5 use syntax::source_map::{self, Span, DUMMY_SP};
6 use rustc::hir::def_id::DefId;
7 use rustc::hir::def::DefKind;
9 use rustc::ty::layout::{
10 self, Size, Align, HasDataLayout, LayoutOf, TyLayout
12 use rustc::ty::subst::{Subst, SubstsRef};
13 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
14 use rustc::ty::query::TyCtxtAt;
15 use rustc_data_structures::indexed_vec::IndexVec;
16 use rustc::mir::interpret::{
18 GlobalId, Scalar, Pointer, FrameInfo, AllocId,
19 InterpResult, truncate, sign_extend,
21 use rustc_data_structures::fx::FxHashMap;
24 Immediate, Operand, MemPlace, MPlaceTy, Place, PlaceTy, ScalarMaybeUndef,
28 pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
29 /// Stores the `Machine` instance.
32 /// The results of the type checker, from rustc.
33 pub tcx: TyCtxtAt<'tcx>,
35 /// Bounds in scope for polymorphic evaluations.
36 pub(crate) param_env: ty::ParamEnv<'tcx>,
38 /// The virtual memory system.
39 pub(crate) memory: Memory<'mir, 'tcx, M>,
41 /// The virtual call stack.
42 pub(crate) stack: Vec<Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>>,
44 /// A cache for deduplicating vtables
46 FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), Pointer<M::PointerTag>>,
51 pub struct Frame<'mir, 'tcx, Tag=(), Extra=()> {
52 ////////////////////////////////////////////////////////////////////////////////
53 // Function and callsite information
54 ////////////////////////////////////////////////////////////////////////////////
55 /// The MIR for the function called on this frame.
56 pub body: &'mir mir::Body<'tcx>,
58 /// The def_id and substs of the current function.
59 pub instance: ty::Instance<'tcx>,
61 /// The span of the call site.
62 pub span: source_map::Span,
64 ////////////////////////////////////////////////////////////////////////////////
65 // Return place and locals
66 ////////////////////////////////////////////////////////////////////////////////
67 /// Work to perform when returning from this function.
68 pub return_to_block: StackPopCleanup,
70 /// The location where the result of the current stack frame should be written to,
71 /// and its layout in the caller.
72 pub return_place: Option<PlaceTy<'tcx, Tag>>,
74 /// The list of locals for this stack frame, stored in order as
75 /// `[return_ptr, arguments..., variables..., temporaries...]`.
76 /// The locals are stored as `Option<Value>`s.
77 /// `None` represents a local that is currently dead, while a live local
78 /// can either directly contain `Scalar` or refer to some part of an `Allocation`.
79 pub locals: IndexVec<mir::Local, LocalState<'tcx, Tag>>,
81 ////////////////////////////////////////////////////////////////////////////////
82 // Current position within the function
83 ////////////////////////////////////////////////////////////////////////////////
84 /// The block that is currently executed (or will be executed after the above call stacks
86 pub block: mir::BasicBlock,
88 /// The index of the currently evaluated statement.
91 /// Extra data for the machine.
95 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
96 pub enum StackPopCleanup {
97 /// Jump to the next block in the caller, or cause UB if None (that's a function
98 /// that may never return). Also store layout of return place so
99 /// we can validate it at that layout.
100 Goto(Option<mir::BasicBlock>),
101 /// Just do nohing: Used by Main and for the box_alloc hook in miri.
102 /// `cleanup` says whether locals are deallocated. Static computation
103 /// wants them leaked to intern what they need (and just throw away
104 /// the entire `ecx` when it is done).
105 None { cleanup: bool },
108 /// State of a local variable including a memoized layout
109 #[derive(Clone, PartialEq, Eq)]
110 pub struct LocalState<'tcx, Tag=(), Id=AllocId> {
111 pub value: LocalValue<Tag, Id>,
112 /// Don't modify if `Some`, this is only used to prevent computing the layout twice
113 pub layout: Cell<Option<TyLayout<'tcx>>>,
116 /// Current value of a local variable
117 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
118 pub enum LocalValue<Tag=(), Id=AllocId> {
119 /// This local is not currently alive, and cannot be used at all.
