1 //! Computations on places -- field projections, going from mir::Place, and writing
3 //! All high-level functions to write to memory work on places as destinations.
5 use std::convert::TryFrom;
8 use rustc_macros::HashStable;
10 use rustc_middle::mir::interpret::truncate;
11 use rustc_middle::ty::layout::{PrimitiveExt, TyAndLayout};
12 use rustc_middle::ty::{self, Ty};
13 use rustc_target::abi::{Abi, Align, DiscriminantKind, FieldsShape};
14 use rustc_target::abi::{HasDataLayout, LayoutOf, Size, VariantIdx, Variants};
17 AllocId, AllocMap, Allocation, AllocationExtra, ImmTy, Immediate, InterpCx, InterpResult,
18 LocalValue, Machine, MemoryKind, OpTy, Operand, Pointer, PointerArithmetic, RawConst, Scalar,
22 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable)]
23 /// Information required for the sound usage of a `MemPlace`.
24 pub enum MemPlaceMeta<Tag = (), Id = AllocId> {
25 /// The unsized payload (e.g. length for slices or vtable pointer for trait objects).
26 Meta(Scalar<Tag, Id>),
27 /// `Sized` types or unsized `extern type`
29 /// The address of this place may not be taken. This protects the `MemPlace` from coming from
30 /// a ZST Operand with a backing allocation and being converted to an integer address. This
31 /// should be impossible, because you can't take the address of an operand, but this is a second
32 /// protection layer ensuring that we don't mess up.
36 impl<Tag, Id> MemPlaceMeta<Tag, Id> {
37 pub fn unwrap_meta(self) -> Scalar<Tag, Id> {
40 Self::None | Self::Poison => {
41 bug!("expected wide pointer extra data (e.g. slice length or trait object vtable)")
45 fn has_meta(self) -> bool {
47 Self::Meta(_) => true,
48 Self::None | Self::Poison => false,
53 impl<Tag> MemPlaceMeta<Tag> {
54 pub fn erase_tag(self) -> MemPlaceMeta<()> {
56 Self::Meta(s) => MemPlaceMeta::Meta(s.erase_tag()),
57 Self::None => MemPlaceMeta::None,
58 Self::Poison => MemPlaceMeta::Poison,
63 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable)]
64 pub struct MemPlace<Tag = (), Id = AllocId> {
65 /// A place may have an integral pointer for ZSTs, and since it might
66 /// be turned back into a reference before ever being dereferenced.
67 /// However, it may never be undef.
68 pub ptr: Scalar<Tag, Id>,
70 /// Metadata for unsized places. Interpretation is up to the type.
71 /// Must not be present for sized types, but can be missing for unsized types
72 /// (e.g., `extern type`).
73 pub meta: MemPlaceMeta<Tag, Id>,
76 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable)]
77 pub enum Place<Tag = (), Id = AllocId> {
78 /// A place referring to a value allocated in the `Memory` system.
79 Ptr(MemPlace<Tag, Id>),
81 /// To support alloc-free locals, we are able to write directly to a local.
82 /// (Without that optimization, we'd just always be a `MemPlace`.)
83 Local { frame: usize, local: mir::Local },
86 #[derive(Copy, Clone, Debug)]
87 pub struct PlaceTy<'tcx, Tag = ()> {
88 place: Place<Tag>, // Keep this private; it helps enforce invariants.
89 pub layout: TyAndLayout<'tcx>,
92 impl<'tcx, Tag> ::std::ops::Deref for PlaceTy<'tcx, Tag> {
93 type Target = Place<Tag>;
95 fn deref(&self) -> &Place<Tag> {
100 /// A MemPlace with its layout. Constructing it is only possible in this module.
101 #[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
102 pub struct MPlaceTy<'tcx, Tag = ()> {
103 mplace: MemPlace<Tag>,
104 pub layout: TyAndLayout<'tcx>,
107 impl<'tcx, Tag> ::std::ops::Deref for MPlaceTy<'tcx, Tag> {
108 type Target = MemPlace<Tag>;
110 fn deref(&self) -> &MemPlace<Tag> {
115 impl<'tcx, Tag> From<MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
117 fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
118 PlaceTy { place: Place::Ptr(mplace.mplace), layout: mplace.layout }
122 impl<Tag> MemPlace<Tag> {
123 /// Replace ptr tag, maintain vtable tag (if any)
125 pub fn replace_tag(self, new_tag: Tag) -> Self {
126 MemPlace { ptr: self.ptr.erase_tag().with_tag(new_tag), align: self.align, meta: self.meta }
130 pub fn erase_tag(self) -> MemPlace {
131 MemPlace { ptr: self.ptr.erase_tag(), align: self.align, meta: self.meta.erase_tag() }
135 fn from_scalar_ptr(ptr: Scalar<Tag>, align: Align) -> Self {
136 MemPlace { ptr, align, meta: MemPlaceMeta::None }
139 /// Produces a Place that will error if attempted to be read from or written to
141 fn null(cx: &impl HasDataLayout) -> Self {
142 Self::from_scalar_ptr(Scalar::null_ptr(cx), Align::from_bytes(1).unwrap())
146 pub fn from_ptr(ptr: Pointer<Tag>, align: Align) -> Self {
147 Self::from_scalar_ptr(ptr.into(), align)
150 /// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
151 /// This is the inverse of `ref_to_mplace`.
153 pub fn to_ref(self) -> Immediate<Tag> {
155 MemPlaceMeta::None => Immediate::Scalar(self.ptr.into()),
156 MemPlaceMeta::Meta(meta) => Immediate::ScalarPair(self.ptr.into(), meta.into()),
157 MemPlaceMeta::Poison => bug!(
158 "MPlaceTy::dangling may never be used to produce a \
159 place that will have the address of its pointee taken"
167 meta: MemPlaceMeta<Tag>,
168 cx: &impl HasDataLayout,
169 ) -> InterpResult<'tcx, Self> {
171 ptr: self.ptr.ptr_offset(offset, cx)?,
172 align: self.align.restrict_for_offset(offset),
178 impl<'tcx, Tag> MPlaceTy<'tcx, Tag> {
179 /// Produces a MemPlace that works for ZST but nothing else
181 pub fn dangling(layout: TyAndLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
182 let align = layout.align.abi;
183 let ptr = Scalar::from_machine_usize(align.bytes(), cx);
184 // `Poison` this to make sure that the pointer value `ptr` is never observable by the program.
185 MPlaceTy { mplace: MemPlace { ptr, align, meta: MemPlaceMeta::Poison }, layout }
188 /// Replace ptr tag, maintain vtable tag (if any)
190 pub fn replace_tag(self, new_tag: Tag) -> Self {
191 MPlaceTy { mplace: self.mplace.replace_tag(new_tag), layout: self.layout }
198 meta: MemPlaceMeta<Tag>,
199 layout: TyAndLayout<'tcx>,
200 cx: &impl HasDataLayout,
201 ) -> InterpResult<'tcx, Self> {
202 Ok(MPlaceTy { mplace: self.mplace.offset(offset, meta, cx)?, layout })
206 fn from_aligned_ptr(ptr: Pointer<Tag>, layout: TyAndLayout<'tcx>) -> Self {
207 MPlaceTy { mplace: MemPlace::from_ptr(ptr, layout.align.abi), layout }
211 pub(super) fn len(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
212 if self.layout.is_unsized() {
213 // We need to consult `meta` metadata
214 match self.layout.ty.kind {
215 ty::Slice(..) | ty::Str => self.mplace.meta.unwrap_meta().to_machine_usize(cx),
216 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
219 // Go through the layout. There are lots of types that support a length,
221 match self.layout.fields {
222 FieldsShape::Array { count, .. } => Ok(count),
223 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
229 pub(super) fn vtable(self) -> Scalar<Tag> {
230 match self.layout.ty.kind {
231 ty::Dynamic(..) => self.mplace.meta.unwrap_meta(),
232 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
237 // These are defined here because they produce a place.
238 impl<'tcx, Tag: ::std::fmt::Debug + Copy> OpTy<'tcx, Tag> {
240 /// Note: do not call `as_ref` on the resulting place. This function should only be used to
241 /// read from the resulting mplace, not to get its address back.
242 pub fn try_as_mplace(
244 cx: &impl HasDataLayout,
245 ) -> Result<MPlaceTy<'tcx, Tag>, ImmTy<'tcx, Tag>> {
247 Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
248 Operand::Immediate(_) if self.layout.is_zst() => {
249 Ok(MPlaceTy::dangling(self.layout, cx))
251 Operand::Immediate(imm) => Err(ImmTy { imm, layout: self.layout }),
256 /// Note: do not call `as_ref` on the resulting place. This function should only be used to
257 /// read from the resulting mplace, not to get its address back.
258 pub fn assert_mem_place(self, cx: &impl HasDataLayout) -> MPlaceTy<'tcx, Tag> {
259 self.try_as_mplace(cx).unwrap()
263 impl<Tag: ::std::fmt::Debug> Place<Tag> {
264 /// Produces a Place that will error if attempted to be read from or written to
266 fn null(cx: &impl HasDataLayout) -> Self {
267 Place::Ptr(MemPlace::null(cx))
271 pub fn assert_mem_place(self) -> MemPlace<Tag> {
273 Place::Ptr(mplace) => mplace,
274 _ => bug!("assert_mem_place: expected Place::Ptr, got {:?}", self),
279 impl<'tcx, Tag: ::std::fmt::Debug> PlaceTy<'tcx, Tag> {
281 pub fn assert_mem_place(self) -> MPlaceTy<'tcx, Tag> {
282 MPlaceTy { mplace: self.place.assert_mem_place(), layout: self.layout }
286 // separating the pointer tag for `impl Trait`, see https://github.com/rust-lang/rust/issues/54385
287 impl<'mir, 'tcx, Tag, M> InterpCx<'mir, 'tcx, M>
289 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
290 Tag: ::std::fmt::Debug + Copy + Eq + Hash + 'static,
291 M: Machine<'mir, 'tcx, PointerTag = Tag>,
292 // FIXME: Working around https://github.com/rust-lang/rust/issues/24159
293 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKind>, Allocation<Tag, M::AllocExtra>)>,
294 M::AllocExtra: AllocationExtra<Tag>,
296 /// Take a value, which represents a (thin or wide) reference, and make it a place.
297 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
299 /// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
300 /// want to ever use the place for memory access!
301 /// Generally prefer `deref_operand`.
302 pub fn ref_to_mplace(
304 val: ImmTy<'tcx, M::PointerTag>,
305 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
307 val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty;
308 let layout = self.layout_of(pointee_type)?;
309 let (ptr, meta) = match *val {
310 Immediate::Scalar(ptr) => (ptr.not_undef()?, MemPlaceMeta::None),
311 Immediate::ScalarPair(ptr, meta) => {
312 (ptr.not_undef()?, MemPlaceMeta::Meta(meta.not_undef()?))
316 let mplace = MemPlace {
318 // We could use the run-time alignment here. For now, we do not, because
319 // the point of tracking the alignment here is to make sure that the *static*
320 // alignment information emitted with the loads is correct. The run-time
321 // alignment can only be more restrictive.
322 align: layout.align.abi,
325 Ok(MPlaceTy { mplace, layout })
328 /// Take an operand, representing a pointer, and dereference it to a place -- that
329 /// will always be a MemPlace. Lives in `place.rs` because it creates a place.
330 pub fn deref_operand(
332 src: OpTy<'tcx, M::PointerTag>,
333 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
334 let val = self.read_immediate(src)?;
335 trace!("deref to {} on {:?}", val.layout.ty, *val);
336 let place = self.ref_to_mplace(val)?;
337 self.mplace_access_checked(place)
340 /// Check if the given place is good for memory access with the given
341 /// size, falling back to the layout's size if `None` (in the latter case,
342 /// this must be a statically sized type).
344 /// On success, returns `None` for zero-sized accesses (where nothing else is
345 /// left to do) and a `Pointer` to use for the actual access otherwise.
347 pub(super) fn check_mplace_access(
349 place: MPlaceTy<'tcx, M::PointerTag>,
351 ) -> InterpResult<'tcx, Option<Pointer<M::PointerTag>>> {
352 let size = size.unwrap_or_else(|| {
353 assert!(!place.layout.is_unsized());
354 assert!(!place.meta.has_meta());
357 self.memory.check_ptr_access(place.ptr, size, place.align)
360 /// Return the "access-checked" version of this `MPlace`, where for non-ZST
361 /// this is definitely a `Pointer`.
362 pub fn mplace_access_checked(
364 mut place: MPlaceTy<'tcx, M::PointerTag>,
365 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
366 let (size, align) = self
367 .size_and_align_of_mplace(place)?
368 .unwrap_or((place.layout.size, place.layout.align.abi));
369 assert!(place.mplace.align <= align, "dynamic alignment less strict than static one?");
370 place.mplace.align = align; // maximally strict checking
371 // When dereferencing a pointer, it must be non-NULL, aligned, and live.
372 if let Some(ptr) = self.check_mplace_access(place, Some(size))? {
373 place.mplace.ptr = ptr.into();
378 /// Force `place.ptr` to a `Pointer`.
379 /// Can be helpful to avoid lots of `force_ptr` calls later, if this place is used a lot.
380 pub(super) fn force_mplace_ptr(
382 mut place: MPlaceTy<'tcx, M::PointerTag>,
383 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
384 place.mplace.ptr = self.force_ptr(place.mplace.ptr)?.into();
388 /// Offset a pointer to project to a field of a struct/union. Unlike `place_field`, this is
389 /// always possible without allocating, so it can take `&self`. Also return the field's layout.
390 /// This supports both struct and array fields.
392 /// This also works for arrays, but then the `usize` index type is restricting.
393 /// For indexing into arrays, use `mplace_index`.
397 base: MPlaceTy<'tcx, M::PointerTag>,
399 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
400 let offset = base.layout.fields.offset(field);
401 let field_layout = base.layout.field(self, field)?;
403 // Offset may need adjustment for unsized fields.
404 let (meta, offset) = if field_layout.is_unsized() {
405 // Re-use parent metadata to determine dynamic field layout.
406 // With custom DSTS, this *will* execute user-defined code, but the same
407 // happens at run-time so that's okay.
408 let align = match self.size_and_align_of(base.meta, field_layout)? {
409 Some((_, align)) => align,
410 None if offset == Size::ZERO => {
411 // An extern type at offset 0, we fall back to its static alignment.
412 // FIXME: Once we have made decisions for how to handle size and alignment
413 // of `extern type`, this should be adapted. It is just a temporary hack
414 // to get some code to work that probably ought to work.
415 field_layout.align.abi
417 None => bug!("Cannot compute offset for extern type field at non-0 offset"),
419 (base.meta, offset.align_to(align))
421 // base.meta could be present; we might be accessing a sized field of an unsized
423 (MemPlaceMeta::None, offset)
426 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
427 // codegen -- mostly to see if we can get away with that
428 base.offset(offset, meta, field_layout, self)
431 /// Index into an array.
435 base: MPlaceTy<'tcx, M::PointerTag>,
437 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
438 // Not using the layout method because we want to compute on u64
439 match base.layout.fields {
440 FieldsShape::Array { stride, .. } => {
441 let len = base.len(self)?;
443 // This can only be reached in ConstProp and non-rustc-MIR.
444 throw_ub!(BoundsCheckFailed { len, index });
446 let offset = stride * index; // `Size` multiplication
447 // All fields have the same layout.
448 let field_layout = base.layout.field(self, 0)?;
450 assert!(!field_layout.is_unsized());
451 base.offset(offset, MemPlaceMeta::None, field_layout, self)
453 _ => bug!("`mplace_index` called on non-array type {:?}", base.layout.ty),
457 // Iterates over all fields of an array. Much more efficient than doing the
458 // same by repeatedly calling `mplace_array`.
459 pub(super) fn mplace_array_fields(
461 base: MPlaceTy<'tcx, Tag>,
462 ) -> InterpResult<'tcx, impl Iterator<Item = InterpResult<'tcx, MPlaceTy<'tcx, Tag>>> + 'tcx>
464 let len = base.len(self)?; // also asserts that we have a type where this makes sense
465 let stride = match base.layout.fields {
466 FieldsShape::Array { stride, .. } => stride,
467 _ => bug!("mplace_array_fields: expected an array layout"),
469 let layout = base.layout.field(self, 0)?;
470 let dl = &self.tcx.data_layout;
471 // `Size` multiplication
472 Ok((0..len).map(move |i| base.offset(stride * i, MemPlaceMeta::None, layout, dl)))
477 base: MPlaceTy<'tcx, M::PointerTag>,
481 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
482 let len = base.len(self)?; // also asserts that we have a type where this makes sense
483 let actual_to = if from_end {
484 if from.checked_add(to).map_or(true, |to| to > len) {
485 // This can only be reached in ConstProp and non-rustc-MIR.
486 throw_ub!(BoundsCheckFailed { len: len, index: from.saturating_add(to) });
488 len.checked_sub(to).unwrap()
493 // Not using layout method because that works with usize, and does not work with slices
494 // (that have count 0 in their layout).
495 let from_offset = match base.layout.fields {
496 FieldsShape::Array { stride, .. } => stride * from, // `Size` multiplication is checked
497 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
500 // Compute meta and new layout
501 let inner_len = actual_to.checked_sub(from).unwrap();
502 let (meta, ty) = match base.layout.ty.kind {
503 // It is not nice to match on the type, but that seems to be the only way to
505 ty::Array(inner, _) => (MemPlaceMeta::None, self.tcx.mk_array(inner, inner_len)),
507 let len = Scalar::from_machine_usize(inner_len, self);
508 (MemPlaceMeta::Meta(len), base.layout.ty)
510 _ => bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
512 let layout = self.layout_of(ty)?;
513 base.offset(from_offset, meta, layout, self)
516 pub(super) fn mplace_downcast(
518 base: MPlaceTy<'tcx, M::PointerTag>,
520 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
521 // Downcasts only change the layout
522 assert!(!base.meta.has_meta());
523 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
526 /// Project into an mplace
527 pub(super) fn mplace_projection(
529 base: MPlaceTy<'tcx, M::PointerTag>,
530 proj_elem: &mir::PlaceElem<'tcx>,
531 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
532 use rustc_middle::mir::ProjectionElem::*;
533 Ok(match *proj_elem {
534 Field(field, _) => self.mplace_field(base, field.index())?,
535 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
536 Deref => self.deref_operand(base.into())?,
539 let layout = self.layout_of(self.tcx.types.usize)?;
540 let n = self.access_local(self.frame(), local, Some(layout))?;
541 let n = self.read_scalar(n)?;
542 let n = u64::try_from(
543 self.force_bits(n.not_undef()?, self.tcx.data_layout.pointer_size)?,
546 self.mplace_index(base, n)?
