[CMake] PROJECT( LANGUAGES ) and m4

[Brad Bell]

If one looks at the documentation
     https://cmake.org/cmake/help/v3.0/command/project.html
one sees
     project(<PROJECT-NAME> [LANGUAGES] [<language-name>...])
and the following text: 'By default C and CXX are enabled if no language 
options are given.'

It there a list of available languages ?

I have a project that has m4 input files. A single m4 input file can be 
used to generate output in Perl, Octave, Python, or C++ language. Can 
CMake handle this type of dependency, or would I have to use custom 
targets in this case ?