5 use either::{Either, Left, Right};
7 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
8 use rustc_index::vec::IndexVec;
10 use rustc_middle::mir::interpret::{ErrorHandled, InterpError, InvalidProgramInfo};
11 use rustc_middle::ty::layout::{
12 self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
15 use rustc_middle::ty::{
16 self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable,
18 use rustc_mir_dataflow::storage::always_storage_live_locals;
19 use rustc_session::Limit;
20 use rustc_span::{Pos, Span};
21 use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayout};
24 AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace,
25 MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, PointerArithmetic, Provenance,
30 pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
31 /// Stores the `Machine` instance.
33 /// Note: the stack is provided by the machine.
36 /// The results of the type checker, from rustc.
37 /// The span in this is the "root" of the evaluation, i.e., the const
38 /// we are evaluating (if this is CTFE).
39 pub tcx: TyCtxtAt<'tcx>,
41 /// Bounds in scope for polymorphic evaluations.
42 pub(crate) param_env: ty::ParamEnv<'tcx>,
44 /// The virtual memory system.
45 pub memory: Memory<'mir, 'tcx, M>,
47 /// The recursion limit (cached from `tcx.recursion_limit(())`)
48 pub recursion_limit: Limit,
51 // The Phantomdata exists to prevent this type from being `Send`. If it were sent across a thread
52 // boundary and dropped in the other thread, it would exit the span in the other thread.
53 struct SpanGuard(tracing::Span, std::marker::PhantomData<*const u8>);
56 /// By default a `SpanGuard` does nothing.
58 Self(tracing::Span::none(), std::marker::PhantomData)
61 /// If a span is entered, we exit the previous span (if any, normally none) and enter the
62 /// new span. This is mainly so we don't have to use `Option` for the `tracing_span` field of
63 /// `Frame` by creating a dummy span to being with and then entering it once the frame has
65 fn enter(&mut self, span: tracing::Span) {
66 // This executes the destructor on the previous instance of `SpanGuard`, ensuring that
67 // we never enter or exit more spans than vice versa. Unless you `mem::leak`, then we
68 // can't protect the tracing stack, but that'll just lead to weird logging, no actual
70 *self = Self(span, std::marker::PhantomData);
71 self.0.with_subscriber(|(id, dispatch)| {
77 impl Drop for SpanGuard {
79 self.0.with_subscriber(|(id, dispatch)| {
86 pub struct Frame<'mir, 'tcx, Prov: Provenance = AllocId, Extra = ()> {
87 ////////////////////////////////////////////////////////////////////////////////
88 // Function and callsite information
89 ////////////////////////////////////////////////////////////////////////////////
90 /// The MIR for the function called on this frame.
91 pub body: &'mir mir::Body<'tcx>,
93 /// The def_id and substs of the current function.
94 pub instance: ty::Instance<'tcx>,
96 /// Extra data for the machine.
99 ////////////////////////////////////////////////////////////////////////////////
100 // Return place and locals
101 ////////////////////////////////////////////////////////////////////////////////
102 /// Work to perform when returning from this function.
103 pub return_to_block: StackPopCleanup,
105 /// The location where the result of the current stack frame should be written to,
106 /// and its layout in the caller.
107 pub return_place: PlaceTy<'tcx, Prov>,
109 /// The list of locals for this stack frame, stored in order as
110 /// `[return_ptr, arguments..., variables..., temporaries...]`.
111 /// The locals are stored as `Option<Value>`s.
112 /// `None` represents a local that is currently dead, while a live local
113 /// can either directly contain `Scalar` or refer to some part of an `Allocation`.
115 /// Do *not* access this directly; always go through the machine hook!
116 pub locals: IndexVec<mir::Local, LocalState<'tcx, Prov>>,
118 /// The span of the `tracing` crate is stored here.
119 /// When the guard is dropped, the span is exited. This gives us
120 /// a full stack trace on all tracing statements.
121 tracing_span: SpanGuard,
123 ////////////////////////////////////////////////////////////////////////////////
124 // Current position within the function
125 ////////////////////////////////////////////////////////////////////////////////
126 /// If this is `Right`, we are not currently executing any particular statement in
127 /// this frame (can happen e.g. during frame initialization, and during unwinding on
128 /// frames without cleanup code).
