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;
9 use rustc::mir::interpret::truncate;
10 use rustc::ty::layout::{
11 self, Align, HasDataLayout, LayoutOf, PrimitiveExt, Size, TyLayout, VariantIdx,
13 use rustc::ty::{self, Ty};
14 use rustc_macros::HashStable;
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: TyLayout<'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: TyLayout<'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::ptr_null(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: TyLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
182 let align = layout.align.abi;
183 let ptr = Scalar::from_uint(align.bytes(), cx.pointer_size());
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: TyLayout<'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: TyLayout<'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 => {
216 return self.mplace.meta.unwrap_meta().to_machine_usize(cx);
218 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
221 // Go through the layout. There are lots of types that support a length,
223 match self.layout.fields {
224 layout::FieldPlacement::Array { count, .. } => Ok(count),
225 _ => bug!("len not supported on sized type {:?}", self.layout.ty),
231 pub(super) fn vtable(self) -> Scalar<Tag> {
232 match self.layout.ty.kind {
233 ty::Dynamic(..) => self.mplace.meta.unwrap_meta(),
234 _ => bug!("vtable not supported on type {:?}", self.layout.ty),
239 // These are defined here because they produce a place.
240 impl<'tcx, Tag: ::std::fmt::Debug + Copy> OpTy<'tcx, Tag> {
242 /// Note: do not call `as_ref` on the resulting place. This function should only be used to
243 /// read from the resulting mplace, not to get its address back.
244 pub fn try_as_mplace(
246 cx: &impl HasDataLayout,
247 ) -> Result<MPlaceTy<'tcx, Tag>, ImmTy<'tcx, Tag>> {
249 Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
250 Operand::Immediate(_) if self.layout.is_zst() => {
251 Ok(MPlaceTy::dangling(self.layout, cx))
253 Operand::Immediate(imm) => Err(ImmTy { imm, layout: self.layout }),
258 /// Note: do not call `as_ref` on the resulting place. This function should only be used to
259 /// read from the resulting mplace, not to get its address back.
260 pub fn assert_mem_place(self, cx: &impl HasDataLayout) -> MPlaceTy<'tcx, Tag> {
261 self.try_as_mplace(cx).unwrap()
265 impl<Tag: ::std::fmt::Debug> Place<Tag> {
266 /// Produces a Place that will error if attempted to be read from or written to
268 fn null(cx: &impl HasDataLayout) -> Self {
269 Place::Ptr(MemPlace::null(cx))
273 pub fn assert_mem_place(self) -> MemPlace<Tag> {
275 Place::Ptr(mplace) => mplace,
276 _ => bug!("assert_mem_place: expected Place::Ptr, got {:?}", self),
281 impl<'tcx, Tag: ::std::fmt::Debug> PlaceTy<'tcx, Tag> {
283 pub fn assert_mem_place(self) -> MPlaceTy<'tcx, Tag> {
284 MPlaceTy { mplace: self.place.assert_mem_place(), layout: self.layout }
288 // separating the pointer tag for `impl Trait`, see https://github.com/rust-lang/rust/issues/54385
289 impl<'mir, 'tcx, Tag, M> InterpCx<'mir, 'tcx, M>
291 // FIXME: Working around https://github.com/rust-lang/rust/issues/54385
292 Tag: ::std::fmt::Debug + Copy + Eq + Hash + 'static,
293 M: Machine<'mir, 'tcx, PointerTag = Tag>,
294 // FIXME: Working around https://github.com/rust-lang/rust/issues/24159
295 M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag, M::AllocExtra>)>,
296 M::AllocExtra: AllocationExtra<Tag>,
298 /// Take a value, which represents a (thin or wide) reference, and make it a place.
299 /// Alignment is just based on the type. This is the inverse of `MemPlace::to_ref()`.
301 /// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
302 /// want to ever use the place for memory access!
303 /// Generally prefer `deref_operand`.
