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