The project() command manages VERSION variables.

CMake version 3.0 introduced the VERSION option of the project() command to specify a project version as well as the name. In order to keep PROJECT_VERSION and related variables consistent with variable PROJECT_NAME it is necessary to set the VERSION variables to the empty string when no VERSION is given to project(). However, this can change behavior for existing projects that set VERSION variables themselves since project() may now clear them. This policy controls the behavior for compatibility with such projects.

The OLD behavior for this policy is to leave VERSION variables untouched. The NEW behavior for this policy is to set VERSION as documented by the project() command.

This policy was introduced in CMake version 3.0. CMake version 3.0.2 warns when the policy is not set and uses OLD behavior. Use the cmake_policy command to set it to OLD or NEW explicitly.