Targets, Properties, And More#

Target Types#

Two basic types: add_executable() and add_library()
add_executable() is simple
- No other node depends on it
- Rather, executables only depend on other nodes
- ⟶ Entry points into dependency graph
- As such, executables rarely have properties attached to them

add_library() …

Type	Description
Normal library	`STATIC` (default), `SHARED`, `MODULE`. Has sources to be built.
Object libraries	Technically much like normal libraries, but not an archive or shared object (only virtual, implemented by CMake)
Interface libraries	No sources; only there to propagate properties to dependers, and to have further dependencies on their own.

(For a complete list see add_library())

Target function	Property name	Description	Documentation
`target_compile_definitions()`	`COMPILE_DEFINITIONS`	Macros set on the compiler command line (`-Dname=value`)	target_compile_definitions()
`target_compile_options()`	`COMPILE_OPTIONS`	Non-macro compiler flags/options	TARGET_COMPILE_OPTIONS()
`target_include_directories()`	`INCLUDE_DIRECTORIES`	Include directories	target_include_directories()
`target_link_libraries()`	(Much more complicated, see documentation)	Dependencies, in the widest sense	target_link_libraries()
`set_target_properties()`	Any property, including custom properties	See documentation	set_target_properties()

PUBLIC: propagated to containing target itself, and to all dependers, transitively
- Dependency through #include <other.h> in a header file ⟶ all includers need to know
- PUBLIC properties only possible when target has compiled code
PRIVATE: propagated to containing target itself, invisible to dependers
- For example, one might structure a target’s source code into src/, private-inc/, and public-inc/ ⟶ private-inc/ would be target_include_directories(... PRIVATE ...)
- For example, target_compile_definitions() for target-local compilation only
INTERFACE: propagated only to dependers, invisible to containing target
- Just like PUBLIC - except that PUBLIC is not possible on INTERFACE targets (e.g. header-only libraries)
- Asymmetric (a smell that is encountered in many dark corners of CMake)
- Documentation has no clear explanation. Exceptions, and paragraph-long explanations.