56 lines
1.2 KiB
Rust
56 lines
1.2 KiB
Rust
// Copied from rustc ui test suite
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// run-pass
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//
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// Test that we can handle unsized types with an extern type tail part.
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// Regression test for issue #91827.
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#![feature(extern_types)]
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use std::ptr::addr_of;
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extern "C" {
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type Opaque;
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}
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unsafe impl Sync for Opaque {}
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#[repr(C)]
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pub struct List<T> {
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len: usize,
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data: [T; 0],
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tail: Opaque,
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}
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#[repr(C)]
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pub struct ListImpl<T, const N: usize> {
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len: usize,
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data: [T; N],
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}
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impl<T> List<T> {
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const fn as_slice(&self) -> &[T] {
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unsafe { std::slice::from_raw_parts(self.data.as_ptr(), self.len) }
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}
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}
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impl<T, const N: usize> ListImpl<T, N> {
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const fn as_list(&self) -> &List<T> {
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unsafe { std::mem::transmute(self) }
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}
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}
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pub static A: ListImpl<u128, 3> = ListImpl { len: 3, data: [5, 6, 7] };
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pub static A_REF: &'static List<u128> = A.as_list();
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pub static A_TAIL_OFFSET: isize = tail_offset(A.as_list());
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const fn tail_offset<T>(list: &List<T>) -> isize {
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unsafe { (addr_of!(list.tail) as *const u8).offset_from(list as *const List<T> as *const u8) }
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}
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fn main() {
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assert_eq!(A_REF.as_slice(), &[5, 6, 7]);
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// Check that interpreter and code generation agree about the position of the tail field.
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assert_eq!(A_TAIL_OFFSET, tail_offset(A_REF));
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}
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