Convert a pointer to u64, then convert the u64 back to a pointer,crash in android ndk

[ChenJiawei94]

I tried this code:

<code>
pub struct Node{}
let node = Rc::new(Node{});
let ptr = Rc::into_raw();
let ptr_u64 : u64 = unsafe{std::mem::transmute(ptr)};
let ptr2 : *const Node = unsafe{std::mem::transmute(ptr_u64)};
unsafe{(*ptr2).some_function()};//crash here.

I expected to see this happen: normal run.

Instead, this happened:crash in android ndk.

Meta

rustc --version --verbose:

<version>1.89

Backtrace

<backtrace>

[ChenJiawei94]

debug work fine,release crash.

[hanna-kruppe]

This is a bug in your code, transmute behaves as documented: https://doc.rust-lang.org/std/mem/fn.transmute.html#transmutation-between-pointers-and-integers

If you want to round-trip a pointer through an integer in a way that you can get back the original pointer, you need to use as casts […] If you specifically need to store something that is “either an integer or a pointer”, use *mut (): integers can be converted to pointers and back without any loss (via as casts or via transmute).

A warning for this is being added in #144531