In CMake how do I make `TARGET_LINK_LIBRARIES` suppress warnings from 3rd party library code?

Question

In CMake, you can make TARGET_INCLUDE_DIRECTORIES() add include directories as system include directories (i.e. use -isystem) in order to not let warnings pop up which have their root in 3rd party code:

TARGET_INCLUDE_DIRECTORIES(mytarget
    SYSTEM
        ${3rdPartyLib_INCLUDE_DIR})

I prefer to use TARGET_LINK_LIBRARIES which also makes include directories from 3rd party libraries available. As far as I know, TARGET_LINK_LIBRARIES does not support the SYSTEM modifier to add those directories as a system include directories.

Did I get something wrong?

Is there a way to make:

TARGET_LINK_LIBRARIES(mytarget
    ${3rdPartyLib_INCLUDE_DIR})

use -isystem? (or any other way to suppress warnings from 3rdPartyLib).

Answer 1

I had a similar question, which I solved with a custom function:

function(target_link_libraries_system target)
  set(libs ${ARGN})
  foreach(lib ${libs})
    get_target_property(lib_include_dirs ${lib} INTERFACE_INCLUDE_DIRECTORIES)
    target_include_directories(${target} SYSTEM PRIVATE ${lib_include_dirs})
    target_link_libraries(${target} ${lib})
  endforeach(lib)
endfunction(target_link_libraries_system)

I can now call target_link_libraries_system(myapp lib::lib) and the include directories are read from the target's properties.

This could now be extended to specify the PUBLIC|PRIVATE|INTERFACE scope but since I use it on an executable, this is sufficient for now.