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) => {
414 field < count as u64,
415 "Tried to access field {} of union {:#?} with {} fields",
420 // Offset is always 0
424 // the only way conversion can fail if is this is an array (otherwise we already panicked
425 // above). In that case, all fields are equal.
426 let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
428 // Offset may need adjustment for unsized fields.
429 let (meta, offset) = if field_layout.is_unsized() {
430 // Re-use parent metadata to determine dynamic field layout.
431 // With custom DSTS, this *will* execute user-defined code, but the same
432 // happens at run-time so that's okay.
433 let align = match self.size_and_align_of(base.meta, field_layout)? {
434 Some((_, align)) => align,
435 None if offset == Size::ZERO =>
436 // An extern type at offset 0, we fall back to its static alignment.
437 // FIXME: Once we have made decisions for how to handle size and alignment
438 // of `extern type`, this should be adapted. It is just a temporary hack
439 // to get some code to work that probably ought to work.
441 field_layout.align.abi
443 None => bug!("Cannot compute offset for extern type field at non-0 offset"),
445 (base.meta, offset.align_to(align))
447 // base.meta could be present; we might be accessing a sized field of an unsized
449 (MemPlaceMeta::None, offset)
452 // We do not look at `base.layout.align` nor `field_layout.align`, unlike
453 // codegen -- mostly to see if we can get away with that
454 base.offset(offset, meta, field_layout, self)
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 layout::FieldPlacement::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 Ok((0..len).map(move |i| base.offset(i * stride, MemPlaceMeta::None, layout, dl)))
476 base: MPlaceTy<'tcx, M::PointerTag>,
480 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
481 let len = base.len(self)?; // also asserts that we have a type where this makes sense
482 let actual_to = if from_end {
484 // This can only be reached in ConstProp and non-rustc-MIR.
485 throw_ub!(BoundsCheckFailed { len: len as u64, index: from as u64 + to as u64 });
492 // Not using layout method because that works with usize, and does not work with slices
493 // (that have count 0 in their layout).
494 let from_offset = match base.layout.fields {
495 layout::FieldPlacement::Array { stride, .. } => stride * from,
496 _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
499 // Compute meta and new layout
500 let inner_len = actual_to - from;
501 let (meta, ty) = match base.layout.ty.kind {
502 // It is not nice to match on the type, but that seems to be the only way to
504 ty::Array(inner, _) => (MemPlaceMeta::None, self.tcx.mk_array(inner, inner_len)),
506 let len = Scalar::from_uint(inner_len, self.pointer_size());
507 (MemPlaceMeta::Meta(len), base.layout.ty)
509 _ => bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
511 let layout = self.layout_of(ty)?;
512 base.offset(from_offset, meta, layout, self)
515 pub(super) fn mplace_downcast(
517 base: MPlaceTy<'tcx, M::PointerTag>,
519 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
520 // Downcasts only change the layout
521 assert!(!base.meta.has_meta());
522 Ok(MPlaceTy { layout: base.layout.for_variant(self, variant), ..base })
525 /// Project into an mplace
526 pub(super) fn mplace_projection(
528 base: MPlaceTy<'tcx, M::PointerTag>,
529 proj_elem: &mir::PlaceElem<'tcx>,
530 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
531 use rustc::mir::ProjectionElem::*;
532 Ok(match *proj_elem {
533 Field(field, _) => self.mplace_field(base, field.index() as u64)?,
534 Downcast(_, variant) => self.mplace_downcast(base, variant)?,
535 Deref => self.deref_operand(base.into())?,
538 let layout = self.layout_of(self.tcx.types.usize)?;
539 let n = self.access_local(self.frame(), local, Some(layout))?;
540 let n = self.read_scalar(n)?;
541 let n = self.force_bits(n.not_undef()?, self.tcx.data_layout.pointer_size)?;
542 self.mplace_field(base, u64::try_from(n).unwrap())?
545 ConstantIndex { offset, min_length, from_end } => {
546 let n = base.len(self)?;
547 if n < min_length as u64 {
548 // This can only be reached in ConstProp and non-rustc-MIR.
