C usage of goto

Question

I have a state machine with some kind of callback mechanism were functions are invoked by a task runner. Behind all of that is a state machine which has 4 kinds of states, some excluding each other, others can be combined, which makes quite a complex rule set. One of the functions should show the user error messages if any illegal action is attempted (for sake of simplicity printf here):

static int state1 = 0;
static bool switch2 = 1;

void do_stuff(int value){
    int errorCode = 0;
    if(state1 == 1){ 
        errorCode = -1;
        goto ERROR;
    }
    if(state1 == 2 && switch2)
    {
        errorCode = 2;
        goto ERROR;
    }


    printf("No error!");
    return;
ERROR:
    printf("%d", errorCode);
}

This was the shortest and most concise way I can think of, but its always been hammered home that using goto is a bad thing. Is there any better way to solve this problem or is this the best way in regards of stability and maintenance?

Answer 1

goto is rarely the right solution for control flow. While there are valid use cases for goto, in this particular function you could simply restructure the control flow into if-else branches like this:

void do_stuff(int value)
{
    int errorCode = 0;

    if (state1 == 1)
    { 
        errorCode = -1;
    }
    else if (state1 == 2 && switch2)
    {
        errorCode = 2;
    }
    else // unconditional case for no errors
    {
        printf("No error!");
        return;
    }
    printf("%s", errorCode);  // if control reaches here, print the error
}