Paniques
Rust handles fatal errors with a "panic".
Rust will trigger a panic if a fatal error happens at runtime:
fn main() { let v = vec![10, 20, 30]; println!("v[100]: {}", v[100]); }
- Panics are for unrecoverable and unexpected errors.
- Panics are symptoms of bugs in the program.
- Runtime failures like failed bounds checks can panic
- Assertions (such as
assert!
) panic on failure - Purpose-specific panics can use the
panic!
macro.
- A panic will "unwind" the stack, dropping values just as if the functions had returned.
- Use non-panicking APIs (such as
Vec::get
) if crashing is not acceptable.
This slide should take about 3 minutes.
By default, a panic will cause the stack to unwind. The unwinding can be caught:
use std::panic; fn main() { let result = panic::catch_unwind(|| "No problem here!"); println!("{result:?}"); let result = panic::catch_unwind(|| { panic!("oh no!"); }); println!("{result:?}"); }
- Catching is unusual; do not attempt to implement exceptions with
catch_unwind
! - This can be useful in servers which should keep running even if a single request crashes.
- This does not work if
panic = 'abort'
is set in yourCargo.toml
.