549 throw_ub!(BoundsCheckFailed { len: min_length as u64, index: n as u64 });
552 let index = if from_end {
553 assert!(0 < offset && offset - 1 < min_length);
554 n - u64::from(offset)
556 assert!(offset < min_length);
560 self.mplace_field(base, index)?
563 Subslice { from, to, from_end } => {
564 self.mplace_subslice(base, u64::from(from), u64::from(to), from_end)?
569 /// Gets the place of a field inside the place, and also the field's type.
570 /// Just a convenience function, but used quite a bit.
571 /// This is the only projection that might have a side-effect: We cannot project
572 /// into the field of a local `ScalarPair`, we have to first allocate it.
575 base: PlaceTy<'tcx, M::PointerTag>,
577 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
578 // FIXME: We could try to be smarter and avoid allocation for fields that span the
580 let mplace = self.force_allocation(base)?;
581 Ok(self.mplace_field(mplace, field)?.into())
584 pub fn place_downcast(
586 base: PlaceTy<'tcx, M::PointerTag>,
588 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
589 // Downcast just changes the layout
590 Ok(match base.place {
591 Place::Ptr(mplace) => {
592 self.mplace_downcast(MPlaceTy { mplace, layout: base.layout }, variant)?.into()
594 Place::Local { .. } => {
595 let layout = base.layout.for_variant(self, variant);
596 PlaceTy { layout, ..base }
601 /// Projects into a place.
602 pub fn place_projection(
604 base: PlaceTy<'tcx, M::PointerTag>,
605 proj_elem: &mir::ProjectionElem<mir::Local, Ty<'tcx>>,
606 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
607 use rustc::mir::ProjectionElem::*;
608 Ok(match *proj_elem {
609 Field(field, _) => self.place_field(base, field.index() as u64)?,
610 Downcast(_, variant) => self.place_downcast(base, variant)?,
611 Deref => self.deref_operand(self.place_to_op(base)?)?.into(),
612 // For the other variants, we have to force an allocation.
613 // This matches `operand_projection`.
614 Subslice { .. } | ConstantIndex { .. } | Index(_) => {
615 let mplace = self.force_allocation(base)?;
616 self.mplace_projection(mplace, proj_elem)?.into()
621 /// Computes a place. You should only use this if you intend to write into this
622 /// place; for reading, a more efficient alternative is `eval_place_for_read`.
625 place: &mir::Place<'tcx>,
626 ) -> InterpResult<'tcx, PlaceTy<'tcx, M::PointerTag>> {
627 let mut place_ty = match place.local {
628 mir::RETURN_PLACE => {
629 // `return_place` has the *caller* layout, but we want to use our
630 // `layout to verify our assumption. The caller will validate
631 // their layout on return.
633 place: match self.frame().return_place {
635 // Even if we don't have a return place, we sometimes need to
636 // create this place, but any attempt to read from / write to it
637 // (even a ZST read/write) needs to error, so let us make this
640 // FIXME: Ideally we'd make sure that the place projections also
642 None => Place::null(&*self),
644 layout: self.layout_of(self.subst_from_frame_and_normalize_erasing_regions(
645 self.frame().body.return_ty(),
650 // This works even for dead/uninitialized locals; we check further when writing
651 place: Place::Local { frame: self.cur_frame(), local: local },
652 layout: self.layout_of_local(self.frame(), local, None)?,
656 for elem in place.projection.iter() {
657 place_ty = self.place_projection(place_ty, elem)?
660 self.dump_place(place_ty.place);
664 /// Write a scalar to a place
668 val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
669 dest: PlaceTy<'tcx, M::PointerTag>,
670 ) -> InterpResult<'tcx> {
671 self.write_immediate(Immediate::Scalar(val.into()), dest)
674 /// Write an immediate to a place
676 pub fn write_immediate(
678 src: Immediate<M::PointerTag>,
679 dest: PlaceTy<'tcx, M::PointerTag>,
680 ) -> InterpResult<'tcx> {
681 self.write_immediate_no_validate(src, dest)?;
683 if M::enforce_validity(self) {
684 // Data got changed, better make sure it matches the type!
