tests/run-make/extern-fn-generic/test.rs

extern crate testcrate;

extern "C" fn bar<T>(ts: testcrate::TestStruct<T>) -> T {
    ts.y
}

#[link(name = "test", kind = "static")]
extern "C" {
    fn call(c: extern "C" fn(testcrate::TestStruct<i32>) -> i32) -> i32;
}

fn main() {
    // Let's test calling it cross crate
    let back = unsafe { testcrate::call(testcrate::foo::<i32>) };
    assert_eq!(3, back);

    // And just within this crate
    let back = unsafe { call(bar::<i32>) };
    assert_eq!(3, back);
}