[Mesa-dev] Lets talk about autotools

[Emil Velikov]

On 20 September 2018 at 19:19, Dylan Baker <dylan at pnwbakers.com> wrote:
> 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.
>
As mentioned elsewhere - if you don't know what you're doing (it's
fine to admit that), simply follow your distribution.
If you do not trust your distribution ... well. Otherwise - read.

No my call - you'll be fixing corner-cases in meson ;-)

-Emil