[betterunix]

I think Common Lisp has a good approach with its restarts system. I try to write something to a file but there is not a enough disk space? How about telling the user, then invoking a restart when the user says, "There is more space available!" and continuing execution as if nothing went wrong? The problem with exceptions is that there is no way to recover from them in most languages, because the exception handler is found by unwinding the stack.

What I do not like about the "check return values" approach is:

1. It means that client code must understand how to handle error conditions. No disk space? Well whoever called the top-level function that invoked write needs to figure out what to do if there is any chance of recovery. It is a maintenance headache that can quickly accumulate bugs.

2. In both Java and C++ there are functions that cannot return values: constructors, and in C++ destructors. No, it is not acceptable for a program to crash just because a constructor call failed. No, it is not any better to have every class have a special variable that indicates that the constructor failed. No, having empty constructors is not the answer, and it is certainly not going to help with destructor calls (the C++ standard library actually requires some destructors to silently fail because of the issues with error reporting).

[asgard1024]

Restarts are perfect! This bothered me greatly when I read Code Complete. It doesn't discuss error handlers (which restarts are a form of) in error handling chapter at all.

I really wish more people knew about this option. Maybe it would even get into mainstream languages.