CMake overhaul (#12)

* Non-effective CMake code removed

This change should not affect functionality.

* Compilation of examples made optional

* Boost made mandatory, better include_dir settings

* Install and cmake package instructions added

* Indentation fixes

* benchmark: submodule -> cmake ExternalProject_Add

Unnecessary download of benchmark can be avoided with CMake.
During CMake configure, benchmark is downloaded if needed and not found.
benchmark is then built and installed during CMake configure step.
We can then use find_package with REQUIRED to use benchmark.
This is cleaner and is the suggested method by google.
https://github.com/google/googletest/blob/master/googletest/README.md
Settings for benchmark build can be set in:
benchmark_download.cmake.in.
This file is configured so use of variables from main build is possible.

* yomm2 given ARCHIVE DESTINATION for install

This fixes an issue that appeared in Travis CI

* Options revamped

Now using CMake's `Option` command to define options.
This allows them to be cached and have default values.
Examples are set to on by default again.
YOMM2_ENABLE_BENCHMARKS only available if tests are built.

* Dependency downloading macro improved

* Readme updated

* Linking instructions added to README.md

* Boost should be PUBLIC, not INTERFACE dependency!

* Make yomm2.a STATIC explicitly (clearer!)

* Unneeded parameter removed

Author: derpda

.gitignore

@@ -1,3 +1,5 @@
 .rtags
 build/
 **/#*#
+
+extern

.gitmodules

@@ -9,15 +9,10 @@ cmake_minimum_required (VERSION 3.0)
 
 project (YOMM2 VERSION 1.0)
 
-find_package(Boost)
-
-include_directories ("${YOMM2_SOURCE_DIR}/include")
-link_directories ("${YOMM2_BINARY_DIR}/src")
-
+# Find Boost dependency
+find_package(Boost 1.53 REQUIRED)
 message(STATUS "Using Boost libraries from ${Boost_INCLUDE_DIRS}")
 
-include_directories("${Boost_INCLUDE_DIR}")
-
 if(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
   if (CMAKE_BUILD_TYPE STREQUAL "Debug")
@@ -29,34 +24,37 @@ if(MSVC)
     set(CMAKE_CXX_FLAGS "/std:c++17 -D_SCL_SECURE_NO_WARNINGS /EHsc")
 endif()
 
-set(YOMM2_BUILD_TYPE ${CMAKE_BUILD_TYPE})
-
-if("${YOMM2_BUILD_TYPE}" STREQUAL "DebugRelease")
+# Only allow Debug or Release
+if("${CMAKE_BUILD_TYPE}" STREQUAL "DebugRelease")
   set(CMAKE_BUILD_TYPE "Debug")
 endif()
 
-if("${YOMM2_BUILD_TYPE}" STREQUAL "ReleaseDebug")
+if("${CMAKE_BUILD_TYPE}" STREQUAL "ReleaseDebug")
   set(CMAKE_BUILD_TYPE "Release")
 endif()
 
 add_subdirectory (src)
 
-if("${YOMM2_BUILD_TYPE}" STREQUAL "DebugRelease")
-  set(CMAKE_BUILD_TYPE "Release")
-endif()
-
-if("${YOMM2_BUILD_TYPE}" STREQUAL "ReleaseDebug")
-  set(CMAKE_BUILD_TYPE "Debug")
-endif()
-
-add_subdirectory (examples)
-
-if (NOT DEFINED(YOMM2_ENABLE_TESTS))
-  set(YOMM2_ENABLE_TESTS CACHE BOOL ON)
+option(YOMM2_ENABLE_EXAMPLES "Set to ON to build examples" ON)
+if (${YOMM2_ENABLE_EXAMPLES})
+  message(STATUS "Examples enabled")
+  add_subdirectory (examples)
 endif()
 
