Enum miri::machine::Provenance

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

Pointer provenance.

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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 copy of the value. Read more
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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
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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: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method 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 Pointer<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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fn join(left: Option<Self>, right: Option<Self>) -> Option<Self>

Defines the ‘join’ of provenance: what happens when doing a pointer load and different bytes have different provenance.
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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

Auto Trait Implementations§

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> 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.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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