47 lines
985 B
Rust
47 lines
985 B
Rust
trait Empty {}
|
|
|
|
#[repr(transparent)]
|
|
pub struct FunnyPointer(dyn Empty);
|
|
|
|
#[repr(C)]
|
|
pub struct Meta {
|
|
drop_fn: fn(&mut ()),
|
|
size: usize,
|
|
align: usize,
|
|
}
|
|
|
|
impl Meta {
|
|
pub fn new() -> Self {
|
|
Meta {
|
|
drop_fn: |_| {},
|
|
size: 0,
|
|
align: 1,
|
|
}
|
|
}
|
|
}
|
|
|
|
#[repr(C)]
|
|
pub struct FatPointer {
|
|
pub data: *const (),
|
|
pub vtable: *const (),
|
|
}
|
|
|
|
impl FunnyPointer {
|
|
pub unsafe fn from_data_ptr(data: &String, ptr: *const Meta) -> &Self {
|
|
let obj = FatPointer {
|
|
data: data as *const _ as *const (),
|
|
vtable: ptr as *const _ as *const (),
|
|
};
|
|
let obj = std::mem::transmute::<FatPointer, *mut FunnyPointer>(obj); //~ ERROR invalid drop function pointer in vtable
|
|
&*obj
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
unsafe {
|
|
let meta = Meta::new();
|
|
let hello = "hello".to_string();
|
|
let _raw: &FunnyPointer = FunnyPointer::from_data_ptr(&hello, &meta as *const _);
|
|
}
|
|
}
|