diff options
Diffstat (limited to 'compiler/rustc_const_eval/src/interpret/eval_context.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/eval_context.rs | 1019 |
1 files changed, 1019 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs new file mode 100644 index 000000000..150d6589b --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs @@ -0,0 +1,1019 @@ +use std::cell::Cell; +use std::fmt; +use std::mem; + +use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData}; +use rustc_index::vec::IndexVec; +use rustc_middle::mir; +use rustc_middle::mir::interpret::{InterpError, InvalidProgramInfo}; +use rustc_middle::ty::layout::{ + self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers, + TyAndLayout, +}; +use rustc_middle::ty::{ + self, query::TyCtxtAt, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable, +}; +use rustc_mir_dataflow::storage::always_storage_live_locals; +use rustc_session::Limit; +use rustc_span::{Pos, Span}; +use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayout}; + +use super::{ + AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine, MemPlace, + MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, PointerArithmetic, Provenance, + Scalar, ScalarMaybeUninit, StackPopJump, +}; +use crate::transform::validate::equal_up_to_regions; + +pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> { + /// Stores the `Machine` instance. + /// + /// Note: the stack is provided by the machine. + pub machine: M, + + /// The results of the type checker, from rustc. + /// The span in this is the "root" of the evaluation, i.e., the const + /// we are evaluating (if this is CTFE). + pub tcx: TyCtxtAt<'tcx>, + + /// Bounds in scope for polymorphic evaluations. + pub(crate) param_env: ty::ParamEnv<'tcx>, + + /// The virtual memory system. + pub memory: Memory<'mir, 'tcx, M>, + + /// The recursion limit (cached from `tcx.recursion_limit(())`) + pub recursion_limit: Limit, +} + +// The Phantomdata exists to prevent this type from being `Send`. If it were sent across a thread +// boundary and dropped in the other thread, it would exit the span in the other thread. +struct SpanGuard(tracing::Span, std::marker::PhantomData<*const u8>); + +impl SpanGuard { + /// By default a `SpanGuard` does nothing. + fn new() -> Self { + Self(tracing::Span::none(), std::marker::PhantomData) + } + + /// If a span is entered, we exit the previous span (if any, normally none) and enter the + /// new span. This is mainly so we don't have to use `Option` for the `tracing_span` field of + /// `Frame` by creating a dummy span to being with and then entering it once the frame has + /// been pushed. + fn enter(&mut self, span: tracing::Span) { + // This executes the destructor on the previous instance of `SpanGuard`, ensuring that + // we never enter or exit more spans than vice versa. Unless you `mem::leak`, then we + // can't protect the tracing stack, but that'll just lead to weird logging, no actual + // problems. + *self = Self(span, std::marker::PhantomData); + self.0.with_subscriber(|(id, dispatch)| { + dispatch.enter(id); + }); + } +} + +impl Drop for SpanGuard { + fn drop(&mut self) { + self.0.with_subscriber(|(id, dispatch)| { + dispatch.exit(id); + }); + } +} + +/// A stack frame. +pub struct Frame<'mir, 'tcx, Prov: Provenance = AllocId, Extra = ()> { + //////////////////////////////////////////////////////////////////////////////// + // Function and callsite information + //////////////////////////////////////////////////////////////////////////////// + /// The MIR for the function called on this frame. + pub body: &'mir mir::Body<'tcx>, + + /// The def_id and substs of the current function. + pub instance: ty::Instance<'tcx>, + + /// Extra data for the machine. + pub extra: Extra, + + //////////////////////////////////////////////////////////////////////////////// + // Return place and locals + //////////////////////////////////////////////////////////////////////////////// + /// Work to perform when returning from this function. + pub return_to_block: StackPopCleanup, + + /// The location where the result of the current stack frame should be written to, + /// and its layout in the caller. + pub return_place: PlaceTy<'tcx, Prov>, + + /// The list of locals for this stack frame, stored in order as + /// `[return_ptr, arguments..., variables..., temporaries...]