Panic when debug-assertions=true in release profile

[pedantic79]

This showed up during advent of code. I was trying different hashing algorithms to see which provided the best times. Out of habit, I keep debug-assertions = true and overflow-checks = false in release profile. Other hashing algorithms would work, but gxhash would panic.

Eventually, I reduced this to a minimum test case, which is just debug-assertions = true in release profile. This seems to occur on MacOS (Apple Silicon), but not Linux (x86-64).

Example repo: https://github.com/pedantic79/gxhash-test

» cargo +stable version
cargo 1.84.0 (66221abde 2024-11-19)
» RUST_BACKTRACE=1 cargo +stable run --release
    Blocking waiting for file lock on package cache
   Compiling rustversion v1.0.19
   Compiling gxhash v3.4.1
   Compiling gxhash-test v0.1.0 (/Users/dnn/gxhash-test)
    Finished `release` profile [optimized + debuginfo] target(s) in 4.13s
     Running `target/release/gxhash-test`
thread 'main' panicked at core/src/panicking.rs:223:5:
unsafe precondition(s) violated: ptr::copy_nonoverlapping requires that both pointer arguments are aligned and non-null and the specified memory ranges do not overlap
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/std/src/panicking.rs:665:5
   1: core::panicking::panic_nounwind_fmt::runtime
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/core/src/panicking.rs:119:22
   2: core::panicking::panic_nounwind_fmt
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/core/src/intrinsics/mod.rs:3535:9
   3: core::panicking::panic_nounwind
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/core/src/panicking.rs:223:5
   4: core::hash::BuildHasher::hash_one
   5: hashbrown::map::make_hash
             at /rust/deps/hashbrown-0.15.0/src/map.rs:258:5
   6: hashbrown::rustc_entry::<impl hashbrown::map::HashMap<K,V,S,A>>::rustc_entry
             at /rust/deps/hashbrown-0.15.0/src/rustc_entry.rs:35:20
   7: std::collections::hash::map::HashMap<K,V,S>::entry
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/std/src/collections/hash/map.rs:854:19
   8: gxhash_test::part2
             at ./src/main.rs:6:15
   9: gxhash_test::main
             at ./src/main.rs:13:20
  10: core::ops::function::FnOnce::call_once
             at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
thread caused non-unwinding panic. aborting.
[1]    34288 abort      RUST_BACKTRACE=1 cargo +stable run --release