304 pub fn ref_to_mplace(
306 val: ImmTy<'tcx, M::PointerTag>,
307 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
309 val.layout.ty.builtin_deref(true).expect("`ref_to_mplace` called on non-ptr type").ty;
310 let layout = self.layout_of(pointee_type)?;
311 let (ptr, meta) = match *val {
312 Immediate::Scalar(ptr) => (ptr.not_undef()?, MemPlaceMeta::None),
313 Immediate::ScalarPair(ptr, meta) => {
314 (ptr.not_undef()?, MemPlaceMeta::Meta(meta.not_undef()?))
318 let mplace = MemPlace {
320 // We could use the run-time alignment here. For now, we do not, because
321 // the point of tracking the alignment here is to make sure that the *static*
322 // alignment information emitted with the loads is correct. The run-time
323 // alignment can only be more restrictive.
324 align: layout.align.abi,
327 Ok(MPlaceTy { mplace, layout })
330 /// Take an operand, representing a pointer, and dereference it to a place -- that
331 /// will always be a MemPlace. Lives in `place.rs` because it creates a place.
332 pub fn deref_operand(
334 src: OpTy<'tcx, M::PointerTag>,
335 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
336 let val = self.read_immediate(src)?;
337 trace!("deref to {} on {:?}", val.layout.ty, *val);
338 let place = self.ref_to_mplace(val)?;
339 self.mplace_access_checked(place)
342 /// Check if the given place is good for memory access with the given
343 /// size, falling back to the layout's size if `None` (in the latter case,
344 /// this must be a statically sized type).
346 /// On success, returns `None` for zero-sized accesses (where nothing else is
347 /// left to do) and a `Pointer` to use for the actual access otherwise.
349 pub(super) fn check_mplace_access(
351 place: MPlaceTy<'tcx, M::PointerTag>,
353 ) -> InterpResult<'tcx, Option<Pointer<M::PointerTag>>> {
354 let size = size.unwrap_or_else(|| {
355 assert!(!place.layout.is_unsized());
356 assert!(!place.meta.has_meta());
359 self.memory.check_ptr_access(place.ptr, size, place.align)
362 /// Return the "access-checked" version of this `MPlace`, where for non-ZST
363 /// this is definitely a `Pointer`.
364 pub fn mplace_access_checked(
366 mut place: MPlaceTy<'tcx, M::PointerTag>,
367 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
368 let (size, align) = self
369 .size_and_align_of_mplace(place)?
370 .unwrap_or((place.layout.size, place.layout.align.abi));
371 assert!(place.mplace.align <= align, "dynamic alignment less strict than static one?");
372 place.mplace.align = align; // maximally strict checking
373 // When dereferencing a pointer, it must be non-NULL, aligned, and live.
374 if let Some(ptr) = self.check_mplace_access(place, Some(size))? {
375 place.mplace.ptr = ptr.into();
380 /// Force `place.ptr` to a `Pointer`.
381 /// Can be helpful to avoid lots of `force_ptr` calls later, if this place is used a lot.
382 pub(super) fn force_mplace_ptr(
384 mut place: MPlaceTy<'tcx, M::PointerTag>,
385 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
386 place.mplace.ptr = self.force_ptr(place.mplace.ptr)?.into();
390 /// Offset a pointer to project to a field. Unlike `place_field`, this is always
391 /// possible without allocating, so it can take `&self`. Also return the field's layout.
392 /// This supports both struct and array fields.
396 base: MPlaceTy<'tcx, M::PointerTag>,
398 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
399 // Not using the layout method because we want to compute on u64
400 let offset = match base.layout.fields {
401 layout::FieldPlacement::Arbitrary { ref offsets, .. } => {
402 offsets[usize::try_from(field).unwrap()]
404 layout::FieldPlacement::Array { stride, .. } => {
405 let len = base.len(self)?;
407 // This can only be reached in ConstProp and non-rustc-MIR.
408 throw_ub!(BoundsCheckFailed { len, index: field });
412 layout::FieldPlacement::Union(count) => {
413 // This is a narrow bug-fix for rust-lang/rust#69191: if we are
414 // trying to access absent field of uninhabited variant, then
415 // signal UB (but don't ICE the compiler).
416 // FIXME temporary hack to work around incoherence between
417 // layout computation and MIR building
418 if field >= count as u64 && base.layout.abi == layout::Abi::Uninhabited {
419 throw_ub!(Unreachable);
422 field < count as u64,
423 "Tried to access field {} of union {:#?} with {} fields",
428 // Offset is always 0
432 // the only way conversion can fail if is this is an array (otherwise we already panicked
433 // above). In that case, all fields are equal.
434 let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
436 // Offset may need adjustment for unsized fields.
437 let (meta, offset) = if field_layout.is_unsized() {
438 // Re-use parent metadata to determine dynamic field layout.
439 // With custom DSTS, this *will* execute user-defined code, but the same
440 // happens at run-time so that's okay.
441 let align = match self.size_and_align_of(base.meta, field_layout)? {
442 Some((_, align)) => align,
443 None if offset == Size::ZERO => {
444 // An extern type at offset 0, we fall back to its static alignment.
445 // FIXME: Once we have made decisions for how to handle size and alignment
446 // of `extern type`, this should be adapted. It is just a temporary hack
447 // to get some code to work that probably ought to work.
448 field_layout.align.abi
450 None => bug!("Cannot compute offset for extern type field at non-0 offset"),
452 (base.meta, offset.align_to(align))
454 // base.meta could be present; we might be accessing a sized field of an unsized
456 (MemPlaceMeta::None, offset)
459 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
460 // codegen -- mostly to see if we can get away with that
461 base.offset(offset, meta, field_layout, self)
464 // Iterates over all fields of an array. Much more efficient than doing the
465 // same by repeatedly calling `mplace_array`.
466 pub(super) fn mplace_array_fields(
468 base: MPlaceTy<'tcx, Tag>,
469 ) -> InterpResult<'tcx, impl Iterator<Item = InterpResult<'tcx, MPlaceTy<'tcx, Tag>>> + 'tcx>
471 let len = base.len(self)?; // also asserts that we have a type where this makes sense
472 let stride = match base.layout.fields {
473 layout::FieldPlacement::Array { stride, .. } => stride,
474 _ => bug!("mplace_array_fields: expected an array layout"),
476 let layout = base.layout.field(self, 0)?;
477 let dl = &self.tcx.data_layout;
478 Ok((0..len).map(move |i| base.offset(i * stride, MemPlaceMeta::None, layout, dl)))
483 base: MPlaceTy<'tcx, M::PointerTag>,
487 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
488 let len = base.len(self)?; // also asserts that we have a type where this makes sense
489 let actual_to = if from_end {
491 // This can only be reached in ConstProp and non-rustc-MIR.
492 throw_ub!(BoundsCheckFailed { len: len as u64, index: from as u64 + to as u64 });
499 // Not using layout method because that works with usize, and does not work with slices
500 // (that have count 0 in their layout).