549 ConstantIndex { offset, min_length, from_end } => {
550 let n = base.len(self)?;
551 if n < u64::from(min_length) {
552 // This can only be reached in ConstProp and non-rustc-MIR.
553 throw_ub!(BoundsCheckFailed { len: min_length.into(), index: n.into() });
556 let index = if from_end {
557 assert!(0 < offset && offset <= min_length);
558 n.checked_sub(u64::from(offset)).unwrap()
560 assert!(offset < min_length);
564 self.mplace_index(base, index)?
567 Subslice { from, to, from_end } => {
568 self.mplace_subslice(base, u64::from(from), u64::from(to), from_end)?
573 /// Gets the place of a field inside the place, and also the field's type.
574 /// Just a convenience function, but used quite a bit.
575 /// This is the only projection that might have a side-effect: We cannot project
576 /// into the field of a local `ScalarPair`, we have to first allocate it.
579 base: PlaceTy<'tcx, M::PointerTag>,
581 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
582 // FIXME: We could try to be smarter and avoid allocation for fields that span the
584 let mplace = self.force_allocation(base)?;
585 Ok(self.mplace_field(mplace, field)?.into())
590 base: PlaceTy<'tcx, M::PointerTag>,
592 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
593 let mplace = self.force_allocation(base)?;
594 Ok(self.mplace_index(mplace, index)?.into())
597 pub fn place_downcast(
599 base: PlaceTy<'tcx, M::PointerTag>,
601 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
602 // Downcast just changes the layout
603 Ok(match base.place {
604 Place::Ptr(mplace) => {
605 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into()
607 Place::Local { .. } => {
608 let layout = base.layout.for_variant(self, variant);
609 PlaceTy { layout, ..base }
614 /// Projects into a place.
615 pub fn place_projection(
617 base: PlaceTy<'tcx, M::PointerTag>,
618 proj_elem: &mir::ProjectionElem<mir::Local, Ty<'tcx>>,
619 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
620 use rustc_middle::mir::ProjectionElem::*;
621 Ok(match *proj_elem {
622 Field(field, _) => self.place_field(base, field.index())?,
623 Downcast(_, variant) => self.place_downcast(base, variant)?,
624 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
625 // For the other variants, we have to force an allocation.
626 // This matches `operand_projection`.
627 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
628 let mplace = self.force_allocation(base)?;
629 self.mplace_projection(mplace, proj_elem)?.into()
634 /// Computes a place. You should only use this if you intend to write into this
635 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
638 place: mir::Place<'tcx>,
639 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
640 let mut place_ty = match place.local {
641 mir::RETURN_PLACE => {
642 // `return_place` has the *caller* layout, but we want to use our
643 // `layout to verify our assumption. The caller will validate
644 // their layout on return.
646 place: match self.frame().return_place {
648 // Even if we don't have a return place, we sometimes need to
649 // create this place, but any attempt to read from / write to it
650 // (even a ZST read/write) needs to error, so let us make this
653 // FIXME: Ideally we'd make sure that the place projections also
655 None => Place::null(&*self),
657 layout: self.layout_of(
658 self.subst_from_current_frame_and_normalize_erasing_regions(
659 self.frame().body.return_ty(),
665 // This works even for dead/uninitialized locals; we check further when writing
666 place: Place::Local { frame: self.cur_frame(), local },
667 layout: self.layout_of_local(self.frame(), local, None)?,
671 for elem in place.projection.iter() {
672 place_ty = self.place_projection(place_ty, elem)?
675 self.dump_place(place_ty.place);
679 /// Write a scalar to a place
683 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
684 dest: PlaceTy<'tcx, M::PointerTag>,
685 ) -> InterpResult<'tcx> {
686 self.write_immediate(Immediate::Scalar(val.into()), dest)
689 /// Write an immediate to a place
691 pub fn write_immediate(
693 src: Immediate<M::PointerTag>,
694 dest: PlaceTy<'tcx, M::PointerTag>,
695 ) -> InterpResult<'tcx> {
696 self.write_immediate_no_validate(src, dest)?;
698 if M::enforce_validity(self) {
699 // Data got changed, better make sure it matches the type!
700 self.validate_operand(self.place_to_op(dest)?)?;
706 /// Write an `Immediate` to memory.
708 pub fn write_immediate_to_mplace(
710 src: Immediate<M::PointerTag>,
711 dest: MPlaceTy<'tcx, M::PointerTag>,
712 ) -> InterpResult<'tcx> {
713 self.write_immediate_to_mplace_no_validate(src, dest)?;
715 if M::enforce_validity(self) {
716 // Data got changed, better make sure it matches the type!
