Best/Shortest way to join a list in CMake

Question

What is the best way to join a list in CMake into a string?

By joining I mean convert SET(somelist \"a\" \"b\" \"c\\;c\") to \"a:b:c;c\" where the glue string (\":\") i

Answer 1

The answers above are ok, when you do not use semicolons or when you can (and want to) escape them. I prefer not to escape semicolons, so I wrote the following function:

function(JOIN OUTPUT GLUE)
    set(_TMP_RESULT "")
    set(_GLUE "") # effective glue is empty at the beginning
    foreach(arg ${ARGN})
        set(_TMP_RESULT "${_TMP_RESULT}${_GLUE}${arg}")
        set(_GLUE "${GLUE}")
    endforeach()
    set(${OUTPUT} "${_TMP_RESULT}" PARENT_SCOPE)
endfunction()

The advantage is that the list can be empty and it doesn't have to be in a variable (but may be written in the place of invocation).

The usage is:

set(SOME_LIST a b c d)
join(RESULT "/" ${SOME_LIST})
message(STATUS "RESULT='${RESULT}'") # outputs RESULT='a/b/c/d'
# or
join(RESULT " " e f g h)
message(STATUS "RESULT='${RESULT}'") # outputs RESULT='e f g h'