5 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
6 use rustc_index::vec::IndexVec;
8 use rustc_middle::mir::interpret::{InterpError, InvalidProgramInfo};
9 use rustc_middle::ty::layout::{
10 self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
13 use rustc_middle::ty::{
14 self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable,
16 use rustc_mir_dataflow::storage::always_storage_live_locals;
17 use rustc_session::Limit;
18 use rustc_span::{Pos, Span};
19 use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayout};
22 AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace,
23 MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, PointerArithmetic, Provenance,
26 use crate::transform::validate::equal_up_to_regions;
28 pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
29 /// Stores the `Machine` instance.
31 /// Note: the stack is provided by the machine.
34 /// The results of the type checker, from rustc.
35 /// The span in this is the "root" of the evaluation, i.e., the const
36 /// we are evaluating (if this is CTFE).
37 pub tcx: TyCtxtAt<'tcx>,
39 /// Bounds in scope for polymorphic evaluations.
40 pub(crate) param_env: ty::ParamEnv<'tcx>,
42 /// The virtual memory system.
43 pub memory: Memory<'mir, 'tcx, M>,
45 /// The recursion limit (cached from `tcx.recursion_limit(())`)
46 pub recursion_limit: Limit,
49 // The Phantomdata exists to prevent this type from being `Send`. If it were sent across a thread
50 // boundary and dropped in the other thread, it would exit the span in the other thread.
51 struct SpanGuard(tracing::Span, std::marker::PhantomData<*const u8>);
54 /// By default a `SpanGuard` does nothing.
56 Self(tracing::Span::none(), std::marker::PhantomData)
59 /// If a span is entered, we exit the previous span (if any, normally none) and enter the
60 /// new span. This is mainly so we don't have to use `Option` for the `tracing_span` field of
61 /// `Frame` by creating a dummy span to being with and then entering it once the frame has
63 fn enter(&mut self, span: tracing::Span) {
64 // This executes the destructor on the previous instance of `SpanGuard`, ensuring that
65 // we never enter or exit more spans than vice versa. Unless you `mem::leak`, then we
66 // can't protect the tracing stack, but that'll just lead to weird logging, no actual
68 *self = Self(span, std::marker::PhantomData);
69 self.0.with_subscriber(|(id, dispatch)| {
75 impl Drop for SpanGuard {
77 self.0.with_subscriber(|(id, dispatch)| {
84 pub struct Frame<'mir, 'tcx, Prov: Provenance = AllocId, Extra = ()> {
85 ////////////////////////////////////////////////////////////////////////////////
86 // Function and callsite information
87 ////////////////////////////////////////////////////////////////////////////////
88 /// The MIR for the function called on this frame.
89 pub body: &'mir mir::Body<'tcx>,
91 /// The def_id and substs of the current function.
92 pub instance: ty::Instance<'tcx>,
94 /// Extra data for the machine.
97 ////////////////////////////////////////////////////////////////////////////////
98 // Return place and locals
99 ////////////////////////////////////////////////////////////////////////////////
100 /// Work to perform when returning from this function.
101 pub return_to_block: StackPopCleanup,
103 /// The location where the result of the current stack frame should be written to,
104 /// and its layout in the caller.
105 pub return_place: PlaceTy<'tcx, Prov>,
107 /// The list of locals for this stack frame, stored in order as
108 /// `[return_ptr, arguments..., variables..., temporaries...]`.
109 /// The locals are stored as `Option<Value>`s.
110 /// `None` represents a local that is currently dead, while a live local
111 /// can either directly contain `Scalar` or refer to some part of an `Allocation`.
113 /// Do *not* access this directly; always go through the machine hook!
114 pub locals: IndexVec<mir::Local, LocalState<'tcx, Prov>>,
116 /// The span of the `tracing` crate is stored here.
117 /// When the guard is dropped, the span is exited. This gives us
118 /// a full stack trace on all tracing statements.
119 tracing_span: SpanGuard,
121 ////////////////////////////////////////////////////////////////////////////////
122 // Current position within the function
123 ////////////////////////////////////////////////////////////////////////////////
124 /// If this is `Err`, we are not currently executing any particular statement in
125 /// this frame (can happen e.g. during frame initialization, and during unwinding on
126 /// frames without cleanup code).
