Re: [Qemu-devel] converting build system to Meson?

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> On Thu, 7 Mar 2019 at 06:39, Thomas Huth <thuth@redhat.com> wrote:
> > On 06/03/2019 19.12, Paolo Bonzini wrote:
> > > lately I have been thinking of converting the QEMU build system to
> > > Meson.  Meson is a relatively new build system that can replace
> > > Autotools or hand-written Makefiles such as QEMU; as a die-hard
> > > Autotools fan, I must say that Meson is by far better than anything else
> > > that has ever tried to replace Autotools, and actually has the potential
> > > to do so.
> > >
> > > Advantages of Meson that directly matter for QEMU include:[...]
> >
> > I'm not objecting a new build system per se, but could you elaborate on
> >  problems of the current QEMU build system that will be fixed by this
> > change? Since apart from some minor glitches (with the *.mak file
> > dependencies for example), the current build system seems to work quite
> > well for me ... so at least I currently don't feel enough pain yet to do
> > such a big step, just because there is another new cool build system
> > around...
> 
> Yes, that tends to be my view. Our current build system:
>  * has no dependencies that are problematic for older hosts
>    (contrast Meson, which needs Python 3.5, even if we take
>    the drastic step of shipping an entire build tool along
>    with QEMU; OSX python is 2.7 still)
>  * is not particularly hard to deal with for the common cases
>    ("add new source file" is straightforward)
>  * covers all our requirements as far as I'm aware
>    (whereas you've listed a couple of places where Meson
>    would need changes/extensions to support things we do already)
>  * is generally flexible enough to be hackable to deal with odd
>    cases (it has escape mechanisms to generic-programmability,
>    even if they're ugly and awkward)

Pretty regularly I just give up on build directories and recreate
them because of changes that our Makefiles haven't realised
when updating a tree.
(I can't say it's any one fault anywhere)

Having said that, the counterpoint in Meson is that it's build
directories seem tobe exact-meson version dependent; doing a minor
host update and you find you have to nuke your build directories.

Dave

> So I think we'd need a more compelling reason to move right now.
> (This might change in the future, eg if Meson catches on to the
> extent that everybody is using it and competitors like CMake are
> more obviously eclipsed by it, in the way that git took over
> from svn and relegated mercurial and bzr to obscurity.)
> 
> thanks
> -- PMM
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK