[exception.when] When to use exceptions

Exceptions are for exceptional program flow – situations that are not ordinarily expected to occur during normal functioning of the program.

Following are some expected events that would normally warrant a return code instead of an exception.

Of course, some of these events border on being expected or exceptional, but here are some examples of exceptional events.

It is better to use data structures to represent expected events.  For example,  a validation function might return a Messages structure that contains errors, warnings and information messages instead of throwing an exception.