Panic
A panic is a runtime failure mechanism that abruptly stops ordinary execution when an unrecoverable error or violated assumption prevents safe continuation.
Go in Practice, Second Edition
A panic is a Go runtime failure mechanism indicating that execution cannot safely continue and causing stack unwinding to locate a handler or terminate the program.
- How it is used
- Signals conditions in which a program or subsystem cannot safely continue, as distinct from errors a caller can handle.
- How deep it goes
- Explains stack unwinding and deferred recovery with runnable examples, then examines goroutine boundaries without detailing runtime internals.
- Examples
- Compares checked and unchecked division, recovers in a deferred closure, and protects a connection handler.
- What you can do after
- Practice/perform it by choosing errors for handleable failures and placing deferred recovery on goroutines that may panic.
Refactoring to Rust
A panic is Rust's runtime mechanism for signaling an unrecoverable error or violated assumption.
- How it is used
- Uses panics to stop execution after unrecoverable errors or violated assumptions, and to signal failed test checks.
- How deep it goes
- Explains thread-level unwinding, Result methods, error formatting, and backtrace activation through worked examples; does not detail unwinding internals.
- Examples
- Contrasts explicit panic!, .unwrap(), and .expect() on a negative FizzBuzz input, then shows a failing equality assertion.
- What you can do after
- Apply panic! or Result methods when execution must stop, and diagnose a panic with its message and an enabled backtrace.
Learn Rust in a Month of Lunches
A panic is Rust's unrecoverable failure behavior that stops ordinary execution and reports diagnostic information.
- How it is used
- Uses panic to expose impossible operations, broken assumptions, and invalid input expected to fail in tests.
- How deep it goes
- Explains panic messages, source locations, and stack unwinding through examples without developing deeper runtime internals.
- Examples
- Shows an out-of-bounds vector access, a three-item length guard, and a calculator test that expects invalid input to panic.
- What you can do after
- Diagnose/debug with panic locations and messages, add panic! guards, and test expected panics with #[should_panic].
Write Powerful Rust Macros
A panic is Rust's unrecoverable failure mechanism that stops ordinary execution and may unwind the stack to clean up resources.
- How it is used
- Distinguishes unrecoverable or impossible states from ordinary failures handled with Result.
- How deep it goes
- Explains selection guidelines, worked Rust examples, unwinding cleanup, and procedural-macro implications.
- Examples
- Uses invalid person validation, checked digit conversion, missing configuration, and Dropper cleanup examples.
- What you can do after
- Evaluate/understand when to stop execution, preserve cleanup, choose Result, or improve panic diagnostics.
Go in Action, Second Edition
A panic is Go's runtime mechanism for terminating ordinary execution and reporting an unrecoverable run-time error unless recovered.
- How it is used
- Uses panics to show why unchecked slice access needs guards and why ordinary failures should use returned errors.
- How deep it goes
- Explains runtime bounds failures, prevention, and criteria for explicit panic; treats recover briefly rather than developing recovery mechanics.
- Examples
- Shows missing command-line arguments and a race-results function that panics on a short slice, then uses len or range.
- What you can do after
- Diagnose/debug with it by recognizing bounds panics, guarding predictable failures, and choosing returned errors over deliberate panics.
Rust Servers, Services, and Apps
A panic is Rust's unrecoverable program-failure mechanism that unwinds or aborts execution when a runtime condition cannot be handled.
- How it is used
- Contrasts panic-based unwrap handling with Result-based propagation in a database-backed course API.
- How deep it goes
- Explains panic through unwrap and contrasts it with ?, without detailing runtime unwinding or abort mechanics.
- Examples
- Uses a SQLx course query, invalid database configuration, HTTP 500 output, and asynchronous handler tests.
- What you can do after
- Diagnose panic-prone unwrap calls and replace them with propagated errors in database-backed handlers.
Rust in Action: Systems programming concepts and techniques
A panic is Rust's runtime failure behavior for terminating execution after an unrecoverable program error.
- How it is used
- Marks unrecoverable runtime failures while illustrating how Rust prevents impossible operations from silently proceeding.
- How deep it goes
- Explains overflow and bounds-checking triggers, optimization-dependent outcomes, diagnostics, and custom no_std handlers.
- Examples
- Demonstrates overflowing u16 and u8 arithmetic, out-of-bounds arrays, and aborting or looping no_std panic handlers.
- What you can do after
- Diagnose overflow and bounds failures, inspect panic locations, and configure a panic handler for no_std programs.
Read how Rust in Action: Systems programming concepts and techniques explains panic →
100 Go Mistakes and How to Avoid Them
panic is a Go built-in function or runtime state that stops normal execution and begins unwinding the current goroutine's call stack.
- How it is used
- Frames panic as an exceptional Go error-management mechanism rather than a routine substitute for returned errors.
- How deep it goes
- Explains control-flow unwinding, deferred recovery, and appropriate use, stopping short of broader runtime internals.
- Examples
- Uses print-before-panic code, deferred recovery, invalid HTTP status validation, and duplicate or nil database-driver registration.
- What you can do after
- Evaluate/understand when to panic, recover a panic in deferred code, and choose ordinary error returns for expected failures.
Read how 100 Go Mistakes and How to Avoid Them explains panic →
Related concepts
- failurecontrasts with · A failure is an unsuccessful outcome or condition in which an operation, process, or system does not achieve an expected result.
- Rust testing systemused by · Rust's built-in testing system is the language and toolchain support for defining, compiling, running, and reporting automated tests.
- result typealternative to · A type that represents an operation’s outcome as either a successful value or a failure value.
- recoveraddressed by · recover is a Go built-in function that retrieves the value of an active panic and stops its propagation when called directly by deferred execution.
- exceptioncontrasts with · An exception is a runtime signal or object representing an abnormal condition that interrupts ordinary program flow and may be handled or propagated.
- unwrapproduced by · unwrap is a Rust method that extracts a value from an Option or Result and panics when it is absent or represents an error.
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