[boost] [cmake] Pull request announcement - update

Subject: [boost] [cmake] Pull request announcement - update
From: mike.dev_at_[hidden]
Date: 2019-01-04 11:03:29

I think it is time for an update on this issue.

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# TLDR: 

There are now ~25 boost libraries that can be directly used 
in a cmake project via the add_subdirectory & 
target_link_library - workflow. And I want to encourage
library maintainers to comment/merge outstanding PRs or
make similar additions to their libraries themselves.

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# A summary what that thread was about:
 
In September last year I was informing the mailing list
that I was about to make a bunch of PRs adding a set of minimal
CMake files to various boost libraries. Their sole purpose
was to enable the following workflow from within a cmake 
project:

    add_subdirectory( <path-to-boost-libfoo-directory> ) 

    target_link_library( my_app Boost::libfoo )

Without needing b2 or the boost super project for that 
matter (although support in the super project would be 
very welcomed)

For that, the cmake file in libfoo has to 
 - provide the target Boost::libfoo
 - attach the dependency information for Boost::libfoo
 - attach the proper include directory for Boost::libfoo
 - if necessary, build libfoo with whatever toolchain 
   and compile flags the parent cmake project defines
 - if necessary, attach any necessary compile definitions
   to Boost::libfoo

Although things like running the unit-tests or provide and 
install target can be added by any library maintainer
(and some have done just that) it is not part of my PRs. 

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# What is the current state.

For a quick overview, I uploaded a picture of the boost 
dependency graph (code based on boostdep) that shows 
which libraries Have a cmake file in their root and 
which don't [1].

So far, about 25 libraries have gained cmake files 
as part of this effort (not all from me). 
And of course there are a couple of libraries that
Already used cmake before I started my efforts, 
but AFAIK, most of them can not be used in the above 
mentioned work-flow.

Of course, there remains a lot to do, but at least 
progress is happening and we now have fitted almost all
"foundational" libraries , so from here on out, the pace 
should increase. 
Currently, I have 7 outstanding PRs and I would ask the 
Respective maintainers to comment on them as soon 
as they can find some spare time, as further PRs are blocked
on them. Even if the PRs get completely rejected, I at 
least know for which part of boost I should no longer 
pursue this quest and/or find a workaround.

Finally a big thanks to all maintainers that added 
such cmake files on their own.

Best

Mike

[1]
https://gist.github.com/Mike-Devel/46d04409d6ae6053861706e3ad91e4dc

Explanation for the linked picture:
It shows the boost dependency graph (generating code based on 
boostdep). 
- Green libs already have a cmake file in their root directory
- Yellow libraries don't have such a cmake file, 
  but all their dependencies have one, so one could 
  be added and most likely there is already a PR for that
- Red libraries have at least one direct or indirect
  Dependency that lacks a cmake file, so I consider
  Them "blocked" for now.