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

Question

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 pro

Answer 1

The short answer is: let your functions return an error code that cannot possibly be a valid value - and always check the return value. For functions returning pointers, this is NULL. For functions returning a non-negative int, it's a negative value, commonly -1, and so on...

If every possible return value is also a valid value, use call-by-reference:

int my_atoi(const char *str, int *val)
{
        // convert str to int
        // store the result in *val
        // return 0 on success, -1 (or any other value except 0) otherwise
}

Checking the return value of every function might seem tedious, but that's the way errors are handled in C. Consider the function nc_dial(). All it does is checking its arguments for validity and making a network connection by calling getaddrinfo(), socket(), setsockopt(), bind()/listen() or connect(), finally freeing unused resources and updating metadata. This could be done in approximately 15 lines. However, the function has nearly 100 lines due to error checking. But that's the way it is in C. Once you get used to it, you can easily mask the error checking in your head.

Furthermore, there's nothing wrong with multiple if (Action() == 0) return -1;. To the contrary: it is usually a sign of a cautious programmer. It's good to be cautious.

And as a final comment: don't use macros for anything but defining values if you can't justify their use while someone is pointing with a gun at your head. More specifically, never use control flow statements in macros: it confuses the shit out of the poor guy who has to maintain your code 5 years after you left the company. There's nothing wrong with if (foo) return -1;. It's simple, clean and obvious to the point that you can't do any better.

Once you drop your tendency to hide control flow in macros, there's really no reason to feel like you're missing something.