Function core::ptr::from_exposed_addr_mut
source · strict_provenance #95228)Expand description
Convert an address back to a mutable pointer, picking up a previously ‘exposed’ provenance.
This is equivalent to addr as *mut T. The provenance of the returned pointer is that of any
pointer that was previously passed to expose_addr or a ptr as usize
cast. If there is no previously ‘exposed’ provenance that justifies the way this pointer will be
used, the program has undefined behavior. Note that there is no algorithm that decides which
provenance will be used. You can think of this as “guessing” the right provenance, and the guess
will be “maximally in your favor”, in the sense that if there is any way to avoid undefined
behavior, then that is the guess that will be taken.
On platforms with multiple address spaces, it is your responsibility to ensure that the address makes sense in the address space that this pointer will be used with.
Using this method means that code is not following strict provenance rules. “Guessing” a
suitable provenance complicates specification and reasoning and may not be supported by
tools that help you to stay conformant with the Rust memory model, so it is recommended to
use with_addr wherever possible.
On most platforms this will produce a value with the same bytes as the address. Platforms which need to store additional information in a pointer may not support this operation, since it is generally not possible to actually compute which provenance the returned pointer has to pick up.
This API and its claimed semantics are part of the Strict Provenance experiment, see the module documentation for details.