Struct MaybeUninitializedPlaces

pub struct MaybeUninitializedPlaces<'a, 'tcx> {
    tcx: TyCtxt<'tcx>,
    body: &'a Body<'tcx>,
    move_data: &'a MoveData<'tcx>,
    mark_inactive_variants_as_uninit: bool,
    skip_unreachable_unwind: BitSet<BasicBlock>,
}

MaybeUninitializedPlaces tracks all places that might be uninitialized upon reaching a particular point in the control flow for a function.

For example, in code like the following, we have corresponding dataflow information shown in the right-hand comments.

struct S;
fn foo(pred: bool) {                        // maybe-uninit:
                                            // {a, b, c, d}
    let a = S; let mut b = S; let c; let d; // {      c, d}

    if pred {
        drop(a);                            // {a,    c, d}
        b = S;                              // {a,    c, d}

    } else {
        drop(b);                            // {   b, c, d}
        d = S;                              // {   b, c   }

    }                                       // {a, b, c, d}

    c = S;                                  // {a, b,    d}
}

To determine whether a place must be uninitialized at a particular control-flow point, one can take the set-difference between this data and the data from MaybeInitializedPlaces at the corresponding control-flow point.

Similarly, at a given drop statement, the set-intersection between this data and MaybeInitializedPlaces yields the set of places that would require a dynamic drop-flag at that statement.

Fields

tcx: TyCtxt<'tcx>

body: &'a Body<'tcx>

move_data: &'a MoveData<'tcx>

mark_inactive_variants_as_uninit: bool

skip_unreachable_unwind: BitSet<BasicBlock>

Implementations

impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx>

pub fn new( tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, move_data: &'a MoveData<'tcx>, ) -> Self

pub fn mark_inactive_variants_as_uninit(self) -> Self

Causes inactive enum variants to be marked as “maybe uninitialized” after a switch on an enum discriminant.

This is correct in a vacuum but is not the default because it causes problems in the borrow checker, where this information gets propagated along FakeEdges.

pub fn skipping_unreachable_unwind( self, unreachable_unwind: BitSet<BasicBlock>, ) -> Self

impl<'tcx> MaybeUninitializedPlaces<'_, 'tcx>

fn update_bits( trans: &mut ChunkedBitSet<MovePathIndex>, path: MovePathIndex, state: DropFlagState, )

Trait Implementations

impl<'tcx> Analysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx>

type Domain = ChunkedBitSet<MovePathIndex>

There can be many more MovePathIndex than there are locals in a MIR body. We use a chunked bitset to avoid paying too high a memory footprint.

const NAME: &'static str = "maybe_uninit"

A descriptive name for this analysis. Used only for debugging.

fn bottom_value(&self, _: &Body<'tcx>) -> Self::Domain

Returns the initial value of the dataflow state upon entry to each basic block.

fn initialize_start_block(&self, _: &Body<'tcx>, state: &mut Self::Domain)

Mutates the initial value of the dataflow state upon entry to the START_BLOCK.

fn apply_statement_effect( &mut self, trans: &mut Self::Domain, _statement: &Statement<'tcx>, location: Location, )

Updates the current dataflow state with the effect of evaluating a statement.

fn apply_terminator_effect<'mir>( &mut self, trans: &mut Self::Domain, terminator: &'mir Terminator<'tcx>, location: Location, ) -> TerminatorEdges<'mir, 'tcx>

Updates the current dataflow state with the effect of evaluating a terminator.

fn apply_call_return_effect( &mut self, trans: &mut Self::Domain, _block: BasicBlock, return_places: CallReturnPlaces<'_, 'tcx>, )

Updates the current dataflow state with the effect of a successful return from a Call terminator.

fn apply_switch_int_edge_effects( &mut self, block: BasicBlock, discr: &Operand<'tcx>, edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>, )

Updates the current dataflow state with the effect of taking a particular branch in a SwitchInt terminator.

type Direction = Forward

The direction of this analysis. Either Forward or Backward.

fn apply_before_statement_effect( &mut self, _state: &mut Self::Domain, _statement: &Statement<'tcx>, _location: Location, )

Updates the current dataflow state with an effect that occurs immediately before the given statement.

fn apply_before_terminator_effect( &mut self, _state: &mut Self::Domain, _terminator: &Terminator<'tcx>, _location: Location, )

Updates the current dataflow state with an effect that occurs immediately before the given terminator.

fn into_engine<'mir>( self, tcx: TyCtxt<'tcx>, body: &'mir Body<'tcx>, ) -> Engine<'mir, 'tcx, Self>

where Self: Sized,

Creates an Engine to find the fixpoint for this dataflow problem.

impl<'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'_, 'tcx>

fn move_data(&self) -> &MoveData<'tcx>

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: 64 bytes