501 let from_offset = match base.layout.fields {
502 layout::FieldPlacement::Array { stride, .. } => stride * from,
503 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
506 // Compute meta and new layout
507 let inner_len = actual_to - from;
508 let (meta, ty) = match base.layout.ty.kind {
509 // It is not nice to match on the type, but that seems to be the only way to
511 ty::Array(inner, _) => (MemPlaceMeta::None, self.tcx.mk_array(inner, inner_len)),
513 let len = Scalar::from_uint(inner_len, self.pointer_size());
514 (MemPlaceMeta::Meta(len), base.layout.ty)
516 _ => bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
518 let layout = self.layout_of(ty)?;
519 base.offset(from_offset, meta, layout, self)
522 pub(super) fn mplace_downcast(
524 base: MPlaceTy<'tcx, M::PointerTag>,
526 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
527 // Downcasts only change the layout
528 assert!(!base.meta.has_meta());
529 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
532 /// Project into an mplace
533 pub(super) fn mplace_projection(
535 base: MPlaceTy<'tcx, M::PointerTag>,
536 proj_elem: &mir::PlaceElem<'tcx>,
537 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
538 use rustc::mir::ProjectionElem::*;
539 Ok(match *proj_elem {
540 Field(field, _) => self.mplace_field(base, field.index() as u64)?,
541 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
542 Deref => self.deref_operand(base.into())?,
545 let layout = self.layout_of(self.tcx.types.usize)?;
546 let n = self.access_local(self.frame(), local, Some(layout))?;
547 let n = self.read_scalar(n)?;
548 let n = self.force_bits(n.not_undef()?, self.tcx.data_layout.pointer_size)?;
549 self.mplace_field(base, u64::try_from(n).unwrap())?
552 ConstantIndex { offset, min_length, from_end } => {
553 let n = base.len(self)?;
554 if n < min_length as u64 {
555 // This can only be reached in ConstProp and non-rustc-MIR.
556 throw_ub!(BoundsCheckFailed { len: min_length as u64, index: n as u64 });
559 let index = if from_end {
560 assert!(0 < offset && offset - 1 < min_length);
561 n - u64::from(offset)
563 assert!(offset < min_length);
567 self.mplace_field(base, index)?
570 Subslice { from, to, from_end } => {
571 self.mplace_subslice(base, u64::from(from), u64::from(to), from_end)?
576 /// Gets the place of a field inside the place, and also the field's type.
577 /// Just a convenience function, but used quite a bit.
578 /// This is the only projection that might have a side-effect: We cannot project
579 /// into the field of a local `ScalarPair`, we have to first allocate it.
582 base: PlaceTy<'tcx, M::PointerTag>,
584 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
585 // FIXME: We could try to be smarter and avoid allocation for fields that span the
587 let mplace = self.force_allocation(base)?;
588 Ok(self.mplace_field(mplace, field)?.into())
591 pub fn place_downcast(
593 base: PlaceTy<'tcx, M::PointerTag>,
595 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
596 // Downcast just changes the layout
597 Ok(match base.place {
598 Place::Ptr(mplace) => {
599 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into()
601 Place::Local { .. } => {
602 let layout = base.layout.for_variant(self, variant);
603 PlaceTy { layout, ..base }
608 /// Projects into a place.
609 pub fn place_projection(
611 base: PlaceTy<'tcx, M::PointerTag>,
612 proj_elem: &mir::ProjectionElem<mir::Local, Ty<'tcx>>,
613 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
614 use rustc::mir::ProjectionElem::*;
615 Ok(match *proj_elem {
616 Field(field, _) => self.place_field(base, field.index() as u64)?,
617 Downcast(_, variant) => self.place_downcast(base, variant)?,
618 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
619 // For the other variants, we have to force an allocation.
620 // This matches `operand_projection`.
621 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
622 let mplace = self.force_allocation(base)?;
623 self.mplace_projection(mplace, proj_elem)?.into()
628 /// Computes a place. You should only use this if you intend to write into this
629 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
632 place: &mir::Place<'tcx>,
633 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
634 let mut place_ty = match place.local {
635 mir::RETURN_PLACE => {
636 // `return_place` has the *caller* layout, but we want to use our
637 // `layout to verify our assumption. The caller will validate
638 // their layout on return.
640 place: match self.frame().return_place {
642 // Even if we don't have a return place, we sometimes need to
643 // create this place, but any attempt to read from / write to it
644 // (even a ZST read/write) needs to error, so let us make this
647 // FIXME: Ideally we'd make sure that the place projections also
649 None => Place::null(&*self),
651 layout: self.layout_of(self.subst_from_frame_and_normalize_erasing_regions(
652 self.frame().body.return_ty(),
657 // This works even for dead/uninitialized locals; we check further when writing
658 place: Place::Local { frame: self.cur_frame(), local },
659 layout: self.layout_of_local(self.frame(), local, None)?,
663 for elem in place.projection.iter() {
664 place_ty = self.place_projection(place_ty, elem)?