+option(YOMM2_ENABLE_TESTS "Set to ON to build tests" OFF)
+include(CMakeDependentOption)
+CMAKE_DEPENDENT_OPTION(YOMM2_ENABLE_BENCHMARKS
+  "Set to ON to build benchmarks" OFF
+  "YOMM2_ENABLE_TESTS" OFF
+)
 if (${YOMM2_ENABLE_TESTS})
   message(STATUS "Tests enabled")
+  if (${YOMM2_ENABLE_BENCHMARKS})
+    message(STATUS "Benchmarks enabled")
+    list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
+    include(find_or_download_package)
+    find_or_download_package(benchmark)
+  endif()
   include(CTest)
   add_subdirectory (tests)
   enable_testing()
@@ -72,16 +70,30 @@ if (${YOMM2_ENABLE_TESTS})
   add_test (containers examples/containers/containers)
 endif()
 
-if (NOT DEFINED(YOMM2_ENABLE_BENCHMARKS))
-  set(YOMM2_ENABLE_BENCHMARKS CACHE BOOL ON)
-endif()
-
-if (${YOMM2_ENABLE_BENCHMARKS})
-  message(STATUS "Benchmarks enabled")
-  set(BENCHMARK_ENABLE_TESTING CACHE BOOL OFF)
-  set(BENCHMARK_ENABLE_GTEST_TESTS CACHE BOOL OFF)
-  add_subdirectory(extern/benchmark)
-  include_directories(extern/benchmark/include)
-endif()
+## Install instruction
+# Create version file for cmake package
+include(CMakePackageConfigHelpers)
+write_basic_package_version_file(
+  YOMM2ConfigVersion.cmake
+  VERSION ${PACKAGE_VERSION}
+  COMPATIBILITY SameMajorVersion
+)
+# Create targets file of yomm2
+install(EXPORT YOMM2Targets
+  FILE YOMM2Targets.cmake
+  NAMESPACE YOMM2::
+  DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/cmake/YOMM2
+)
+# Configure package config (tells using code about dependencies)
+configure_package_config_file(
+  cmake/Config.cmake.in ${CMAKE_CURRENT_BINARY_DIR}/YOMM2Config.cmake
+  INSTALL_DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/cmake/YOMM2
+)
+# Copy config files to install directory
+install(FILES
+  "${CMAKE_CURRENT_BINARY_DIR}/YOMM2Config.cmake"
+  "${CMAKE_CURRENT_BINARY_DIR}/YOMM2ConfigVersion.cmake"
+  DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/cmake/YOMM2
+)
 
 INSTALL (DIRECTORY include/yorel DESTINATION include)

CMakeLists.txt

@@ -178,13 +178,6 @@ git clone https://github.com/jll63/yomm2.git
 cd yomm2
 ```
 
-If you want to run the benchmarks, fetch the Google Benchmark submodule:
-
-```
-git submodule init
-git submodule update
-```
-
 Create a build directory and run cmake then make:
 
 ```
@@ -208,6 +201,9 @@ build):
 cmake .. -DYOMM2_ENABLE_TESTS=1 -DYOMM2_ENABLE_BENCHMARKS=1 -DCMAKE_BUILD_TYPE=Release
 make && tests/benchmarks # wow it's fast!
 ```
+This will automatically download the dependency
+[benchmark](https://github.com/google/benchmark), build it and finally install
+it to `./extern` within the root directory of yomm2.
 
 Finally, if you like it and you want to install it:
 
@@ -217,6 +213,13 @@ sudo make install
 # or:
 make install DESTDIR=/path/to/my/libs
 ```
+This will install the library and headers, as well as a CMake package
+configuration.
+Make sure to add the install location to `CMAKE_PREFIX_PATH` so that you can use
+`find_package(YOMM2)` from your including project. For linking, the use
+`target_link_library(<your_target> YOMM2::yomm2)`. This will automatically add
+the necessary include directories, so this should be all you need to do to link
+to yomm2.
 
