rustc_mir_dataflow::impls

Struct MaybeUninitializedPlaces

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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>,
}
Expand description

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 is definitely uninitialized at a particular control-flow point, one can take the set-complement of 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.

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§tcx: TyCtxt<'tcx>§body: &'a Body<'tcx>§move_data: &'a MoveData<'tcx>§mark_inactive_variants_as_uninit: bool§skip_unreachable_unwind: BitSet<BasicBlock>

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

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

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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.

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

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

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

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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.

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const NAME: &'static str = "maybe_uninit"

A descriptive name for this analysis. Used only for debugging. Read more
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fn bottom_value(&self, _: &Body<'tcx>) -> Self::Domain

Returns the initial value of the dataflow state upon entry to each basic block.
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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. Read more
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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.
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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. Read more
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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. Read more
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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. Read more
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type Direction = Forward

The direction of this analysis. Either Forward or Backward.
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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. Read more
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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. Read more
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fn iterate_to_fixpoint<'mir>( self, tcx: TyCtxt<'tcx>, body: &'mir Body<'tcx>, pass_name: Option<&'static str>, ) -> Results<'tcx, Self>
where Self: Sized, Self::Domain: DebugWithContext<Self>,

Finds the fixpoint for this dataflow problem. Read more
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impl<'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'_, 'tcx>

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

Auto Trait Implementations§

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

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

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

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impl<'a, 'tcx> !RefUnwindSafe for MaybeUninitializedPlaces<'a, 'tcx>

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impl<'a, 'tcx> !Send for MaybeUninitializedPlaces<'a, 'tcx>

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impl<'a, 'tcx> !Sync for MaybeUninitializedPlaces<'a, 'tcx>

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

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impl<'a, 'tcx> !UnwindSafe for MaybeUninitializedPlaces<'a, 'tcx>

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impl<T> Aligned for T

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const ALIGN: Alignment = _

Alignment of Self.
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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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where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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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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fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to f(&iter.collect::<Vec<_>>()).

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type Output = R

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fn filterable( self, filter_name: &'static str, ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>

Creates a filterable data provider with the given name for debugging. Read more
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Calls U::from(self).

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

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
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Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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type Error = !

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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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