Struct ptr::Shared [−][src]
pub struct Shared<T: ?Sized> { /* fields omitted */ }
Expand description
*mut T but non-zero and covariant.
This is often the correct thing to use when building data structures using
raw pointers, but is ultimately more dangerous to use because of its additional
properties. If you’re not sure if you should use Shared<T>, just use *mut T!
Unlike *mut T, the pointer must always be non-null, even if the pointer
is never dereferenced. This is so that enums may use this forbidden value
as a discriminant – Option<Shared<T>> has the same size as Shared<T>.
However the pointer may still dangle if it isn’t dereferenced.
Unlike *mut T, Shared<T> is covariant over T. If this is incorrect
for your use case, you should include some PhantomData in your type to
provide invariance, such as PhantomData<Cell<T>> or PhantomData<&'a mut T>.
Usually this won’t be necessary; covariance is correct for most safe abstractions,
such as Box, Rc, Arc, Vec, and LinkedList. This is the case because they
provide a public API that follows the normal shared XOR mutable rules of Rust.
Implementations
Dereferences the content.
The resulting lifetime is bound to self so this behaves “as if”
it were actually an instance of T that is getting borrowed. If a longer
(unbound) lifetime is needed, use &*my_ptr.ptr().