121 /// This local is alive but not yet initialized. It can be written to
122 /// but not read from or its address taken. Locals get initialized on
123 /// first write because for unsized locals, we do not know their size
126 /// A normal, live local.
127 /// Mostly for convenience, we re-use the `Operand` type here.
128 /// This is an optimization over just always having a pointer here;
129 /// we can thus avoid doing an allocation when the local just stores
130 /// immediate values *and* never has its address taken.
131 Live(Operand<Tag, Id>),
134 impl<'tcx, Tag: Copy + 'static> LocalState<'tcx, Tag> {
135 pub fn access(&self) -> InterpResult<'tcx, Operand<Tag>> {
137 LocalValue::Dead => throw_unsup!(DeadLocal),
138 LocalValue::Uninitialized =>
139 bug!("The type checker should prevent reading from a never-written local"),
140 LocalValue::Live(val) => Ok(val),
144 /// Overwrite the local. If the local can be overwritten in place, return a reference
145 /// to do so; otherwise return the `MemPlace` to consult instead.
148 ) -> InterpResult<'tcx, Result<&mut LocalValue<Tag>, MemPlace<Tag>>> {
150 LocalValue::Dead => throw_unsup!(DeadLocal),
151 LocalValue::Live(Operand::Indirect(mplace)) => Ok(Err(mplace)),
152 ref mut local @ LocalValue::Live(Operand::Immediate(_)) |
153 ref mut local @ LocalValue::Uninitialized => {
160 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for InterpCx<'mir, 'tcx, M> {
162 fn data_layout(&self) -> &layout::TargetDataLayout {
163 &self.tcx.data_layout
167 impl<'mir, 'tcx, M> layout::HasTyCtxt<'tcx> for InterpCx<'mir, 'tcx, M>
169 M: Machine<'mir, 'tcx>,
172 fn tcx(&self) -> TyCtxt<'tcx> {
177 impl<'mir, 'tcx, M> layout::HasParamEnv<'tcx> for InterpCx<'mir, 'tcx, M>
179 M: Machine<'mir, 'tcx>,
181 fn param_env(&self) -> ty::ParamEnv<'tcx> {
186 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> {
188 type TyLayout = InterpResult<'tcx, TyLayout<'tcx>>;
191 fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
193 .layout_of(self.param_env.and(ty))
195 err_inval!(Layout(layout)).into()
200 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
203 param_env: ty::ParamEnv<'tcx>,
205 memory_extra: M::MemoryExtra,
211 memory: Memory::new(tcx, memory_extra),
213 vtables: FxHashMap::default(),
218 pub fn memory(&self) -> &Memory<'mir, 'tcx, M> {
223 pub fn memory_mut(&mut self) -> &mut Memory<'mir, 'tcx, M> {
230 scalar: Scalar<M::PointerTag>,
231 ) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
232 self.memory.force_ptr(scalar)
238 scalar: Scalar<M::PointerTag>,
240 ) -> InterpResult<'tcx, u128> {
241 self.memory.force_bits(scalar, size)
245 pub fn tag_static_base_pointer(&self, ptr: Pointer) -> Pointer<M::PointerTag> {
246 self.memory.tag_static_base_pointer(ptr)
250 pub fn stack(&self) -> &[Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>] {
255 pub fn cur_frame(&self) -> usize {
256 assert!(self.stack.len() > 0);
261 pub fn frame(&self) -> &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra> {
262 self.stack.last().expect("no call frames exist")
266 pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra> {
267 self.stack.last_mut().expect("no call frames exist")
271 pub(super) fn body(&self) -> &'mir mir::Body<'tcx> {
276 pub fn sign_extend(&self, value: u128, ty: TyLayout<'_>) -> u128 {
277 assert!(ty.abi.is_signed());
278 sign_extend(value, ty.size)
282 pub fn truncate(&self, value: u128, ty: TyLayout<'_>) -> u128 {
283 truncate(value, ty.size)
287 pub fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