685 self.validate_operand(self.place_to_op(dest)?, vec![], None)?;
691 /// Write an `Immediate` to memory.
693 pub fn write_immediate_to_mplace(
695 src: Immediate<M::PointerTag>,
696 dest: MPlaceTy<'tcx, M::PointerTag>,
697 ) -> InterpResult<'tcx> {
698 self.write_immediate_to_mplace_no_validate(src, dest)?;
700 if M::enforce_validity(self) {
701 // Data got changed, better make sure it matches the type!
702 self.validate_operand(dest.into(), vec![], None)?;
708 /// Write an immediate to a place.
709 /// If you use this you are responsible for validating that things got copied at the
711 fn write_immediate_no_validate(
713 src: Immediate<M::PointerTag>,
714 dest: PlaceTy<'tcx, M::PointerTag>,
715 ) -> InterpResult<'tcx> {
716 if cfg!(debug_assertions) {
717 // This is a very common path, avoid some checks in release mode
718 assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
720 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) => assert_eq!(
723 "Size mismatch when writing pointer"
725 Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Raw { size, .. })) => {
727 Size::from_bytes(size.into()),
729 "Size mismatch when writing bits"
732 Immediate::Scalar(ScalarMaybeUndef::Undef) => {} // undef can have any size
733 Immediate::ScalarPair(_, _) => {
734 // FIXME: Can we check anything here?
738 trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
740 // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
741 // but not factored as a separate function.
742 let mplace = match dest.place {
743 Place::Local { frame, local } => {
744 match self.stack[frame].locals[local].access_mut()? {
746 // Local can be updated in-place.
747 *local = LocalValue::Live(Operand::Immediate(src));
751 // The local is in memory, go on below.
756 Place::Ptr(mplace) => mplace, // already referring to memory
758 let dest = MPlaceTy { mplace, layout: dest.layout };
760 // This is already in memory, write there.
761 self.write_immediate_to_mplace_no_validate(src, dest)
764 /// Write an immediate to memory.
765 /// If you use this you are responsible for validating that things got copied at the
767 fn write_immediate_to_mplace_no_validate(
769 value: Immediate<M::PointerTag>,
770 dest: MPlaceTy<'tcx, M::PointerTag>,
771 ) -> InterpResult<'tcx> {
772 // Note that it is really important that the type here is the right one, and matches the
773 // type things are read at. In case `src_val` is a `ScalarPair`, we don't do any magic here
774 // to handle padding properly, which is only correct if we never look at this data with the
777 // Invalid places are a thing: the return place of a diverging function
778 let ptr = match self.check_mplace_access(dest, None)? {
780 None => return Ok(()), // zero-sized access
783 let tcx = &*self.tcx;
784 // FIXME: We should check that there are dest.layout.size many bytes available in
785 // memory. The code below is not sufficient, with enough padding it might not
786 // cover all the bytes!
788 Immediate::Scalar(scalar) => {
789 match dest.layout.abi {
790 layout::Abi::Scalar(_) => {} // fine
792 bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}", dest.layout)
795 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(
802 Immediate::ScalarPair(a_val, b_val) => {
803 // We checked `ptr_align` above, so all fields will have the alignment they need.
804 // We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
805 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
806 let (a, b) = match dest.layout.abi {
807 layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
809 "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
813 let (a_size, b_size) = (a.size(self), b.size(self));
814 let b_offset = a_size.align_to(b.align(self).abi);
815 let b_ptr = ptr.offset(b_offset, self)?;
817 // It is tempting to verify `b_offset` against `layout.fields.offset(1)`,
818 // but that does not work: We could be a newtype around a pair, then the
819 // fields do not match the `ScalarPair` components.
821 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(tcx, ptr, a_val, a_size)?;
822 self.memory.get_raw_mut(b_ptr.alloc_id)?.write_scalar(tcx, b_ptr, b_val, b_size)
827 /// Copies the data from an operand to a place. This does not support transmuting!