`. + /// The locals are stored as `Option<Value>`s. + /// `None` represents a local that is currently dead, while a live local + /// can either directly contain `Scalar` or refer to some part of an `Allocation`. + /// + /// Do *not* access this directly; always go through the machine hook! + pub locals: IndexVec<mir::Local, LocalState<'tcx, Prov>>, + + /// The span of the `tracing` crate is stored here. + /// When the guard is dropped, the span is exited. This gives us + /// a full stack trace on all tracing statements. + tracing_span: SpanGuard, + + //////////////////////////////////////////////////////////////////////////////// + // Current position within the function + //////////////////////////////////////////////////////////////////////////////// + /// If this is `Err`, we are not currently executing any particular statement in + /// this frame (can happen e.g. during frame initialization, and during unwinding on + /// frames without cleanup code). + /// We basically abuse `Result` as `Either`. + /// + /// Needs to be public because ConstProp does unspeakable things to it. + pub loc: Result<mir::Location, Span>, +} + +/// What we store about a frame in an interpreter backtrace. +#[derive(Debug)] +pub struct FrameInfo<'tcx> { + pub instance: ty::Instance<'tcx>, + pub span: Span, + pub lint_root: Option<hir::HirId>, +} + +/// Unwind information. +#[derive(Clone, Copy, Eq, PartialEq, Debug)] +pub enum StackPopUnwind { + /// The cleanup block. + Cleanup(mir::BasicBlock), + /// No cleanup needs to be done. + Skip, + /// Unwinding is not allowed (UB). + NotAllowed, +} + +#[derive(Clone, Copy, Eq, PartialEq, Debug)] // Miri debug-prints these +pub enum StackPopCleanup { + /// Jump to the next block in the caller, or cause UB if None (that's a function + /// that may never return). Also store layout of return place so + /// we can validate it at that layout. + /// `ret` stores the block we jump to on a normal return, while `unwind` + /// stores the block used for cleanup during unwinding. + Goto { ret: Option<mir::BasicBlock>, unwind: StackPopUnwind }, + /// The root frame of the stack: nowhere else to jump to. + /// `cleanup` says whether locals are deallocated. Static computation + /// wants them leaked to intern what they need (and just throw away + /// the entire `ecx` when it is done). + Root { cleanup: bool }, +} + +/// State of a local variable including a memoized layout +#[derive(Clone, Debug)] +pub struct LocalState<'tcx, Prov: Provenance = AllocId> { + pub value: LocalValue<Prov>, + /// Don't modify if `Some`, this is only used to prevent computing the layout twice + pub layout: Cell<Option<TyAndLayout<'tcx>>>, +} + +/// Current value of a local variable +#[derive(Copy, Clone, Debug)] // Miri debug-prints these +pub enum LocalValue<Prov: Provenance = AllocId> { + /// This local is not currently alive, and cannot be used at all. + Dead, + /// A normal, live local. + /// Mostly for convenience, we re-use the `Operand` type here. + /// This is an optimization over just always having a pointer here; + /// we can thus avoid doing an allocation when the local just stores + /// immediate values *and* never has its address taken. + Live(Operand<Prov>), +} + +impl<'tcx, Prov: Provenance + 