CMP0102ΒΆ
New in version 3.17.
The mark_as_advanced() command no longer creates a cache entry if one
does not already exist.
In CMake 3.16 and below, if a variable was not defined at all or just defined
locally, the mark_as_advanced() command would create a new cache
entry with an UNINITIALIZED type and no value. When a find_path()
(or other similar find_ command) would next run, it would find this
undefined cache entry and set it up with an empty string value. This process
would end up deleting the local variable in the process (due to the way the
cache works), effectively clearing any stored find_ results that were only
available in the local scope.
The OLD behavior for this policy is to create the empty cache definition.
The NEW behavior of this policy is to ignore variables which do not
already exist in the cache.
This policy was introduced in CMake version 3.17. Use the
cmake_policy() command to set it to OLD or NEW explicitly.
Unlike many policies, CMake version 3.20.3 does not warn
when this policy is not set and simply uses OLD behavior.
Note
The OLD behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.