This is how we can use the set_compiler_flag function in our CMakeLists.txt:

1. In the preamble, we define the minimum CMake version, project name, and supported languages (in this case, C and C++):

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
  
project(recipe-03 LANGUAGES C CXX)

2. Then, we include set_compiler_flag.cmake, in this case explicitly:

include(set_compiler_flag.cmake)

3. Then, we try a list of C flags:

set_compiler_flag(
  working_compile_flag C REQUIRED
  "-foo"             # this should fail
  "-wrong"           # this should fail
  "-wrong"           # this should fail
  "-Wall"            # this should work with GNU
  "-warn all"        # this should work with Intel
  "-Minform=inform"  # this should work with PGI
  "-nope"            # this should fail
  )

message(STATUS "working C compile flag: ${working_compile_flag}")

4. And we try a list of C++ flags:

set_compiler_flag(
  working_compile_flag CXX REQUIRED
  "-foo"    # this should fail
  "-g"      # this should work with GNU, Intel, PGI
  "/RTCcsu" # this should work with MSVC
  )

message(STATUS "working CXX compile flag: ${working_compile_flag}")

5. Now, we can configure the project and verify the output. Only the relevant output is shown and the output may differ depending on the compiler:

$ mkdir -p build
$ cd build
$ cmake ..

-- ...
-- Performing Test _flag_works
-- Performing Test _flag_works - Failed
-- Performing Test _flag_works
-- Performing Test _flag_works - Failed
-- Performing Test _flag_works
-- Performing Test _flag_works - Failed
-- Performing Test _flag_works
-- Performing Test _flag_works - Success
-- working C compile flag: -Wall
-- Performing Test _flag_works
-- Performing Test _flag_works - Failed
-- Performing Test _flag_works
-- Performing Test _flag_works - Success
-- working CXX compile flag: -g
-- ...