'static> LocalState<'tcx, Prov> { + /// Read the local's value or error if the local is not yet live or not live anymore. + /// + /// Note: This may only be invoked from the `Machine::access_local` hook and not from + /// anywhere else. You may be invalidating machine invariants if you do! + #[inline] + pub fn access(&self) -> InterpResult<'tcx, &Operand<Prov>> { + match &self.value { + LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"? + LocalValue::Live(val) => Ok(val), + } + } + + /// Overwrite the local. If the local can be overwritten in place, return a reference + /// to do so; otherwise return the `MemPlace` to consult instead. + /// + /// Note: This may only be invoked from the `Machine::access_local_mut` hook and not from + /// anywhere else. You may be invalidating machine invariants if you do! + #[inline] + pub fn access_mut(&mut self) -> InterpResult<'tcx, &mut Operand<Prov>> { + match &mut self.value { + LocalValue::Dead => throw_ub!(DeadLocal), // could even be "invalid program"? + LocalValue::Live(val) => Ok(val), + } + } +} + +impl<'mir, 'tcx, Prov: Provenance> Frame<'mir, 'tcx, Prov> { + pub fn with_extra<Extra>(self, extra: Extra) -> Frame<'mir, 'tcx, Prov, Extra> { + Frame { + body: self.body, + instance: self.instance, + return_to_block: self.return_to_block, + return_place: self.return_place, + locals: self.locals, + loc: self.loc, + extra, + tracing_span: self.tracing_span, + } + } +} + +impl<'mir, 'tcx, Prov: Provenance, Extra> Frame<'mir, 'tcx, Prov, Extra> { + /// Get the current location within the Frame. + /// + /// If this is `Err`, we are not currently executing any particular statement in + /// this frame (can happen e.g. during frame initialization, and during unwinding on + /// frames without cleanup code). + /// We basically abuse `Result` as `Either`. + /// + /// Used by priroda. + pub fn current_loc(&self) -> Result<mir::Location, Span> { + self.loc + } + + /// Return the `SourceInfo` of the current instruction. + pub fn current_source_info(&self) -> Option<&mir::SourceInfo> { + self.loc.ok().map(|loc| self.body.source_info(loc)) + } + + pub fn current_span(&self) -> Span { + match self.loc { + Ok(loc) => self.body.source_info(loc).span, + Err(span) => span, + } + } +} + +impl<'tcx> fmt::Display for FrameInfo<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + ty::tls::with(|tcx| { + if tcx.def_key(self.instance.def_id()).disambiguated_data.data + == DefPathData::ClosureExpr + { + write!(f, "inside closure")?; + } else { + write!(f, "inside `{}`", self.instance)?; + } + if !self.span.is_dummy() { + let sm = tcx.sess.source_map(); + let lo = sm.lookup_char_pos(self.span.lo()); + write!( + f, + " at {}:{}:{}", + sm.filename_for_diagnostics(&lo.file.name), + lo.line, + lo.col.to_usize() + 1 + )?; + } + Ok(()) + }) + } +} + +impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for InterpCx<'mir, 'tcx, M> { + #[inline] + fn data_layout(&self) -> &TargetDataLayout { + &self.tcx.data_layout + } +} + +impl<'mir, 'tcx, M> layout::HasTyCtxt<'tcx> for InterpCx<'mir, 'tcx, M> +where + M: Machine<'mir, 'tcx>, +{ + #[inline] + fn tcx(&self) -> TyCtxt<'tcx> { + *self.tcx + } +} + +impl<'mir, 'tcx, M> layout::HasParamEnv<'tcx> for InterpCx<'mir, 'tcx, M> +where + M: Machine<'mir, 'tcx>, +{ + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.param_env + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> { + type LayoutOfResult = InterpResult<'tcx, TyAndLayout<'tcx>>; + + #[inline] + fn layout_tcx_at_span(&self) -> Span { + // Using the cheap root span for performance. + self.tcx.span + } + + #[inline] + fn handle_layout_err( + &self, + err: LayoutError<'tcx>, + _: Span, + _: Ty<'tcx>, + ) -> InterpErrorInfo<'tcx> { + err_inval!