412 tokens

Unsafe

Raw pointers are inert.

Unsafe

Safe Destack code can create and carry raw pointers, because there is nothing directly unsafe about just looking at pointers. Raw pointers are inert: they do not keep storage alive, do not participate in borrow checking, and do not prove exclusivity.

Converting a borrow to a raw pointer is still safe because it does not touch the pointed-to memory:

1class User {}2 3let user = new User();4 5let borrow: &User = &user;6let pointer: *User = borrow; // OK: this only creates a raw pointer value

Unsafe begins when code relies on a memory invariant the compiler cannot prove:

Operation	Example	Safe?	Why
create or carry raw pointer values	`let pointer: *User = &user`, `pointer == other`	yes	does not touch memory
reinterpret raw pointer values	`pointer as uint8`, `0x1000 as uint8`	yes	makes no validity claim
wrapping address arithmetic	`raw.wrappingOffset(pointer, 4)`	yes	makes no allocation claim
allocation-relative pointer math	`raw.offset(pointer, 4)`, `raw.offsetFrom(pointer, origin)`	no	claims same live allocation
access memory through a pointer	`raw.asReference(pointer)`, `raw.read(pointer)`, `raw.write(pointer, value)`	no	bypasses borrow checking
build a raw slice descriptor from raw parts	`sliceFromRaw<T>(pointer, length)`	no	claims a valid region of `T`
raw bytes and layout tricks	`raw.copyBytes(dst, src, n)`, `raw.readVolatile(pointer)`, `raw.transmute<T, U>(value)`	no	touches or reinterprets unchecked memory

The compiler rejects unsafe operations, like raw pointer dereferencing, outside explicit @unsafe / @safe contexts.