Cmake include_directories()

Quoting the documentation for include_directories:

The include directories are added to the directory property INCLUDE_DIRECTORIES for the current CMakeLists file. They are also added to the target property INCLUDE_DIRECTORIES for each target in the current CMakeLists file. The target property values are the ones used by the generators.

The INCLUDE_DIRECTORIES directory property is inherited to all subdirectories and all targets in the directory.

• Specifying ${CMAKE_CURRENT_SOURCE_DIR} for include_directories is redundant as relative paths are interpreted as relative to this directory by default. You should throw it out to increase readability.
• Specifying an include directory in both a subdirectory and its parent is redundant. You should avoid this and settle on one location.
• Use get_property and message to double-check that all directories and targets end up with the correct entries in their INCLUDE_DIRECTORIES property.
• If you are free to require CMake 2.8.11 as a minimum requirement, consider abandoning include_directories completely and use target_include_directories instead. This has the advantage that include dependencies get resolved on a per-target basis exclusively which is usually the more desirable behavior.