Doxygen: Force undeclared functions to be documented - doxygen

Question

Our C++ program has a built-in script interface and is able to run scripts in it. The scripts have access to convenience functions provided by the C++ program.
Now we would like Doxygen to create the documentation of the functions the script has access to. Such a function declaration looks like this:
void ScriptEngine::load_script(const QString &path) {
//...
/*! \fn sleep_ms(const unsigned int timeout_ms)
\brief sleeps for timeout_ms milliseconds.
\param timeout_ms
*/
(*lua)["sleep_ms"] = [](const unsigned int timeout_ms) {
//sleep(timeout_ms)
};
//more convenience functions..
//...
}
Obviously Doxygen won't include a
sleep_ms(const unsigned int timeout_ms)
into the documentation. Is there a way to to tell Doxygen to do so?

Answer 1

Do this:
Add the following line to your Doxyfile:
PREDEFINED = _DOXYGEN_
Make sure the ENABLE_PREPROCESSING tag in the Doxyfile is set to YES.
Put your declarations and documentation for the undeclared functions inside an #ifdef _DOXYGEN_ section.
#ifdef _DOXYGEN_
/*! \fn sleep_ms(const unsigned int timeout_ms)
\brief sleeps for timeout_ms milliseconds.
\param timeout_ms
*/
void sleep_ms(const unsigned int timeout_ms);
#endif
Don't put the above code inside a method or function such as ScriptEngine::load_script(), as you previously tried. And don't put it inside a namespace or class, unless in fact the function being declared is a member of that namespace or class.
With this method, your declarations will not create linker errors during a normal build, but will be seen by Doxygen.
See Also
http://www.doxygen.nl/manual/config.html#cfg_predefined