Quick and dirty state machine with function pointers in C

function_pointer_array.c

#include <stdio.h>

// Declare three functions that return nothing and accept a single pointer to an int as an argument
void state1(int *);
void state2(int *);
void state3(int *);

// Set up our state definitions.  Using bare numbers in code itself is an anti-pattern.
const int STATE_1 = 0;
const int STATE_2 = 1;
const int STATE_3 = 2;
const int STATE_4 = 3;


// Define the state transition functions.  These are just toys right now.
void state1(int *nextState) {
    printf("Just entered state %d.\n", STATE_1);
    printf("Hardcoded to enter state %d.\n", STATE_2);
    *nextState = STATE_2;
}

void state2(int *nextState) {
    printf("Just entered state %d.\n", STATE_2);
    printf("Hardcoded to enter state %d.\n", STATE_3);
    *nextState = STATE_3;
}

void state3(int *nextState) {
    printf("Just entered state %d.\n", STATE_3);
    printf("Hardcoded to enter state %d.\n", STATE_4);
    *nextState = STATE_4;
}

// Set up our table of function pointers
void (*stateFunctions[3])(int *) = {state1, state2, state3};

int main(int argc, char **argv) {
    // Define an intial state
    int state = 1;
    
    // While we haven't reached the terminal state, continue to call the state transition function as defined by the current state
    while (state != STATE_4) {
        (stateFunctions[state])(&state);
    }
    printf("Done!\n");
}