CMP0175
-------

.. versionadded:: 3.31

:command:`add_custom_command` rejects invalid arguments.

CMake 3.30 and earlier silently ignored unsupported keywords and missing or
invalid arguments for the different forms of the :command:`add_custom_command`
command. CMake 3.31 implements more rigorous argument checking and will flag
invalid or missing arguments as errors.

The ``OLD`` behavior of this policy will accept the same invalid keywords or
arguments as CMake 3.30 and earlier. The ``NEW`` behavior will flag the
following as errors that previously went unreported:

* The ``OUTPUT`` form does not accept ``PRE_BUILD``, ``PRE_LINK``, or
  ``POST_BUILD`` keywords.
* When the ``APPEND`` keyword is given, the ``OUTPUT`` form also does not
  accept ``BYPRODUCTS``, ``COMMAND_EXPAND_LISTS``, ``DEPENDS_EXPLICIT_ONLY``,
  ``DEPFILE``, ``JOB_POOL``, ``JOB_SERVER_AWARE``, ``USES_TERMINAL``, or
  ``VERBATIM`` keywords.
* The ``TARGET`` form requires exactly one of ``PRE_BUILD``, ``PRE_LINK``, or
  ``POST_BUILD`` to be given.  Previously, if none were given, ``POST_BUILD``
  was assumed, or if multiple keywords were given, the last one was used.
* The ``TARGET`` form does not accept ``DEPENDS``, ``DEPENDS_EXPLICIT_ONLY``,
  ``DEPFILE``, ``IMPLICIT_DEPENDS``, ``MAIN_DEPENDENCY``, ``JOB_POOL``, or
  ``JOB_SERVER_AWARE`` keywords.
* The ``TARGET`` form now requires at least one ``COMMAND`` to be given.
* If a keyword expects a value to be given after it, but no value is provided,
  that was previously treated as though the keyword was not given at all.
* The ``COMMENT`` keyword expects exactly one value after it.  If multiple
  values are given, or if the ``COMMENT`` keyword is given more than once,
  this is an error.

.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.31
.. |WARNS_OR_DOES_NOT_WARN| replace:: warns
.. include:: include/STANDARD_ADVICE.rst

.. include:: include/DEPRECATED.rst
