[CMake] How is ARGN passed to a macro
Andreas Naumann
Andreas-Naumann at gmx.net
Wed Nov 21 14:18:26 EST 2018
Hey Torsten,
Am 21.11.18 um 13:15 schrieb 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?
I think the behavior is explained in [1] and [2]. In particular the
second section of [2] states that the parameter " [...] such as ARGN are
not variables in the usual CMake sense. They are string replacements
[...]". And the example at the end of [2] seems to match your test
perfectly.
Hope that helps a bit,
Andreas
[1] https://cmake.org/cmake/help/latest/command/function.html
[2] https://cmake.org/cmake/help/latest/command/macro.html
>
> TIA and kind regards,
>
> Torsten
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