How to call a function in CMake whose name is stored in a variable

Just a quick update: It seems like CMake added this functionality in the current 3.18 Versions via the cmake_language command, the Syntax:

cmake_language(CALL <command> [<args>...])
cmake_language(EVAL CODE <code>...)

Reference for cmake_language https://cmake.org/cmake/help/v3.18/command/cmake_language.html#command:cmake_language

I have solved this with a workaround using files.

Lets say you have:

function(do what)
  ...
endfunction()

You want to call different specializations depending on 'what'. You can then do:

function(do what)
  include("do-${what}.cmake")
  do_dynamic()
endfunction()

And in file do-something.cmake:

function(do_dynamic)
  ...
endfunction()

You can create as many specialization files as you want...

Hi I have written eval for cmake (and it is as fast as i can make it) here and here is the code as it is part of my cmakepp library.

I have written two versions of eval (eval and eval_ref because the first does not give you access to the PARENT_SCOPE whereas the latter does)

however this will only help if your use cmakepp and as that might be a dealbreaker for you I modified it to work with vanilla cmake:

## evals the specified cmake code.
## WARNING: there is no way to set(<var> <value> PARENT_SCOPE) 
## because of the extra function scope defined by eval.
## WARNING: allowing eval can of course be dangerous.
function(eval __eval_code)

  # one file per execution of cmake (if this file were in memory it would probably be faster...)
  # this is where the temporary eval file will be stored.  it will only be used once per eval
  # and since cmake is not multihreaded no race conditions should occure.  however if you start 
  # two cmake processes in the same project this could lead to collisions
  set(__eval_temp_file "${CMAKE_CURRENT_BINARY_DIR}/__eval_temp.cmake")


  # write the content of temp file and include it directly, this overwrite the 
  # eval function you are currently defining (initializer function pattern)
  file(WRITE "${__eval_temp_file}" "
function(eval __eval_code)
  file(WRITE ${__eval_temp_file} \"\${__eval_code}\")
  include(${__eval_temp_file})
endfunction()
  ")

include("${__eval_temp_file}")
## now eval is defined as what was just written into __eval_temp_file


## since we are still in first definition we just need to execute eval now
## (which calls the second definition of eval).
eval("${__eval_code}")


endfunction()