CMake Cookbook

How to do it

Let us have a look at our static/shared library example from the previous recipe. Instead of hardcoding USE_LIBRARY to ON or OFF, we will now prefer to expose it as an option with a default value that can be changed from the outside:

1. Replace the set(USE_LIBRARY OFF) command of the previous recipe with an option. The option will have the same name and its default value will be OFF:

option(USE_LIBRARY "Compile sources into a library" OFF)

2. Now, we can switch the generation of the library by passing the information to CMake via its -D CLI option:

$ mkdir -p build$ cd build$ cmake -D USE_LIBRARY=ON ..-- ...-- Compile sources into a library? ON-- ...$ cmake --build .Scanning dependencies of target message[ 25%] Building CXX object ...