Start recording a function for later invocation as a command.

function(<name> [arg1 [arg2 [arg3 ...]]])

Define a function named <name> that takes arguments named arg1 arg2 arg3 (…). Commands listed after function, but before the matching endfunction, are not invoked until the function is invoked. When it is invoked, the commands recorded in the function are first modified by replacing formal parameters (${arg1}) with the arguments passed, and then invoked as normal commands. In addition to referencing the formal parameters you can reference the variable ARGC which will be set to the number of arguments passed into the function as well as ARGV0 ARGV1 ARGV2 … which will have the actual values of the arguments passed in. This facilitates creating functions with optional arguments. Additionally ARGV holds the list of all arguments given to the function and ARGN holds the list of arguments past the last expected argument.

A function opens a new scope: see set(var PARENT_SCOPE) for details.

See the cmake_policy() command documentation for the behavior of policies inside functions.