CMP0165

Added in version 3.30.

enable_language() must not be called before project().

In CMake 3.29 and below, if a project called enable_language() before the first call to project(), the language would be enabled but possibly using unset details that were expected to be set. In CMake 3.30 and above, enable_language() prefers to reject this case and stop with a fatal error instead if it detects that project() has not yet been called. This policy provides compatibility for projects that happened to work when enable_language() was called before project() and have not been updated to call these commands in the required order.

The OLD behavior for this policy is to allow enable_language() to be called before project(). The NEW behavior for this policy is to fail with a fatal error in such cases.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

Note

The OLD behavior of a policy is deprecated by definition and may be removed in a future version of CMake.