130 /// Needs to be public because ConstProp does unspeakable things to it.
131 pub loc: Either<mir::Location, Span>,
134 /// What we store about a frame in an interpreter backtrace.
136 pub struct FrameInfo<'tcx> {
137 pub instance: ty::Instance<'tcx>,
139 pub lint_root: Option<hir::HirId>,
142 /// Unwind information.
143 #[derive(Clone, Copy, Eq, PartialEq, Debug)]
144 pub enum StackPopUnwind {
145 /// The cleanup block.
146 Cleanup(mir::BasicBlock),
147 /// No cleanup needs to be done.
149 /// Unwinding is not allowed (UB).
153 #[derive(Clone, Copy, Eq, PartialEq, Debug)] // Miri debug-prints these
154 pub enum StackPopCleanup {
155 /// Jump to the next block in the caller, or cause UB if None (that's a function
156 /// that may never return). Also store layout of return place so
157 /// we can validate it at that layout.
158 /// `ret` stores the block we jump to on a normal return, while `unwind`
159 /// stores the block used for cleanup during unwinding.
160 Goto { ret: Option<mir::BasicBlock>, unwind: StackPopUnwind },
161 /// The root frame of the stack: nowhere else to jump to.
162 /// `cleanup` says whether locals are deallocated. Static computation
163 /// wants them leaked to intern what they need (and just throw away
164 /// the entire `ecx` when it is done).
165 Root { cleanup: bool },
168 /// State of a local variable including a memoized layout
169 #[derive(Clone, Debug)]
170 pub struct LocalState<'tcx, Prov: Provenance = AllocId> {
171 pub value: LocalValue<Prov>,
172 /// Don't modify if `Some`, this is only used to prevent computing the layout twice
173 pub layout: Cell<Option<TyAndLayout<'tcx>>>,
176 /// Current value of a local variable
177 #[derive(Copy, Clone, Debug)] // Miri debug-prints these
178 pub enum LocalValue<Prov: Provenance = AllocId> {
179 /// This local is not currently alive, and cannot be used at all.
181 /// A normal, live local.
182 /// Mostly for convenience, we re-use the `Operand` type here.
183 /// This is an optimization over just always having a pointer here;
184 /// we can thus avoid doing an allocation when the local just stores
185 /// immediate values *and* never has its address taken.
189 impl<'tcx, Prov: Provenance + 'static> LocalState<'tcx, Prov> {
190 /// Read the local's value or error if the local is not yet live or not live anymore.
192 pub fn access(&self) -> InterpResult<'tcx, &Operand<Prov>> {
194 LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"?
195 LocalValue::Live(val) => Ok(val),
199 /// Overwrite the local. If the local can be overwritten in place, return a reference
200 /// to do so; otherwise return the `MemPlace` to consult instead.
202 /// Note: This may only be invoked from the `Machine::access_local_mut` hook and not from
203 /// anywhere else. You may be invalidating machine invariants if you do!
205 pub fn access_mut(&mut self) -> InterpResult<'tcx, &mut Operand<Prov>> {
206 match &mut self.value {
207 LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"?
208 LocalValue::Live(val) => Ok(val),
213 impl<'mir, 'tcx, Prov: Provenance> Frame<'mir, 'tcx, Prov> {
214 pub fn with_extra<Extra>(self, extra: Extra) -> Frame<'mir, 'tcx, Prov, Extra> {
217 instance: self.instance,
218 return_to_block: self.return_to_block,
219 return_place: self.return_place,
223 tracing_span: self.tracing_span,
228 impl<'mir, 'tcx, Prov: Provenance, Extra> Frame<'mir, 'tcx, Prov, Extra> {
229 /// Get the current location within the Frame.
231 /// If this is `Left`, we are not currently executing any particular statement in
232 /// this frame (can happen e.g. during frame initialization, and during unwinding on
233 /// frames without cleanup code).
236 pub fn current_loc(&self) -> Either<mir::Location, Span> {
240 /// Return the `SourceInfo` of the current instruction.
241 pub fn current_source_info(&self) -> Option<&mir::SourceInfo> {
242 self.loc.left().map(|loc| self.body.source_info(loc))
245 pub fn current_span(&self) -> Span {
247 Left(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 // Note: this triggers a `good_path_bug` state, which means that if we ever get here
262 // we must emit a diagnostic. We should never display a `FrameInfo` unless we
263 // actually want to emit a warning or error to the user.