(Layout(err)).into() + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> FnAbiOfHelpers<'tcx> for InterpCx<'mir, 'tcx, M> { + type FnAbiOfResult = InterpResult<'tcx, &'tcx FnAbi<'tcx, Ty<'tcx>>>; + + fn handle_fn_abi_err( + &self, + err: FnAbiError<'tcx>, + _span: Span, + _fn_abi_request: FnAbiRequest<'tcx>, + ) -> InterpErrorInfo<'tcx> { + match err { + FnAbiError::Layout(err) => err_inval!(Layout(err)).into(), + FnAbiError::AdjustForForeignAbi(err) => { + err_inval!(FnAbiAdjustForForeignAbi(err)).into() + } + } + } +} + +/// Test if it is valid for a MIR assignment to assign `src`-typed place to `dest`-typed value. +/// This test should be symmetric, as it is primarily about layout compatibility. +pub(super) fn mir_assign_valid_types<'tcx>( + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + src: TyAndLayout<'tcx>, + dest: TyAndLayout<'tcx>, +) -> bool { + // Type-changing assignments can happen when subtyping is used. While + // all normal lifetimes are erased, higher-ranked types with their + // late-bound lifetimes are still around and can lead to type + // differences. So we compare ignoring lifetimes. + if equal_up_to_regions(tcx, param_env, src.ty, dest.ty) { + // Make sure the layout is equal, too -- just to be safe. Miri really + // needs layout equality. For performance reason we skip this check when + // the types are equal. Equal types *can* have different layouts when + // enum downcast is involved (as enum variants carry the type of the + // enum), but those should never occur in assignments. + if cfg!(debug_assertions) || src.ty != dest.ty { + assert_eq!(src.layout, dest.layout); + } + true + } else { + false + } +} + +/// Use the already known layout if given (but sanity check in debug mode), +/// or compute the layout. +#[cfg_attr(not(debug_assertions), inline(always))] +pub(super) fn from_known_layout<'tcx>( + tcx: TyCtxtAt<'tcx>, + param_env: ParamEnv<'tcx>, + known_layout: Option<TyAndLayout<'tcx>>, + compute: impl FnOnce() -> InterpResult<'tcx, TyAndLayout<'tcx>>, +) -> InterpResult<'tcx, TyAndLayout<'tcx>> { + match known_layout { + None => compute(), + Some(known_layout) => { + if cfg!(debug_assertions) { + let check_layout = compute()?; + if !mir_assign_valid_types(tcx.tcx, param_env, check_layout, known_layout) { + span_bug!( + tcx.span, + "expected type differs from actual type.\nexpected: {:?}\nactual: {:?}", + known_layout.ty, + check_layout.ty, + ); + } + } + Ok(known_layout) + } + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + pub fn new( + tcx: TyCtxt<'tcx>, + root_span: Span, + param_env: ty::ParamEnv<'tcx>, + machine: M, + ) -> Self { + InterpCx { + machine, + tcx: tcx.at(root_span), + param_env, + memory: Memory::new(), + recursion_limit: tcx.recursion_limit(), + } + } + + #[inline(always)] + pub fn cur_span(&self) -> Span { + // This deliberately does *not* honor `requires_caller_location` since it is used for much + // more than just panics. + self.stack().last().map_or(self.tcx.span, |f| f.current_span()) + } + + #[inline(always)] + pub(crate) fn stack(&self) -> &[Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>] { + M::stack(self) + } + + #[inline(always)] + pub(crate) fn stack_mut( + &mut self, + ) -> &mut Vec<Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>> { + M::stack_mut(self) + } + + #[inline(always)] + pub fn frame_idx(&self) -> usize { + let stack = self.stack(); + assert!(!stack.is_empty()); + stack.len() - 1 + } + + #[inline(always)] + pub fn frame(&self) -> &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> { + self.stack().last().expect("no call frames exist") + } + + #[inline(always)] + pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx, M::Provenance, M::FrameExtra> { + self.stack_mut().last_mut().expect("no call frames exist") + } + + #[inline(always)] + pub(super) fn body(&self) -> &'mir mir::Body<'tcx> { + self.frame().body + } + + #[inline(always)] + pub fn sign_extend(&self, value: u128, ty: TyAndLayout<'_>) -> u128 { + assert!