Provenance in miri::machine - Rust
Description: Pointer provenance.

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## Provenance

# Enum Provenance

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    pub enum Provenance {
        Concrete {
            alloc_id: AllocId,
            tag: BorTag,
        },
        Wildcard,
    }

Expand description

Pointer provenance.

## Variants§

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### Concrete

For pointers with concrete provenance. we exactly know which allocation they are attached to and what their borrow tag is.

#### Fields

§`alloc_id: AllocId`
§`tag: BorTag`

Borrow Tracker tag.

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### Wildcard

Pointers with wildcard provenance are created on int-to-ptr casts. According to the specification, we should at that point angelically “guess” a provenance that will make all future uses of this pointer work, if at all possible. Of course such a semantics cannot be actually implemented in Miri. So instead, we approximate this, erroring on the side of accepting too much code rather than rejecting correct code: a pointer with wildcard provenance “acts like” any previously exposed pointer. Each time it is used, we check whether some exposed pointer could have done what we want to do, and if the answer is yes then we allow the access. This allows too much code in two ways:

- The same wildcard pointer can “take the role” of multiple different exposed pointers on subsequent memory accesses.
- In the aliasing model, we don’t just have to know the borrow tag of the pointer used for the access, we also have to update the aliasing state – and that update can be very different depending on which borrow tag we pick! Stacked Borrows has support for this by switching to a stack that is only approximately known, i.e. we over-approximate the effect of using any exposed pointer for this access, and only keep information about the borrow stack that would be true with all possible choices.

## Trait Implementations§

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### impl Clone for Provenance

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#### fn clone(&self) -> Provenance

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for Provenance

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl Hash for Provenance

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#### fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given `Hasher`. Read more
1.3.0 · Source§

#### fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
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### impl PartialEq for Provenance

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#### fn eq(&self, other: &Provenance) -> bool

Tests for `self` and `other` values to be equal, and is used by `==`.
1.0.0 (const: unstable) · Source§

#### fn ne(&self, other: &Rhs) -> bool

Tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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### impl Provenance for Provenance

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#### const OFFSET_IS_ADDR: bool = true

We use absolute addresses in the `offset` of a `StrictPointer`.

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#### const WILDCARD: Option<Self>

Miri implements wildcard provenance.

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#### fn get_alloc_id(self) -> Option<AllocId>

If `OFFSET_IS_ADDR == false`, provenance must always be able to identify the allocation this ptr points to (i.e., this must return `Some`). Otherwise this function is best-effort (but must agree with `Machine::ptr_get_alloc`). (Identifying the offset in that allocation, however, is harder – use `Memory::ptr_get_alloc` for that.)
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#### fn fmt(ptr: &Pointer<Self>, f: &mut Formatter<'_>) -> Result

Determines how a pointer should be printed.
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### impl VisitProvenance for Provenance

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#### fn visit_provenance(&self, visit: &mut VisitWith<'_>)

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### impl Copy for Provenance

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### impl Eq for Provenance

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### impl StructuralPartialEq for Provenance

## Auto Trait Implementations§

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### impl Freeze for Provenance

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### impl RefUnwindSafe for Provenance

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### impl Send for Provenance

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### impl Sync for Provenance

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### impl Unpin for Provenance

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### impl UnsafeUnpin for Provenance

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### impl UnwindSafe for Provenance

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes

Size for each variant:

- `Concrete`: 16 bytes
- `Wildcard`: 0 bytes