264 write!(f, "inside `{}`", self.instance)?;
266 if !self.span.is_dummy() {
267 let sm = tcx.sess.source_map();
268 let lo = sm.lookup_char_pos(self.span.lo());
272 sm.filename_for_diagnostics(&lo.file.name),
274 lo.col.to_usize() + 1
282 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for InterpCx<'mir, 'tcx, M> {
284 fn data_layout(&self) -> &TargetDataLayout {
285 &self.tcx.data_layout
289 impl<'mir, 'tcx, M> layout::HasTyCtxt<'tcx> for InterpCx<'mir, 'tcx, M>
291 M: Machine<'mir, 'tcx>,
294 fn tcx(&self) -> TyCtxt<'tcx> {
299 impl<'mir, 'tcx, M> layout::HasParamEnv<'tcx> for InterpCx<'mir, 'tcx, M>
301 M: Machine<'mir, 'tcx>,
303 fn param_env(&self) -> ty::ParamEnv<'tcx> {
308 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> {
309 type LayoutOfResult = InterpResult<'tcx, TyAndLayout<'tcx>>;
312 fn layout_tcx_at_span(&self) -> Span {
313 // Using the cheap root span for performance.
318 fn handle_layout_err(
320 err: LayoutError<'tcx>,
323 ) -> InterpErrorInfo<'tcx> {
324 err_inval!(Layout(err)).into()
328 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> FnAbiOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> {
329 type FnAbiOfResult = InterpResult<'tcx, &'tcx FnAbi<'tcx, Ty<'tcx>>>;
331 fn handle_fn_abi_err(
333 err: FnAbiError<'tcx>,
335 _fn_abi_request: FnAbiRequest<'tcx>,
336 ) -> InterpErrorInfo<'tcx> {
338 FnAbiError::Layout(err) => err_inval!(Layout(err)).into(),
339 FnAbiError::AdjustForForeignAbi(err) => {
340 err_inval!(FnAbiAdjustForForeignAbi(err)).into()
346 /// Test if it is valid for a MIR assignment to assign `src`-typed place to `dest`-typed value.
347 /// This test should be symmetric, as it is primarily about layout compatibility.
348 pub(super) fn mir_assign_valid_types<'tcx>(
350 param_env: ParamEnv<'tcx>,
351 src: TyAndLayout<'tcx>,
352 dest: TyAndLayout<'tcx>,
354 // Type-changing assignments can happen when subtyping is used. While
355 // all normal lifetimes are erased, higher-ranked types with their
356 // late-bound lifetimes are still around and can lead to type
358 if util::is_subtype(tcx, param_env, src.ty, dest.ty) {
359 // Make sure the layout is equal, too -- just to be safe. Miri really
360 // needs layout equality. For performance reason we skip this check when
361 // the types are equal. Equal types *can* have different layouts when
362 // enum downcast is involved (as enum variants carry the type of the
363 // enum), but those should never occur in assignments.
364 if cfg!(debug_assertions) || src.ty != dest.ty {
365 assert_eq!(src.layout, dest.layout);
373 /// Use the already known layout if given (but sanity check in debug mode),
374 /// or compute the layout.
375 #[cfg_attr(not(debug_assertions), inline(always))]
376 pub(super) fn from_known_layout<'tcx>(
378 param_env: ParamEnv<'tcx>,
379 known_layout: Option<TyAndLayout<'tcx>>,
380 compute: impl FnOnce() -> InterpResult<'tcx, TyAndLayout<'tcx>>,
381 ) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
384 Some(known_layout) => {
385 if cfg!(debug_assertions) {
386 let check_layout = compute()?;
387 if !mir_assign_valid_types(tcx.tcx, param_env, check_layout, known_layout) {
390 "expected type differs from actual type.\nexpected: {:?}\nactual: {:?}",
401 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
405 param_env: ty::ParamEnv<'tcx>,
410 tcx: tcx.at(root_span),
412 memory: Memory::new(),
413 recursion_limit: tcx.recursion_limit(),
418 pub fn cur_span(&self) -> Span {
419 // This deliberately does *not* honor `requires_caller_location` since it is used for much
420 // more than just panics.
