Fix uninitialized memory references#300
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- Fix uninitialized memory reference UB in from_mutated_str. Creating a &mut [u8; 64] reference pointing to uninitialized bytes from MaybeUninit violates Rust's validity invariants. Replaced the slice cast with safe raw pointer arithmetic (ptr::copy_nonoverlapping) and slice creation over only the initialized portion of memory. - Refactor magic number 64 into a named const MAX_STACK_SIZE. - Add UB test case.
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Fixes #260
Fixes #279
This PR resolves a critical memory safety issue in
Atom::from_mutated_str.Previously, the code did
&mut *buffer.as_mut_ptr()on aMaybeUninit<[u8; 64]>. Creating a mutable reference to uninitialized memory is instant Undefined Behavior in Rust, and it violated Stacked Borrows (caught by Miri).This is fixed by:
1. Using raw pointers (
buffer.as_mut_ptr()) andstd::ptr::copy_nonoverlappingto write to the buffer.2. Slicing only the initialized portion (
slice::from_raw_parts_mut) before creating the&mut strreference, ensuring we never create a reference to uninitialized bytes.