288 ty.is_sized(self.tcx, self.param_env)
292 pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool {
293 ty.is_freeze(*self.tcx, self.param_env, DUMMY_SP)
296 pub(super) fn subst_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>(
299 ) -> InterpResult<'tcx, T> {
300 match self.stack.last() {
301 Some(frame) => Ok(self.tcx.subst_and_normalize_erasing_regions(
302 frame.instance.substs,
306 None => if substs.needs_subst() {
307 throw_inval!(TooGeneric)
314 pub(super) fn resolve(
317 substs: SubstsRef<'tcx>
318 ) -> InterpResult<'tcx, ty::Instance<'tcx>> {
319 trace!("resolve: {:?}, {:#?}", def_id, substs);
320 trace!("param_env: {:#?}", self.param_env);
321 let substs = self.subst_and_normalize_erasing_regions(substs)?;
322 trace!("substs: {:#?}", substs);
323 ty::Instance::resolve(
328 ).ok_or_else(|| err_inval!(TooGeneric).into())
333 instance: ty::InstanceDef<'tcx>,
334 ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
335 // do not continue if typeck errors occurred (can only occur in local crate)
336 let did = instance.def_id();
338 && self.tcx.has_typeck_tables(did)
339 && self.tcx.typeck_tables_of(did).tainted_by_errors
341 throw_inval!(TypeckError)
343 trace!("load mir {:?}", instance);
345 ty::InstanceDef::Item(def_id) => if self.tcx.is_mir_available(did) {
346 Ok(self.tcx.optimized_mir(did))
348 throw_unsup!(NoMirFor(self.tcx.def_path_str(def_id)))
350 _ => Ok(self.tcx.instance_mir(instance)),
354 pub(super) fn monomorphize<T: TypeFoldable<'tcx> + Subst<'tcx>>(
357 ) -> InterpResult<'tcx, T> {
358 match self.stack.last() {
359 Some(frame) => Ok(self.monomorphize_with_substs(t, frame.instance.substs)?),
360 None => if t.needs_subst() {
361 throw_inval!(TooGeneric)
368 fn monomorphize_with_substs<T: TypeFoldable<'tcx> + Subst<'tcx>>(
371 substs: SubstsRef<'tcx>
372 ) -> InterpResult<'tcx, T> {
373 // miri doesn't care about lifetimes, and will choke on some crazy ones
374 // let's simply get rid of them
375 let substituted = t.subst(*self.tcx, substs);
377 if substituted.needs_subst() {
378 throw_inval!(TooGeneric)
381 Ok(self.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substituted))
384 pub fn layout_of_local(
386 frame: &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>,
388 layout: Option<TyLayout<'tcx>>,
389 ) -> InterpResult<'tcx, TyLayout<'tcx>> {
390 match frame.locals[local].layout.get() {
392 let layout = crate::interpret::operand::from_known_layout(layout, || {
393 let local_ty = frame.body.local_decls[local].ty;
394 let local_ty = self.monomorphize_with_substs(local_ty, frame.instance.substs)?;
395 self.layout_of(local_ty)
397 // Layouts of locals are requested a lot, so we cache them.
398 frame.locals[local].layout.set(Some(layout));
401 Some(layout) => Ok(layout),
405 /// Returns the actual dynamic size and alignment of the place at the given type.
406 /// Only the "meta" (metadata) part of the place matters.
407 /// This can fail to provide an answer for extern types.
408 pub(super) fn size_and_align_of(
410 metadata: Option<Scalar<M::PointerTag>>,
411 layout: TyLayout<'tcx>,
412 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
413 if !layout.is_unsized() {
414 return Ok(Some((layout.size, layout.align.abi)));
416 match layout.ty.sty {
417 ty::Adt(..) | ty::Tuple(..) => {
418 // First get the size of all statically known fields.
419 // Don't use type_of::sizing_type_of because that expects t to be sized,
420 // and it also rounds up to alignment, which we want to avoid,
421 // as the unsized field's alignment could be smaller.
