Do not produce legacy _LIB_DEPENDS cache entries

Introduce policy `CMP0073` to avoid producing these cache entries.

Fixes: #16364

3 files changed, 38 insertions, 0 deletions

diff --git a/Help/manual/cmake-policies.7.rst b/Help/manual/cmake-policies.7.rst
index 96d5c7d..254656a 100644
--- a/Help/manual/cmake-policies.7.rst
+++ b/Help/manual/cmake-policies.7.rst
@@ -51,6 +51,14 @@ The :variable:`CMAKE_MINIMUM_REQUIRED_VERSION` variable may also be used
 to determine whether to report an error on use of deprecated macros or
 functions.
 
+Policies Introduced by CMake 3.12
+=================================
+
+.. toctree::
+   :maxdepth: 1
+
+   CMP0073: Do not produce legacy _LIB_DEPENDS cache entries. </policy/CMP0073>
+
 Policies Introduced by CMake 3.11
 =================================
 
diff --git a/Help/policy/CMP0073.rst b/Help/policy/CMP0073.rst
new file mode 100644
index 0000000..9bfa0e9
--- /dev/null
+++ b/Help/policy/CMP0073.rst
@@ -0,0 +1,25 @@
+CMP0073
+-------
+
+Do not produce legacy ``_LIB_DEPENDS`` cache entries.
+
+Ancient CMake versions once used ``<tgt>_LIB_DEPENDS`` cache entries to
+propagate library link dependencies.  This has long been done by other
+means, leaving the :command:`export_library_dependencies` command as the
+only user of these values.  That command has long been disallowed by
+policy :policy:`CMP0033`, but the ``<tgt>_LIB_DEPENDS`` cache entries
+were left for compatibility with possible non-standard uses by projects.
+
+CMake 3.12 and above now prefer to not produce these cache entries
+at all.  This policy provides compatibility with projects that have
+not been updated to avoid using them.
+
+The ``OLD`` behavior for this policy is to set ``<tgt>_LIB_DEPENDS`` cache
+entries.  The ``NEW`` behavior for this policy is to not set them.
+
+This policy was introduced in CMake version 3.12.  Use the
+:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
+Unlike most policies, CMake version |release| does *not* warn
+when this policy is not set and simply uses ``OLD`` behavior.
+
+.. include:: DEPRECATED.txt
diff --git a/Help/release/dev/avoid-LIB_DEPENDS.rst b/Help/release/dev/avoid-LIB_DEPENDS.rst
new file mode 100644
index 0000000..b89d8f9
--- /dev/null
+++ b/Help/release/dev/avoid-LIB_DEPENDS.rst
@@ -0,0 +1,5 @@
+avoid-LIB_DEPENDS
+-----------------
+
+* CMake no longer produces ``<tgt>_LIB_DEPENDS`` cache entries
+  for library targets.  See policy :policy:`CMP0073`.