[cwzwarich]

> If exceptions are so great, why Rust and Swift aren't using them?

Technically speaking, Rust does have exceptions with its unwinding feature. The panic! macro throws an exception, and catch_panic allows you to catch it. It is implemented exactly the same way as C++ exceptions, with the accompanying code bloat and performance pessimization, and you have to think about exception safety exactly the same way when writing unsafe code.

[kibwen]

Rust has unwinding, which indeed opens a whole can of worms, but to say that it has exceptions is to miss the point. Rust has nothing anywhere near close to first-class resumable exceptions as surfaced in, say, Java. Not only is the `catch_unwind` function (it's not called `catch_panic`, btw) deliberately difficult to use (specifically to deter people from using it as a general error handling mechanism), the language deliberately defines an alternate compilation mode where unwinding does not exist and hence any attempt to "catch" it will fail. As a result, I have never once seen Rust code APIs that use `catch_unwind` as a mechanism for error handling; the purpose of that function is to prevent unwinding from crossing FFI boundaries.