 ## Going Further
 

README.md

@@ -0,0 +1,7 @@
+include(CMakeFindDependencyMacro)
+
+# Tell library users about the Boost dependency
+find_dependency(Boost 1.53)
+
+# Add the targets file
+include("${CMAKE_CURRENT_LIST_DIR}/YOMM2Targets.cmake")

cmake/Config.cmake.in

@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 3.5)
+project(benchmarkDownload)
+include(ExternalProject)
+
+ExternalProject_Add(benchmark
+    GIT_REPOSITORY      https://github.com/google/benchmark.git
+    GIT_TAG             master
+    GIT_PROGRESS        True
+    SOURCE_DIR          "${CMAKE_SOURCE_DIR}/extern/benchmark"
+    BINARY_DIR          "${CMAKE_CURRENT_BINARY_DIR}/benchmark-build"
+    INSTALL_DIR         ${CMAKE_SOURCE_DIR}/extern
+    CMAKE_ARGS          -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+                        -DCMAKE_BUILD_TYPE=Release
+                        -DBENCHMARK_ENABLE_TESTING=OFF
+                        -DBENCHMARK_ENABLE_GTEST_TESTS=OFF
+)

cmake/benchmark_download.cmake.in

@@ -0,0 +1,44 @@
+macro(find_or_download_package PACKAGE)
+  find_package(${PACKAGE} QUIET)
+  if(NOT ${${PACKAGE}_FOUND})
+    message(STATUS "Package \"${PACKAGE}\" not found in system.")
+    message(STATUS
+      "Downloading dependency \"${PACKAGE}\" and building from source."
+    )
+
+    # Prepare download instructions for dependency
+    configure_file(
+      ${CMAKE_SOURCE_DIR}/cmake/${PACKAGE}_download.cmake.in
+      ${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE}-download/CMakeLists.txt
+    )
+
+    # Download dependency
+    execute_process(
+      COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
+      RESULT_VARIABLE result
+      WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE}-download
+      OUTPUT_QUIET
+    )
+    if(result)
+      message(FATAL_ERROR "Download of dependency ${PACKAGE} failed: ${result}")
+    endif()
+
+    # Build dependency
+    execute_process(
+      COMMAND ${CMAKE_COMMAND} --build .
+      RESULT_VARIABLE result
+      WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE}-download
+    )
+    if(result)
+      message(FATAL_ERROR "Build of  dependency ${PACKAGE} failed: ${result}")
+    endif()
+
+    # Update search path and use regular find_package to add dependency
+    # TODO Use same directory here as for configure_file up there and inside
+    # download instructions!
+    list(
+      APPEND CMAKE_PREFIX_PATH "${CMAKE_SOURCE_DIR}/extern/lib/cmake/${PACKAGE}"
+    )
+    find_package(${PACKAGE} REQUIRED)
+  endif()
+endmacro()

cmake/find_or_download_package.cmake

@@ -34,6 +34,8 @@ if(NOT MSVC)
   set(CMAKE_SKIP_BUILD_RPATH TRUE)
   add_executable(dl_main dl_main.cpp)
   add_library(dl_shared SHARED dl_shared.cpp)
+  get_target_property(YOMM2_INCLUDE_DIRS yomm2 INTERFACE_INCLUDE_DIRECTORIES)
+  target_include_directories(dl_shared PUBLIC ${YOMM2_INCLUDE_DIRS})
   add_dependencies(dl_main dl_shared)
   if(APPLE)
     set_target_properties(dl_main PROPERTIES LINK_FLAGS "-Wl,-export_dynamic")

examples/CMakeLists.txt

@@ -3,8 +3,16 @@
 # See accompanying file LICENSE_1_0.txt
 # or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-add_library(yomm2 yomm2.cpp)
+add_library(yomm2 STATIC yomm2.cpp)
 
-INSTALL(TARGETS yomm2
-  DESTINATION lib
+target_include_directories(yomm2 PUBLIC
+  $<BUILD_INTERFACE:${YOMM2_SOURCE_DIR}/include>
+  $<INSTALL_INTERFACE:include>
+)
+target_include_directories(yomm2 SYSTEM PUBLIC ${Boost_INCLUDE_DIR})
+
+install(TARGETS yomm2
+  EXPORT YOMM2Targets
+  LIBRARY DESTINATION lib
+  ARCHIVE DESTINATION lib
 )