How to do it

Now that we have the sources in place, our goal will be to configure the project and experiment with compiler flags:

1. We set the minimum required version of CMake:

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

2. We declare the name of the project and the language:

project(recipe-08 LANGUAGES CXX)

3. Then, we print the current set of compiler flags. CMake will use these for all C++ targets:

message("C++ compiler flags: ${CMAKE_CXX_FLAGS}")

4. We prepare a list of flags for our targets. Some of these will not be available on Windows and we make sure to account for that case:

list(APPEND flags "-fPIC" "-Wall")
if(NOT WIN32)
  list(APPEND flags "-Wextra" "-Wpedantic")
endif()

5. We add a new target, the geometry library and list its source dependencies:

add_library(geometry
  STATIC
    geometry_circle.cpp
    geometry_circle.hpp
    geometry_polygon.cpp
    geometry_polygon.hpp
    geometry_rhombus.cpp
    geometry_rhombus.hpp
    geometry_square.cpp
    geometry_square.hpp
  )

6. We set compile options for this library target:

target_compile_options(geometry
  PRIVATE
    ${flags}
  )

7. We then add a target for the compute-areas executable:

add_executable(compute-areas compute-areas.cpp)

8. We also set compile options for the executable target:

target_compile_options(compute-areas
  PRIVATE
    "-fPIC"
  )

9. Finally, we link the executable to the geometry library:

target_link_libraries(compute-areas geometry)