How can I check in CMake whether a list contains a specific entry?

Question

I want to check whether a lists contains a specific entry like in the following code snippet:

macro(foo)
if ($(ARGN} contains "bar")
  ...
endif
endmacro()

CMake does not offer a contains. What is best / easiest way to get the desired result?

In CMake's wiki, I found a LIST_CONTAINS macro, but the wiki page is outdated. Is this still the best way to go, or has CMake gained new capabilities?

Answer 1

With CMake 3.3 or later, the if command supports an IN_LIST operator, e.g.:

if ("bar" IN_LIST _list)
 ...
endif()

For older versions of CMake, you can use the built-in list(FIND) function:

list (FIND _list "bar" _index)
if (${_index} GREATER -1)
  ...
endif()

Answer 2

Fewer lines:

if (";${ARGN};" MATCHES ";bar;")
  #  ...
endif()

But see the IN_LIST syntax from @sakra for a more-modern syntax.

Answer 3

I have been using one liner like if ("${PLATFORM}" MATCHES "^(os|ios|android|linux|win32)$") to check if PLATFORM is in the list

Answer 4

If the intention here is to add a value to a list but only if it's not already in the list, then an alternative approach is to just add it to the list and immediately remove possible duplicates again:

list(APPEND            SOME_LIST "value")
list(REMOVE_DUPLICATES SOME_LIST)