127 /// We basically abuse `Result` as `Either`.
129 /// Needs to be public because ConstProp does unspeakable things to it.
130 pub loc: Result<mir::Location, Span>,
133 /// What we store about a frame in an interpreter backtrace.
135 pub struct FrameInfo<'tcx> {
136 pub instance: ty::Instance<'tcx>,
138 pub lint_root: Option<hir::HirId>,
141 /// Unwind information.
142 #[derive(Clone, Copy, Eq, PartialEq, Debug)]
143 pub enum StackPopUnwind {
144 /// The cleanup block.
145 Cleanup(mir::BasicBlock),
146 /// No cleanup needs to be done.
148 /// Unwinding is not allowed (UB).
152 #[derive(Clone, Copy, Eq, PartialEq, Debug)] // Miri debug-prints these
153 pub enum StackPopCleanup {
154 /// Jump to the next block in the caller, or cause UB if None (that's a function
155 /// that may never return). Also store layout of return place so
156 /// we can validate it at that layout.
157 /// `ret` stores the block we jump to on a normal return, while `unwind`
158 /// stores the block used for cleanup during unwinding.
159 Goto { ret: Option<mir::BasicBlock>, unwind: StackPopUnwind },
160 /// The root frame of the stack: nowhere else to jump to.
161 /// `cleanup` says whether locals are deallocated. Static computation
162 /// wants them leaked to intern what they need (and just throw away
163 /// the entire `ecx` when it is done).
164 Root { cleanup: bool },
167 /// State of a local variable including a memoized layout
168 #[derive(Clone, Debug)]
169 pub struct LocalState<'tcx, Prov: Provenance = AllocId> {
170 pub value: LocalValue<Prov>,
171 /// Don't modify if `Some`, this is only used to prevent computing the layout twice
172 pub layout: Cell<Option<TyAndLayout<'tcx>>>,
175 /// Current value of a local variable
176 #[derive(Copy, Clone, Debug)] // Miri debug-prints these
177 pub enum LocalValue<Prov: Provenance = AllocId> {
178 /// This local is not currently alive, and cannot be used at all.
180 /// A normal, live local.
181 /// Mostly for convenience, we re-use the `Operand` type here.
182 /// This is an optimization over just always having a pointer here;
183 /// we can thus avoid doing an allocation when the local just stores
184 /// immediate values *and* never has its address taken.
188 impl<'tcx, Prov: Provenance + 'static> LocalState<'tcx, Prov> {
189 /// Read the local's value or error if the local is not yet live or not live anymore.
191 pub fn access(&self) -> InterpResult<'tcx, &Operand<Prov>> {
193 LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"?
194 LocalValue::Live(val) => Ok(val),
198 /// Overwrite the local. If the local can be overwritten in place, return a reference
199 /// to do so; otherwise return the `MemPlace` to consult instead.
201 /// Note: This may only be invoked from the `Machine::access_local_mut` hook and not from
202 /// anywhere else. You may be invalidating machine invariants if you do!
204 pub fn access_mut(&mut self) -> InterpResult<'tcx, &mut Operand<Prov>> {
205 match &mut self.value {
206 LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"?
207 LocalValue::Live(val) => Ok(val),
212 impl<'mir, 'tcx, Prov: Provenance> Frame<'mir, 'tcx, Prov> {
213 pub fn with_extra<Extra>(self, extra: Extra) -> Frame<'mir, 'tcx, Prov, Extra> {
216 instance: self.instance,
217 return_to_block: self.return_to_block,
218 return_place: self.return_place,
222 tracing_span: self.tracing_span,
227 impl<'mir, 'tcx, Prov: Provenance, Extra> Frame<'mir, 'tcx, Prov, Extra> {
228 /// Get the current location within the Frame.
230 /// If this is `Err`, we are not currently executing any particular statement in
231 /// this frame (can happen e.g. during frame initialization, and during unwinding on
232 /// frames without cleanup code).
233 /// We basically abuse `Result` as `Either`.
236 pub fn current_loc(&self) -> Result<mir::Location, Span> {
240 /// Return the `SourceInfo` of the current instruction.
