG_WITH([QEMU_USER], [username to run QEMU system instance as],
>                     ['platform dependent'])
>    LIBVIRT_ARG_WITH([QEMU_GROUP], [groupname to run QEMU system instance as],
> @@ -26,6 +26,12 @@ AC_DEFUN([LIBVIRT_DRIVER_ARG_QEMU], [
>  ])
>  
>  AC_DEFUN([LIBVIRT_DRIVER_CHECK_QEMU], [
> +  if test "$with_qemu:$with_jansson" = "yes:no"; then
> +    AC_MSG_ERROR([Jansson >= 2.7 is required to build QEMU driver])
> +  fi

So is the ordering of execution of these guaranteed? In other words,
will 'with_najsson' be always resolved at this point?

Also I agree with this check, but I'm not entirely persuaded by the rest
of the patch. Maybe it can be split into two, since it does two separate
things.

> +  if test "$with_qemu" = "check"; then
> +    with_qemu=$with_jansson
> +  fi
>    if test "$with_qemu" = "yes" ; then
>      AC_DEFINE_UNQUOTED([WITH_QEMU], 1, [whether QEMU driver is enabled])
>    fi
> -- 
> 2.16.1
> 
> --
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> libvir-list at redhat.com
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