421 self.stack().last().map_or(self.tcx.span, |f| f.current_span())
425 pub(crate) fn stack(&self) -> &[Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>] {
430 pub(crate) fn stack_mut(
432 ) -> &mut Vec<Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>> {
437 pub fn frame_idx(&self) -> usize {
438 let stack = self.stack();
439 assert!(!stack.is_empty());
444 pub fn frame(&self) -> &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> {
445 self.stack().last().expect("no call frames exist")
449 pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> {
450 self.stack_mut().last_mut().expect("no call frames exist")
454 pub(super) fn body(&self) -> &'mir mir::Body<'tcx> {
459 pub fn sign_extend(&self, value: u128, ty: TyAndLayout<'_>) -> u128 {
460 assert!(ty.abi.is_signed());
461 ty.size.sign_extend(value)
465 pub fn truncate(&self, value: u128, ty: TyAndLayout<'_>) -> u128 {
466 ty.size.truncate(value)
470 pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool {
471 ty.is_freeze(*self.tcx, self.param_env)
476 instance: ty::InstanceDef<'tcx>,
477 promoted: Option<mir::Promoted>,
478 ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
479 let def = instance.with_opt_param();
480 trace!("load mir(instance={:?}, promoted={:?})", instance, promoted);
481 let body = if let Some(promoted) = promoted {
482 &self.tcx.promoted_mir_opt_const_arg(def)[promoted]
484 M::load_mir(self, instance)?
486 // do not continue if typeck errors occurred (can only occur in local crate)
487 if let Some(err) = body.tainted_by_errors {
488 throw_inval!(AlreadyReported(err));
493 /// Call this on things you got out of the MIR (so it is as generic as the current
494 /// stack frame), to bring it into the proper environment for this interpreter.
495 pub(super) fn subst_from_current_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
498 ) -> Result<T, InterpError<'tcx>> {
499 self.subst_from_frame_and_normalize_erasing_regions(self.frame(), value)
502 /// Call this on things you got out of the MIR (so it is as generic as the provided
503 /// stack frame), to bring it into the proper environment for this interpreter.
504 pub(super) fn subst_from_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
506 frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>,
508 ) -> Result<T, InterpError<'tcx>> {
511 .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value)
513 self.tcx.sess.delay_span_bug(
515 format!("failed to normalize {}", e.get_type_for_failure()).as_str(),
518 InterpError::InvalidProgram(InvalidProgramInfo::TooGeneric)
522 /// The `substs` are assumed to already be in our interpreter "universe" (param_env).
523 pub(super) fn resolve(
525 def: ty::WithOptConstParam<DefId>,
526 substs: SubstsRef<'tcx>,
527 ) -> InterpResult<'tcx, ty::Instance<'tcx>> {
528 trace!("resolve: {:?}, {:#?}", def, substs);
529 trace!("param_env: {:#?}", self.param_env);
530 trace!("substs: {:#?}", substs);
531 match ty::Instance::resolve_opt_const_arg(*self.tcx, self.param_env, def, substs) {
532 Ok(Some(instance)) => Ok(instance),
533 Ok(None) => throw_inval!(TooGeneric),
535 // FIXME(eddyb) this could be a bit more specific than `AlreadyReported`.
536 Err(error_reported) => throw_inval!(AlreadyReported(error_reported)),
541 pub fn layout_of_local(
543 frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>,
545 layout: Option<TyAndLayout<'tcx>>,
546 ) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
547 // `const_prop` runs into this with an invalid (empty) frame, so we
548 // have to support that case (mostly by skipping all caching).
549 match frame.locals.get(local).and_then(|state| state.layout.get()) {
551 let layout = from_known_layout(self.tcx, self.param_env, layout, || {
552 let local_ty = frame.body.local_decls[local].ty;
554 self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty)?;
555 self.layout_of(local_ty)
557 if let Some(state) = frame.locals.get(local) {
558 // Layouts of locals are requested a lot, so we cache them.
559 state.layout.set(Some(layout));
563 Some(layout) => Ok(layout),
567 /// Returns the actual dynamic size and alignment of the place at the given type.
568 /// Only the "meta" (metadata) part of the place matters.
569 /// This can fail to provide an answer for extern types.
