Data Rust active any

Handle zero-sized types explicitly in unsafe generic storage

data-rust-034

Intent

Prevent undefined behavior in unsafe generic containers that assume every type has ordinary allocation semantics.

Applicability

Applies to unsafe generic Rust collections or allocators. Return unknown when generic storage internals are hidden.

What to inspect

Allocation math, pointer arithmetic, deallocation logic, and special cases for size_of::<T>() == 0.

Pass criteria

Unsafe generic storage explicitly handles zero-sized types without fake allocation, invalid offset math, or invalid deallocation.

Fail criteria

Generic unsafe storage treats zero-sized types like ordinary allocated elements and performs invalid pointer arithmetic or deallocation.

Do not flag

Safe standard-library containers or generic code that never manipulates raw storage.

Confidence guidance

HIGH when raw generic storage ignores zero-sized types. MEDIUM when helper abstractions may already special-case them. LOW when only type parameters are visible.

Remediation

Add explicit zero-sized-type handling for allocation, pointer math, and drop or deallocation paths.

Pass example

if mem::size_of::<T>() == 0 { return NonNull::dangling(); }

Fail example

let layout = Layout::array::<T>(cap).unwrap();
alloc(layout)