CMP0113
-------

.. versionadded:: 3.19

:ref:`Makefile Generators` do not repeat custom commands from target
dependencies.

Consider a chain of custom commands split across two dependent targets:

.. code-block:: cmake

  add_custom_command(OUTPUT output-not-created
    COMMAND ... DEPENDS ...)
  set_property(SOURCE output-not-created PROPERTY SYMBOLIC 1)
  add_custom_command(OUTPUT output-created
    COMMAND ... DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/output-not-created)
  add_custom_target(first DEPENDS output-not-created)
  add_custom_target(second DEPENDS output-created)
  add_dependencies(second first)

In CMake 3.18 and lower, the Makefile generators put a copy of both custom
commands in the Makefile for target ``second`` even though its dependency on
target ``first`` ensures that the first custom command runs before the second.
Running ``make second`` would cause the first custom command to run once in
the ``first`` target and then again in the ``second`` target.

CMake 3.19 and above prefer to not duplicate custom commands in a target that
are already generated in other targets on which the target depends (directly or
indirectly).  This policy provides compatibility for projects that have not
been updated to expect the new behavior.  In particular, projects that relied
on the duplicate execution or that did not properly set the :prop_sf:`SYMBOLIC`
source file property may be affected.

The ``OLD`` behavior for this policy is to duplicate custom commands in
dependent targets.  The ``NEW`` behavior of this policy is to not duplicate
custom commands in dependent targets.

This policy was introduced in CMake version 3.19.  Unlike many policies,
CMake version |release| does *not* warn when this policy is not set and
simply uses ``OLD`` behavior.

.. include:: DEPRECATED.txt