422 assert!(!layout.ty.is_simd());
423 trace!("DST layout: {:?}", layout);
425 let sized_size = layout.fields.offset(layout.fields.count() - 1);
426 let sized_align = layout.align.abi;
428 "DST {} statically sized prefix size: {:?} align: {:?}",
434 // Recurse to get the size of the dynamically sized field (must be
435 // the last field). Can't have foreign types here, how would we
436 // adjust alignment and size for them?
437 let field = layout.field(self, layout.fields.count() - 1)?;
438 let (unsized_size, unsized_align) = match self.size_and_align_of(metadata, field)? {
439 Some(size_and_align) => size_and_align,
441 // A field with extern type. If this field is at offset 0, we behave
442 // like the underlying extern type.
443 // FIXME: Once we have made decisions for how to handle size and alignment
444 // of `extern type`, this should be adapted. It is just a temporary hack
445 // to get some code to work that probably ought to work.
446 if sized_size == Size::ZERO {
449 bug!("Fields cannot be extern types, unless they are at offset 0")
454 // FIXME (#26403, #27023): We should be adding padding
455 // to `sized_size` (to accommodate the `unsized_align`
456 // required of the unsized field that follows) before
457 // summing it with `sized_size`. (Note that since #26403
458 // is unfixed, we do not yet add the necessary padding
459 // here. But this is where the add would go.)
461 // Return the sum of sizes and max of aligns.
462 let size = sized_size + unsized_size;
464 // Choose max of two known alignments (combined value must
465 // be aligned according to more restrictive of the two).
466 let align = sized_align.max(unsized_align);
468 // Issue #27023: must add any necessary padding to `size`
469 // (to make it a multiple of `align`) before returning it.
471 // Namely, the returned size should be, in C notation:
473 // `size + ((size & (align-1)) ? align : 0)`
475 // emulated via the semi-standard fast bit trick:
477 // `(size + (align-1)) & -align`
479 Ok(Some((size.align_to(align), align)))
482 let vtable = metadata.expect("dyn trait fat ptr must have vtable");
483 // the second entry in the vtable is the dynamic size of the object.
484 Ok(Some(self.read_size_and_align_from_vtable(vtable)?))
487 ty::Slice(_) | ty::Str => {
488 let len = metadata.expect("slice fat ptr must have vtable").to_usize(self)?;
489 let elem = layout.field(self, 0)?;
490 Ok(Some((elem.size * len, elem.align.abi)))
497 _ => bug!("size_and_align_of::<{:?}> not supported", layout.ty),
501 pub fn size_and_align_of_mplace(
503 mplace: MPlaceTy<'tcx, M::PointerTag>
504 ) -> InterpResult<'tcx, Option<(Size, Align)>> {
505 self.size_and_align_of(mplace.meta, mplace.layout)
508 pub fn push_stack_frame(
510 instance: ty::Instance<'tcx>,
511 span: source_map::Span,
512 body: &'mir mir::Body<'tcx>,
513 return_place: Option<PlaceTy<'tcx, M::PointerTag>>,
514 return_to_block: StackPopCleanup,
515 ) -> InterpResult<'tcx> {
516 if self.stack.len() > 0 {
517 info!("PAUSING({}) {}", self.cur_frame(), self.frame().instance);
519 ::log_settings::settings().indentation += 1;
521 // first push a stack frame so we have access to the local substs
522 let extra = M::stack_push(self)?;
523 self.stack.push(Frame {
525 block: mir::START_BLOCK,
528 // empty local array, we fill it in below, after we are inside the stack frame and
529 // all methods actually know about the frame
530 locals: IndexVec::new(),
537 // don't allocate at all for trivial constants
538 if body.local_decls.len() > 1 {
539 // Locals are initially uninitialized.
540 let dummy = LocalState {
541 value: LocalValue::Uninitialized,
542 layout: Cell::new(None),
544 let mut locals = IndexVec::from_elem(dummy, &body.local_decls);
545 // Return place is handled specially by the `eval_place` functions, and the
546 // entry in `locals` should never be used. Make it dead, to be sure.
