Let us examine the changes that we applied to CMakeLists.txt, by discussing them backwards.

We executed a Python script that generates print_info.c. To run the Python script, we first had to detect Python and construct the Python script. The Python script imports the configure_file function, which we defined in configurator.py. It requires that we provide it with file locations for reading and writing, as well as a dictionary holding CMake variables and their values as key-value pairs.

This recipe has shown an alternative way of generating a configuration report that can be compiled into an executable, or even a library target, by delegating the generation of sources to an external script. The first approach that we discussed in the previous recipe was cleaner and simpler, but with the approach that we have presented in this recipe, we have the flexibility to implement, in principle, any configure-time step that Python (or another language) allows. Using the present approach, we can perform actions that go beyond what cmake_host_system_information() currently provides.

However, we need to remember the limitation of this approach which cannot generate an automatic dependency which would regenerate print_info.c at build time. In the next recipe we will overcome this limitation.