[Mesa-dev] Lets talk about autotools

[Dylan Baker]

Quoting Eric Engestrom (2018-09-20 07:56:45)
> On Thursday, 2018-09-20 15:28:09 +0100, Emil Velikov wrote:
> > Hi Chuck,
> > 
> > On 18 September 2018 at 16:00, Chuck Atkins <chuck.atkins at kitware.com> wrote:
> > > First, I'm fully in support of killing off autotools woo-hoo to that.  And
> > > given the substantial investment already put into the meson build that
> > > certainly seems like a good direction to go.
> > >
> > > That being said, the way "auto" is currently implemented leaves quite a bit
> > > to be desired.  One of the nice features of the Autotools build was how
> > > auto-enabled options were treated in that the dependencies were searched for
> > > and if they were all found and met then the option would be enabled.  My
> > > experience so far with the meson build has shown this not to be the case and
> > > a "configure" with no options has yet to be successful for me.  Many of the
> > > 'auto' options are treated as 'set to true if your platform supports it'
> > > regardless of whether your system has the requisite dependencies available.
> > > For example"
> > >
> > > The 'gallium-va' option defaults to 'auto' but the implementation ends up
> > > setting the '_va' option to true if the other option conditions are met,
> > > long before libva is searched for.  So then when libva isn't found one gets
> > > an error.
> > >
> > > if set to auto then missing the libva dependencies should be a failure, it
> > > should just disable the gallium va state tracker
> > >
> > > The platform options set to 'auto'  has a set of checks to determine which
> > > platforms are enabled as required.  If the system_has_kms_drm check is true
> > > then Wayland is enabled as required.  Later if the check for wayland
> > > dependencies fails, an error occurs.
> > >
> > > If platforms are set to auto then a failure to locate dependencies for a
> > > given platform should disable the platform.
> > >
> > > I realize these are just two specific examples, each of which can be readily
> > > dealt with in their own specific way so I'm not asking "how to I address #1
> > > and #2?" because I can certainly do that.  These are just two instances of
> > > many though in the way "auto" is dealt with.  My point is really a broader
> > > one that before meson becomes the primary build then the behavior of "auto"
> > > should create a successful configure out of the box without additional
> > > options.
> > >
> > I would like to revive an idea from a few years ago:
> > Drop the "auto" all-together.
> > 
> > It adds a _ton_ of complexity while making the build semi-magical/not
> > as deterministic.
> > IIRC the Gnome people have been actively working for removing such
> > autodetection in their packages.
> > 
> > The only downside is that we may need to tweak our scripts _once_ to
> > list exactly what we want to build ;-)
> 
> _Once_ for you, because you have everything already set up, but for all
> the new users this means that nothing will work out of the box, they'll
> need to understand each and every options and figure out what they need
> them set to, before they can even start.
> 
> That sounds like a huge step backwards to me :/

Especially when one of the explicit goals was to support 4 OS families
(Unix-like, windows, mac, haiku). To make that all work out of the box we'd end
up building *nothing* by default.

Dylan
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