Struct miri::borrow_tracker::stacked_borrows::stack::Stack

pub struct Stack {
    borrows: Vec<Item>,
    unknown_bottom: Option<BorTag>,
    cache: StackCache,
    unique_range: Range<usize>,
}

Extra per-location state.

Fields

borrows: Vec<Item>

Used mostly as a stack; never empty. Invariants:

• Above a SharedReadOnly there can only be more SharedReadOnly.
• Except for Untagged, no tag occurs in the stack more than once.

unknown_bottom: Option<BorTag>

If this is Some(id), then the actual current stack is unknown. This can happen when wildcard pointers are used to access this location. What we do know is that borrows are at the top of the stack, and below it are arbitrarily many items whose tag is strictly less than id. When the bottom is unknown, borrows always has a SharedReadOnly or Unique at the bottom; we never have the unknown-to-known boundary in an SRW group.

cache: StackCache

A small LRU cache of searches of the borrow stack.

unique_range: Range<usize>

On a read, we need to disable all Unique above the granting item. We can avoid most of this scan by keeping track of the region of the borrow stack that may contain Uniques.

Implementations

impl Stack

pub fn retain(&mut self, tags: &FxHashSet<BorTag>)

impl<'tcx> Stack

pub(super) fn find_granting( &mut self, access: AccessKind, tag: ProvenanceExtra, exposed_tags: &FxHashSet<BorTag> ) -> Result<Option<usize>, ()>

Find the item granting the given kind of access to the given tag, and return where it is on the stack. For wildcard tags, the given index is approximate, but if no index is given it means the match was not in the known part of the stack. Ok(None) indicates it matched the “unknown” part of the stack. Err indicates it was not found.

fn find_granting_tagged( &mut self, access: AccessKind, tag: BorTag ) -> Option<usize>

fn find_granting_cache( &mut self, access: AccessKind, tag: BorTag ) -> Option<usize>

pub fn insert(&mut self, new_idx: usize, new: Item)

fn insert_cache(&mut self, new_idx: usize, new: Item)

pub fn new(item: Item) -> Self

Construct a new Stack using the passed Item as the root tag.

pub fn get(&self, idx: usize) -> Option<Item>

pub fn len(&self) -> usize

pub fn unknown_bottom(&self) -> Option<BorTag>

pub fn set_unknown_bottom(&mut self, tag: BorTag)

pub fn disable_uniques_starting_at( &mut self, disable_start: usize, visitor: impl FnMut(Item) -> InterpResult<'tcx> ) -> InterpResult<'tcx>

Find all Unique elements in this borrow stack above granting_idx, pass a copy of them to the visitor, then set their Permission to Disabled.

pub fn pop_items_after<V: FnMut(Item) -> InterpResult<'tcx>>( &mut self, start: usize, visitor: V ) -> InterpResult<'tcx>

Produces an iterator which iterates over range in reverse, and when dropped removes that range of Items from this Stack.

impl<'tcx> Stack

Core per-location operations: access, dealloc, reborrow.

fn find_first_write_incompatible(&self, granting: usize) -> usize

Find the first write-incompatible item above the given one – i.e, find the height to which the stack will be truncated when writing to granting.

fn item_invalidated( item: &Item, global: &GlobalStateInner, dcx: &DiagnosticCx<'_, '_, '_, 'tcx>, cause: ItemInvalidationCause ) -> InterpResult<'tcx>

The given item was invalidated – check its protectors for whether that will cause UB.

fn access( &mut self, access: AccessKind, tag: ProvenanceExtra, global: &GlobalStateInner, dcx: &mut DiagnosticCx<'_, '_, '_, 'tcx>, exposed_tags: &FxHashSet<BorTag> ) -> InterpResult<'tcx>

Test if a memory access using pointer tagged tag is granted. If yes, return the index of the item that granted it. range refers the entire operation, and offset refers to the specific offset into the allocation that we are currently checking.

fn dealloc( &mut self, tag: ProvenanceExtra, global: &GlobalStateInner, dcx: &mut DiagnosticCx<'_, '_, '_, 'tcx>, exposed_tags: &FxHashSet<BorTag> ) -> InterpResult<'tcx>

Deallocate a location: Like a write access, but also there must be no active protectors at all because we will remove all items.

fn grant( &mut self, derived_from: ProvenanceExtra, new: Item, access: Option<AccessKind>, global: &GlobalStateInner, dcx: &mut DiagnosticCx<'_, '_, '_, 'tcx>, exposed_tags: &FxHashSet<BorTag> ) -> InterpResult<'tcx>

Derive a new pointer from one with the given tag.

access indicates which kind of memory access this retag itself should correspond to.

Trait Implementations

impl Clone for Stack

fn clone(&self) -> Stack

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Stack

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

Formats the value using the given formatter.

impl PartialEq for Stack

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

This method tests for self and other values to be equal, and is used by ==.

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.

impl Eq for Stack

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: 560 bytes