[LLVMdev] [RFC] Raise minimum required CMake version to 3.0

[Mehdi Amini]

> On Mar 10, 2015, at 3:53 PM, Richard Gorton <rcgorton at cognitive-electronics.com> wrote:
> 
> What are the benefits of using/requiring CMake 3.0?  I've got a (non-published) target based upon RHEL6, and already am dancing on my head to build on that.

What is the CMake version you have on your RHEL and how do you get it (backport?)? 
According to http://www.cmake.org/Wiki/CMake_Life_Cycle_Considerations RHEL shipped in 2010 with CMake 2.6.4.

It would be interesting to know if CMake 3.0 builds successfully out-of-the-box on your RHEL6, after installing the other dependencies required to build LLVM 3.7. 
Can you give a try? The basic process is really simple: http://www.cmake.org/install/ 

I also wonder if the Linux binary they provide http://www.cmake.org/download/ would work for you?

As of the benefits, Renato and Chris already listed multiple of them.

Thanks,

Mehdi



> 
> Regards,
> 
>    Richard
> 
> On 3/10/2015 6:31 PM, Benjamin Kramer wrote:
>>> On 10.03.2015, at 22:59, Chris Bieneman <beanz at apple.com> wrote:
>>> 
>>> 
>>>> On Mar 10, 2015, at 2:53 PM, Renato Golin <renato.golin at linaro.org> wrote:
>>>> 
>>>> On 10 March 2015 at 21:30, Chandler Carruth <chandlerc at google.com> wrote:
>>>>> In the absence of specific features which would make our use of CMake
>>>>> significantly better, I'm inclined to stick roughly to the version of CMake
>>>>> in the latest LTS release of ubuntu (I don't know the stable releases of
>>>>> debian well enough to cite it, but likely the same applies).
>>>> 2.8.12.2 seems to be the common minimum version.
>>> Not if you include Debian stable, which is 2.8.9.
>> I don't think Debian wheezy should be an important target for us now. It looks like the next stable version 'jessie' is coming out in April and comes with CMake 3.0.2. That gives people enough time to upgrade in time for LLVM 3.7 :)
>> 
>> - Ben
>> 
>>>> Another thing to consider is the impact of CMake changes on buildbots.
>>>> It may not be possible to migrate all buildbots to newer versions, for
>>>> instance, Ubuntu is still stuck with 2.8.12.2 I think, but Debian
>>>> Jesse is already on 3.0.2 and Arch Linux on 3.1.3.
>>>> 
>>>> The "advanced" features I want from CMake are:
>>>> * use pool = console (available in 3.0) to get rid of our ugly hack
>>>> due to short timeouts
>>>> * specify -DCMAKE_NINJA_LINK_POOL=2 so we can build on
>>>> multi-core/low-mem environments (or distcc).
>>>> 
>>>> I don't think the second is even on the drawing board, though I
>>>> remember having suggested it a few years back.
>>>> 
>>>> None of them would make the life of a new developer easier, though... :)
>>> Unless we have new developers who enjoy cross compilation.
>>> 
>>>> cheers,
>>>> --renato
>>> 
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