(ty.abi.is_signed()); + ty.size.sign_extend(value) + } + + #[inline(always)] + pub fn truncate(&self, value: u128, ty: TyAndLayout<'_>) -> u128 { + ty.size.truncate(value) + } + + #[inline] + pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool { + ty.is_freeze(self.tcx, self.param_env) + } + + pub fn load_mir( + &self, + instance: ty::InstanceDef<'tcx>, + promoted: Option<mir::Promoted>, + ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> { + let def = instance.with_opt_param(); + trace!("load mir(instance={:?}, promoted={:?})", instance, promoted); + let body = if let Some(promoted) = promoted { + &self.tcx.promoted_mir_opt_const_arg(def)[promoted] + } else { + M::load_mir(self, instance)? + }; + // do not continue if typeck errors occurred (can only occur in local crate) + if let Some(err) = body.tainted_by_errors { + throw_inval!(AlreadyReported(err)); + } + Ok(body) + } + + /// Call this on things you got out of the MIR (so it is as generic as the current + /// stack frame), to bring it into the proper environment for this interpreter. + pub(super) fn subst_from_current_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>( + &self, + value: T, + ) -> Result<T, InterpError<'tcx>> { + self.subst_from_frame_and_normalize_erasing_regions(self.frame(), value) + } + + /// Call this on things you got out of the MIR (so it is as generic as the provided + /// stack frame), to bring it into the proper environment for this interpreter. + pub(super) fn subst_from_frame_and_normalize_erasing_regions<T: TypeFoldable<'tcx>>( + &self, + frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>, + value: T, + ) -> Result<T, InterpError<'tcx>> { + frame + .instance + .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value) + .map_err(|e| { + self.tcx.sess.delay_span_bug( + self.cur_span(), + format!("failed to normalize {}", e.get_type_for_failure()).as_str(), + ); + + InterpError::InvalidProgram(InvalidProgramInfo::TooGeneric) + }) + } + + /// The `substs` are assumed to already be in our interpreter "universe" (param_env). + pub(super) fn resolve( + &self, + def: ty::WithOptConstParam<DefId>, + substs: SubstsRef<'tcx>, + ) -> InterpResult<'tcx, ty::Instance<'tcx>> { + trace!("resolve: {:?}, {:#?}", def, substs); + trace!("param_env: {:#?}", self.param_env); + trace!("substs: {:#?}", substs); + match ty::Instance::resolve_opt_const_arg(*self.tcx, self.param_env, def, substs) { + Ok(Some(instance)) => Ok(instance), + Ok(None) => throw_inval!(TooGeneric), + + // FIXME(eddyb) this could be a bit more specific than `AlreadyReported`. + Err(error_reported) => throw_inval!(AlreadyReported(error_reported)), + } + } + + #[inline(always)] + pub fn layout_of_local( + &self, + frame: &Frame<'mir, 'tcx, M::Provenance, M::FrameExtra>, + local: mir::Local, + layout: Option<TyAndLayout<'tcx>>, + ) -> InterpResult<'tcx, TyAndLayout<'tcx>> { + // `const_prop` runs into this with an invalid (empty) frame, so we + // have to support that case (mostly by skipping all caching). + match frame.locals.get(local).and_then(|state| state.layout.get()) { + None => { + let layout = from_known_layout(self.tcx, self.param_env, layout, || { + let local_ty = frame.body.local_decls[local].ty; + let local_ty = + self.subst_from_frame_and_normalize_erasing_regions(frame, local_ty)?; + self.layout_of(local_ty) + })?; + if let Some(state) = frame.locals.get(local) { + // Layouts of locals are requested a lot, so we cache them. + state.layout.set(Some(layout)); + } + Ok(layout) + } + Some(layout) => Ok(layout), + } + } + + /// Returns the actual dynamic size and alignment of the place at the given type. + /// Only the "meta" (metadata) part of the place matters. + /// This can fail to