Re: [boost] CMake Announcement from Boost Steering Committee

Subject: Re: [boost] CMake Announcement from Boost Steering Committee
From: Florent Castelli (florent.castelli_at_[hidden])
Date: 2017-07-19 21:24:03

On 19/07/2017 23:14, Edward Diener via Boost wrote:
> On 7/19/2017 4:46 PM, Oliver Kowalke via Boost wrote:
>> As mentioned before - it is not only your cmake port, all presented
>> boost-cmake files have ported only fraction of the required 
>> functionality.
>> For instance feature tests used in Jamfile to test for 
>> presence/absence of
>> some C++ features to control the build.
>> If it's so easy to do it with Cmake I'm wondering why it wasn't done.
>> I've the impression that only the easy parts of Jamfile have been 
>> ported.
>> The difficult parts are left ...
>
> Boost Build has the ability to run a 'program' and change the logic of 
> what is to be built, or how something is to be built, based on the 
> return value of that program. I do not know CMake well enough but I am 
> assuming that CMake also has such a feature, else it would really be 
> deficient IMO. That is essentially what Boost Config offers and Boost 
> Predef offers and my briefly discussed Cxxd library also offered, 
> through the facility in Boost Build which allows this. Porting Boost 
> Config and Boost Predef to use CMake would have to port this ability 
> also in an easy to use way, since other libraries also depend on the 
> Boost Config and Boost Predef facilities when they use Boost Build for 
> their purposes.

This is indeed possible: 
https://cmake.org/cmake/help/v3.8/command/try_compile.html#command:try_compile
Usually, you don't need to run them since you might be cross compiling 
for a weird platform and can't run programs for it, so it's better if 
the check can be done at compile time.

If you just want to check a header exists or just symbols, there are 
some other dedicated functions too that are a bit more convenient.

>
>>
>> As Klemens already mentioned, I'm missing a discussion about the
>> requirements of the boost build system and a comparison of pros/cons of
>> other build systems on the ML.
>
>
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