Re: [PATCH v2 1/2] meson: Select 'have_system' when virtiofsd is enabled

[Paolo Bonzini]

On 29/04/21 10:44, Peter Maydell wrote:
> On Thu, 29 Apr 2021 at 09:33, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> > When not explicitly select a sysemu target and building virtiofsd,
> > the seccomp/cap-ng libraries are not resolved, leading to this error:
> >
> >    $ configure --target-list=i386-linux-user --disable-tools --enable-virtiofsd
> >    tools/meson.build:12:6: ERROR: Problem encountered: virtiofsd requires 
> > libcap-ng-devel and seccomp-devel
> >
> > Fix by enabling sysemu (have_system) when virtiofsd is built.
> >
> > Reported-by: Mahmoud Mandour <ma.mandourr@gmail.com>
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > ---
> >   meson.build | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/meson.build b/meson.build
> > index c6f4b0cf5e8..f858935ad95 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -51,6 +51,8 @@
> >     have_system = have_system or target.endswith('-softmmu')
> >   endforeach
> >   have_tools = 'CONFIG_TOOLS' in config_host
> > +# virtiofsd depends on sysemu
> > +have_system = have_system or not get_option('virtiofsd').disabled()
>
> This looks odd. The natural assumption is that "have_system" ought to mean
> "we are building a system emulator", not "we are building a system emulator
> or virtiofsd".

I agree this is a bit jarring.

If virtiofsd requires libcap-ng-devel and seccomp-devel, those tests 
only should use

  have_system or not get_option('virtiofsd').disabled()

instead of just have_system.  (The reason why we have those complicated 
expressions is to avoid getting warnings on static builds, for libraries 
that are only available as shared libraries.  There are plans to make it 
look a bit nicer in upstream Meson which the maintainers have already 
accepted; however, I haven't been able to contribute much to it lately).

Thanks,

Paolo