List of public include directories requirements for a library.

Targets may populate this property to publish the include directories required to compile against the headers for the target. The target_include_directories() command populates this property with values given to the PUBLIC and INTERFACE keywords. Projects may also get and set the property directly.

When target dependencies are specified using target_link_libraries(), CMake will read this property from all target dependencies to determine the build properties of the consumer.

Contents of INTERFACE_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.

Include directories usage requirements commonly differ between the build-tree and the install-tree. The BUILD_INTERFACE and INSTALL_INTERFACE generator expressions can be used to describe separate usage requirements based on the usage location. Relative paths are allowed within the INSTALL_INTERFACE expression and are interpreted relative to the installation prefix. For example:

target_include_directories(mylib INTERFACE
  $<INSTALL_INTERFACE:include/mylib>  # <prefix>/include/mylib

Creating Relocatable Packages

Note that it is not advisable to populate the INSTALL_INTERFACE of the INTERFACE_INCLUDE_DIRECTORIES of a target with absolute paths to the include directories of dependencies. That would hard-code into installed packages the include directory paths for dependencies as found on the machine the package was made on.

The INSTALL_INTERFACE of the INTERFACE_INCLUDE_DIRECTORIES is only suitable for specifying the required include directories for headers provided with the target itself, not those provided by the transitive dependencies listed in its INTERFACE_LINK_LIBRARIES target property. Those dependencies should themselves be targets that specify their own header locations in INTERFACE_INCLUDE_DIRECTORIES.

See the Creating Relocatable Packages section of the cmake-packages(7) manual for discussion of additional care that must be taken when specifying usage requirements while creating packages for redistribution.