570 pub(super) fn size_and_align_of(
572 metadata: &MemPlaceMeta<M::Provenance>,
573 layout: &TyAndLayout<'tcx>,
574 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
575 if layout.is_sized() {
576 return Ok(Some((layout.size, layout.align.abi)));
578 match layout.ty.kind() {
579 ty::Adt(..) | ty::Tuple(..) => {
580 // First get the size of all statically known fields.
581 // Don't use type_of::sizing_type_of because that expects t to be sized,
582 // and it also rounds up to alignment, which we want to avoid,
583 // as the unsized field's alignment could be smaller.
584 assert!(!layout.ty.is_simd());
585 assert!(layout.fields.count() > 0);
586 trace!("DST layout: {:?}", layout);
588 let sized_size = layout.fields.offset(layout.fields.count() - 1);
589 let sized_align = layout.align.abi;
591 "DST {} statically sized prefix size: {:?} align: {:?}",
597 // Recurse to get the size of the dynamically sized field (must be
598 // the last field). Can't have foreign types here, how would we
599 // adjust alignment and size for them?
600 let field = layout.field(self, layout.fields.count() - 1);
601 let Some((unsized_size, mut unsized_align)) = self.size_and_align_of(metadata, &field)? else {
602 // A field with an extern type. We don't know the actual dynamic size
607 // FIXME (#26403, #27023): We should be adding padding
608 // to `sized_size` (to accommodate the `unsized_align`
609 // required of the unsized field that follows) before
610 // summing it with `sized_size`. (Note that since #26403
611 // is unfixed, we do not yet add the necessary padding
612 // here. But this is where the add would go.)
614 // Return the sum of sizes and max of aligns.
615 let size = sized_size + unsized_size; // `Size` addition
617 // Packed types ignore the alignment of their fields.
618 if let ty::Adt(def, _) = layout.ty.kind() {
619 if def.repr().packed() {
620 unsized_align = sized_align;
624 // Choose max of two known alignments (combined value must
625 // be aligned according to more restrictive of the two).
626 let align = sized_align.max(unsized_align);
628 // Issue #27023: must add any necessary padding to `size`
629 // (to make it a multiple of `align`) before returning it.
630 let size = size.align_to(align);
632 // Check if this brought us over the size limit.
633 if size > self.max_size_of_val() {
634 throw_ub!(InvalidMeta("total size is bigger than largest supported object"));
636 Ok(Some((size, align)))
639 let vtable = metadata.unwrap_meta().to_pointer(self)?;
640 // Read size and align from vtable (already checks size).
641 Ok(Some(self.get_vtable_size_and_align(vtable)?))
644 ty::Slice(_) | ty::Str => {
645 let len = metadata.unwrap_meta().to_machine_usize(self)?;
646 let elem = layout.field(self, 0);
648 // Make sure the slice is not too big.
649 let size = elem.size.bytes().saturating_mul(len); // we rely on `max_size_of_val` being smaller than `u64::MAX`.
650 let size = Size::from_bytes(size);
651 if size > self.max_size_of_val() {
652 throw_ub!(InvalidMeta("slice is bigger than largest supported object"));
654 Ok(Some((size, elem.align.abi)))
657 ty::Foreign(_) => Ok(None),
659 _ => span_bug!(self.cur_span(), "size_and_align_of::<{:?}> not supported", layout.ty),
663 pub fn size_and_align_of_mplace(
665 mplace: &MPlaceTy<'tcx, M::Provenance>,
666 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
667 self.size_and_align_of(&mplace.meta, &mplace.layout)
670 #[instrument(skip(self, body, return_place, return_to_block), level = "debug")]
671 pub fn push_stack_frame(
673 instance: ty::Instance<'tcx>,
674 body: &'mir mir::Body<'tcx>,
675 return_place: &PlaceTy<'tcx, M::Provenance>,
676 return_to_block: StackPopCleanup,
677 ) -> InterpResult<'tcx> {
678 trace!("body: {:#?}", body);
679 // first push a stack frame so we have access to the local substs
680 let pre_frame = Frame {
682 loc: Right(body.span), // Span used for errors caused during preamble.
684 return_place: return_place.clone(),
685 // empty local array, we fill it in below, after we are inside the stack frame and
686 // all methods actually know about the frame
687 locals: IndexVec::new(),
689 tracing_span: SpanGuard::new(),
692 let frame = M::init_frame_extra(self, pre_frame)?;
693 self.stack_mut().push(frame);
695 // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check).