667 self.dump_place(place_ty.place);
671 /// Write a scalar to a place
675 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
676 dest: PlaceTy<'tcx, M::PointerTag>,
677 ) -> InterpResult<'tcx> {
678 self.write_immediate(Immediate::Scalar(val.into()), dest)
681 /// Write an immediate to a place
683 pub fn write_immediate(
685 src: Immediate<M::PointerTag>,
686 dest: PlaceTy<'tcx, M::PointerTag>,
687 ) -> InterpResult<'tcx> {
688 self.write_immediate_no_validate(src, dest)?;
690 if M::enforce_validity(self) {
691 // Data got changed, better make sure it matches the type!
692 self.validate_operand(self.place_to_op(dest)?, vec![], None)?;
698 /// Write an `Immediate` to memory.
700 pub fn write_immediate_to_mplace(
702 src: Immediate<M::PointerTag>,
703 dest: MPlaceTy<'tcx, M::PointerTag>,
704 ) -> InterpResult<'tcx> {
705 self.write_immediate_to_mplace_no_validate(src, dest)?;
707 if M::enforce_validity(self) {
708 // Data got changed, better make sure it matches the type!
709 self.validate_operand(dest.into(), vec![], None)?;
715 /// Write an immediate to a place.
716 /// If you use this you are responsible for validating that things got copied at the
718 fn write_immediate_no_validate(
720 src: Immediate<M::PointerTag>,
721 dest: PlaceTy<'tcx, M::PointerTag>,
722 ) -> InterpResult<'tcx> {
723 if cfg!(debug_assertions) {
724 // This is a very common path, avoid some checks in release mode
725 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
727 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) => assert_eq!(
730 "Size mismatch when writing pointer"
732 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Raw { size, .. })) => {
734 Size::from_bytes(size.into()),
736 "Size mismatch when writing bits"
739 Immediate::Scalar(ScalarMaybeUndef::Undef) => {} // undef can have any size
740 Immediate::ScalarPair(_, _) => {
741 // FIXME: Can we check anything here?
745 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
747 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
748 // but not factored as a separate function.
749 let mplace = match dest.place {
750 Place::Local { frame, local } => {
751 match self.stack[frame].locals[local].access_mut()? {
753 // Local can be updated in-place.
754 *local = LocalValue::Live(Operand::Immediate(src));
758 // The local is in memory, go on below.
763 Place::Ptr(mplace) => mplace, // already referring to memory
765 let dest = MPlaceTy { mplace, layout: dest.layout };
767 // This is already in memory, write there.
768 self.write_immediate_to_mplace_no_validate(src, dest)
771 /// Write an immediate to memory.
772 /// If you use this you are responsible for validating that things got copied at the
774 fn write_immediate_to_mplace_no_validate(
776 value: Immediate<M::PointerTag>,
777 dest: MPlaceTy<'tcx, M::PointerTag>,
778 ) -> InterpResult<'tcx> {
779 // Note that it is really important that the type here is the right one, and matches the
780 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
781 // to handle padding properly, which is only correct if we never look at this data with the
784 // Invalid places are a thing: the return place of a diverging function
785 let ptr = match self.check_mplace_access(dest, None)? {
787 None => return Ok(()), // zero-sized access
790 let tcx = &*self.tcx;
791 // FIXME: We should check that there are dest.layout.size many bytes available in
792 // memory. The code below is not sufficient, with enough padding it might not
793 // cover all the bytes!
795 Immediate::Scalar(scalar) => {
796 match dest.layout.abi {
797 layout::Abi::Scalar(_) => {} // fine
799 bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}", dest.layout)
802 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(
809 Immediate::ScalarPair(a_val, b_val) => {
810 // We checked `ptr_align` above, so all fields will have the alignment they need.