241 pub fn current_source_info(&self) -> Option<&mir::SourceInfo> {
242 self.loc.ok().map(|loc| self.body.source_info(loc))
245 pub fn current_span(&self) -> Span {
247 Ok(loc) => self.body.source_info(loc).span,
253 impl<'tcx> fmt::Display for FrameInfo<'tcx> {
254 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
255 ty::tls::with(|tcx| {
256 if tcx.def_key(self.instance.def_id()).disambiguated_data.data
257 == DefPathData::ClosureExpr
259 write!(f, "inside closure")?;
261 write!(f, "inside `{}`", self.instance)?;
263 if !self.span.is_dummy() {
264 let sm = tcx.sess.source_map();
265 let lo = sm.lookup_char_pos(self.span.lo());
269 sm.filename_for_diagnostics(&lo.file.name),
271 lo.col.to_usize() + 1
279 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for InterpCx<'mir, 'tcx, M> {
281 fn data_layout(&self) -> &TargetDataLayout {
282 &self.tcx.data_layout
286 impl<'mir, 'tcx, M> layout::HasTyCtxt<'tcx> for InterpCx<'mir, 'tcx, M>
288 M: Machine<'mir, 'tcx>,
291 fn tcx(&self) -> TyCtxt<'tcx> {
296 impl<'mir, 'tcx, M> layout::HasParamEnv<'tcx> for InterpCx<'mir, 'tcx, M>
298 M: Machine<'mir, 'tcx>,
300 fn param_env(&self) -> ty::ParamEnv<'tcx> {
305 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> {
306 type LayoutOfResult = InterpResult<'tcx, TyAndLayout<'tcx>>;
309 fn layout_tcx_at_span(&self) -> Span {
310 // Using the cheap root span for performance.
315 fn handle_layout_err(
317 err: LayoutError<'tcx>,
320 ) -> InterpErrorInfo<'tcx> {
321 err_inval!(Layout(err)).into()
325 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> FnAbiOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> {
326 type FnAbiOfResult = InterpResult<'tcx, &'tcx FnAbi<'tcx, Ty<'tcx>>>;
328 fn handle_fn_abi_err(
330 err: FnAbiError<'tcx>,
332 _fn_abi_request: FnAbiRequest<'tcx>,
333 ) -> InterpErrorInfo<'tcx> {
335 FnAbiError::Layout(err) => err_inval!(Layout(err)).into(),
336 FnAbiError::AdjustForForeignAbi(err) => {
337 err_inval!(FnAbiAdjustForForeignAbi(err)).into()
343 /// Test if it is valid for a MIR assignment to assign `src`-typed place to `dest`-typed value.
344 /// This test should be symmetric, as it is primarily about layout compatibility.
345 pub(super) fn mir_assign_valid_types<'tcx>(
347 param_env: ParamEnv<'tcx>,
348 src: TyAndLayout<'tcx>,
349 dest: TyAndLayout<'tcx>,
351 // Type-changing assignments can happen when subtyping is used. While
352 // all normal lifetimes are erased, higher-ranked types with their
353 // late-bound lifetimes are still around and can lead to type
354 // differences. So we compare ignoring lifetimes.
355 if equal_up_to_regions(tcx, param_env, src.ty, dest.ty) {
356 // Make sure the layout is equal, too -- just to be safe. Miri really
357 // needs layout equality. For performance reason we skip this check when
358 // the types are equal. Equal types *can* have different layouts when
359 // enum downcast is involved (as enum variants carry the type of the
360 // enum), but those should never occur in assignments.
361 if cfg!(debug_assertions) || src.ty != dest.ty {
362 assert_eq!(src.layout, dest.layout);
370 /// Use the already known layout if given (but sanity check in debug mode),
371 /// or compute the layout.
372 #[cfg_attr(not(debug_assertions), inline(always))]
373 pub(super) fn from_known_layout<'tcx>(
375 param_env: ParamEnv<'tcx>,
376 known_layout: Option<TyAndLayout<'tcx>>,
377 compute: impl FnOnce() -> InterpResult<'tcx, TyAndLayout<'tcx>>,
378 ) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
381 Some(known_layout) => {
382 if cfg!(debug_assertions) {
383 let check_layout = compute()?;
384 if !mir_assign_valid_types(tcx.tcx, param_env, check_layout, known_layout) {
387 "expected type differs from actual type.\nexpected: {:?}\nactual: {:?}",
398 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
402 param_env: ty::ParamEnv<'tcx>,
407 tcx: tcx.at(root_span),
409 memory: Memory::new(),
410 recursion_limit: tcx.recursion_limit(),
415 pub fn cur_span(&self) -> Span {
416 // This deliberately does *not* honor `requires_caller_location` since it is used for much
417 // more than just panics.
