[boost] CMake followup

Subject: [boost] CMake followup
From: Peter Dimov (lists_at_[hidden])
Date: 2017-06-29 15:29:41

In a previous post I identified several scenarios for CMake support, where 
number one was

1. The user installs a Boost release as usual with `b2 install`, which makes 
the installation visible to CMake and usable via 
find_package(boost_libname).

For this, I said

"The changes to the `b2 install` procedure significantly exceed my bjam-fu 
however, so if we decide to proceed with this - and I don't see how we could 
claim CMake support in a meaningful way without it - the interested parties 
would need to figure out a way to make that happen."

but I lied. (Well, not entirely, I had a lot of help.)

Here

https://github.com/pdimov/boost-cmake-demo

is a proof-of-concept implementation that more or less works for our beloved 
test case of Boost.System.

To test (the instructions are for Windows, where I tested), clone the repo, 
do

b2 headers
b2 --build-type=complete install

as usual, then

b2 cmake//install variant=debug,release link=static,shared 
runtime-link=shared

(or whatever combination of options you prefer.)

This should install -config.cmake files into $prefix/libs/cmake.

Then, in a CMakeLists.txt,

cmake_minimum_required(VERSION 3.5)

project(cmake_demo CXX)

#set(BOOST_BUILD_VARIANT RELEASE)
#set(BOOST_LINK_TYPE SHARED)
#set(BOOST_RUNTIME_LINK STATIC)

find_package(boost_core 1.63.0)
find_package(boost_system 1.63.0)

# disable autolink globally
# could also do it per-target

add_definitions(-DBOOST_ALL_NO_LIB=1)

# sample program

add_executable(cmake_demo cmake_demo.cpp)
target_link_libraries(cmake_demo boost::core boost::system)

or similar.

Ideally, cmake//install would be integrated into the install target (and 
cmake//stage into stage, respectively.)