Question

What is the meaning of following statement.

((void*(*)(void*))keepfunc)(val)

Note:- In general I have problem understanding such expressions. Could, someone
Please suggest me some good material(web or book) for this?

Answer 1

You should try “parsing” the expression from inside out:

void*(*)(void*)

function pointer to a function expecting a pointer of void and returnning a pointer of void

(void*(*)(void*))keepfunc    

cast to a function pointer expecting a pointer of void and returnning a pointer of void

((void*(*)(void*))keepfunc)(val)

This should be wrong, since a function pointer must be dereferenced before it can be called. It should look something like this:

(*(void*(*)(void*))keepfunc)(val)

Was this a working example from a textbook on C programming?