717 self.validate_operand(dest.into())?;
723 /// Write an immediate to a place.
724 /// If you use this you are responsible for validating that things got copied at the
726 fn write_immediate_no_validate(
728 src: Immediate<M::PointerTag>,
729 dest: PlaceTy<'tcx, M::PointerTag>,
730 ) -> InterpResult<'tcx> {
731 if cfg!(debug_assertions) {
732 // This is a very common path, avoid some checks in release mode
733 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
735 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) => assert_eq!(
738 "Size mismatch when writing pointer"
740 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Raw { size, .. })) => {
742 Size::from_bytes(size),
744 "Size mismatch when writing bits"
747 Immediate::Scalar(ScalarMaybeUndef::Undef) => {} // undef can have any size
748 Immediate::ScalarPair(_, _) => {
749 // FIXME: Can we check anything here?
753 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
755 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
756 // but not factored as a separate function.
757 let mplace = match dest.place {
758 Place::Local { frame, local } => {
759 match self.stack[frame].locals[local].access_mut()? {
761 // Local can be updated in-place.
762 *local = LocalValue::Live(Operand::Immediate(src));
766 // The local is in memory, go on below.
771 Place::Ptr(mplace) => mplace, // already referring to memory
773 let dest = MPlaceTy { mplace, layout: dest.layout };
775 // This is already in memory, write there.
776 self.write_immediate_to_mplace_no_validate(src, dest)
779 /// Write an immediate to memory.
780 /// If you use this you are responsible for validating that things got copied at the
782 fn write_immediate_to_mplace_no_validate(
784 value: Immediate<M::PointerTag>,
785 dest: MPlaceTy<'tcx, M::PointerTag>,
786 ) -> InterpResult<'tcx> {
787 // Note that it is really important that the type here is the right one, and matches the
788 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
789 // to handle padding properly, which is only correct if we never look at this data with the
792 // Invalid places are a thing: the return place of a diverging function
793 let ptr = match self.check_mplace_access(dest, None)? {
795 None => return Ok(()), // zero-sized access
798 let tcx = &*self.tcx;
799 // FIXME: We should check that there are dest.layout.size many bytes available in
800 // memory. The code below is not sufficient, with enough padding it might not
801 // cover all the bytes!
803 Immediate::Scalar(scalar) => {
804 match dest.layout.abi {
805 Abi::Scalar(_) => {} // fine
807 bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}", dest.layout)
810 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(
817 Immediate::ScalarPair(a_val, b_val) => {
818 // We checked `ptr_align` above, so all fields will have the alignment they need.
819 // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
820 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
821 let (a, b) = match dest.layout.abi {
822 Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
824 "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
828 let (a_size, b_size) = (a.size(self), b.size(self));
829 let b_offset = a_size.align_to(b.align(self).abi);
830 let b_ptr = ptr.offset(b_offset, self)?;
832 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
833 // but that does not work: We could be a newtype around a pair, then the
834 // fields do not match the `ScalarPair` components.
836 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(tcx, ptr, a_val, a_size)?;
837 self.memory.get_raw_mut(b_ptr.alloc_id)?.write_scalar(tcx, b_ptr, b_val, b_size)
842 /// Copies the data from an operand to a place. This does not support transmuting!
843 /// Use `copy_op_transmute` if the layouts could disagree.
847 src: OpTy<'tcx, M::PointerTag>,
848 dest: PlaceTy<'tcx, M::PointerTag>,
849 ) -> InterpResult<'tcx> {
850 self.copy_op_no_validate(src, dest)?;
852 if M::enforce_validity(self) {
853 // Data got changed, better make sure it matches the type!
854 self.validate_operand(self.place_to_op(dest)?)?;
860 /// Copies the data from an operand to a place. This does not support transmuting!
861 /// Use `copy_op_transmute` if the layouts could disagree.
862 /// Also, if you use this you are responsible for validating that things get copied at the
864 fn copy_op_no_validate(
866 src: OpTy<'tcx, M::PointerTag>,
867 dest: PlaceTy<'tcx, M::PointerTag>,
868 ) -> InterpResult<'tcx> {
869 // We do NOT compare the types for equality, because well-typed code can
870 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
872 src.layout.layout == dest.layout.layout,
873 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}",
878 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
879 let src = match self.try_read_immediate(src)? {
881 assert!(!src.layout.is_unsized(), "cannot have unsized immediates");
882 // Yay, we got a value that we can write directly.
883 // FIXME: Add a check to make sure that if `src` is indirect,
884 // it does not overlap with `dest`.
885 return self.write_immediate_no_validate(*src_val, dest);
887 Err(mplace) => mplace,
889 // Slow path, this does not fit into an immediate. Just memcpy.
