[Mesa-dev] last call for autotools

[Marek Olšák]

Another usability issue is that meson doesn't re-run llvm-config when
auto-reconfiguring.

Marek

On Tue, Feb 5, 2019 at 1:20 PM Marek Olšák <maraeo at gmail.com> wrote:

> PKG_CONFIG_PATH still seems to be forgotten by meson. Is there an
> alternative?
>
> Thanks,
> Marek
>
> On Sun, Dec 23, 2018 at 9:32 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>
>> On Wed, Dec 19, 2018 at 1:30 PM Dylan Baker <dylan at pnwbakers.com> wrote:
>> >
>> > Quoting Nicolai Hähnle (2018-12-18 09:37:43)
>> > > On 17.12.18 23:46, Dylan Baker wrote:
>> > > > Quoting Marek Olšák (2018-12-17 12:25:29)
>> > > >> On Mon, Dec 17, 2018 at 1:18 PM Eric Anholt <eric at anholt.net>
>> wrote:
>> > > >>
>> > > >>      Eero Tamminen <eero.t.tamminen at intel.com> writes:
>> > > >>
>> > > >>      > Hi,
>> > > >>      >
>> > > >>      > On 17.12.2018 8.08, Marek Olšák wrote:
>> > > >>      > [...]
>> > > >>      >> I think one of the serious usability issues is that
>> environment
>> > > >>      >> variables such as CFLAGS, CXXFLAGS, LDFLAGS, and
>> PKG_CONFIG_PATH are not
>> > > >>      >> saved by meson for future reconfigures.
>> > > >>      >
>> > > >>      > I don't know what Meson is supposed to do, but to me that
>> would be
>> > > >>      > a bug in a build tool.
>> > > >>      >
>> > > >>      > Re-configure is supposed to adapt SW to the changes in the
>> build
>> > > >>      > environment, and environment variables are part of that
>> (along with
>> > > >>      > command line options and SW installed to to the system).
>> Build
>> > > >>      > configure tool deciding to "remember" some of those things
>> instead
>> > > >>      > of checking the new situation, seems like a great
>> opportunity for
>> > > >>      > confusion.
>> > > >>
>> > > >>      A user-triggered reconfigure, sure.  Recapture env vars
>> then.  But "git
>> > > >>      pull; ninja -C build" losing track of the configuration state
>> is broken.
>> > > >>      We don't have to specify all of your meson -Doption=state
>> configuration
>> > > >>      on every build, why should you need to specify your
>> PKG_CONFIG_PATH
>> > > >>      configure options on every build?
>> > > >>
>> > > >>
>> > > >> Thanks, Eric.
>> > > >>
>> > > >> Yes, meson behaves such that users have to set all environment
>> variables for
>> > > >> every "ninja" command that might reconfigure.
>> > > >>
>> > > >> I see 2 solutions:
>> > > >> 1) meson needs to remember the relevant env vars
>> > > >> 2) meson should FAIL to configure if any of the env vars are set
>> (if it wants
>> > > >> to ignore them)
>> > > >>
>> > > >> Marek
>> > > >
>> > > > Meson does remember the *_FLAGS variables. Those are translated on
>> configure
>> > > > into meson's internal ${lang}_args and ${lang}_link args. It does
>> look like
>> > > > those aren't remembered when --wipe is called though, I filed a bug
>> for that:
>> > > > https://github.com/mesonbuild/meson/issues/4650
>> > >
>> > > I ran into this same problem and noticed that Meson is already able to
>> > > *warn* about such changes.
>> > >
>> > > It should either ignore the changes, or better yet, fail.
>> > >
>> > > (Or even better: ignore environment variables entirely; IMO sourcing
>> the
>> > > environment implicitly in a build system with an explicit configure is
>> > > just a broken design that was unfortunately inherited from plain make
>> > > without really considering the UI implications.)
>> >
>> > I agree with this, as do most of the upstream meson developers. So do
>> the
>> > autotools developers, who recommend passing CFLAGS (and friends) as
>> arguments
>> > instead of as env variables:
>> >
>> > ./configure CFLAGS='-march=native -03' LDFLAGS='-O3' --enable-foo
>> >
>> > meson supports this using:
>> >
>> > meson -Dc_args='-march-native' -Dc_link_args='-O3' -Dfoo=true
>> >
>> > Meson basically inherited this from autotools, and in hindsight we
>> shouldn't
>> > have.
>> >
>> > I'm going to do 3 things I think:
>> > - Update our documentation to strongly recommend -Dc_args and not CLFAGS
>> > - Push for meson to warn about using environment variables and
>> recommend command
>> >   line options.
>> > - Push for meson to remove CFLAGS and friends support:
>> >   https://github.com/mesonbuild/meson/issues/4664
>>
>> FWIW when I was talking about env vars, I was very much referring to
>>
>> ./configure CFLAGS=..., not the CFLAGS=... ./configure variant -- that's
>> fraught with peril.
>>
>> An especially important one to be able to bake in is PKG_CONFIG_PATH.
>> Having support for just doing it rather than knowing what the mapping to
>> meson is would be rather preferable -- e.g.
>>
>> meson CFLAGS=...
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>
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