696 for ct in &body.required_consts {
698 let ct = self.subst_from_current_frame_and_normalize_erasing_regions(ct.literal)?;
699 self.eval_mir_constant(&ct, Some(span), None)?;
702 // Most locals are initially dead.
703 let dummy = LocalState { value: LocalValue::Dead, layout: Cell::new(None) };
704 let mut locals = IndexVec::from_elem(dummy, &body.local_decls);
706 // Now mark those locals as live that have no `Storage*` annotations.
707 let always_live = always_storage_live_locals(self.body());
708 for local in locals.indices() {
709 if always_live.contains(local) {
710 locals[local].value = LocalValue::Live(Operand::Immediate(Immediate::Uninit));
714 self.frame_mut().locals = locals;
715 M::after_stack_push(self)?;
716 self.frame_mut().loc = Left(mir::Location::START);
718 let span = info_span!("frame", "{}", instance);
719 self.frame_mut().tracing_span.enter(span);
724 /// Jump to the given block.
726 pub fn go_to_block(&mut self, target: mir::BasicBlock) {
727 self.frame_mut().loc = Left(mir::Location { block: target, statement_index: 0 });
730 /// *Return* to the given `target` basic block.
731 /// Do *not* use for unwinding! Use `unwind_to_block` instead.
733 /// If `target` is `None`, that indicates the function cannot return, so we raise UB.
734 pub fn return_to_block(&mut self, target: Option<mir::BasicBlock>) -> InterpResult<'tcx> {
735 if let Some(target) = target {
736 self.go_to_block(target);
739 throw_ub!(Unreachable)
743 /// *Unwind* to the given `target` basic block.
744 /// Do *not* use for returning! Use `return_to_block` instead.
746 /// If `target` is `StackPopUnwind::Skip`, that indicates the function does not need cleanup
747 /// during unwinding, and we will just keep propagating that upwards.
749 /// If `target` is `StackPopUnwind::NotAllowed`, that indicates the function does not allow
750 /// unwinding, and doing so is UB.
751 pub fn unwind_to_block(&mut self, target: StackPopUnwind) -> InterpResult<'tcx> {
752 self.frame_mut().loc = match target {
753 StackPopUnwind::Cleanup(block) => Left(mir::Location { block, statement_index: 0 }),
754 StackPopUnwind::Skip => Right(self.frame_mut().body.span),
755 StackPopUnwind::NotAllowed => {
756 throw_ub_format!("unwinding past a stack frame that does not allow unwinding")
762 /// Pops the current frame from the stack, deallocating the
763 /// memory for allocated locals.
765 /// If `unwinding` is `false`, then we are performing a normal return
766 /// from a function. In this case, we jump back into the frame of the caller,
767 /// and continue execution as normal.
769 /// If `unwinding` is `true`, then we are in the middle of a panic,
770 /// and need to unwind this frame. In this case, we jump to the
771 /// `cleanup` block for the function, which is responsible for running
772 /// `Drop` impls for any locals that have been initialized at this point.
773 /// The cleanup block ends with a special `Resume` terminator, which will
774 /// cause us to continue unwinding.
775 #[instrument(skip(self), level = "debug")]
776 pub(super) fn pop_stack_frame(&mut self, unwinding: bool) -> InterpResult<'tcx> {
778 "popping stack frame ({})",
779 if unwinding { "during unwinding" } else { "returning from function" }
782 // Check `unwinding`.
785 match self.frame().loc {
786 Left(loc) => self.body().basic_blocks[loc.block].is_cleanup,
790 if unwinding && self.frame_idx() == 0 {
791 throw_ub_format!("unwinding past the topmost frame of the stack");
794 // Copy return value. Must of course happen *before* we deallocate the locals.
795 let copy_ret_result = if !unwinding {
797 .local_to_op(self.frame(), mir::RETURN_PLACE, None)
798 .expect("return place should always be live");
799 let dest = self.frame().return_place.clone();
800 let err = self.copy_op(&op, &dest, /*allow_transmute*/ true);
801 trace!("return value: {:?}", self.dump_place(*dest));
802 // We delay actually short-circuiting on this error until *after* the stack frame is
803 // popped, since we want this error to be attributed to the caller, whose type defines
810 // Cleanup: deallocate locals.