811 // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
812 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
813 let (a, b) = match dest.layout.abi {
814 layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
816 "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
820 let (a_size, b_size) = (a.size(self), b.size(self));
821 let b_offset = a_size.align_to(b.align(self).abi);
822 let b_ptr = ptr.offset(b_offset, self)?;
824 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
825 // but that does not work: We could be a newtype around a pair, then the
826 // fields do not match the `ScalarPair` components.
828 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(tcx, ptr, a_val, a_size)?;
829 self.memory.get_raw_mut(b_ptr.alloc_id)?.write_scalar(tcx, b_ptr, b_val, b_size)
834 /// Copies the data from an operand to a place. This does not support transmuting!
835 /// Use `copy_op_transmute` if the layouts could disagree.
839 src: OpTy<'tcx, M::PointerTag>,
840 dest: PlaceTy<'tcx, M::PointerTag>,
841 ) -> InterpResult<'tcx> {
842 self.copy_op_no_validate(src, dest)?;
844 if M::enforce_validity(self) {
845 // Data got changed, better make sure it matches the type!
846 self.validate_operand(self.place_to_op(dest)?, vec![], None)?;
852 /// Copies the data from an operand to a place. This does not support transmuting!
853 /// Use `copy_op_transmute` if the layouts could disagree.
854 /// Also, if you use this you are responsible for validating that things get copied at the
856 fn copy_op_no_validate(
858 src: OpTy<'tcx, M::PointerTag>,
859 dest: PlaceTy<'tcx, M::PointerTag>,
860 ) -> InterpResult<'tcx> {
861 // We do NOT compare the types for equality, because well-typed code can
862 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
864 src.layout.details == dest.layout.details,
865 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}",
870 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
871 let src = match self.try_read_immediate(src)? {
873 assert!(!src.layout.is_unsized(), "cannot have unsized immediates");
874 // Yay, we got a value that we can write directly.
875 // FIXME: Add a check to make sure that if `src` is indirect,
876 // it does not overlap with `dest`.
877 return self.write_immediate_no_validate(*src_val, dest);
879 Err(mplace) => mplace,
881 // Slow path, this does not fit into an immediate. Just memcpy.
882 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
884 // This interprets `src.meta` with the `dest` local's layout, if an unsized local
885 // is being initialized!
886 let (dest, size) = self.force_allocation_maybe_sized(dest, src.meta)?;
887 let size = size.unwrap_or_else(|| {
889 !dest.layout.is_unsized(),
890 "Cannot copy into already initialized unsized place"
894 assert_eq!(src.meta, dest.meta, "Can only copy between equally-sized instances");
897 .check_mplace_access(src, Some(size))
898 .expect("places should be checked on creation");
900 .check_mplace_access(dest, Some(size))
901 .expect("places should be checked on creation");
902 let (src_ptr, dest_ptr) = match (src, dest) {
903 (Some(src_ptr), Some(dest_ptr)) => (src_ptr, dest_ptr),
904 (None, None) => return Ok(()), // zero-sized copy
905 _ => bug!("The pointers should both be Some or both None"),
908 self.memory.copy(src_ptr, dest_ptr, size, /*nonoverlapping*/ true)
911 /// Copies the data from an operand to a place. The layouts may disagree, but they must
912 /// have the same size.
913 pub fn copy_op_transmute(
915 src: OpTy<'tcx, M::PointerTag>,
916 dest: PlaceTy<'tcx, M::PointerTag>,
917 ) -> InterpResult<'tcx> {
918 if src.layout.details == dest.layout.details {
919 // Fast path: Just use normal `copy_op`
920 return self.copy_op(src, dest);
922 // We still require the sizes to match.
923 if src.layout.size != dest.layout.size {
924 // FIXME: This should be an assert instead of an error, but if we transmute within an
925 // array length computation, `typeck` may not have yet been run and errored out. In fact
926 // most likey we *are* running `typeck` right now. Investigate whether we can bail out
927 // on `typeck_tables().has_errors` at all const eval entry points.