provide an answer for extern types. + pub(super) fn size_and_align_of( + &self, + metadata: &MemPlaceMeta<M::Provenance>, + layout: &TyAndLayout<'tcx>, + ) -> InterpResult<'tcx, Option<(Size, Align)>> { + if !layout.is_unsized() { + return Ok(Some((layout.size, layout.align.abi))); + } + match layout.ty.kind() { + ty::Adt(..) | ty::Tuple(..) => { + // First get the size of all statically known fields. + // Don't use type_of::sizing_type_of because that expects t to be sized, + // and it also rounds up to alignment, which we want to avoid, + // as the unsized field's alignment could be smaller. + assert!(!layout.ty.is_simd()); + assert!(layout.fields.count() > 0); + trace!("DST layout: {:?}", layout); + + let sized_size = layout.fields.offset(layout.fields.count() - 1); + let sized_align = layout.align.abi; + trace!( + "DST {} statically sized prefix size: {:?} align: {:?}", + layout.ty, + sized_size, + sized_align + ); + + // Recurse to get the size of the dynamically sized field (must be + // the last field). Can't have foreign types here, how would we + // adjust alignment and size for them? + let field = layout.field(self, layout.fields.count() - 1); + let Some((unsized_size, unsized_align)) = self.size_and_align_of(metadata, &field)? else { + // A field with an extern type. We don't know the actual dynamic size + // or the alignment. + return Ok(None); + }; + + // FIXME (#26403, #27023): We should be adding padding + // to `sized_size` (to accommodate the `unsized_align` + // required of the unsized field that follows) before + // summing it with `sized_size`. (Note that since #26403 + // is unfixed, we do not yet add the necessary padding + // here. But this is where the add would go.) + + // Return the sum of sizes and max of aligns. + let size = sized_size + unsized_size; // `Size` addition + + // Choose max of two known alignments (combined value must + // be aligned according to more restrictive of the two). + let align = sized_align.max(unsized_align); + + // Issue #27023: must add any necessary padding to `size` + // (to make it a multiple of `align`) before returning it. + let size = size.align_to(align); + + // Check if this brought us over the size limit. + if size > self.max_size_of_val() { + throw_ub!(InvalidMeta("total size is bigger than largest supported object")); + } + Ok(Some((size, align))) + } + ty::Dynamic(..) => { + let vtable = metadata.unwrap_meta().to_pointer(self)?; + // Read size and align from vtable (already checks size). + Ok(Some(self.get_vtable_size_and_align(vtable)?)) + } + + ty::Slice(_) | ty::Str => { + let len = metadata.unwrap_meta().to_machine_usize(self)?; + let elem = layout.field(self, 0); + + // Make sure the slice is not too big. + let size = elem.size.bytes().saturating_mul(len); // we rely on `max_size_of_val` being smaller than `u64::MAX`. + let size = Size::from_bytes(size); + if size > self.max_size_of_val() { + throw_ub!(InvalidMeta("slice is bigger than largest supported object")); + } + Ok(Some((size, elem.align.abi))) + } + + ty::Foreign(_) => Ok(None), + + _ => span_bug!(self.cur_span(), "size_and_align_of::<{:?}> not supported", layout.ty), + } + } + #[inline] + pub fn size_and_align_of_mplace( + &self, + mplace: &MPlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, Option<(Size, Align)>> { + self.size_and_align_of(&mplace.meta, &mplace.layout) + } + + #[instrument(skip(self, body, return_place, return_to_block), level = "debug")] + pub fn push_stack_frame( + &mut self, + instance: ty::Instance<'tcx>, + body: &'mir mir::Body<'tcx>, + return_place: &PlaceTy<'tcx, M::Provenance>, + return_to_block: StackPopCleanup, + ) -> InterpResult<'tcx> { + trace!("body: {:#?