This command adds compile definitions to a target. These definitions are added to the compiler command line via `-D` flags and are visible during compilation of source files associated with the target. For example, `target_compile_definitions(my_target PUBLIC FOO=1 BAR)` would result in the compiler flags `-DFOO=1 -DBAR` being added to the compile command for `my_target`. Definitions can be set to specific values, or simply defined without a value. Scopes available are `PUBLIC` (visible to dependents), `PRIVATE` (visible only to the target itself), and `INTERFACE` (visible only to dependents).
Managing compile definitions through this command promotes organized and maintainable build configurations. Centralizing definitions within the CMakeLists.txt file enhances clarity, simplifies debugging, and improves collaboration among developers. Before CMake 3.12, using `add_definitions()` was the common approach. However, this method applied definitions globally, potentially leading to unintended consequences and making complex projects harder to manage. The target-specific approach offers finer control and avoids the pitfalls of global definitions, particularly vital for larger projects and libraries with dependencies.
