Re: [boost] Proposal for moving Boost to CMake

Subject: Re: [boost] Proposal for moving Boost to CMake
From: Olaf van der Spek (ml_at_[hidden])
Date: 2017-06-19 16:43:11

On Mon, Jun 19, 2017 at 5:14 PM, P F <pfultz2_at_[hidden]> wrote:
>
>> On Jun 19, 2017, at 3:58 AM, Olaf van der Spek via Boost <boost_at_[hidden]> wrote:
>>
>> On Sat, Jun 17, 2017 at 3:36 PM, P F via Boost <boost_at_[hidden]> wrote:
>>> It would be nice to not just support cmake, but pkgconfig as well. There are many times I need to use boost in non-cmake projects, so having pkgconfig would be helpful as well.
>>
>> I don't really get find_package and pkgconfig etc.
>>
>> I use package management to install the dependencies I need.
>> I then include and link to the stuff I need. It'd be nice if the
>> linking was automatic like it is on MSVC but okay.
>>
>> Why does one need all kinds of extra complexity in every single make
>> file for things like find_package or pkgconfig?
>
> I find writing something like `g++ $(pkgconfig boost_asio --cflags —libs) foo.cpp` much easier to write. In fact, I would need some investigating to know what flags I need. Other users would like boost to support pkgconfig as well as there are tickets open for this. Almost the same applies for `find_package` in cmake as well.

`g++ foo.cpp` would be even easier.. but Linux still doesn't support
auto-linking like GCC AFAIK.

Such dependencies for header-only libs are a problem though, I agree.
Do other libs have the same problem?

> It doesn’t add too much complexity. The files for pkgconfig are a simple text format, and for find_package, cmake can already generate the code the exported target. What is different is that all the dependencies between boost libraries are explicit. So the `boost_core-config.cmake` look like this:
>
> include(CMakeFindDependencyMacro)
> find_dependency(boost_config)
> find_dependency(boost_assert)
> # Include the targets generated by cmake
> include("${CMAKE_CURRENT_LIST_DIR}/boost_core-targets.cmake”)
>
> And then targets file is generate by calling `install(EXPORT boost_core-targets FILE FooTargets.cmake DESTINATION lib/cmake/boost_core)` in the main CMakeLists.txt.
>
> I actually wrote BCM to help reduce this boilerplate, here:
>
> http://bcm.readthedocs.io/en/latest/
>
> However, I planning to refactor this from feedback I got.
>

-- 
Olaf