Unsafety

Unsafe operations are those that can potentially violate the memory-safety guarantees of Rust’s static semantics.

The following language level features cannot be used in the safe subset of Rust:

• Dereferencing a raw pointer.

• Reading or writing a mutable or unsafe external static variable.

• Accessing a field of a union, other than to assign to it.

• Calling an unsafe function.

• Calling a safe function marked with a target_feature from a function that does not have a target_feature attribute enabling the same features (see attributes.codegen.target_feature.safety-restrictions).

• Implementing an unsafe trait.

• Declaring an extern block¹.

• Applying an unsafe attribute to an item.

1. Prior to the 2024 edition, extern blocks were allowed to be declared without unsafe. ↩