547 locals[mir::RETURN_PLACE].value = LocalValue::Dead;
548 // Now mark those locals as dead that we do not want to initialize
549 match self.tcx.def_kind(instance.def_id()) {
550 // statics and constants don't have `Storage*` statements, no need to look for them
551 Some(DefKind::Static)
552 | Some(DefKind::Const)
553 | Some(DefKind::AssocConst) => {},
555 trace!("push_stack_frame: {:?}: num_bbs: {}", span, body.basic_blocks().len());
556 for block in body.basic_blocks() {
557 for stmt in block.statements.iter() {
558 use rustc::mir::StatementKind::{StorageDead, StorageLive};
561 StorageDead(local) => {
562 locals[local].value = LocalValue::Dead;
571 self.frame_mut().locals = locals;
574 info!("ENTERING({}) {}", self.cur_frame(), self.frame().instance);
576 if self.stack.len() > self.tcx.sess.const_eval_stack_frame_limit {
577 throw_exhaust!(StackFrameLimitReached)
583 pub(super) fn pop_stack_frame(&mut self) -> InterpResult<'tcx> {
584 info!("LEAVING({}) {}", self.cur_frame(), self.frame().instance);
585 ::log_settings::settings().indentation -= 1;
586 let frame = self.stack.pop().expect(
587 "tried to pop a stack frame, but there were none",
589 M::stack_pop(self, frame.extra)?;
590 // Abort early if we do not want to clean up: We also avoid validation in that case,
591 // because this is CTFE and the final value will be thoroughly validated anyway.
592 match frame.return_to_block {
593 StackPopCleanup::Goto(_) => {},
594 StackPopCleanup::None { cleanup } => {
596 assert!(self.stack.is_empty(), "only the topmost frame should ever be leaked");
597 // Leak the locals, skip validation.
602 // Deallocate all locals that are backed by an allocation.
603 for local in frame.locals {
604 self.deallocate_local(local.value)?;
606 // Validate the return value. Do this after deallocating so that we catch dangling
608 if let Some(return_place) = frame.return_place {
609 if M::enforce_validity(self) {
610 // Data got changed, better make sure it matches the type!
611 // It is still possible that the return place held invalid data while
612 // the function is running, but that's okay because nobody could have
613 // accessed that same data from the "outside" to observe any broken
614 // invariant -- that is, unless a function somehow has a ptr to
615 // its return place... but the way MIR is currently generated, the
616 // return place is always a local and then this cannot happen.
617 self.validate_operand(
618 self.place_to_op(return_place)?,
624 // Uh, that shouldn't happen... the function did not intend to return
625 throw_ub!(Unreachable)
627 // Jump to new block -- *after* validation so that the spans make more sense.
628 match frame.return_to_block {
629 StackPopCleanup::Goto(block) => {
630 self.goto_block(block)?;
632 StackPopCleanup::None { .. } => {}
635 if self.stack.len() > 0 {
636 info!("CONTINUING({}) {}", self.cur_frame(), self.frame().instance);
642 /// Mark a storage as live, killing the previous content and returning it.
643 /// Remember to deallocate that!
647 ) -> InterpResult<'tcx, LocalValue<M::PointerTag>> {
648 assert!(local != mir::RETURN_PLACE, "Cannot make return place live");
649 trace!("{:?} is now live", local);
651 let local_val = LocalValue::Uninitialized;
652 // StorageLive *always* kills the value that's currently stored.
653 // However, we do not error if the variable already is live;
654 // see <https://github.com/rust-lang/rust/issues/42371>.
655 Ok(mem::replace(&mut self.frame_mut().locals[local].value, local_val))
658 /// Returns the old value of the local.
659 /// Remember to deallocate that!
660 pub fn storage_dead(&mut self, local: mir::Local) -> LocalValue<M::PointerTag> {
661 assert!(local != mir::RETURN_PLACE, "Cannot make return place dead");
662 trace!("{:?} is now dead", local);
664 mem::replace(&mut self.frame_mut().locals[local].value, LocalValue::Dead)
667 pub(super) fn deallocate_local(
669 local: LocalValue<M::PointerTag>,
670 ) -> InterpResult<'tcx> {
671 // FIXME: should we tell the user that there was a local which was never written to?