}", body); + // first push a stack frame so we have access to the local substs + let pre_frame = Frame { + body, + loc: Err(body.span), // Span used for errors caused during preamble. + return_to_block, + return_place: return_place.clone(), + // empty local array, we fill it in below, after we are inside the stack frame and + // all methods actually know about the frame + locals: IndexVec::new(), + instance, + tracing_span: SpanGuard::new(), + extra: (), + }; + let frame = M::init_frame_extra(self, pre_frame)?; + self.stack_mut().push(frame); + + // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check). + for const_ in &body.required_consts { + let span = const_.span; + let const_ = + self.subst_from_current_frame_and_normalize_erasing_regions(const_.literal)?; + self.mir_const_to_op(&const_, None).map_err(|err| { + // If there was an error, set the span of the current frame to this constant. + // Avoiding doing this when evaluation succeeds. + self.frame_mut().loc = Err(span); + err + })?; + } + + // Most locals are initially dead. + let dummy = LocalState { value: LocalValue::Dead, layout: Cell::new(None) }; + let mut locals = IndexVec::from_elem(dummy, &body.local_decls); + + // Now mark those locals as live that have no `Storage*` annotations. + let always_live = always_storage_live_locals(self.body()); + for local in locals.indices() { + if always_live.contains(local) { + locals[local].value = LocalValue::Live(Operand::Immediate(Immediate::Uninit)); + } + } + // done + self.frame_mut().locals = locals; + M::after_stack_push(self)?; + self.frame_mut().loc = Ok(mir::Location::START); + + let span = info_span!("frame", "{}", instance); + self.frame_mut().tracing_span.enter(span); + + Ok(()) + } + + /// Jump to the given block. + #[inline] + pub fn go_to_block(&mut self, target: mir::BasicBlock) { + self.frame_mut().loc = Ok(mir::Location { block: target, statement_index: 0 }); + } + + /// *Return* to the given `target` basic block. + /// Do *not* use for unwinding! Use `unwind_to_block` instead. + /// + /// If `target` is `None`, that indicates the function cannot return, so we raise UB. + pub fn return_to_block(&mut self, target: Option<mir::BasicBlock>) -> InterpResult<'tcx> { + if let Some(target) = target { + self.go_to_block(target); + Ok(()) + } else { + throw_ub!(Unreachable) + } + } + + /// *Unwind* to the given `target` basic block. + /// Do *not* use for returning! Use `return_to_block` instead. + /// + /// If `target` is `StackPopUnwind::Skip`, that indicates the function does not need cleanup + /// during unwinding, and we will just keep propagating that upwards. + /// + /// If `target` is `StackPopUnwind::NotAllowed`, that indicates the function does not allow + /// unwinding, and doing so is UB. + pub fn unwind_to_block(&mut self, target: StackPopUnwind) -> InterpResult<'tcx> { + self.frame_mut().loc = match target { + StackPopUnwind::Cleanup(block) => Ok(mir::Location { block, statement_index: 0 }), + StackPopUnwind::Skip => Err(self.frame_mut().body.span), + StackPopUnwind::NotAllowed => { + throw_ub_format!("unwinding past a stack frame that does not allow unwinding") + } + }; + Ok(()) + } + + /// Pops the current frame from the stack, deallocating the + /// memory for allocated locals. + /// + /// If `unwinding` is `false`, then we are performing a normal return + /// from a function. In this case, we jump back into the frame of the caller, + /// and continue execution as normal. + /// + /// If `unwinding` is `true`, then we are in the middle of a panic, + /// and need to unwind this frame. In this case, we jump to the + /// `cleanup` block for the function, which is responsible for running + /// `Drop` impls for any locals that have been initialized at this point. + /// The cleanup block ends with a special `Resume` terminator, which will + /// cause us to continue unwinding. + #[instrument(skip(self), level = "debug")] + pub(super) fn pop_stack_frame(&mut self, unwinding: bool) -> InterpResult<'tcx> { + info!