CXX_SCAN_FOR_MODULES
--------------------

.. versionadded:: 3.28

``CXX_SCAN_FOR_MODULES`` is a boolean specifying whether CMake will scan the
source for C++ module dependencies.  See also the
:prop_fs:`CXX_SCAN_FOR_MODULES` file set property which, if set,
overrides the per-source settings and the
:prop_tgt:`CXX_SCAN_FOR_MODULES` target property.

When this property is set ``ON``, CMake will scan the source at build time and
add module dependency information to the compile line as necessary.  When this
property is set ``OFF``, CMake will not scan the source at build time.  When
this property is unset, the :prop_tgt:`CXX_SCAN_FOR_MODULES` target property is
consulted.

Note that scanning is only performed if C++20 or higher is enabled for the
target and the source uses the ``CXX`` language.  Scanning for modules in
sources belonging to file sets of type ``CXX_MODULES`` is always performed.
