How can I declare a function that can return a p

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How can I declare a function that can return a pointer to a function of the same type?

C Interview Questions and Answers

How can I declare a function that can return a pointer to a function of the same type?

Q: How can I declare a function that can return a pointer to a function of the same type? I'm building a state machine with one function for each state, each of which returns a pointer to the function for the next state. But I can't find a way to declare the functions--I seem to need a function returning a pointer to a function returning a pointer to a function returning a pointer to a function..., ad infinitum.

A: You can't quite do it directly. One way is to have the function return a generic function pointer, with some judicious casts to adjust the types as the pointers are passed around:

typedef int (*funcptr)(); /* generic function pointer */
typedef funcptr (*ptrfuncptr)(); /* ptr to fcn returning g.f.p. */

funcptr start(), stop();
funcptr state1(), state2(), state3();

void statemachine()
{
ptrfuncptr state = start;

while(state != stop)
state = (ptrfuncptr)(*state)();
}

funcptr start()
{
return (funcptr)state1;
}
(The second ptrfuncptr typedef hides some particularly dark syntax; without it, the state variable would have to be declared as funcptr (*state)() and the call would contain a bewildering cast of the form (funcptr (*)())(*state)().)

Another way is to have each function return a structure containing only a pointer to a function returning that structure:

struct functhunk {
struct functhunk (*func)();
};

struct functhunk start(), stop();
struct functhunk state1(), state2(), state3();

void statemachine()
{
struct functhunk state = {start};

while(state.func != stop)
state = (*state.func)();
}

struct functhunk start()
{
struct functhunk ret;
ret.func = state1;
return ret;
}
(Note that these examples use the older, explicit style of calling via function pointers;

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