[Mesa-dev] Lets talk about autotools

[Kai Wasserbäch]

Dylan Baker wrote on 9/18/18 5:35 PM:
> Quoting Kai Wasserbäch (2018-09-18 07:43:08)
>> Hey,
>> Dylan Baker wrote on 9/17/18 6:44 PM:
>>> I feel like for !windows meson is in good enough shape at this point that we
>>> can start having the discussion about deleting the autotools build. So, is there
>>> anything left that autotools can do that meson cannot (that we actually want to
>>> implement)? And, what is a reasonable time-table to remove the autotools build?
>>> I think we could reasonably remove it as soon as 18.3 if others felt confident
>>> that it would work for them.
>>
>> How do I set a specific llvm-config name to look for? I have build environments
>> with multiple LLVM versions (eg. 6, 7 and 8) installed in parallel. So far I
>> could convince each build system with LLVM_CONFIG or similar means to choose a
>> particular llvm-config-${LLVM_VERSION], meson can't do that AFAICT.
>>
>> Eric pointed me to an ugly hack on IRC, which involves symlinking the particular
>> llvm-config-${VERSION} to llvm-config in $PATH
>> (<https://gitlab.freedesktop.org/mesa/mesa/commit/b5b912dfeebabafbaff176fe4205eb74607f709b>).
>> But I think this should be fixed properly before making meson mandatory. Other
>> modern build systems like CMake react to something like -DLLVM_DIR during
>> configure (see
>> <https://llvm.org/docs/CMake.html#embedding-llvm-in-your-project>) and Mesa's
>> stable build systems use LLVM_CONFIG, if set.
>>
>> Cheers,
>> Kai
> 
> This is something we've discussed upstream several times. I will freely admit
> that llvm-config is a huge pain in the ass to deal with for a ton of reasons,
> and since we don't use it at Intel

Since there's now an „APU“ from Intel with an AMD GPU, I guess that is no longer
the case?

> it hasn't been on the top of my list of
> things to do, and also because the solution upstream wants is very non-trival to
> implement. This has come up already and I am working on it right now.

If upstream support is unreasonable, I'd like to see a similar solution to
LLVM_CONFIG as it's in autotools today. It must be possible to mangle/override
the meson variables right? (This might be totally ignorant, because I was able
to avoid Meson so far and all other build systems I've worked with, have one or
more options to set variables. Either by having an option in the build files or
by passing some option into the configure step.)

> The other option you have it to set the $PATH variable, as long as the
> llvm-config you want returns the highest version things will work as you expect.

This might do as a workaround, though I'm not too keen on extending $PATH. But
as the /usr/lib/llvm-${LLVM_VERSION}/bin directories should only contain that
versions binaries, putting it first into the path could work.

Cheers,
Kai

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