Function Returning Itself

No, you cannot declare recursive function types in C. Except inside a structure (or an union), it's not possible to declare a recursive type in C.

Now for the void * solution, void * is only guaranteed to hold pointers to objects and not pointers to functions. Being able to convert function pointers and void * is available only as an extension.

In other words, is it possible for a function to return itself?

It depends on what you mean by "itself"; if you mean a pointer to itself then the answer is yes! While it is not possible for a function to return its type a function can return a pointer to itself and this pointer can then be converted to the appropriate type before calling.

The details are explained in the question comp.lang.c faq: Function that can return a pointer to a function of the same type.

Check my answer for details.

You can't cast function pointers to void* (they can be different sizes), but that's not a problem since we can cast to another function pointer type and cast it back to get the original value.

typedef void (*fun2)();
typedef fun2 (*fun1)();

fun2 rec_fun()
{
    puts("Called a function");
    return (fun2)rec_fun;
}

// later in code...
fun1 fp = (fun1)((fun1)rec_fun())();
fp();

Output:

Called a function
Called a function
Called a function

A possible solution with structs:

struct func_wrap
{
    struct func_wrap (*func)(void);
};

struct func_wrap func_test(void)
{
    struct func_wrap self;

    self.func = func_test;
    return self;
}

Compiling with gcc -Wall gave no warnings, but I'm not sure if this is 100% portable.