Closed
Description
I tried this code:
use std::sync::Weak;
fn main() {
println!("{:?}", Weak::into_raw(Weak::<usize>::new()));
}When I run it under miri, I get this:
error: Undefined Behavior: inbounds test failed: 0xffffffffffffffff is not a valid pointer
--> /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:2367:45
|
2367 | unsafe { data_offset_align(align_of_val(&*ptr)) }
| ^^^^^ inbounds test failed: 0xffffffffffffffff is not a valid 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 `alloc::sync::data_offset::<usize>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:2367:45
= note: inside `std::sync::Weak::<usize>::as_ptr` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:1575:26
= note: inside `std::sync::Weak::<usize>::into_raw` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/sync.rs:1609:22
note: inside `main` at src/main.rs:4:22
--> src/main.rs:4:22
|
4 | println!("{:?}", Weak::into_raw(Weak::<usize>::new()));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
= note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:125:18
= note: inside closure at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:66:18
= note: inside `std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:259:13
= note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:379:40
= note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:343:19
= note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:396:14
= note: inside `std::rt::lang_start_internal` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:51:25
= note: inside `std::rt::lang_start::<()>` at /home/vorner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:65:5
Creating a reference from such pointer looks suspicious indeed. I could send a pull request that adds a condition there, but I want to ask first if this is being done because „we are std, we can“, or if this is something that really should be fixed.
Meta
rustc --version --verbose:
rustc 1.50.0-nightly (f74583445 2020-12-18)
binary: rustc
commit-hash: f74583445702e2e27ec4415376f2c540a83d7ded
commit-date: 2020-12-18
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly
(but I've looked at the git sources and the thing is still there)