928 debug!("Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
929 throw_unsup!(TransmuteSizeDiff(src.layout.ty, dest.layout.ty));
931 // Unsized copies rely on interpreting `src.meta` with `dest.layout`, we want
932 // to avoid that here.
934 !src.layout.is_unsized() && !dest.layout.is_unsized(),
935 "Cannot transmute unsized data"
938 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
939 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
940 // We have to write them to `dest` at the offsets they were *read at*, which is
941 // not necessarily the same as the offsets in `dest.layout`!
942 // Hence we do the copy with the source layout on both sides. We also make sure to write
943 // into memory, because if `dest` is a local we would not even have a way to write
944 // at the `src` offsets; the fact that we came from a different layout would
946 let dest = self.force_allocation(dest)?;
947 self.copy_op_no_validate(
949 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
952 if M::enforce_validity(self) {
953 // Data got changed, better make sure it matches the type!
954 self.validate_operand(dest.into(), vec![], None)?;
960 /// Ensures that a place is in memory, and returns where it is.
961 /// If the place currently refers to a local that doesn't yet have a matching allocation,
962 /// create such an allocation.
963 /// This is essentially `force_to_memplace`.
965 /// This supports unsized types and returns the computed size to avoid some
966 /// redundant computation when copying; use `force_allocation` for a simpler, sized-only
968 pub fn force_allocation_maybe_sized(
970 place: PlaceTy<'tcx, M::PointerTag>,
971 meta: MemPlaceMeta<M::PointerTag>,
972 ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::PointerTag>, Option<Size>)> {
973 let (mplace, size) = match place.place {
974 Place::Local { frame, local } => {
975 match self.stack[frame].locals[local].access_mut()? {
976 Ok(&mut local_val) => {
977 // We need to make an allocation.
979 // We need the layout of the local. We can NOT use the layout we got,
980 // that might e.g., be an inner field of a struct with `Scalar` layout,
981 // that has different alignment than the outer field.
982 let local_layout = self.layout_of_local(&self.stack[frame], local, None)?;
983 // We also need to support unsized types, and hence cannot use `allocate`.
984 let (size, align) = self
985 .size_and_align_of(meta, local_layout)?
986 .expect("Cannot allocate for non-dyn-sized type");
987 let ptr = self.memory.allocate(size, align, MemoryKind::Stack);
988 let mplace = MemPlace { ptr: ptr.into(), align, meta };
989 if let LocalValue::Live(Operand::Immediate(value)) = local_val {
990 // Preserve old value.
991 // We don't have to validate as we can assume the local
992 // was already valid for its type.
993 let mplace = MPlaceTy { mplace, layout: local_layout };
994 self.write_immediate_to_mplace_no_validate(value, mplace)?;
996 // Now we can call `access_mut` again, asserting it goes well,
997 // and actually overwrite things.
998 *self.stack[frame].locals[local].access_mut().unwrap().unwrap() =
999 LocalValue::Live(Operand::Indirect(mplace));
1000 (mplace, Some(size))
1002 Err(mplace) => (mplace, None), // this already was an indirect local
1005 Place::Ptr(mplace) => (mplace, None),
1007 // Return with the original layout, so that the caller can go on
1008 Ok((MPlaceTy { mplace, layout: place.layout }, size))
1012 pub fn force_allocation(
1014 place: PlaceTy<'tcx, M::PointerTag>,
1015 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1016 Ok(self.force_allocation_maybe_sized(place, MemPlaceMeta::None)?.0)
1021 layout: TyLayout<'tcx>,
1022 kind: MemoryKind<M::MemoryKinds>,
1023 ) -> MPlaceTy<'tcx, M::PointerTag> {
1024 let ptr = self.memory.allocate(layout.size, layout.align.abi, kind);
1025 MPlaceTy::from_aligned_ptr(ptr, layout)
1028 /// Returns a wide MPlace.
