[CMake] Generate cmake target that other libraries can use (#86)

Generates cmake target that other libraries can use to express
their dependency on this library and retrieve any configuration
information such as the include directory.

.travis.yml

@@ -48,6 +48,24 @@ matrix:
   exclude:
     - env: TRAVIS_EMPTY_JOB_WORKAROUND=true
   include:
+    # cmake self-test
+    - env: TEST_CMAKE=TRUE #Only for easier identification in travis web gui
+      os: linux
+
+      # skip all the unneeded steps from the normal unit test jobs
+      install: true
+      before_script: true
+      before_cache: true
+      before_cache: true
+      after_success: true
+      after_failure: true
+      after_script: true
+      script:
+        - mkdir __build__ && cd __build__
+        - cmake ../test/test_cmake
+        - cmake --build .
+
+
     - env: TOOLSET=clang-3.4
     - env: TOOLSET=clang-3.5
     - env: TOOLSET=clang-3.6

CMakeLists.txt

@@ -0,0 +1,26 @@
+# Copyright 2018 Mike Dev
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
+#
+# NOTE: CMake support for Boost.Predef is currently experimental at best
+#       and the interface is likely to change in the future
+#
+# This file provides mininmal cmake support (no unit-tests,
+# no installation) for integration into a "host" cmake project
+# via the "add_subdirectory( <path-to-boost-predef> )" command.
+#
+# Other cmake targets can then use the public target name
+# "Boost::predef" in order to express their dependency
+# on this library. I.e:
+#
+# target_link_libraries( <my-exe/lib> PUBLIC Boost::predef )
+#
+
+cmake_minimum_required( VERSION 3.5 )
+project( BoostPredef )
+
+add_library( boost_predef INTERFACE )
+target_include_directories( boost_predef INTERFACE include )
+
+add_library( Boost::predef ALIAS boost_predef )
+

test/test_cmake/CMakeLists.txt

@@ -0,0 +1,21 @@
+# Copyright 2018 Mike Dev
+# Distributed under the Boost Software License, Version 1.0.
+# See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
+#
+# NOTE: This does NOT run the unit tests for Boost.Predef.
+#       It only tests, if the CMakeLists.txt file in predef's
+#       root directory works as expected (i.e. it provides the
+#       target Boost::predef which in turn provides the
+#       correct include directory )
+
+cmake_minimum_required( VERSION 3.5 )
+
+project( BoostPredefCMakeSelfTest )
+
+# Process cmake file at root of library and use ${CMAKE_CURRENT_BINARY_DIR}/libs/boost_predef as workspace
+add_subdirectory( ../.. ${CMAKE_CURRENT_BINARY_DIR}/libs/boost_predef )
+
+add_executable( boost_predef_cmake_test_prj main.cpp )
+
+target_link_libraries( boost_predef_cmake_test_prj Boost::predef )
+

test/test_cmake/main.cpp

@@ -0,0 +1,7 @@
+// Dummy executable, just to make sure
+// that we can find the Boost.predef header files
+#include <boost/predef.h>
+
+int main() {
+
+}