890 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
892 // This interprets `src.meta` with the `dest` local's layout, if an unsized local
893 // is being initialized!
894 let (dest, size) = self.force_allocation_maybe_sized(dest, src.meta)?;
895 let size = size.unwrap_or_else(|| {
897 !dest.layout.is_unsized(),
898 "Cannot copy into already initialized unsized place"
902 assert_eq!(src.meta, dest.meta, "Can only copy between equally-sized instances");
905 .check_mplace_access(src, Some(size))
906 .expect("places should be checked on creation");
908 .check_mplace_access(dest, Some(size))
909 .expect("places should be checked on creation");
910 let (src_ptr, dest_ptr) = match (src, dest) {
911 (Some(src_ptr), Some(dest_ptr)) => (src_ptr, dest_ptr),
912 (None, None) => return Ok(()), // zero-sized copy
913 _ => bug!("The pointers should both be Some or both None"),
916 self.memory.copy(src_ptr, dest_ptr, size, /*nonoverlapping*/ true)
919 /// Copies the data from an operand to a place. The layouts may disagree, but they must
920 /// have the same size.
921 pub fn copy_op_transmute(
923 src: OpTy<'tcx, M::PointerTag>,
924 dest: PlaceTy<'tcx, M::PointerTag>,
925 ) -> InterpResult<'tcx> {
926 if src.layout.layout == dest.layout.layout {
927 // Fast path: Just use normal `copy_op`
928 return self.copy_op(src, dest);
930 // We still require the sizes to match.
931 if src.layout.size != dest.layout.size {
932 // FIXME: This should be an assert instead of an error, but if we transmute within an
933 // array length computation, `typeck` may not have yet been run and errored out. In fact
934 // most likey we *are* running `typeck` right now. Investigate whether we can bail out
935 // on `typeck_tables().has_errors` at all const eval entry points.
936 debug!("Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
937 self.tcx.sess.delay_span_bug(
939 "size-changing transmute, should have been caught by transmute checking",
941 throw_inval!(TransmuteSizeDiff(src.layout.ty, dest.layout.ty));
943 // Unsized copies rely on interpreting `src.meta` with `dest.layout`, we want
944 // to avoid that here.
946 !src.layout.is_unsized() && !dest.layout.is_unsized(),
947 "Cannot transmute unsized data"
950 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
951 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
952 // We have to write them to `dest` at the offsets they were *read at*, which is
953 // not necessarily the same as the offsets in `dest.layout`!
954 // Hence we do the copy with the source layout on both sides. We also make sure to write
955 // into memory, because if `dest` is a local we would not even have a way to write
956 // at the `src` offsets; the fact that we came from a different layout would
958 let dest = self.force_allocation(dest)?;
959 self.copy_op_no_validate(
961 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
964 if M::enforce_validity(self) {
965 // Data got changed, better make sure it matches the type!
966 self.validate_operand(dest.into())?;
972 /// Ensures that a place is in memory, and returns where it is.
973 /// If the place currently refers to a local that doesn't yet have a matching allocation,
974 /// create such an allocation.
975 /// This is essentially `force_to_memplace`.
977 /// This supports unsized types and returns the computed size to avoid some
978 /// redundant computation when copying; use `force_allocation` for a simpler, sized-only
980 pub fn force_allocation_maybe_sized(
982 place: PlaceTy<'tcx, M::PointerTag>,
983 meta: MemPlaceMeta<M::PointerTag>,
984 ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::PointerTag>, Option<Size>)> {
985 let (mplace, size) = match place.place {
986 Place::Local { frame, local } => {
987 match self.stack[frame].locals[local].access_mut()? {
988 Ok(&mut local_val) => {
989 // We need to make an allocation.
991 // We need the layout of the local. We can NOT use the layout we got,
992 // that might e.g., be an inner field of a struct with `Scalar` layout,
993 // that has different alignment than the outer field.
994 let local_layout = self.layout_of_local(&self.stack[frame], local, None)?;
995 // We also need to support unsized types, and hence cannot use `allocate`.
996 let (size, align) = self
997 .size_and_align_of(meta, local_layout)?
998 .expect("Cannot allocate for non-dyn-sized type");
999 let ptr = self.memory.allocate(size, align, MemoryKind::Stack);
1000 let mplace = MemPlace { ptr: ptr.into(), align, meta };
1001 if let LocalValue::Live(Operand::Immediate(value)) = local_val {
1002 // Preserve old value.
1003 // We don't have to validate as we can assume the local
1004 // was already valid for its type.
1005 let mplace = MPlaceTy { mplace, layout: local_layout };
1006 self.write_immediate_to_mplace_no_validate(value, mplace)?;
1008 // Now we can call `access_mut` again, asserting it goes well,
1009 // and actually overwrite things.
