Re:You’re better off using Exceptions
by jcranmer on Monday February 03, 2020 @02:30PM
(#22227996)
As my opinions on exceptions have evolved throughout the years, I've come to think that there is value to unchecked exceptions, but unchecked exceptions need a fundamentally different mode from checked exceptions.
The best motivation for unchecked exceptions are things like division by 0, or null pointer dereferences: these are things that result from programmers misusing the API, and are generally unrecoverable. What you want instead is some sort of "graceful crash"--for example, if you're a web server, display a 500 page and log the stack trace somewhere internally. Using a pretty distinct mechanism for driving these error cases (e.g., Rust's panic mechanism) I think works better for emphasizing the crash aspect here.
Of course, now you have the regular checked exceptions which are a fundamental part of the function type. It's not clear to me that the try/catch/throw model is necessarily the best model for propagating these exceptions, and there are several cases where the overhead involved in the (misleadingly named) zero-cost exception handling model are not appropriate for the model.
Although there is something to be said for easy upgrading of checked into unchecked exceptions. It's a relatively natural assertion that something can't fail for reasons the compiler doesn't understand (which means informing the programmer when and where it failed is very critical!). I've always been annoyed by Eclipse deciding that the default implementation of catch should be "ignore the exception" instead of "wrap it in a RuntimeException."
The best motivation for unchecked exceptions are things like division by 0, or null pointer dereferences: these are things that result from programmers misusing the API, and are generally unrecoverable. What you want instead is some sort of "graceful crash"--for example, if you're a web server, display a 500 page and log the stack trace somewhere internally. Using a pretty distinct mechanism for driving these error cases (e.g., Rust's panic mechanism) I think works better for emphasizing the crash aspect here.
Of course, now you have the regular checked exceptions which are a fundamental part of the function type. It's not clear to me that the try/catch/throw model is necessarily the best model for propagating these exceptions, and there are several cases where the overhead involved in the (misleadingly named) zero-cost exception handling model are not appropriate for the model.
Although there is something to be said for easy upgrading of checked into unchecked exceptions. It's a relatively natural assertion that something can't fail for reasons the compiler doesn't understand (which means informing the programmer when and where it failed is very critical!). I've always been annoyed by Eclipse deciding that the default implementation of catch should be "ignore the exception" instead of "wrap it in a RuntimeException."