CMake 3.0 INTERFACE 类型的 add_library 中断 get_target_property

Question

I want to add a header only directory to a cmake project which I am using in Windows 7 with Visual Studio 2013 Update 2. I did some research and came up with this Cmakelists.txt file:

add_library(AAA_lib INTERFACE)
target_include_directories(AAA_lib
    INTERFACE
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
    )

This appears to work however in some of our internal cmake code we call get_target_property:

get_target_property(target_libraries ${target} LINK_LIBRARIES)

This generates a CMake error:

CMake Error at x_common_libs/xml/xsdmap.cmake:41 (get_target_property):
  INTERFACE_LIBRARY targets may only have whitelisted properties.  The
  property "LINK_LIBRARIES" is not allowed.

It seems like an odd error since a get should only return targets with the appropriate property. Is this a bug in CMake? Or is there some other way that this should be implemented?

Why do we need to call get_target_property? We have a cmake helper function which recursively goes through all of dependencies of a project building up a list of all dependent projects that require some custom post processing. So if project X uses project B and C and C uses D, then we get a list of X, B, C, D and then check to see which directories match a requirement and then call a custom_command.

Thanks, Jason

Answer 1

Seems that it is CMake bug. There is new target type in CMake 3.0 called INTERFACE_LIBRARY. You are supposed to use only some of properties for this type. However, I don't think it was expected to raise an error in case of reading other properties.

I came out with the following workaround:

get_target_property(_TARGET_TYPE ${target} TYPE)
if(_TARGET_TYPE STREQUAL "INTERFACE_LIBRARY")
  unset(target_libraries)
else()
  get_target_property(target_libraries ${target} LINK_LIBRARIES)
endif()

Answer 2

This is a restriction that was lifted in CMake 3.19.

See https://gitlab.kitware.com/cmake/cmake/-/issues/19145 for details.