Re: [boost] Proposal for moving Boost to CMake

Subject: Re: [boost] Proposal for moving Boost to CMake
From: P F (pfultz2_at_[hidden])
Date: 2017-06-17 18:42:17

> On Jun 17, 2017, at 1:15 PM, Robert Ramey via Boost <boost_at_[hidden]> wrote:
> 
> On 6/17/17 10:30 AM, Niall Douglas via Boost wrote:
>>>> So tl;dr; I strongly recommend placing all cmake complexity into
>>>> runnable scripts which generate .cmake files to be include()d to avoid
>>>> boilerplate, and keep the CMakeLists.txt etc completely free of any
>>>> custom macros or functions.
>>> 
>>> Niall, could you please show how an idiomatic CMakeLists.txt file
>>> should, in your opinion, look like, for a run-of-the-mill Boost library?
>>> Pick some existing library to illustrate the point, such as for example
>>> System, or SmartPtr, or even the simplest one, Assert. Or any other, if
>>> you prefer.
>> Sure, though I'm talking really vanilla cmake here. But I guess it will
>> narrow the discussion by demonstrating idiomatic cmake 3. Too much cmake
>> 2 still kicks around. I really wish cmake would kill off cmake2-isms, as
>> in, refuse to use them.
>> According to Jens'
>> https://meetingcpp.com/tl_files/blog/bda/boostdepbargraph.png, System
>> looks the most tractable. I'll see if I can find some hours to do it up,
>> I can guarantee it won't be today nor tomorrow. Maybe tomorrow night
>> after the kids are asleep.
>> Niall
> 
> Hmmm - I would be curious if a CMake enthusiast took a look at the Safe Numerics repo and commented on the CMake files listed there.  I think its pretty simple and canonical usage of CMake as it relates to a Boost library.  The only think I want to change is the existence of some code in a CMake directory which I'll soon eliminate - but all in all it's pretty simple.  What would be missing from this for it it to meet expectations of CMake Promotors?

* It should not use global `include_directories`. 

* Its not necessary to put CMakeLists.txt in every directory with modern cmake. 

* There is no installation, and there is no support for `find_package(SafeNumerics)` which can provide a cmake target for downstream user to use. Nor does it provide a cmake target for people to use with `add_subdirectory` either. 

* Tests are always built even when the user sets `BUILD_TESTING` to off.

Boost.Hana is much better example of modern cmake.