418 self.stack().last().map_or(self.tcx.span, |f| f.current_span())
422 pub(crate) fn stack(&self) -> &[Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>] {
427 pub(crate) fn stack_mut(
429 ) -> &mut Vec<Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>> {
434 pub fn frame_idx(&self) -> usize {
435 let stack = self.stack();
436 assert!(!stack.is_empty());
441 pub fn frame(&self) -> &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> {
442 self.stack().last().expect("no call frames exist")
446 pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> {
447 self.stack_mut().last_mut().expect("no call frames exist")
451 pub(super) fn body(&self) -> &'mir mir::Body<'tcx> {
456 pub fn sign_extend(&self, value: u128, ty: TyAndLayout<'_>) -> u128 {
457 assert!(ty.abi.is_signed());
458 ty.size.sign_extend(value)
462 pub fn truncate(&self, value: u128, ty: TyAndLayout<'_>) -> u128 {
463 ty.size.truncate(value)
467 pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool {
468 ty.is_freeze(self.tcx, self.param_env)
473 instance: ty::InstanceDef<'tcx>,
474 promoted: Option<mir::Promoted>,
475 ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
476 let def = instance.with_opt_param();
477 trace!("load mir(instance={:?}, promoted={:?})", instance, promoted);
478 let body = if let Some(promoted) = promoted {
479 &self.tcx.promoted_mir_opt_const_arg(def)[promoted]
481 M::load_mir(self, instance)?
483 // do not continue if typeck errors occurred (can only occur in local crate)
484 if let Some(err) = body.tainted_by_errors {
485 throw_inval!(AlreadyReported(err));
490 /// Call this on things you got out of the MIR (so it is as generic as the current
491 /// stack frame), to bring it into the proper environment for this interpreter.
492 pub(super) fn subst_from_current_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
495 ) -> Result<T, InterpError<'tcx>> {
496 self.subst_from_frame_and_normalize_erasing_regions(self.frame(), value)
499 /// Call this on things you got out of the MIR (so it is as generic as the provided
500 /// stack frame), to bring it into the proper environment for this interpreter.
501 pub(super) fn subst_from_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
503 frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>,
505 ) -> Result<T, InterpError<'tcx>> {
508 .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value)
510 self.tcx.sess.delay_span_bug(
512 format!("failed to normalize {}", e.get_type_for_failure()).as_str(),
515 InterpError::InvalidProgram(InvalidProgramInfo::TooGeneric)
519 /// The `substs` are assumed to already be in our interpreter "universe" (param_env).
520 pub(super) fn resolve(
522 def: ty::WithOptConstParam<DefId>,
523 substs: SubstsRef<'tcx>,
524 ) -> InterpResult<'tcx, ty::Instance<'tcx>> {
525 trace!("resolve: {:?}, {:#?}", def, substs);
526 trace!("param_env: {:#?}", self.param_env);
527 trace!("substs: {:#?}", substs);
528 match ty::Instance::resolve_opt_const_arg(*self.tcx, self.param_env, def, substs) {
529 Ok(Some(instance)) => Ok(instance),
530 Ok(None) => throw_inval!(TooGeneric),
532 // FIXME(eddyb) this could be a bit more specific than `AlreadyReported`.
533 Err(error_reported) => throw_inval!(AlreadyReported(error_reported)),
538 pub fn layout_of_local(
540 frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>,
542 layout: Option<TyAndLayout<'tcx>>,
543 ) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
544 // `const_prop` runs into this with an invalid (empty) frame, so we
545 // have to support that case (mostly by skipping all caching).