811 // Usually we want to clean up (deallocate locals), but in a few rare cases we don't.
812 // We do this while the frame is still on the stack, so errors point to the callee.
813 let return_to_block = self.frame().return_to_block;
814 let cleanup = match return_to_block {
815 StackPopCleanup::Goto { .. } => true,
816 StackPopCleanup::Root { cleanup, .. } => cleanup,
819 // We need to take the locals out, since we need to mutate while iterating.
820 let locals = mem::take(&mut self.frame_mut().locals);
821 for local in &locals {
822 self.deallocate_local(local.value)?;
826 // All right, now it is time to actually pop the frame.
827 // Note that its locals are gone already, but that's fine.
829 self.stack_mut().pop().expect("tried to pop a stack frame, but there were none");
830 // Report error from return value copy, if any.
833 // If we are not doing cleanup, also skip everything else.
835 assert!(self.stack().is_empty(), "only the topmost frame should ever be leaked");
836 assert!(!unwinding, "tried to skip cleanup during unwinding");
837 // Skip machine hook.
840 if M::after_stack_pop(self, frame, unwinding)? == StackPopJump::NoJump {
841 // The hook already did everything.
845 // Normal return, figure out where to jump.
847 // Follow the unwind edge.
848 let unwind = match return_to_block {
849 StackPopCleanup::Goto { unwind, .. } => unwind,
850 StackPopCleanup::Root { .. } => {
851 panic!("encountered StackPopCleanup::Root when unwinding!")
854 self.unwind_to_block(unwind)
856 // Follow the normal return edge.
857 match return_to_block {
858 StackPopCleanup::Goto { ret, .. } => self.return_to_block(ret),
859 StackPopCleanup::Root { .. } => {
861 self.stack().is_empty(),
862 "only the topmost frame can have StackPopCleanup::Root"
870 /// Mark a storage as live, killing the previous content.
871 pub fn storage_live(&mut self, local: mir::Local) -> InterpResult<'tcx> {
872 assert!(local != mir::RETURN_PLACE, "Cannot make return place live");
873 trace!("{:?} is now live", local);
875 let local_val = LocalValue::Live(Operand::Immediate(Immediate::Uninit));
876 // StorageLive expects the local to be dead, and marks it live.
877 let old = mem::replace(&mut self.frame_mut().locals[local].value, local_val);
878 if !matches!(old, LocalValue::Dead) {
879 throw_ub_format!("StorageLive on a local that was already live");
884 pub fn storage_dead(&mut self, local: mir::Local) -> InterpResult<'tcx> {
885 assert!(local != mir::RETURN_PLACE, "Cannot make return place dead");
886 trace!("{:?} is now dead", local);
888 // It is entirely okay for this local to be already dead (at least that's how we currently generate MIR)
889 let old = mem::replace(&mut self.frame_mut().locals[local].value, LocalValue::Dead);
890 self.deallocate_local(old)?;
894 #[instrument(skip(self), level = "debug")]
895 fn deallocate_local(&mut self, local: LocalValue<M::Provenance>) -> InterpResult<'tcx> {
896 if let LocalValue::Live(Operand::Indirect(MemPlace { ptr, .. })) = local {
897 // All locals have a backing allocation, even if the allocation is empty
898 // due to the local having ZST type. Hence we can `unwrap`.
900 "deallocating local {:?}: {:?}",
902 // Locals always have a `alloc_id` (they are never the result of a int2ptr).
903 self.dump_alloc(ptr.provenance.unwrap().get_alloc_id().unwrap())
905 self.deallocate_ptr(ptr, None, MemoryKind::Stack)?;
910 /// Call a query that can return `ErrorHandled`. If `span` is `Some`, point to that span when an error occurs.
911 pub fn ctfe_query<T>(
914 query: impl FnOnce(TyCtxtAt<'tcx>) -> Result<T, ErrorHandled>,
915 ) -> InterpResult<'tcx, T> {
916 // Use a precise span for better cycle errors.
917 query(self.tcx.at(span.unwrap_or_else(|| self.cur_span()))).map_err(|err| {
919 ErrorHandled::Reported(err) => {
920 if let Some(span) = span {
921 // To make it easier to figure out where this error comes from, also add a note at the current location.
