How to set the global variable in a function for cmake?

Question

I'm writing a CMakeLists.txt to generate files and compile the generated files. I create a function to add some file path strings to a global list variable.

My CMakeLists.txt:

set(source_list "nothing") function(test file_path)     list(APPEND source_list ${file_path}) endfunction(test) test(abc.txt) test(def.txt) message("At last, the source_list is:\"${source_list}\"") 

The cmake output:

At last, the source_list is:"nothing" 

Someone suggested that to use macro instead of function, but I do need use local variable, so I need to use the function instead of macro.

How can I correctly set the global variable source_list in the function test()? Can't cmake do it in a simple and normal way?

Answer 1

PARENT_SCOPE is only for parent, it won't work if you have other non-parent script that want to see it as well.

You need cache for the true "global-like" variable. In your case, use:

SET(source_list  "${source_list}" CACHE INTERNAL "source_list") 

Answer 2

Another approach is to use global properties. Once you set it:

set_property(GLOBAL PROPERTY source_list_property "${source_list}") 

you can read it from everywhere:

get_property(source_list GLOBAL PROPERTY source_list_property) 

I used in examples above the different names for property (source_list_property) and for variable (source_list). Maybe it is better to use the same name. But point is to use a property as global variables, and not about naming.

Such global properties aren't in cache.