546 match frame.locals.get(local).and_then(|state| state.layout.get()) {
548 let layout = from_known_layout(self.tcx, self.param_env, layout, || {
549 let local_ty = frame.body.local_decls[local].ty;
551 self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty)?;
552 self.layout_of(local_ty)
554 if let Some(state) = frame.locals.get(local) {
555 // Layouts of locals are requested a lot, so we cache them.
556 state.layout.set(Some(layout));
560 Some(layout) => Ok(layout),
564 /// Returns the actual dynamic size and alignment of the place at the given type.
565 /// Only the "meta" (metadata) part of the place matters.
566 /// This can fail to provide an answer for extern types.
567 pub(super) fn size_and_align_of(
569 metadata: &MemPlaceMeta<M::Provenance>,
570 layout: &TyAndLayout<'tcx>,
571 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
572 if !layout.is_unsized() {
573 return Ok(Some((layout.size, layout.align.abi)));
575 match layout.ty.kind() {
576 ty::Adt(..) | ty::Tuple(..) => {
577 // First get the size of all statically known fields.
578 // Don't use type_of::sizing_type_of because that expects t to be sized,
579 // and it also rounds up to alignment, which we want to avoid,
580 // as the unsized field's alignment could be smaller.
581 assert!(!layout.ty.is_simd());
582 assert!(layout.fields.count() > 0);
583 trace!("DST layout: {:?}", layout);
585 let sized_size = layout.fields.offset(layout.fields.count() - 1);
586 let sized_align = layout.align.abi;
588 "DST {} statically sized prefix size: {:?} align: {:?}",
594 // Recurse to get the size of the dynamically sized field (must be
595 // the last field). Can't have foreign types here, how would we
596 // adjust alignment and size for them?
597 let field = layout.field(self, layout.fields.count() - 1);
598 let Some((unsized_size, unsized_align)) = self.size_and_align_of(metadata, &field)? else {
599 // A field with an extern type. We don't know the actual dynamic size
604 // FIXME (#26403, #27023): We should be adding padding
605 // to `sized_size` (to accommodate the `unsized_align`
606 // required of the unsized field that follows) before
607 // summing it with `sized_size`. (Note that since #26403
608 // is unfixed, we do not yet add the necessary padding
609 // here. But this is where the add would go.)
611 // Return the sum of sizes and max of aligns.
612 let size = sized_size + unsized_size; // `Size` addition
614 // Choose max of two known alignments (combined value must
615 // be aligned according to more restrictive of the two).
616 let align = sized_align.max(unsized_align);
618 // Issue #27023: must add any necessary padding to `size`
619 // (to make it a multiple of `align`) before returning it.
620 let size = size.align_to(align);
622 // Check if this brought us over the size limit.
623 if size > self.max_size_of_val() {
624 throw_ub!(InvalidMeta("total size is bigger than largest supported object"));
626 Ok(Some((size, align)))
629 let vtable = metadata.unwrap_meta().to_pointer(self)?;
630 // Read size and align from vtable (already checks size).
631 Ok(Some(self.get_vtable_size_and_align(vtable)?))
634 ty::Slice(_) | ty::Str => {
635 let len = metadata.unwrap_meta().to_machine_usize(self)?;
636 let elem = layout.field(self, 0);
638 // Make sure the slice is not too big.
639 let size = elem.size.bytes().saturating_mul(len); // we rely on `max_size_of_val` being smaller than `u64::MAX`.
640 let size = Size::from_bytes(size);
641 if size > self.max_size_of_val() {
642 throw_ub!(InvalidMeta("slice is bigger than largest supported object"));
644 Ok(Some((size, elem.align.abi)))
647 ty::Foreign(_) => Ok(None),
649 _ => span_bug!(self.cur_span(), "size_and_align_of::<{:?}> not supported", layout.ty),
653 pub fn size_and_align_of_mplace(
655 mplace: &MPlaceTy<'tcx, M::Provenance>,
656 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
657 self.size_and_align_of(&mplace.meta, &mplace.layout)
660 #[instrument(skip(self, body, return_place, return_to_block), level = "debug")]
661 pub fn push_stack_frame(
663 instance: ty::Instance<'tcx>,
664 body: &'mir mir::Body<'tcx>,
665 return_place: &PlaceTy<'tcx, M::Provenance>,
666 return_to_block: StackPopCleanup,
667 ) -> InterpResult<'tcx> {
668 trace!("body: {:#?}", body);
669 // first push a stack frame so we have access to the local substs
670 let pre_frame = Frame {
672 loc: Err(body.span), // Span used for errors caused during preamble.
