[libvirt PATCH 037/351] meson: add readline build option

[Andrea Bolognani]

On Thu, 2020-07-16 at 11:54 +0200, Pavel Hrdina wrote:
> +++ b/meson_options.txt
> @@ -12,3 +12,4 @@ option('test_coverage', type: 'boolean', value: false, description: 'turn on cod
>  option('apparmor', type: 'feature', value: 'auto', description: 'apparmor support')
>  option('attr', type: 'feature', value: 'auto', description: 'attr support')
>  option('audit', type: 'feature', value: 'auto', description: 'audit support')
> +option('readline', type: 'feature', value: 'auto', description: 'readline support')

Erik reports that there are issues with building RPMs on CentOS. He
opened https://gitlab.com/libvirt/libvirt-ci/-/merge_requests/42, but
it seems to me that the topic should be discussed here instead, so
I'm quoting his message and replying inline.

> After libvirt switched to the meson build system, rpmbuild on
> CentOS is no longer viable as meson >= 0.54.0 is required while
> only 0.49.2 (at the time of this patch) is available from the
> package manager. Even if --nodeps is passed, the "%meson" RPM macro
> won't expand and the build will fail.

The question is, was dropping RPM build support for CentOS an
intentional change? I'm not sure it was, because otherwise the spec
file could have been cleaned up a bit at the same time. If it was
not, then we need to make use of the `%meson` macro conditional.

As an aside, I haven't actually checked, but I think that even though
CentOS 8 ships a version of Meson that's too old for us it should at
least have the `%meson` macro. Maybe that won't work with a Meson
installed from PyPi, though...

> It doesn't end there though, even if meson 0.54.0 were available,
> the rpm build would still fail because of readline-devel not
> providing the pkg config file on CentOS-8 which we rely on.

Looking at the lastest pipeline, all CentOS versions have "readline:
NO" in their build summary, but the build still succeeded, so I'm not
sure why the RPM build would fail? readline is an optional
dependency, and we're not passing `-Dreadline=enabled`.

Additionally, the complex logic necessary to detect readline
correctly, even in the absence of its pkg-config file, is still
present in `meson.build`, so I'm not sure why it's not doing what
it's supposed to do...

-- 
Andrea Bolognani / Red Hat / Virtualization