1010 *self.stack[frame].locals[local].access_mut().unwrap().unwrap() =
1011 LocalValue::Live(Operand::Indirect(mplace));
1012 (mplace, Some(size))
1014 Err(mplace) => (mplace, None), // this already was an indirect local
1017 Place::Ptr(mplace) => (mplace, None),
1019 // Return with the original layout, so that the caller can go on
1020 Ok((MPlaceTy { mplace, layout: place.layout }, size))
1024 pub fn force_allocation(
1026 place: PlaceTy<'tcx, M::PointerTag>,
1027 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1028 Ok(self.force_allocation_maybe_sized(place, MemPlaceMeta::None)?.0)
1033 layout: TyAndLayout<'tcx>,
1034 kind: MemoryKind<M::MemoryKind>,
1035 ) -> MPlaceTy<'tcx, M::PointerTag> {
1036 let ptr = self.memory.allocate(layout.size, layout.align.abi, kind);
1037 MPlaceTy::from_aligned_ptr(ptr, layout)
1040 /// Returns a wide MPlace.
1041 pub fn allocate_str(
1044 kind: MemoryKind<M::MemoryKind>,
1045 ) -> MPlaceTy<'tcx, M::PointerTag> {
1046 let ptr = self.memory.allocate_bytes(str.as_bytes(), kind);
1047 let meta = Scalar::from_machine_usize(u64::try_from(str.len()).unwrap(), self);
1048 let mplace = MemPlace {
1050 align: Align::from_bytes(1).unwrap(),
1051 meta: MemPlaceMeta::Meta(meta),
1054 let layout = self.layout_of(self.tcx.mk_static_str()).unwrap();
1055 MPlaceTy { mplace, layout }
1058 pub fn write_discriminant_index(
1060 variant_index: VariantIdx,
1061 dest: PlaceTy<'tcx, M::PointerTag>,
1062 ) -> InterpResult<'tcx> {
1063 // Layout computation excludes uninhabited variants from consideration
1064 // therefore there's no way to represent those variants in the given layout.
1065 if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() {
1066 throw_ub!(Unreachable);
1069 match dest.layout.variants {
1070 Variants::Single { index } => {
1071 assert_eq!(index, variant_index);
1073 Variants::Multiple {
1074 discr_kind: DiscriminantKind::Tag,
1075 discr: ref discr_layout,
1079 // No need to validate that the discriminant here because the
1080 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
1083 dest.layout.ty.discriminant_for_variant(*self.tcx, variant_index).unwrap().val;
1085 // raw discriminants for enums are isize or bigger during
1086 // their computation, but the in-memory tag is the smallest possible
1088 let size = discr_layout.value.size(self);
1089 let discr_val = truncate(discr_val, size);
1091 let discr_dest = self.place_field(dest, discr_index)?;
1092 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
1094 Variants::Multiple {
1096 DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start },
1097 discr: ref discr_layout,
1101 // No need to validate that the discriminant here because the
1102 // `TyAndLayout::for_variant()` call earlier already checks the variant is valid.
1104 if variant_index != dataful_variant {
1105 let variants_start = niche_variants.start().as_u32();
1106 let variant_index_relative = variant_index
1108 .checked_sub(variants_start)
1109 .expect("overflow computing relative variant idx");
1110 // We need to use machine arithmetic when taking into account `niche_start`:
1111 // discr_val = variant_index_relative + niche_start_val
1112 let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
1113 let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
1114 let variant_index_relative_val =
1115 ImmTy::from_uint(variant_index_relative, discr_layout);
1116 let discr_val = self.binary_op(
1118 variant_index_relative_val,
1122 let niche_dest = self.place_field(dest, discr_index)?;
1123 self.write_immediate(*discr_val, niche_dest)?;
1131 pub fn raw_const_to_mplace(
1133 raw: RawConst<'tcx>,
1134 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1135 // This must be an allocation in `tcx`
1136 assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
1137 let ptr = self.tag_global_base_pointer(Pointer::from(raw.alloc_id));
1138 let layout = self.layout_of(raw.ty)?;
1139 Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
1142 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
1143 /// Also return some more information so drop doesn't have to run the same code twice.
1144 pub(super) fn unpack_dyn_trait(
1146 mplace: MPlaceTy<'tcx, M::PointerTag>,
1147 ) -> InterpResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
1148 let vtable = mplace.vtable(); // also sanity checks the type
1149 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
1150 let layout = self.layout_of(ty)?;
1152 // More sanity checks
1153 if cfg!(debug_assertions) {
1154 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
1155 assert_eq!(size, layout.size);
1156 // only ABI alignment is preserved
1157 assert_eq!(align, layout.align.abi);
1160 let mplace = MPlaceTy { mplace: MemPlace { meta: MemPlaceMeta::None, ..*mplace }, layout };
1161 Ok((instance, mplace))