674 return_place: return_place.clone(),
675 // empty local array, we fill it in below, after we are inside the stack frame and
676 // all methods actually know about the frame
677 locals: IndexVec::new(),
679 tracing_span: SpanGuard::new(),
682 let frame = M::init_frame_extra(self, pre_frame)?;
683 self.stack_mut().push(frame);
685 // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check).
686 for const_ in &body.required_consts {
687 let span = const_.span;
689 self.subst_from_current_frame_and_normalize_erasing_regions(const_.literal)?;
690 self.mir_const_to_op(&const_, None).map_err(|err| {
691 // If there was an error, set the span of the current frame to this constant.
692 // Avoiding doing this when evaluation succeeds.
693 self.frame_mut().loc = Err(span);
698 // Most locals are initially dead.
699 let dummy = LocalState { value: LocalValue::Dead, layout: Cell::new(None) };
700 let mut locals = IndexVec::from_elem(dummy, &body.local_decls);
702 // Now mark those locals as live that have no `Storage*` annotations.
703 let always_live = always_storage_live_locals(self.body());
704 for local in locals.indices() {
705 if always_live.contains(local) {
706 locals[local].value = LocalValue::Live(Operand::Immediate(Immediate::Uninit));
710 self.frame_mut().locals = locals;
711 M::after_stack_push(self)?;
712 self.frame_mut().loc = Ok(mir::Location::START);
714 let span = info_span!("frame", "{}", instance);
715 self.frame_mut().tracing_span.enter(span);
720 /// Jump to the given block.
722 pub fn go_to_block(&mut self, target: mir::BasicBlock) {
723 self.frame_mut().loc = Ok(mir::Location { block: target, statement_index: 0 });
726 /// *Return* to the given `target` basic block.
727 /// Do *not* use for unwinding! Use `unwind_to_block` instead.
729 /// If `target` is `None`, that indicates the function cannot return, so we raise UB.
730 pub fn return_to_block(&mut self, target: Option<mir::BasicBlock>) -> InterpResult<'tcx> {
731 if let Some(target) = target {
732 self.go_to_block(target);
735 throw_ub!(Unreachable)
739 /// *Unwind* to the given `target` basic block.
740 /// Do *not* use for returning! Use `return_to_block` instead.
742 /// If `target` is `StackPopUnwind::Skip`, that indicates the function does not need cleanup
743 /// during unwinding, and we will just keep propagating that upwards.
745 /// If `target` is `StackPopUnwind::NotAllowed`, that indicates the function does not allow
746 /// unwinding, and doing so is UB.
747 pub fn unwind_to_block(&mut self, target: StackPopUnwind) -> InterpResult<'tcx> {
748 self.frame_mut().loc = match target {
749 StackPopUnwind::Cleanup(block) => Ok(mir::Location { block, statement_index: 0 }),
750 StackPopUnwind::Skip => Err(self.frame_mut().body.span),
751 StackPopUnwind::NotAllowed => {
752 throw_ub_format!("unwinding past a stack frame that does not allow unwinding")
758 /// Pops the current frame from the stack, deallocating the
759 /// memory for allocated locals.
761 /// If `unwinding` is `false`, then we are performing a normal return
762 /// from a function. In this case, we jump back into the frame of the caller,
763 /// and continue execution as normal.
765 /// If `unwinding` is `true`, then we are in the middle of a panic,
766 /// and need to unwind this frame. In this case, we jump to the
767 /// `cleanup` block for the function, which is responsible for running
768 /// `Drop` impls for any locals that have been initialized at this point.
769 /// The cleanup block ends with a special `Resume` terminator, which will
770 /// cause us to continue unwinding.
771 #[instrument(skip(self), level = "debug")]
772 pub(super) fn pop_stack_frame(&mut self, unwinding: bool) -> InterpResult<'tcx> {
774 "popping stack frame ({})",
775 if unwinding { "during unwinding" } else { "returning from function" }
778 // Check `unwinding`.
