error: Undefined Behavior: invalid use of 8 as a pointer
    --> components/servo_arc/lib.rs:716:69
     |                                                                                                                                       
716  |             let fake_ref: &ArcInner<HeaderSlice<H, [T]>> = unsafe { &*fake_ptr };
     |                                                                     ^^^^^^^^^^ invalid use of 8 as a pointer                                |
     = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior                                 = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information                            = note: inside `Arc::<HeaderSlice<HeaderWithLength<u32>, [i32]>>::from_header_and_iter_alloc::<[closure@components/servo_arc/lib.rs:815:1
3: 826:14], std::iter::Empty<i32>>` at components/servo_arc/lib.rs:716:69