# INTERFACE_SYSTEM_INCLUDE_DIRECTORIES

List of public system include directories for a library.

Targets may populate this property to publish the include directories which contain system headers, and therefore should not result in compiler warnings. The `target_include_directories(SYSTEM)` command signature populates this property with values given to the `PUBLIC` and `INTERFACE` keywords.

Projects may also get and set the property directly, but must be aware that adding directories to this property does not make those directories used during compilation. Adding directories to this property marks directories as `SYSTEM` which otherwise would be used in a non-`SYSTEM` manner. This can appear similar to ‘duplication’, so prefer the high-level `target_include_directories(SYSTEM)` command and avoid setting the property by low-level means.

When target dependencies are specified using `target_link_libraries()`, CMake will read this property from all target dependencies to mark the same include directories as containing system headers.

Contents of `INTERFACE_SYSTEM_INCLUDE_DIRECTORIES` may use “generator expressions” with the syntax `$<...>`. See the `cmake-generator-expressions(7)` manual for available expressions. See the `cmake-buildsystem(7)` manual for more on defining buildsystem properties.