cmake - Return a list from the function using OUT parameter

Question

I would like to create a CMake function as:

function(test src_list dst_list)
# do something
endfunction()

usage:

test(${my_list} chg_list)

It means, my_list is a list with several fields, and chg_list will receive a list modified inside test function.

How can I create a function in CMake to do that?

Answer 1

In CMake, functions have their own scope, and by default, all modification of variables are local, unless you pass CACHE or PARENT_SCOPE as parameter to set. Inside a function, if you want to modify a variable in the scope of the caller, you should use:

set(${dst_list} <something> PARENT_SCOPE)

See documentation:

A function opens a new scope: see set(var PARENT_SCOPE) for details.