Use the link information as a source of compile definitions and includes.
After evaluating the INTERFACE_INCLUDE_DIRECTORIES, of a target in a generator expression, also read the INTERFACE_INCLUDE_DIRECTORIES of its link interface dependencies. That means that code such as this will result in the 'user' target using /bar/include and /foo/include: add_library(foo ...) target_include_directories(foo INTERFACE /foo/include) add_library(bar ...) target_include_directories(bar INTERFACE /bar/include) target_link_libraries(bar LINK_PUBLIC foo) add_executable(user ...) target_include_directories(user PRIVATE $<TARGET_PROPERTY:bar,INTERFACE_INCLUDE_DIRECTORIES>) Also process the interface include directories from direct link dependencies for in-build targets. The situation is similar for the INTERFACE_COMPILE_DEFINITIONS. The include directories related code is currently more complex because we also need to store a backtrace at configure-time for the purpose of debugging includes. The compile definitions related code will use the same pattern in the future. This is not a change in behavior, as existing code has the same effect, but that existing code will be removed in follow-up commits.