What does an asterisk before a function name mean?

Question

In the following lines of code, what does the asterisk in front of dup_func, free_func, and clear_free func, do?

void *(*dup_func)(void *);
void (*free_func)(void *);
void (*clear_free_func)(void *);

Answer 1

In your examples it means they are function pointers.

In a nutshell, they allow you to do things like this:

void example()
{
    printf("Example called!\n");
}

void call_my_function(void (*fun)())
{
    printf("Calling some function\n");
    (*fun)();
}

/* Later. */
call_my_function(example);