[−][src]Crate safe_uninit
Goal of the crate is to allow using safe uninitialized values. Many similar features
are already in the Rust core
library as MaybeUninit
and functions in standard types.
For example, currently (stable Rust 1.41) as nightly feature of a compiler one can see
Box::new_uninit()
which allows to allocate memory with MaybeUninit
value. Basically,
this new
crate allows creating not 'Maybe' but surely uninitialized values that are safe to use
despite they are uninitialized. Because of this they are directly presented as a value without
any wrappers like MaybeUninit
and no requirement for unsafe block.
Main trait is SafeUninit
which indicated the type which can be safely used without
initialization and without further wrappers. It is implemented for all primitive integer
types and their atomic variants, for fixed-size arrays of SafeUninit
of up to 32 values
(but there is a way of creating bigger arrays),
for tuples of SafeUninit
objects of up to 12 elements and for unit type ()
.
This crate is no-std
but also implements traits for alloc
types where appropriate.
Pointers
Pointers are safe to be uninitialized. Even if the values they are pointing to are not
SafeUninit
.
Firstly, pointers are internally a plain number of type usize which is safe.
Secondly, dereferencing pointers is an unsafe operation anyway and even if pointer
with uninitialized address gets dereferenced this will be done under unsafe block
and programmer will be fully responsible for any consequences of using it.
Common Types That are Unsafe
These types are not safe to use uninitialized and one should use MaybeUninit
instead.
bool
Boolean valid values are true
and false
. If boolean is internally
(as an example) stored as a byte which holds values different from 0 or 1 then this will
lead to unexpected behaviour and thus this type is not safe to use uninitialized. One
should use MaybeUninit
for bool
.
NonZero
Such types as NonZeroI32
are unsafe to leave uninitialized. These types are assumed to
never be zero. Uninitialized value though can occur zero and this will cause undefined
behaviour.
Might be Unsafe
Here are listed types that can be unsafe and should be further investigated:
char
f32
f64
Traits
ResizeUninit | To be used with |
SafeUninit | Marks the type that is safe to use uninitialized. For example, if you create uninitialized |
UninitContent | Similar to |
Functions
safe_uninit | Shorthand for types that are |
Derive Macros
SafeUninit |