Snippet

Intercepting Panic Unwinding for Safe Boundaries

In Rust, panics cause stack unwinding unless configured to abort. Using catch_unwind, we can catch panics at FFI boundaries or thread roots, preventing the process from crashing. AssertUnwindSafe is used to declare that the captured environment won't break logic invariants if a panic occurs.

snippet.rs

rust

use std::panic::{catch_unwind, AssertUnwindSafe};
 
fn run_untrusted_code<F: FnOnce()>(f: F) -> Result<(), &'static str> {
    let result = catch_unwind(AssertUnwindSafe(f));
    match result {
        Ok(_) => Ok(()),
        Err(_) => Err("Untrusted execution panicked!"),
    }
}
 
fn main() {
    let res = run_untrusted_code(|| {
        panic!("Oops!");
    });
    assert!(res.is_err());
}

Breakdown

catch_unwind(AssertUnwindSafe(f))

Executes the closure and catches any panic that occurs during execution, wrapping the result in a Result.

AssertUnwindSafe(f)

Asserts that the closure is safe to unwind, bypassing the compiler's default, conservative UnwindSafe checks.

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Intercepting Panic Unwinding for Safe Boundaries

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