Default for CMake Policy CMP<NNNN> when it is otherwise left unset.

Commands cmake_minimum_required(VERSION) and cmake_policy(VERSION) by default leave policies introduced after the given version unset. Set CMAKE_POLICY_DEFAULT_CMP<NNNN> to OLD or NEW to specify the default for policy CMP<NNNN>, where <NNNN> is the policy number.

This variable should not be set by a project in CMake code as a way to set its own policies; use cmake_policy(SET) instead. This variable is meant to externally set policies for which a project has not itself been updated:

  • Users running CMake may set this variable in the cache (e.g. -DCMAKE_POLICY_DEFAULT_CMP<NNNN>=<OLD|NEW>). Set it to OLD to quiet a policy warning while using old behavior or to NEW to try building the project with new behavior.

  • Projects may set this variable before a call to add_subdirectory() that adds a third-party project in order to set its policies without modifying third-party code.