Updated December 2018: Parts of this article have been reworked to account for improvements made with the CMake 3.13.0 release. Key updates are noted within the article.
In all but trivial CMake projects, it is common to find targets built from a large number of source files. These files may be distributed across various subdirectories, which may themselves be nested multiple levels deep. In such projects, traditional approaches usually either list all source files at the top-most level or build up the list of source files in a variable and pass that to add_library(), add_executable(), etc. With CMake 3.1, a new command target_sources() was introduced which provides the missing piece among the various target_... commands. While the CMake documentation succintly describes what target_sources() does, it fails to highlight just how useful the new command is and why it promotes better CMake projects:
- It can lead to cleaner and more concise CMakeLists.txt project files.
- Dependency information can be specified closer to where the actual dependencies exist in the directory hierarchy.
- Source files gain the ability to become part of a target’s interface.
- Source files can be added to third party project targets without having to modify the third party project files.