bjoernager/rust
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fix dynamically determining size and alignment

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This commit is contained in:
Ralf Jung 2018-08-16 09:05:01 +02:00
parent e314a4e75f
commit 61e7ba15fd
1 changed files with 20 additions and 17 deletions
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37
src/librustc_mir/interpret/eval_context.rs
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@ -24,7 +24,7 @@ use syntax::source_map::{self, Span};
use syntax::ast::Mutability;
use super::{
Value, ValTy, Operand, MemPlace, MPlaceTy, Place, PlaceExtra,
Value, Operand, MemPlace, MPlaceTy, Place, PlaceExtra,
Memory, Machine
};
@ -466,18 +466,19 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
self.layout_of(local_ty)
}
/// Return the size and alignment of the value at the given type.
/// Return the actual dynamic size and alignment of the place at the given type.
/// Note that the value does not matter if the type is sized. For unsized types,
/// the value has to be a fat pointer, and we only care about the "extra" data in it.
pub fn size_and_align_of_val(
pub fn size_and_align_of_mplace(
&self,
val: ValTy<'tcx>,
mplace: MPlaceTy<'tcx>,
) -> EvalResult<'tcx, (Size, Align)> {
let pointee_ty = val.layout.ty.builtin_deref(true).unwrap().ty;
let layout = self.layout_of(pointee_ty)?;
if !layout.is_unsized() {
Ok(layout.size_and_align())
if let PlaceExtra::None = mplace.extra {
assert!(!mplace.layout.is_unsized());
Ok(mplace.layout.size_and_align())
} else {
let layout = mplace.layout;
assert!(layout.is_unsized());
match layout.ty.sty {
ty::TyAdt(..) | ty::TyTuple(..) => {
// First get the size of all statically known fields.
@ -498,12 +499,8 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
// Recurse to get the size of the dynamically sized field (must be
// the last field).
let field_layout = layout.field(self, layout.fields.count() - 1)?;
let (unsized_size, unsized_align) =
self.size_and_align_of_val(ValTy {
value: val.value,
layout: field_layout
})?;
let field = self.mplace_field(mplace, layout.fields.count() as u64 - 1)?;
let (unsized_size, unsized_align) = self.size_and_align_of_mplace(field)?;
// FIXME (#26403, #27023): We should be adding padding
// to `sized_size` (to accommodate the `unsized_align`
@ -533,18 +530,24 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
Ok((size.abi_align(align), align))
}
ty::TyDynamic(..) => {
let (_, vtable) = val.to_scalar_dyn_trait()?;
let vtable = match mplace.extra {
PlaceExtra::Vtable(vtable) => vtable,
_ => bug!("Expected vtable"),
};
// the second entry in the vtable is the dynamic size of the object.
self.read_size_and_align_from_vtable(vtable)
}
ty::TySlice(_) | ty::TyStr => {
let len = match mplace.extra {
PlaceExtra::Length(len) => len,
_ => bug!("Expected length"),
};
let (elem_size, align) = layout.field(self, 0)?.size_and_align();
let (_, len) = val.to_scalar_slice(self)?;
Ok((elem_size * len, align))
}
_ => bug!("size_of_val::<{:?}>", layout.ty),
_ => bug!("size_of_val::<{:?}> not supported", layout.ty),
}
}
}