828 /// Use `copy_op_transmute` if the layouts could disagree.
832 src: OpTy<'tcx, M::PointerTag>,
833 dest: PlaceTy<'tcx, M::PointerTag>,
834 ) -> InterpResult<'tcx> {
835 self.copy_op_no_validate(src, dest)?;
837 if M::enforce_validity(self) {
838 // Data got changed, better make sure it matches the type!
839 self.validate_operand(self.place_to_op(dest)?, vec![], None)?;
845 /// Copies the data from an operand to a place. This does not support transmuting!
846 /// Use `copy_op_transmute` if the layouts could disagree.
847 /// Also, if you use this you are responsible for validating that things get copied at the
849 fn copy_op_no_validate(
851 src: OpTy<'tcx, M::PointerTag>,
852 dest: PlaceTy<'tcx, M::PointerTag>,
853 ) -> InterpResult<'tcx> {
854 // We do NOT compare the types for equality, because well-typed code can
855 // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
857 src.layout.details == dest.layout.details,
858 "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}",
863 // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
864 let src = match self.try_read_immediate(src)? {
866 assert!(!src.layout.is_unsized(), "cannot have unsized immediates");
867 // Yay, we got a value that we can write directly.
868 // FIXME: Add a check to make sure that if `src` is indirect,
869 // it does not overlap with `dest`.
870 return self.write_immediate_no_validate(*src_val, dest);
872 Err(mplace) => mplace,
874 // Slow path, this does not fit into an immediate. Just memcpy.
875 trace!("copy_op: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
877 // This interprets `src.meta` with the `dest` local's layout, if an unsized local
878 // is being initialized!
879 let (dest, size) = self.force_allocation_maybe_sized(dest, src.meta)?;
880 let size = size.unwrap_or_else(|| {
882 !dest.layout.is_unsized(),
883 "Cannot copy into already initialized unsized place"
887 assert_eq!(src.meta, dest.meta, "Can only copy between equally-sized instances");
890 .check_mplace_access(src, Some(size))
891 .expect("places should be checked on creation");
893 .check_mplace_access(dest, Some(size))
894 .expect("places should be checked on creation");
895 let (src_ptr, dest_ptr) = match (src, dest) {
896 (Some(src_ptr), Some(dest_ptr)) => (src_ptr, dest_ptr),
897 (None, None) => return Ok(()), // zero-sized copy
898 _ => bug!("The pointers should both be Some or both None"),
901 self.memory.copy(src_ptr, dest_ptr, size, /*nonoverlapping*/ true)
904 /// Copies the data from an operand to a place. The layouts may disagree, but they must
905 /// have the same size.
906 pub fn copy_op_transmute(
908 src: OpTy<'tcx, M::PointerTag>,
909 dest: PlaceTy<'tcx, M::PointerTag>,
910 ) -> InterpResult<'tcx> {
911 if src.layout.details == dest.layout.details {
912 // Fast path: Just use normal `copy_op`
913 return self.copy_op(src, dest);
915 // We still require the sizes to match.
916 if src.layout.size != dest.layout.size {
917 // FIXME: This should be an assert instead of an error, but if we transmute within an
918 // array length computation, `typeck` may not have yet been run and errored out. In fact
919 // most likey we *are* running `typeck` right now. Investigate whether we can bail out
920 // on `typeck_tables().has_errors` at all const eval entry points.
921 debug!("Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
922 throw_unsup!(TransmuteSizeDiff(src.layout.ty, dest.layout.ty));
924 // Unsized copies rely on interpreting `src.meta` with `dest.layout`, we want
925 // to avoid that here.
927 !src.layout.is_unsized() && !dest.layout.is_unsized(),
928 "Cannot transmute unsized data"
931 // The hard case is `ScalarPair`. `src` is already read from memory in this case,
932 // using `src.layout` to figure out which bytes to use for the 1st and 2nd field.
