target_link_libraries() allows use with targets in other directories.
Prior to CMake 3.13 the
target_link_libraries() command did not accept targets not created in the calling directory as its first argument for calls that update the
LINK_LIBRARIES of the target itself. It did accidentally accept targets from other directories on calls that only update the
INTERFACE_LINK_LIBRARIES, but would simply add entries to the property as if the call were made in the original directory. Thus link interface libraries specified this way were always looked up by generators in the scope of the original target rather than in the scope that called
CMake 3.13 now allows the
target_link_libraries() command to be called from any directory to add link dependencies and link interface libraries to targets created in other directories. The entries are added to
INTERFACE_LINK_LIBRARIES using a special (internal) suffix to tell the generators to look up the names in the calling scope rather than the scope that created the target.
This policy provides compatibility with projects that already use
target_link_libraries() with the
INTERFACE keyword on a target in another directory to add
INTERFACE_LINK_LIBRARIES entries to be looked up in the target’s directory. Such projects should be updated to be aware of the new scoping rules in that case.
OLD behavior of this policy is to disallow
target_link_libraries() calls naming targets from another directory except in the previously accidentally allowed case of using the
INTERFACE keyword only. The
NEW behavior of this policy is to allow all such calls but use the new scoping rules.
This policy was introduced in CMake version 3.13. CMake version 3.15.2 warns when the policy is not set and uses
OLD behavior. Use the
cmake_policy() command to set it to
OLD behavior of a policy is
deprecated by definition and may be removed in a future version of CMake.
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