Struct miri::Tree

pub struct Tree {
    pub(super) tag_mapping: UniKeyMap<BorTag>,
    pub(super) nodes: UniValMap<Node>,
    pub(super) rperms: RangeMap<UniValMap<LocationState>>,
    pub(super) root: UniIndex,
}

Tree structure with both parents and children since we want to be able to traverse the tree efficiently in both directions.

Fields

tag_mapping: UniKeyMap<BorTag>

Mapping from tags to keys. The key obtained can then be used in any of the UniValMap relative to this allocation, i.e. both the nodes and rperms of the same Tree. The parent-child relationship in Node is encoded in terms of these same keys, so traversing the entire tree needs exactly one access to tag_mapping.

nodes: UniValMap<Node>

All nodes of this tree.

rperms: RangeMap<UniValMap<LocationState>>

Maps a tag and a location to a perm, with possible lazy initialization.

NOTE: not all tags registered in nodes are necessarily in all ranges of rperms, because rperms is in part lazily initialized. Just because nodes.get(key) is Some(_) does not mean you can safely unwrap any perm.get(key).

We do uphold the fact that keys(perms) is a subset of keys(nodes)

root: UniIndex

The index of the root node.

Implementations

impl<'tcx> Tree

fn nth_parent(&self, tag: BorTag, nth_parent: u8) -> Option<BorTag>

Climb the tree to get the tag of a distant ancestor. Allows operations on tags that are unreachable by the program but still exist in the tree. Not guaranteed to perform consistently if tag-gc=1.

pub fn give_pointer_debug_name( &mut self, tag: BorTag, nth_parent: u8, name: &str ) -> InterpResult<'tcx>

Debug helper: assign name to tag.

pub fn is_allocation_of(&self, tag: BorTag) -> bool

Debug helper: determines if the tree contains a tag.

impl<'tcx> Tree

pub fn print_tree( &self, protected_tags: &FxHashMap<BorTag, ProtectorKind>, show_unnamed: bool ) -> InterpResult<'tcx>

Display the contents of the tree.

impl Tree

pub fn new(root_tag: BorTag, size: Size, span: Span) -> Self

Create a new tree, with only a root pointer.

impl<'tcx> Tree

pub fn new_child( &mut self, parent_tag: BorTag, new_tag: BorTag, default_initial_perm: Permission, reborrow_range: AllocRange, span: Span ) -> InterpResult<'tcx>

Insert a new tag in the tree

pub fn dealloc( &mut self, tag: BorTag, access_range: AllocRange, global: &RefCell<GlobalStateInner>, span: Span ) -> InterpResult<'tcx>

Deallocation requires

• a pointer that permits write accesses
• the absence of Strong Protectors anywhere in the allocation

pub fn perform_access( &mut self, access_kind: AccessKind, tag: BorTag, access_range: AllocRange, global: &RefCell<GlobalStateInner>, span: Span, access_cause: AccessCause ) -> InterpResult<'tcx>

Map the per-node and per-location LocationState::perform_access to each location of access_range, on every tag of the allocation.

LocationState::perform_access will take care of raising transition errors and updating the initialized status of each location, this traversal adds to that:

• inserting into the map locations that do not exist yet,
• trimming the traversal,
• recording the history.

impl Tree

Integration with the BorTag garbage collector

pub fn remove_unreachable_tags(&mut self, live_tags: &FxHashSet<BorTag>)

fn keep_only_needed(&mut self, idx: UniIndex, live: &FxHashSet<BorTag>) -> bool

Traverses the entire tree looking for useless tags. Returns true iff the tag it was called on is still live or has live children, and removes from the tree all tags that have no live children.

NOTE: This leaves in the middle of the tree tags that are unreachable but have reachable children. There is a potential for compacting the tree by reassigning children of dead tags to the nearest live parent, but it must be done with care not to remove UB.

Example: Consider the tree root - parent - child, with parent: Frozen and child: Reserved. This tree can exist. If we blindly delete parent and reassign child to be a direct child of root then Writes to child are now permitted whereas they were not when parent was still there.

impl<'tcx> Tree

pub fn new_allocation( id: AllocId, size: Size, state: &mut GlobalStateInner, _kind: MemoryKind<MiriMemoryKind>, machine: &MiriMachine<'_, 'tcx> ) -> Self

Create a new allocation, i.e. a new tree

pub fn before_memory_access( &mut self, access_kind: AccessKind, alloc_id: AllocId, prov: ProvenanceExtra, range: AllocRange, machine: &MiriMachine<'_, 'tcx> ) -> InterpResult<'tcx>

Check that an access on the entire range is permitted, and update the tree.

pub fn before_memory_deallocation( &mut self, _alloc_id: AllocId, prov: ProvenanceExtra, range: AllocRange, machine: &MiriMachine<'_, 'tcx> ) -> InterpResult<'tcx>

Check that this pointer has permission to deallocate this range.

pub fn expose_tag(&mut self, _tag: BorTag)

Trait Implementations

impl Clone for Tree

fn clone(&self) -> Tree

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Tree

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

Formats the value using the given formatter.

impl VisitTags for Tree

fn visit_tags(&self, visit: &mut dyn FnMut(BorTag))

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: 112 bytes