Creates an invalid pointer with the given address.
This is currently equivalent to
addr as *const T but it expresses the intended semantic
more clearly, and may become important under future memory models.
The module’s top-level documentation discusses the precise meaning of an “invalid” pointer but essentially this expresses that the pointer is not associated with any actual allocation and is little more than a usize address in disguise.
This pointer will have no provenance associated with it and is therefore UB to read/write/offset. This mostly exists to facilitate things like ptr::null and NonNull::dangling which make invalid pointers.
(Standard “Zero-Sized-Types get to cheat and lie” caveats apply, although it may be desirable to give them their own API just to make that 100% clear.)
This API and its claimed semantics are part of the Strict Provenance experiment, see the module documentation for details.