Return a list from the function using OUT parameter
Solution 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.
Solution 2:
Check that inside your function you are set()ing not dst_list but ${dst_list}. You need this to return data to the parent scope.