add CMAKE_CURRENT_MACRO_LIST_DIR

Development
#1

Is there any plan to introduce CMAKE_CURRENT_MACRO_LIST_DIR which works like the CMAKE_CURRENT_FUNCTION_LIST_DIR that was added in CMake 3.17? I have run into a use case related to the setup up an environment. There I can’t use a function, but have to use a macro, because things in the parent scope have to be changed and some local CMake files have to be included. My current work-around is what had to be done before CMAKE_CURRENT_FUNCTION_LIST_DIR existed. Create a helper var that stores CMAKE_CURRENT_LIST_DIR and then use this in the macro - hoping nobody modified it.

Thanks, Axel

#2

Macros don’t have their own variable scope. The ${arg} references to their arguments are evaluated as placeholder substitution rather than variable evaluation. One may be able to implement ${CMAKE_CURRENT_MACRO_LIST_DIR}, but it would probably have to be as a placeholder substitution. Maybe it could even be done at the time the macro is defined/recorded.

#3

I can see you point and maybe asking for CMAKE_CURRENT_MACRO_LIST_DIR could be seen as an indication that my approach is fundamentally broken. Seem I try to use a macro ‘foo’ as a way to replace a include('foo.cmake'), where foo.cmake basically contains what the macro contains. The reason I’m doing this is, because I also have a macro bar that would need a file bar.cmake in the same folder then - and I want to have all in one file. The other way to solve this would be

set(USE_FOO ON)
include(/path/to/foo_bar.cmake')
set(USE_FOO OFF)
...
set(USE_BAR ON)
include('/path/to/foo_bar.cmake')
set(USE_BAR OFF)

and then ‘/path/to/foo_bar.cmake’ basically holds

if(USE_FOO)
.....
endif()

if(USE_BAR)
.....
endif()
#4

If you decide to go down the route of including the file and selectively enabling just bits of it (USE_FOO x USE_BAR), I suggest a small usability improvement: disable all the switches at the end of the file:

if(USE_FOO)
.....
endif()

if(USE_BAR)
.....
endif()

unset(USE_FOO)
unset(USE_BAR)

That way, the use requres just two lines instead of three.

#5

Thanks for the tip. My fear with this would just be, that it becomes even more “magical” then. I was actually thinking that having a new macro there might hide this

macro(selective_include flag file)
    set(${flag} ON)
    include(file)
    unset(${flag})
endmacro()

...

selective_include(USE_FOO '/path/to/foo_bar.cmake')
selective_include(USE_BAR '/path/to/foo_bar.cmake')