933 // We have to write them to `dest` at the offsets they were *read at*, which is
934 // not necessarily the same as the offsets in `dest.layout`!
935 // Hence we do the copy with the source layout on both sides. We also make sure to write
936 // into memory, because if `dest` is a local we would not even have a way to write
937 // at the `src` offsets; the fact that we came from a different layout would
939 let dest = self.force_allocation(dest)?;
940 self.copy_op_no_validate(
942 PlaceTy::from(MPlaceTy { mplace: *dest, layout: src.layout }),
945 if M::enforce_validity(self) {
946 // Data got changed, better make sure it matches the type!
947 self.validate_operand(dest.into(), vec![], None)?;
953 /// Ensures that a place is in memory, and returns where it is.
954 /// If the place currently refers to a local that doesn't yet have a matching allocation,
955 /// create such an allocation.
956 /// This is essentially `force_to_memplace`.
958 /// This supports unsized types and returns the computed size to avoid some
959 /// redundant computation when copying; use `force_allocation` for a simpler, sized-only
961 pub fn force_allocation_maybe_sized(
963 place: PlaceTy<'tcx, M::PointerTag>,
964 meta: MemPlaceMeta<M::PointerTag>,
965 ) -> InterpResult<'tcx, (MPlaceTy<'tcx, M::PointerTag>, Option<Size>)> {
966 let (mplace, size) = match place.place {
967 Place::Local { frame, local } => {
968 match self.stack[frame].locals[local].access_mut()? {
969 Ok(&mut local_val) => {
970 // We need to make an allocation.
972 // We need the layout of the local. We can NOT use the layout we got,
973 // that might e.g., be an inner field of a struct with `Scalar` layout,
974 // that has different alignment than the outer field.
975 let local_layout = self.layout_of_local(&self.stack[frame], local, None)?;
976 // We also need to support unsized types, and hence cannot use `allocate`.
977 let (size, align) = self
978 .size_and_align_of(meta, local_layout)?
979 .expect("Cannot allocate for non-dyn-sized type");
980 let ptr = self.memory.allocate(size, align, MemoryKind::Stack);
981 let mplace = MemPlace { ptr: ptr.into(), align, meta };
982 if let LocalValue::Live(Operand::Immediate(value)) = local_val {
983 // Preserve old value.
984 // We don't have to validate as we can assume the local
985 // was already valid for its type.
986 let mplace = MPlaceTy { mplace, layout: local_layout };
987 self.write_immediate_to_mplace_no_validate(value, mplace)?;
989 // Now we can call `access_mut` again, asserting it goes well,
990 // and actually overwrite things.
991 *self.stack[frame].locals[local].access_mut().unwrap().unwrap() =
992 LocalValue::Live(Operand::Indirect(mplace));
995 Err(mplace) => (mplace, None), // this already was an indirect local
998 Place::Ptr(mplace) => (mplace, None),
1000 // Return with the original layout, so that the caller can go on
1001 Ok((MPlaceTy { mplace, layout: place.layout }, size))
1005 pub fn force_allocation(
1007 place: PlaceTy<'tcx, M::PointerTag>,
1008 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1009 Ok(self.force_allocation_maybe_sized(place, MemPlaceMeta::None)?.0)
1014 layout: TyLayout<'tcx>,
1015 kind: MemoryKind<M::MemoryKinds>,
1016 ) -> MPlaceTy<'tcx, M::PointerTag> {
1017 let ptr = self.memory.allocate(layout.size, layout.align.abi, kind);
1018 MPlaceTy::from_aligned_ptr(ptr, layout)
1021 /// Returns a wide MPlace.
