Rust for C-Programmers

15.1 Introduction to Error Handling

Rust classifies runtime errors into two broad categories:

• Recoverable Errors: Failures that can be handled gracefully, allowing the program to proceed. A common example is a file-open failure due to inadequate permissions; the program could request the correct permissions or ask for an alternate file path.

• Unrecoverable Errors: Situations from which the program cannot safely recover. Examples include out-of-memory conditions, invalid array indexing, or integer overflow in debug mode, where continuing execution could lead to undefined or dangerous behavior.

For recoverable errors, Rust’s Result type demands explicit handling of success (Ok) and failure (Err). For unrecoverable errors, Rust uses panic! to stop execution in a controlled manner. C’s approach of signaling errors through special return values or by setting errno relies heavily on developer diligence. Rust, by contrast, uses the type system to ensure that all potential failures receive due attention.