922 self.tcx.sess.span_note_without_error(span, "erroneous constant used");
924 err_inval!(AlreadyReported(err))
926 ErrorHandled::TooGeneric => err_inval!(TooGeneric),
936 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
937 // For statics we pick `ParamEnv::reveal_all`, because statics don't have generics
938 // and thus don't care about the parameter environment. While we could just use
939 // `self.param_env`, that would mean we invoke the query to evaluate the static
940 // with different parameter environments, thus causing the static to be evaluated
942 let param_env = if self.tcx.is_static(gid.instance.def_id()) {
943 ty::ParamEnv::reveal_all()
947 let param_env = param_env.with_const();
948 let val = self.ctfe_query(span, |tcx| tcx.eval_to_allocation_raw(param_env.and(gid)))?;
949 self.raw_const_to_mplace(val)
953 pub fn dump_place(&self, place: Place<M::Provenance>) -> PlacePrinter<'_, 'mir, 'tcx, M> {
954 PlacePrinter { ecx: self, place }
958 pub fn generate_stacktrace_from_stack(
959 stack: &[Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>],
960 ) -> Vec<FrameInfo<'tcx>> {
961 let mut frames = Vec::new();
962 // This deliberately does *not* honor `requires_caller_location` since it is used for much
963 // more than just panics.
964 for frame in stack.iter().rev() {
965 let lint_root = frame.current_source_info().and_then(|source_info| {
966 match &frame.body.source_scopes[source_info.scope].local_data {
967 mir::ClearCrossCrate::Set(data) => Some(data.lint_root),
968 mir::ClearCrossCrate::Clear => None,
971 let span = frame.current_span();
973 frames.push(FrameInfo { span, instance: frame.instance, lint_root });
975 trace!("generate stacktrace: {:#?}", frames);
980 pub fn generate_stacktrace(&self) -> Vec<FrameInfo<'tcx>> {
981 Self::generate_stacktrace_from_stack(self.stack())
986 /// Helper struct for the `dump_place` function.
987 pub struct PlacePrinter<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> {
988 ecx: &'a InterpCx<'mir, 'tcx, M>,
989 place: Place<M::Provenance>,
992 impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> std::fmt::Debug
993 for PlacePrinter<'a, 'mir, 'tcx, M>
995 fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
997 Place::Local { frame, local } => {
998 let mut allocs = Vec::new();
999 write!(fmt, "{:?}", local)?;
1000 if frame != self.ecx.frame_idx() {
1001 write!(fmt, " ({} frames up)", self.ecx.frame_idx() - frame)?;
1005 match self.ecx.stack()[frame].locals[local].value {
1006 LocalValue::Dead => write!(fmt, " is dead")?,
1007 LocalValue::Live(Operand::Immediate(Immediate::Uninit)) => {
1008 write!(fmt, " is uninitialized")?
1010 LocalValue::Live(Operand::Indirect(mplace)) => {
1015 MemPlaceMeta::Meta(meta) => format!(" meta({:?})", meta),
1016 MemPlaceMeta::None => String::new(),
1020 allocs.extend(mplace.ptr.provenance.map(Provenance::get_alloc_id));
1022 LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => {
1023 write!(fmt, " {:?}", val)?;
1024 if let Scalar::Ptr(ptr, _size) = val {
1025 allocs.push(ptr.provenance.get_alloc_id());
1028 LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => {
1029 write!(fmt, " ({:?}, {:?})", val1, val2)?;
1030 if let Scalar::Ptr(ptr, _size) = val1 {
1031 allocs.push(ptr.provenance.get_alloc_id());
1033 if let Scalar::Ptr(ptr, _size) = val2 {
1034 allocs.push(ptr.provenance.get_alloc_id());
1039 write!(fmt, ": {:?}", self.ecx.dump_allocs(allocs.into_iter().flatten().collect()))
1041 Place::Ptr(mplace) => match mplace.ptr.provenance.and_then(Provenance::get_alloc_id) {
1043 write!(fmt, "by ref {:?}: {:?}", mplace.ptr, self.ecx.dump_alloc(alloc_id))
1045 ptr => write!(fmt, " integral by ref: {:?}", ptr),