Re: [boost] Proposal for moving Boost to CMake

Subject: Re: [boost] Proposal for moving Boost to CMake
From: Klemens Morgenstern (klemens.morgenstern_at_[hidden])
Date: 2017-06-17 07:11:53

I am dead set against that. CMake is inferior to boost.build and it's 
only popular for the lack of alternatives. Boost.build could be one (I 
use it in my projects outside of boost) but it a steep learning curve 
and is not distributed outside of boost. But even the syntax is less 
horrible than the CMake one in my opinion.

I do think CMake is broken in it's core, because it doesn't build but 
create a description (i.e. makefile or similar). And in order to change 
that I have to clear the cache and reconstruct it. Boost.build on the 
other hand works like a charm if I have a proper build description and 
write `b2 toolset=gcc toolset=msvc` - it will build both and test on 
both without any conflicts. I think we should definitely keep 
boost.build around, if only to have it's concepts (as in meta-targets) 
in a working build-system. I also don't think CMake will be around 
forever, it's a deficient solution. As ist boost.build, but boost.build 
gets the job done for boost. I don't see the point of moving from one 
deficient tool to a worse one, just because everybody seems to be using it.

Am 17.06.2017 um 01:44 schrieb David Sankel via Boost:
> Howdy all,
>
> This is a request for comments on a possible path for migrating Boost's
> build
> system to CMake. I am not speaking for the Boost Program Committee here,
> but I
> plan on bringing this up with them after getting feedback.
>
> The motivation is simple. CMake is currently the dominant player in the
> area of
> open-source, cross-platform, C++ build-systems. I make this claim based on
> Google trends graphs and discussions with others at the conferences I attend
> (CppCon, C++Now, and ISO C++ meetings). If we make Boost buildable and
> usable
> out-of-the-box with CMake, we would significantly lower the barriers to
> entry
> for both Boost users and new Boost developers. Boost serves the greater C++
> community and making Boost more accessible would be of great utility.
>
> * To ease the migration path, both Boost.Build (the current jam-based build
>    system) and CMake will be supported for a time.
> * Boost sources would provide a compatible, drop-in replacement for the
>    'FindBoost' module that is distributed with CMake. A CMake-based
> application
>    could point to it and, instead of using the system Boost libraries, Boost
>    targets would be built from source as part of the user build.
> * The built Boost **binaries** would also provide a compatible, drop-in
>    replacement for the 'FindBoost' module distributed with CMake. The
> behavior
>    is similar to the previous bullet, except the built binaries would be used
>    instead of the source code.
> * The style of the 'CMakeLists.txt' files would follow current best
> practice.
>    We'd resist the temptation to write macros which replace the core CMake
>    functions. There would be repetition in the files, to be sure, but I
> think we
>    should avoid attempting to innovate CMake. I've seen this fail on many
>    occasions and would like to keep our goal focused, at this point, on
>    migrating Boost to CMake. In the future we could revisit this.
> * There would be a list of CMake guidelines that we'd use.
> * Boost libraries should be buildable in isolation and use
>    'find_package(Boost...)' to discover their Boost dependencies.
> * We would work with CMake towards eventually taking over maintenance of the
>    FindBoost module distributed with CMake.
>
> I see this progressing with several milestones.
>
> 1. Release of a CMake-buildable Boost and the CMake conventions. In this
> stage
>     each Boost library can be built in isolation or with the entire
> distribution
>     and all the 'FindBoost' functionality mentioned above would be
> incorporated.
> 2. The unit tests for all Boost libraries are incorporated into CTest (the
>     CMake unit test orchestration tools).
> 3. The Boost infrastructure is modified to use CTest for unit testing.
> 4. Unit testing functionality is removed from Boost.Build.
> 5. Boost.Build is removed.
>
> Although there are many other great ideas floating around (e.g.
> modularization
> of Boost, Boost-Classic, and Boost2), I'd like to keep this focused on
> CMakification of Boost because I think it is something that would have big
> impact and is small enough to be doable.
>
> One question that is going to come up is "who is going to do all this
> work?".
> Once we decide on a direction, I don't foresee a problem making this happen.
> Between volunteers, the importance this project has for companies, and the
> Steering Committee reserves, we should have the resources necessary.
>
> Another concern is that some authors may resist. Authors have a lot of
> leeway
> when it comes to how they maintain their libraries, what conventions they
> use,
> and backwards compatibility concerns. However, there are some things that
> authors need to conform to, such as our current Boost.Build build and
> testing
> infrastructure. I liken this to the development of a city: building
> developers
> can make their buildings however they want, but the streets, which control
> transit between buildings, are centrally regulated.
>
> Thanks for your consideration.
>
> -- David Sankel
>
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