To use goto or not?

Question

This question may sound cliched, but I am in a situation here.

I am trying to implement a finite state automaton to parse a certain string in C. As I started writing the code, I realised the code may be more readable if I used labels to mark the different states and use goto to jump from one state to another as the case comes.

Using the standard breaks and flag variables is quite cumbersome in this case and hard to keep track of the state.

What approach is better? More than anything else I am worried it may leave a bad impression on my boss, as I am on an internship.

Answer 1

Using a goto for implementing a state machine often makes good sense. If you're really concerned about using a goto, a reasonable alternative is often to have a state variable that you modify, and a switch statement based on that:

typedef enum {s0,s1,s2,s3,s4,...,sn,sexit} state;

state nextstate;
int done = 0;

nextstate = s0;  /* set up to start with the first state */
while(!done)
   switch(nextstate)
      {
         case s0:
            nextstate = do_state_0();
            break;
         case s1:
            nextstate = do_state_1();
            break;
         case s2:
            nextstate = do_state_2();
            break;
         case s3:
             .
             .
             .
             .
         case sn:
            nextstate = do_state_n();
            break;
         case sexit:
            done = TRUE;
            break;
         default:
            /*  some sort of unknown state */
            break;
      }