Is there a better way to do C style error handling?

I'm trying to learn C by writing a simple parser / compiler. So far its been a very enlightening experience, however coming from a strong background in C# I'm having some problems adjusting - in particular to the lack of exceptions.

Now I've read Cleaner, more elegant, and harder to recognize and I agree with every word in that article; In my C# code I avoid throwing exceptions whenever possible, however now that I'm faced with a world where I can't throw exceptions my error handling is completely swamping the otherwise clean and easy-to-read logic of my code.

At the moment I'm writing code which needs to fail fast if there is a problem, and it also potentially deeply nested - I've settled on a error handling pattern whereby "Get" functions return NULL on an error, and other functions return -1 on failure. In both cases the function that fails calls NS_SetError() and so all the calling function needs to do is to clean up and immediately return on a failure.

My issue is that the number of if (Action() < 0) return -1; statements that I have is doing my head in - it's very repetitive and completely obscures the underlying logic. I've ended up creating myself a simple macro to try and improve the situation, for example:

#define NOT_ERROR(X)    if ((X) < 0) return -1

int NS_Expression(void)
{
    NOT_ERROR(NS_Term());
    NOT_ERROR(Emit("MOVE D0, D1\n"));

    if (strcmp(current->str, "+") == 0)
    {
        NOT_ERROR(NS_Add());
    }
    else if (strcmp(current->str, "-") == 0)
    {
        NOT_ERROR(NS_Subtract());
    }
    else
    {
        NS_SetError("Expected: operator");
        return -1;
    }
    return 0;
}

Each of the functions NS_Term, NS_Add and NS_Subtract do a NS_SetError()


                        
                        c
                        
                        error-handling

Besides goto, standard C has another construct to handle exceptional flow control setjmp/longjmp. It has the advantage that you can break out of multiply nested control statements more easily than with break as was proposed by someone, and in addition to what goto provides has a status indication that can encode the reason for what went wrong.

Another issue is just the syntax of your construct. It is not a good idea to use a control statement that can inadvertibly be added to. In your case

if (bla) NOT_ERROR(X);
else printf("wow!\n");

would go fundamentally wrong. I'd use something like

#define NOT_ERROR(X)          \
  if ((X) >= 0) { (void)0; }  \
  else return -1

instead.

answered 2011-04-15T14:11:29.473

Is there a better way to do C style error handling?

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