672 if let LocalValue::Live(Operand::Indirect(MemPlace { ptr, .. })) = local {
673 trace!("deallocating local");
674 let ptr = ptr.to_ptr()?;
675 self.memory.dump_alloc(ptr.alloc_id);
676 self.memory.deallocate_local(ptr)?;
681 pub fn const_eval_raw(
684 ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
685 // FIXME(oli-obk): make this check an assertion that it's not a static here
686 // FIXME(RalfJ, oli-obk): document that `Place::Static` can never be anything but a static
687 // and `ConstValue::Unevaluated` can never be a static
688 let param_env = if self.tcx.is_static(gid.instance.def_id()) {
689 ty::ParamEnv::reveal_all()
693 // We use `const_eval_raw` here, and get an unvalidated result. That is okay:
694 // Our result will later be validated anyway, and there seems no good reason
695 // to have to fail early here. This is also more consistent with
696 // `Memory::get_static_alloc` which has to use `const_eval_raw` to avoid cycles.
697 let val = self.tcx.const_eval_raw(param_env.and(gid)).map_err(|err| {
699 ErrorHandled::Reported =>
700 err_inval!(ReferencedConstant),
701 ErrorHandled::TooGeneric =>
702 err_inval!(TooGeneric),
705 self.raw_const_to_mplace(val)
708 pub fn dump_place(&self, place: Place<M::PointerTag>) {
710 if !log_enabled!(::log::Level::Trace) {
714 Place::Local { frame, local } => {
715 let mut allocs = Vec::new();
716 let mut msg = format!("{:?}", local);
717 if frame != self.cur_frame() {
718 write!(msg, " ({} frames up)", self.cur_frame() - frame).unwrap();
720 write!(msg, ":").unwrap();
722 match self.stack[frame].locals[local].value {
723 LocalValue::Dead => write!(msg, " is dead").unwrap(),
724 LocalValue::Uninitialized => write!(msg, " is uninitialized").unwrap(),
725 LocalValue::Live(Operand::Indirect(mplace)) => {
727 Scalar::Ptr(ptr) => {
728 write!(msg, " by align({}){} ref:",
729 mplace.align.bytes(),
731 Some(meta) => format!(" meta({:?})", meta),
732 None => String::new()
735 allocs.push(ptr.alloc_id);
737 ptr => write!(msg, " by integral ref: {:?}", ptr).unwrap(),
740 LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => {
741 write!(msg, " {:?}", val).unwrap();
742 if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val {
743 allocs.push(ptr.alloc_id);
746 LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => {
747 write!(msg, " ({:?}, {:?})", val1, val2).unwrap();
748 if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val1 {
749 allocs.push(ptr.alloc_id);
751 if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val2 {
752 allocs.push(ptr.alloc_id);
758 self.memory.dump_allocs(allocs);
760 Place::Ptr(mplace) => {
762 Scalar::Ptr(ptr) => {
763 trace!("by align({}) ref:", mplace.align.bytes());
764 self.memory.dump_alloc(ptr.alloc_id);
766 ptr => trace!(" integral by ref: {:?}", ptr),
772 pub fn generate_stacktrace(&self, explicit_span: Option<Span>) -> Vec<FrameInfo<'tcx>> {
773 let mut last_span = None;
774 let mut frames = Vec::new();
775 for &Frame { instance, span, body, block, stmt, .. } in self.stack().iter().rev() {
776 // make sure we don't emit frames that are duplicates of the previous
777 if explicit_span == Some(span) {
778 last_span = Some(span);
781 if let Some(last) = last_span {
786 last_span = Some(span);
788 let block = &body.basic_blocks()[block];
789 let source_info = if stmt < block.statements.len() {
790 block.statements[stmt].source_info
792 block.terminator().source_info
794 let lint_root = match body.source_scope_local_data {
795 mir::ClearCrossCrate::Set(ref ivs) => Some(ivs[source_info.scope].lint_root),
796 mir::ClearCrossCrate::Clear => None,
798 frames.push(FrameInfo { call_site: span, instance, lint_root });
800 trace!("generate stacktrace: {:#?}, {:?}", frames, explicit_span);