heap-vec is potentially unsound

[KisaragiEffective]

Cargo.lock:

# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 3

[[package]]
name = "heap-vec"
version = "0.1.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "a39c5a6cd0011a69d1f643be9b2f6d52b7ad45e447936bed1640d57eceb18fc2"

[[package]]
name = "heap_vec_ub"
version = "0.1.0"
dependencies = [
 "heap-vec",
]

main.rs:

use heap_vec::HeapVec;

fn main() {
    let mut v = HeapVec::new();
    v.push(1u8);
}

MIRIFLAGS="-Zmiri-ignore-leaks -Zmiri-backtrace=full" cargo +nightly miri run:

full output

Preparing a sysroot for Miri (target: x86_64-unknown-linux-gnu)... done
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
     Running `/home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/cargo-miri runner target/miri/x86_64-unknown-linux-gnu/debug/heap_vec_ub`
warning: integer-to-pointer cast
  --> /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:93:33
   |
93 |         Self { ptr: Unique::new(0 as *mut T)}
   |                                 ^^^^^^^^^^^ integer-to-pointer cast
   |
   = help: This program is using integer-to-pointer casts or (equivalently) `ptr::from_exposed_addr`,
   = help: which means that Miri might miss pointer bugs in this program.
   = help: See https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html for more details on that operation.
   = help: To ensure that Miri does not miss bugs in your program, use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead.
   = help: You can then pass the `-Zmiri-strict-provenance` flag to Miri, to ensure you are not relying on `from_exposed_addr` semantics.
   = help: Alternatively, the `-Zmiri-permissive-provenance` flag disables this warning.
   = note: BACKTRACE:
   = note: inside `heap_vec::HeapVec::<u8>::new` at /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:93:33: 93:44
note: inside `main`
  --> src/main.rs:4:17
   |
4  |     let mut v = HeapVec::new();
   |                 ^^^^^^^^^^^^^^
   = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5: 250:71
   = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:155:18: 155:21
   = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:166:18: 166:82
   = 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/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:284:13: 284:31
   = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
   = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
   = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
   = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:48: 148:73
   = note: inside `std::panicking::r#try::do_call::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
   = note: inside `std::panicking::r#try::<isize, {closure@std::rt::lang_start_internal::{closure#2}}>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
   = note: inside `std::panic::catch_unwind::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
   = note: inside `std::rt::lang_start_internal` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:20: 148:98
   = note: inside `std::rt::lang_start::<()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6

warning: integer-to-pointer cast
   --> /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:126:18
    |
126 |                 *((self.ptr.as_ptr() as usize + mem::size_of::<usize>()) as *const usize)
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ integer-to-pointer cast
    |
    = note: inside `heap_vec::HeapVec::<u8>::len` at /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:126:18: 126:90
    = note: inside `heap_vec::HeapVec::<u8>::push` at /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:185:48: 185:58
note: inside `main`
   --> src/main.rs:5:5
    |
5   |     v.push(1u8);
    |     ^^^^^^^^^^^
    = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5: 250:71
    = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:155:18: 155:21
    = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:166:18: 166:82
    = 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/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:284:13: 284:31
    = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
    = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
    = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
    = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:48: 148:73
    = note: inside `std::panicking::r#try::do_call::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
    = note: inside `std::panicking::r#try::<isize, {closure@std::rt::lang_start_internal::{closure#2}}>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
    = note: inside `std::panic::catch_unwind::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
    = note: inside `std::rt::lang_start_internal` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:20: 148:98
    = note: inside `std::rt::lang_start::<()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6

error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
   --> /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:126:17
    |
126 |                 *((self.ptr.as_ptr() as usize + mem::size_of::<usize>()) as *const usize)
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory
    |
    = 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: BACKTRACE:
    = note: inside `heap_vec::HeapVec::<u8>::len` at /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:126:17: 126:90
    = note: inside `heap_vec::HeapVec::<u8>::push` at /home/kisaragi/.cargo/registry/src/index.crates.io-6f17d22bba15001f/heap-vec-0.1.0/src/lib.rs:185:48: 185:58
note: inside `main`
   --> src/main.rs:5:5
    |
5   |     v.push(1u8);
    |     ^^^^^^^^^^^
    = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5: 250:71
    = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:155:18: 155:21
    = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:166:18: 166:82
    = 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/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:284:13: 284:31
    = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
    = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
    = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
    = note: inside closure at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:48: 148:73
    = note: inside `std::panicking::r#try::do_call::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:552:40: 552:43
    = note: inside `std::panicking::r#try::<isize, {closure@std::rt::lang_start_internal::{closure#2}}>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:516:19: 516:81
    = note: inside `std::panic::catch_unwind::<{closure@std::rt::lang_start_internal::{closure#2}}, isize>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
    = note: inside `std::rt::lang_start_internal` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:148:20: 148:98
    = note: inside `std::rt::lang_start::<()>` at /home/kisaragi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6

error: aborting due to 1 previous error; 2 warnings emitted

output of cargo +nightly -vV:

cargo 1.76.0-nightly (1a2666ddd 2023-12-17)
release: 1.76.0-nightly
commit-hash: 1a2666ddd14cf0a255d4ddb61c63531c259a7b39
commit-date: 2023-12-17
host: x86_64-unknown-linux-gnu
libgit2: 1.7.1 (sys:0.18.1 vendored)
libcurl: 8.5.0-DEV (sys:0.4.70+curl-8.5.0 vendored ssl:OpenSSL/1.1.1w)
ssl: OpenSSL 1.1.1w  11 Sep 2023
os: Debian 12 (bookworm) [64-bit]

I can't reproduce on heap_vec's test code with same command, but running miri on the main.rs reports UB.