[CMake] How is ARGN passed to a macro

[Torsten Robitzki]

Hi,
I’ve stumbled over following behavior and now I’m searching for the rules, that explains that behavior:

test.cmake:

  macro(check_argn)
    message("in macro check_argn ARGN: ${ARGN}")

    if(ARGN)
      foreach(item IN LISTS ARGN)
        message("ARG: ${item}")
      endforeach(item)
      message("ARGN: ${ARGN}")
    endif()
  endmacro()

  function(f1 a)
    message("in function ARGN: ${ARGN}")
    check_argn()
  endfunction()

  f1(1)
  f1(1 2)

This will yield the following output:

  $ cmake -P ./test.cmake 
  in function ARGN: 
  in macro check_argn ARGN: 
  in function ARGN: 2
  in macro check_argn ARGN: 
  ARG: 2
  ARGN: 

I would expect ARGN to behave exactly the same in the macro, as in the function, but apparently there is a difference. Can someone of you explain that to me?

TIA and kind regards,

Torsten