}
/// Visits the given value as a union. No automatic recursion can happen here.
#[inline(always)]
- fn visit_union(&mut self, _v: Self::V) -> InterpResult<'tcx>
+ fn visit_union(&mut self, _v: Self::V, _fields: usize) -> InterpResult<'tcx>
{
Ok(())
}
) -> InterpResult<'tcx> {
self.visit_value(new_val)
}
-
/// Called when recursing into an enum variant.
+ /// This gives the visitor the chance to track the stack of nested fields that
+ /// we are descending through.
#[inline(always)]
fn visit_variant(
&mut self,
self.visit_value(new_val)
}
- /// Called whenever we reach a value with uninhabited layout.
- /// Recursing to fields will *always* continue after this! This is not meant to control
- /// whether and how we descend recursively/ into the scalar's fields if there are any,
- /// it is meant to provide the chance for additional checks when a value of uninhabited
- /// layout is detected.
- #[inline(always)]
- fn visit_uninhabited(&mut self) -> InterpResult<'tcx>
- { Ok(()) }
- /// Called whenever we reach a value with scalar layout.
- /// We do NOT provide a `ScalarMaybeUndef` here to avoid accessing memory if the
- /// visitor is not even interested in scalars.
- /// Recursing to fields will *always* continue after this! This is not meant to control
- /// whether and how we descend recursively/ into the scalar's fields if there are any,
- /// it is meant to provide the chance for additional checks when a value of scalar
- /// layout is detected.
- #[inline(always)]
- fn visit_scalar(&mut self, _v: Self::V, _layout: &layout::Scalar) -> InterpResult<'tcx>
- { Ok(()) }
-
- /// Called whenever we reach a value of primitive type. There can be no recursion
- /// below such a value. This is the leaf function.
- /// We do *not* provide an `ImmTy` here because some implementations might want
- /// to write to the place this primitive lives in.
- #[inline(always)]
- fn visit_primitive(&mut self, _v: Self::V) -> InterpResult<'tcx>
- { Ok(()) }
-
// Default recursors. Not meant to be overloaded.
fn walk_aggregate(
&mut self,
fn walk_value(&mut self, v: Self::V) -> InterpResult<'tcx>
{
trace!("walk_value: type: {}", v.layout().ty);
- // If this is a multi-variant layout, we have to find the right one and proceed with
- // that.
- match v.layout().variants {
- layout::Variants::Multiple { .. } => {
- let op = v.to_op(self.ecx())?;
- let idx = self.ecx().read_discriminant(op)?.1;
- let inner = v.project_downcast(self.ecx(), idx)?;
- trace!("walk_value: variant layout: {:#?}", inner.layout());
- // recurse with the inner type
- return self.visit_variant(v, idx, inner);
- }
- layout::Variants::Single { .. } => {}
- }
- // Even for single variants, we might be able to get a more refined type:
- // If it is a trait object, switch to the actual type that was used to create it.
+ // Special treatment for special types, where the (static) layout is not sufficient.
match v.layout().ty.kind {
+ // If it is a trait object, switch to the real type that was used to create it.
ty::Dynamic(..) => {
// immediate trait objects are not a thing
let dest = v.to_op(self.ecx())?.assert_mem_place(self.ecx());
// recurse with the inner type
return self.visit_field(v, 0, Value::from_mem_place(inner));
},
- ty::Generator(..) => {
- // FIXME: Generator layout is lying: it claims a whole bunch of fields exist
- // when really many of them can be uninitialized.
- // Just treat them as a union for now, until hopefully the layout
- // computation is fixed.
- return self.visit_union(v);
- }
+ // Slices do not need special handling here: they have `Array` field
+ // placement with length 0, so we enter the `Array` case below which
+ // indirectly uses the metadata to determine the actual length.
_ => {},
};
- // If this is a scalar, visit it as such.
- // Things can be aggregates and have scalar layout at the same time, and that
- // is very relevant for `NonNull` and similar structs: We need to visit them
- // at their scalar layout *before* descending into their fields.
- // FIXME: We could avoid some redundant checks here. For newtypes wrapping
- // scalars, we do the same check on every "level" (e.g., first we check
- // MyNewtype and then the scalar in there).
- match v.layout().abi {
- layout::Abi::Uninhabited => {
- self.visit_uninhabited()?;
- }
- layout::Abi::Scalar(ref layout) => {
- self.visit_scalar(v, layout)?;
- }
- // FIXME: Should we do something for ScalarPair? Vector?
- _ => {}
- }
-
- // Check primitive types. We do this after checking the scalar layout,
- // just to have that done as well. Primitives can have varying layout,
- // so we check them separately and before aggregate handling.
- // It is CRITICAL that we get this check right, or we might be
- // validating the wrong thing!
- let primitive = match v.layout().fields {
- // Primitives appear as Union with 0 fields - except for Boxes and fat pointers.
- layout::FieldPlacement::Union(0) => true,
- _ => v.layout().ty.builtin_deref(true).is_some(),
- };
- if primitive {
- return self.visit_primitive(v);
- }
-
- // Proceed into the fields.
+ // Visit the fields of this value.
match v.layout().fields {
layout::FieldPlacement::Union(fields) => {
- // Empty unions are not accepted by rustc. That's great, it means we can
- // use that as an unambiguous signal for detecting primitives. Make sure
- // we did not miss any primitive.
- assert!(fields > 0);
- self.visit_union(v)
+ self.visit_union(v, fields)?;
},
layout::FieldPlacement::Arbitrary { ref offsets, .. } => {
// FIXME: We collect in a vec because otherwise there are lifetime
v.project_field(self.ecx(), i as u64)
})
.collect();
- self.visit_aggregate(v, fields.into_iter())
+ self.visit_aggregate(v, fields.into_iter())?;
},
layout::FieldPlacement::Array { .. } => {
// Let's get an mplace first.
let mplace = v.to_op(self.ecx())?.assert_mem_place(self.ecx());
// Now we can go over all the fields.
+ // This uses the *run-time length*, i.e., if we are a slice,
+ // the dynamic info from the metadata is used.
let iter = self.ecx().mplace_array_fields(mplace)?
.map(|f| f.and_then(|f| {
Ok(Value::from_mem_place(f))
}));
- self.visit_aggregate(v, iter)
+ self.visit_aggregate(v, iter)?;
+ }
+ }
+
+ match v.layout().variants {
+ // If this is a multi-variant layout, find the right variant and proceed
+ // with *its* fields.
+ layout::Variants::Multiple { .. } => {
+ let op = v.to_op(self.ecx())?;
+ let idx = self.ecx().read_discriminant(op)?.1;
+ let inner = v.project_downcast(self.ecx(), idx)?;
+ trace!("walk_value: variant layout: {:#?}", inner.layout());
+ // recurse with the inner type
+ self.visit_variant(v, idx, inner)
}
+ // For single-variant layouts, we already did anything there is to do.
+ layout::Variants::Single { .. } => Ok(())
}
}
}
projects / rust.git / blobdiff