1029 pub fn allocate_str(
1032 kind: MemoryKind<M::MemoryKinds>,
1033 ) -> MPlaceTy<'tcx, M::PointerTag> {
1034 let ptr = self.memory.allocate_static_bytes(str.as_bytes(), kind);
1035 let meta = Scalar::from_uint(str.len() as u128, self.pointer_size());
1036 let mplace = MemPlace {
1038 align: Align::from_bytes(1).unwrap(),
1039 meta: MemPlaceMeta::Meta(meta),
1042 let layout = self.layout_of(self.tcx.mk_static_str()).unwrap();
1043 MPlaceTy { mplace, layout }
1046 pub fn write_discriminant_index(
1048 variant_index: VariantIdx,
1049 dest: PlaceTy<'tcx, M::PointerTag>,
1050 ) -> InterpResult<'tcx> {
1051 // Layout computation excludes uninhabited variants from consideration
1052 // therefore there's no way to represent those variants in the given layout.
1053 if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() {
1054 throw_ub!(Unreachable);
1057 match dest.layout.variants {
1058 layout::Variants::Single { index } => {
1059 assert_eq!(index, variant_index);
1061 layout::Variants::Multiple {
1062 discr_kind: layout::DiscriminantKind::Tag,
1063 discr: ref discr_layout,
1067 // No need to validate that the discriminant here because the
1068 // `TyLayout::for_variant()` call earlier already checks the variant is valid.
1071 dest.layout.ty.discriminant_for_variant(*self.tcx, variant_index).unwrap().val;
1073 // raw discriminants for enums are isize or bigger during
1074 // their computation, but the in-memory tag is the smallest possible
1076 let size = discr_layout.value.size(self);
1077 let discr_val = truncate(discr_val, size);
1079 let discr_dest = self.place_field(dest, discr_index as u64)?;
1080 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
1082 layout::Variants::Multiple {
1084 layout::DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start },
1085 discr: ref discr_layout,
1089 // No need to validate that the discriminant here because the
1090 // `TyLayout::for_variant()` call earlier already checks the variant is valid.
1092 if variant_index != dataful_variant {
1093 let variants_start = niche_variants.start().as_u32();
1094 let variant_index_relative = variant_index
1096 .checked_sub(variants_start)
1097 .expect("overflow computing relative variant idx");
1098 // We need to use machine arithmetic when taking into account `niche_start`:
1099 // discr_val = variant_index_relative + niche_start_val
1100 let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
1101 let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
1102 let variant_index_relative_val =
1103 ImmTy::from_uint(variant_index_relative, discr_layout);
1104 let discr_val = self.binary_op(
1106 variant_index_relative_val,
1110 let niche_dest = self.place_field(dest, discr_index as u64)?;
1111 self.write_immediate(*discr_val, niche_dest)?;
1119 pub fn raw_const_to_mplace(
1121 raw: RawConst<'tcx>,
1122 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1123 // This must be an allocation in `tcx`
1124 assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
1125 let ptr = self.tag_static_base_pointer(Pointer::from(raw.alloc_id));
1126 let layout = self.layout_of(raw.ty)?;
1127 Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
1130 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
1131 /// Also return some more information so drop doesn't have to run the same code twice.
1132 pub(super) fn unpack_dyn_trait(
1134 mplace: MPlaceTy<'tcx, M::PointerTag>,
1135 ) -> InterpResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
1136 let vtable = mplace.vtable(); // also sanity checks the type
1137 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
1138 let layout = self.layout_of(ty)?;
1140 // More sanity checks
1141 if cfg!(debug_assertions) {
1142 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
1143 assert_eq!(size, layout.size);
1144 // only ABI alignment is preserved
1145 assert_eq!(align, layout.align.abi);
1148 let mplace = MPlaceTy { mplace: MemPlace { meta: MemPlaceMeta::None, ..*mplace }, layout };
1149 Ok((instance, mplace))