cache list in CMake

Question

Is is possible to use list instead of variables in case of cache variables?

Here how I use cache variables

set(VAR "Value" CACHE INTERNAL "My Var")
set(VAR "${VAR} Value2" CACHE INTERNAL "My Var")

Answer 1

CMake lists are semi-colon separated, so you can set the list directly like this:

set(VAR Value;Value2 CACHE INTERNAL "My Var")

Having said that, even though lists are held as semi-colon separated items, they can be constructed using set with spaces between each item; e.g.

set(MyList Value Value2)  # list is  Value;Value2

So, if your values contain spaces, you need to wrap the list in quotation marks ":

set(VAR "Value 1;Value 2" CACHE INTERNAL "My Var")  # list is  Value 1;Value 2

The final point is that if you already have your list constructed, you don't need to wrap the list variable in quotation marks when caching it:

set(MyList "Value 1;Value 2")  # list is  Value 1;Value 2
set(VAR ${MyList} CACHE INTERNAL "My Var")  # no quotes required

Edit:

As I now understand it, you're asking if the list(APPEND...) command can be used to cache values directly.

The answer is no, but you were almost correct in your attempt. To get the desired effect, you'd need to use a semi-colon rather than space when caching the list:

set(VAR "${VAR};Value2" CACHE INTERNAL "My Var")