781 match self.frame().loc {
782 Ok(loc) => self.body().basic_blocks[loc.block].is_cleanup,
786 if unwinding && self.frame_idx() == 0 {
787 throw_ub_format!("unwinding past the topmost frame of the stack");
790 // Copy return value. Must of course happen *before* we deallocate the locals.
791 let copy_ret_result = if !unwinding {
793 .local_to_op(self.frame(), mir::RETURN_PLACE, None)
794 .expect("return place should always be live");
795 let dest = self.frame().return_place.clone();
796 let err = self.copy_op(&op, &dest, /*allow_transmute*/ true);
797 trace!("return value: {:?}", self.dump_place(*dest));
798 // We delay actually short-circuiting on this error until *after* the stack frame is
799 // popped, since we want this error to be attributed to the caller, whose type defines
806 // Cleanup: deallocate locals.
807 // Usually we want to clean up (deallocate locals), but in a few rare cases we don't.
808 // We do this while the frame is still on the stack, so errors point to the callee.
809 let return_to_block = self.frame().return_to_block;
810 let cleanup = match return_to_block {
811 StackPopCleanup::Goto { .. } => true,
812 StackPopCleanup::Root { cleanup, .. } => cleanup,
815 // We need to take the locals out, since we need to mutate while iterating.
816 let locals = mem::take(&mut self.frame_mut().locals);
817 for local in &locals {
818 self.deallocate_local(local.value)?;
822 // All right, now it is time to actually pop the frame.
823 // Note that its locals are gone already, but that's fine.
825 self.stack_mut().pop().expect("tried to pop a stack frame, but there were none");
826 // Report error from return value copy, if any.
829 // If we are not doing cleanup, also skip everything else.
831 assert!(self.stack().is_empty(), "only the topmost frame should ever be leaked");
832 assert!(!unwinding, "tried to skip cleanup during unwinding");
833 // Skip machine hook.
836 if M::after_stack_pop(self, frame, unwinding)? == StackPopJump::NoJump {
837 // The hook already did everything.
841 // Normal return, figure out where to jump.
843 // Follow the unwind edge.
844 let unwind = match return_to_block {
845 StackPopCleanup::Goto { unwind, .. } => unwind,
846 StackPopCleanup::Root { .. } => {
847 panic!("encountered StackPopCleanup::Root when unwinding!")
850 self.unwind_to_block(unwind)
852 // Follow the normal return edge.
853 match return_to_block {
854 StackPopCleanup::Goto { ret, .. } => self.return_to_block(ret),
855 StackPopCleanup::Root { .. } => {
857 self.stack().is_empty(),
858 "only the topmost frame can have StackPopCleanup::Root"
866 /// Mark a storage as live, killing the previous content.
867 pub fn storage_live(&mut self, local: mir::Local) -> InterpResult<'tcx> {
868 assert!(local != mir::RETURN_PLACE, "Cannot make return place live");
869 trace!("{:?} is now live", local);
871 let local_val = LocalValue::Live(Operand::Immediate(Immediate::Uninit));
872 // StorageLive expects the local to be dead, and marks it live.
873 let old = mem::replace(&mut self.frame_mut().locals[local].value, local_val);
874 if !matches!(old, LocalValue::Dead) {
875 throw_ub_format!("StorageLive on a local that was already live");
880 pub fn storage_dead(&mut self, local: mir::Local) -> InterpResult<'tcx> {
881 assert!(local != mir::RETURN_PLACE, "Cannot make return place dead");
882 trace!("{:?} is now dead", local);
884 // It is entirely okay for this local to be already dead (at least that's how we currently generate MIR)
885 let old = mem::replace(&mut self.frame_mut().locals[local].value, LocalValue::Dead);
886 self.deallocate_local(old)?;
890 #[instrument(skip(self), level = "debug")]
891 fn deallocate_local(&mut self, local: LocalValue<M::Provenance>) -> InterpResult<'tcx> {
892 if let LocalValue::Live(Operand::Indirect(MemPlace { ptr, .. })) = local {
893 // All locals have a backing allocation, even if the allocation is empty
894 // due to the local having ZST type. Hence we can `unwrap`.
896 "deallocating local {:?}: {:?}",
898 // Locals always have a `alloc_id` (they are never the result of a int2ptr).
