CMP0028

Warning

The OLD behavior of this policy was removed in CMake version 4.0. This policy must be set to NEW by a call to cmake_minimum_required() or cmake_policy().

Double colon in target name means ALIAS or IMPORTED target.

CMake 2.8.12 and lower allowed the use of targets and files with double colons in target_link_libraries(), with some buildsystem generators.

The use of double-colons is a common pattern used to namespace IMPORTED targets and ALIAS targets. When computing the link dependencies of a target, the name of each dependency could either be a target, or a file on disk. Previously, if a target was not found with a matching name, the name was considered to refer to a file on disk. This can lead to confusing error messages if there is a typo in what should be a target name.

See also the LINK_LIBRARIES_ONLY_TARGETS target property.

The OLD behavior for this policy is to search for targets, then files on disk, even if the search term contains double-colons. The NEW behavior for this policy is to issue a FATAL_ERROR if a link dependency contains double-colons but is not an IMPORTED target or an ALIAS target.

This policy was introduced in CMake version 3.0. Prior to removal in CMake version 4.0, it could be set by cmake_policy() or cmake_minimum_required(). If it was not set, CMake warned, and used OLD behavior.