1022 pub fn allocate_str(
1025 kind: MemoryKind<M::MemoryKinds>,
1026 ) -> MPlaceTy<'tcx, M::PointerTag> {
1027 let ptr = self.memory.allocate_static_bytes(str.as_bytes(), kind);
1028 let meta = Scalar::from_uint(str.len() as u128, self.pointer_size());
1029 let mplace = MemPlace {
1031 align: Align::from_bytes(1).unwrap(),
1032 meta: MemPlaceMeta::Meta(meta),
1035 let layout = self.layout_of(self.tcx.mk_static_str()).unwrap();
1036 MPlaceTy { mplace, layout }
1039 pub fn write_discriminant_index(
1041 variant_index: VariantIdx,
1042 dest: PlaceTy<'tcx, M::PointerTag>,
1043 ) -> InterpResult<'tcx> {
1044 // Layout computation excludes uninhabited variants from consideration
1045 // therefore there's no way to represent those variants in the given layout.
1046 if dest.layout.for_variant(self, variant_index).abi.is_uninhabited() {
1047 throw_ub!(Unreachable);
1050 match dest.layout.variants {
1051 layout::Variants::Single { index } => {
1052 assert_eq!(index, variant_index);
1054 layout::Variants::Multiple {
1055 discr_kind: layout::DiscriminantKind::Tag,
1056 discr: ref discr_layout,
1060 // No need to validate that the discriminant here because the
1061 // `TyLayout::for_variant()` call earlier already checks the variant is valid.
1064 dest.layout.ty.discriminant_for_variant(*self.tcx, variant_index).unwrap().val;
1066 // raw discriminants for enums are isize or bigger during
1067 // their computation, but the in-memory tag is the smallest possible
1069 let size = discr_layout.value.size(self);
1070 let discr_val = truncate(discr_val, size);
1072 let discr_dest = self.place_field(dest, discr_index as u64)?;
1073 self.write_scalar(Scalar::from_uint(discr_val, size), discr_dest)?;
1075 layout::Variants::Multiple {
1077 layout::DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start },
1078 discr: ref discr_layout,
1082 // No need to validate that the discriminant here because the
1083 // `TyLayout::for_variant()` call earlier already checks the variant is valid.
1085 if variant_index != dataful_variant {
1086 let variants_start = niche_variants.start().as_u32();
1087 let variant_index_relative = variant_index
1089 .checked_sub(variants_start)
1090 .expect("overflow computing relative variant idx");
1091 // We need to use machine arithmetic when taking into account `niche_start`:
1092 // discr_val = variant_index_relative + niche_start_val
1093 let discr_layout = self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
1094 let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
1095 let variant_index_relative_val =
1096 ImmTy::from_uint(variant_index_relative, discr_layout);
1097 let discr_val = self.binary_op(
1099 variant_index_relative_val,
1103 let niche_dest = self.place_field(dest, discr_index as u64)?;
1104 self.write_immediate(*discr_val, niche_dest)?;
1112 pub fn raw_const_to_mplace(
1114 raw: RawConst<'tcx>,
1115 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
1116 // This must be an allocation in `tcx`
1117 assert!(self.tcx.alloc_map.lock().get(raw.alloc_id).is_some());
1118 let ptr = self.tag_static_base_pointer(Pointer::from(raw.alloc_id));
1119 let layout = self.layout_of(raw.ty)?;
1120 Ok(MPlaceTy::from_aligned_ptr(ptr, layout))
1123 /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type.
1124 /// Also return some more information so drop doesn't have to run the same code twice.
1125 pub(super) fn unpack_dyn_trait(
1127 mplace: MPlaceTy<'tcx, M::PointerTag>,
1128 ) -> InterpResult<'tcx, (ty::Instance<'tcx>, MPlaceTy<'tcx, M::PointerTag>)> {
1129 let vtable = mplace.vtable(); // also sanity checks the type
1130 let (instance, ty) = self.read_drop_type_from_vtable(vtable)?;
1131 let layout = self.layout_of(ty)?;
1133 // More sanity checks
1134 if cfg!(debug_assertions) {
1135 let (size, align) = self.read_size_and_align_from_vtable(vtable)?;
1136 assert_eq!(size, layout.size);
1137 // only ABI alignment is preserved
1138 assert_eq!(align, layout.align.abi);
1141 let mplace = MPlaceTy { mplace: MemPlace { meta: MemPlaceMeta::None, ..*mplace }, layout };
1142 Ok((instance, mplace))