899 self.dump_alloc(ptr.provenance.unwrap().get_alloc_id().unwrap())
901 self.deallocate_ptr(ptr, None, MemoryKind::Stack)?;
906 pub fn eval_to_allocation(
909 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
910 // For statics we pick `ParamEnv::reveal_all`, because statics don't have generics
911 // and thus don't care about the parameter environment. While we could just use
912 // `self.param_env`, that would mean we invoke the query to evaluate the static
913 // with different parameter environments, thus causing the static to be evaluated
915 let param_env = if self.tcx.is_static(gid.instance.def_id()) {
916 ty::ParamEnv::reveal_all()
920 let param_env = param_env.with_const();
921 // Use a precise span for better cycle errors.
922 let val = self.tcx.at(self.cur_span()).eval_to_allocation_raw(param_env.and(gid))?;
923 self.raw_const_to_mplace(val)
927 pub fn dump_place(&self, place: Place<M::Provenance>) -> PlacePrinter<'_, 'mir, 'tcx, M> {
928 PlacePrinter { ecx: self, place }
932 pub fn generate_stacktrace_from_stack(
933 stack: &[Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>],
934 ) -> Vec<FrameInfo<'tcx>> {
935 let mut frames = Vec::new();
936 // This deliberately does *not* honor `requires_caller_location` since it is used for much
937 // more than just panics.
938 for frame in stack.iter().rev() {
939 let lint_root = frame.current_source_info().and_then(|source_info| {
940 match &frame.body.source_scopes[source_info.scope].local_data {
941 mir::ClearCrossCrate::Set(data) => Some(data.lint_root),
942 mir::ClearCrossCrate::Clear => None,
945 let span = frame.current_span();
947 frames.push(FrameInfo { span, instance: frame.instance, lint_root });
949 trace!("generate stacktrace: {:#?}", frames);
954 pub fn generate_stacktrace(&self) -> Vec<FrameInfo<'tcx>> {
955 Self::generate_stacktrace_from_stack(self.stack())
960 /// Helper struct for the `dump_place` function.
961 pub struct PlacePrinter<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> {
962 ecx: &'a InterpCx<'mir, 'tcx, M>,
963 place: Place<M::Provenance>,
966 impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> std::fmt::Debug
967 for PlacePrinter<'a, 'mir, 'tcx, M>
969 fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
971 Place::Local { frame, local } => {
972 let mut allocs = Vec::new();
973 write!(fmt, "{:?}", local)?;
974 if frame != self.ecx.frame_idx() {
975 write!(fmt, " ({} frames up)", self.ecx.frame_idx() - frame)?;
979 match self.ecx.stack()[frame].locals[local].value {
980 LocalValue::Dead => write!(fmt, " is dead")?,
981 LocalValue::Live(Operand::Immediate(Immediate::Uninit)) => {
982 write!(fmt, " is uninitialized")?
984 LocalValue::Live(Operand::Indirect(mplace)) => {
989 MemPlaceMeta::Meta(meta) => format!(" meta({:?})", meta),
990 MemPlaceMeta::None => String::new(),
994 allocs.extend(mplace.ptr.provenance.map(Provenance::get_alloc_id));
996 LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => {
997 write!(fmt, " {:?}", val)?;
998 if let Scalar::Ptr(ptr, _size) = val {
999 allocs.push(ptr.provenance.get_alloc_id());
1002 LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => {
1003 write!(fmt, " ({:?}, {:?})", val1, val2)?;
1004 if let Scalar::Ptr(ptr, _size) = val1 {
1005 allocs.push(ptr.provenance.get_alloc_id());
1007 if let Scalar::Ptr(ptr, _size) = val2 {
1008 allocs.push(ptr.provenance.get_alloc_id());
1013 write!(fmt, ": {:?}", self.ecx.dump_allocs(allocs.into_iter().flatten().collect()))
1015 Place::Ptr(mplace) => match mplace.ptr.provenance.and_then(Provenance::get_alloc_id) {
1017 write!(fmt, "by ref {:?}: {:?}", mplace.ptr, self.ecx.dump_alloc(alloc_id))
1019 ptr => write!(fmt, " integral by ref: {:?}", ptr),