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//! A test for calling `C-unwind` functions across foreign function boundaries.
//!
//! This test triggers a panic when calling a foreign function that calls *back* into Rust.
use std::panic::{catch_unwind, AssertUnwindSafe};
fn main() {
// Call `add_small_numbers`, passing arguments that will NOT trigger a panic.
let (a, b) = (9, 1);
let c = unsafe { add_small_numbers(a, b) };
assert_eq!(c, 10);
// Call `add_small_numbers`, passing arguments that will trigger a panic, and catch it.
let caught_unwind = catch_unwind(AssertUnwindSafe(|| {
let (a, b) = (10, 1);
let _c = unsafe { add_small_numbers(a, b) };
unreachable!("should have unwound instead of returned");
}));
// Assert that we did indeed panic, then unwrap and downcast the panic into the sum.
assert!(caught_unwind.is_err());
let panic_obj = caught_unwind.unwrap_err();
let msg = panic_obj.downcast_ref::<String>().unwrap();
assert_eq!(msg, "11");
}
#[link(name = "add", kind = "static")]
extern "C-unwind" {
/// An external function, defined in C.
///
/// Returns the sum of two numbers, or panics if the sum is greater than 10.
fn add_small_numbers(a: u32, b: u32) -> u32;
}
/// This function will panic if `x` is greater than 10.
///
/// This function is called by `add_small_numbers`.
#[no_mangle]
pub extern "C-unwind" fn panic_if_greater_than_10(x: u32) {
if x > 10 {
panic!("{}", x); // That is too big!
}
}
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