( + "popping stack frame ({})", + if unwinding { "during unwinding" } else { "returning from function" } + ); + + // Check `unwinding`. + assert_eq!( + unwinding, + match self.frame().loc { + Ok(loc) => self.body().basic_blocks()[loc.block].is_cleanup, + Err(_) => true, + } + ); + if unwinding && self.frame_idx() == 0 { + throw_ub_format!("unwinding past the topmost frame of the stack"); + } + + // Copy return value. Must of course happen *before* we deallocate the locals. + let copy_ret_result = if !unwinding { + let op = self + .local_to_op(self.frame(), mir::RETURN_PLACE, None) + .expect("return place should always be live"); + let dest = self.frame().return_place.clone(); + let err = self.copy_op(&op, &dest, /*allow_transmute*/ true); + trace!("return value: {:?}", self.dump_place(*dest)); + // We delay actually short-circuiting on this error until *after* the stack frame is + // popped, since we want this error to be attributed to the caller, whose type defines + // this transmute. + err + } else { + Ok(()) + }; + + // Cleanup: deallocate locals. + // Usually we want to clean up (deallocate locals), but in a few rare cases we don't. + // We do this while the frame is still on the stack, so errors point to the callee. + let return_to_block = self.frame().return_to_block; + let cleanup = match return_to_block { + StackPopCleanup::Goto { .. } => true, + StackPopCleanup::Root { cleanup, .. } => cleanup, + }; + if cleanup { + // We need to take the locals out, since we need to mutate while iterating. + let locals = mem::take(&mut self.frame_mut().locals); + for local in &locals { + self.deallocate_local(local.value)?; + } + } + + // All right, now it is time to actually pop the frame. + // Note that its locals are gone already, but that's fine. + let frame = + self.stack_mut().pop().expect("tried to pop a stack frame, but there were none"); + // Report error from return value copy, if any. + copy_ret_result?; + + // If we are not doing cleanup, also skip everything else. + if !cleanup { + assert!(self.stack().is_empty(), "only the topmost frame should ever be leaked"); + assert!(!unwinding, "tried to skip cleanup during unwinding"); + // Skip machine hook. + return Ok(()); + } + if M::after_stack_pop(self, frame, unwinding)? == StackPopJump::NoJump { + // The hook already did everything. + return Ok(()); + } + + // Normal return, figure out where to jump. + if unwinding { + // Follow the unwind edge. + let unwind = match return_to_block { + StackPopCleanup::Goto { unwind, .. } => unwind, + StackPopCleanup::Root { .. } => { + panic!("encountered StackPopCleanup::Root when unwinding!") + } + }; + self.unwind_to_block(unwind) + } else { + // Follow the normal return edge. + match return_to_block { + StackPopCleanup::Goto { ret, .. } => self.return_to_block(ret), + StackPopCleanup::Root { .. } => { + assert!( + self.stack().is_empty(), + "only the topmost frame can have StackPopCleanup::Root" + ); + Ok(()) + } + } + } + } + + /// Mark a storage as live, killing the previous content. + pub fn storage_live(&mut self, local: mir::Local) -> InterpResult<'tcx> { + assert!(local != mir::RETURN_PLACE, "Cannot make return place live"); + trace!("{:?} is now live", local); + + let local_val = LocalValue::Live(Operand::Immediate(Immediate::Uninit)); + // StorageLive expects the local to be dead, and marks it live. + let old = mem::replace(&mut self.frame_mut().locals[local].value, local_val); + if !matches!(old, LocalValue::Dead) { + throw_ub_format!("StorageLive on a local that was already live"); + } + Ok(()) + } + + pub fn storage_dead(&mut self, local: mir::Local) -> InterpResult<'tcx> { + assert!(local != mir::RETURN_PLACE, "Cannot make return place dead"); + trace!("{:?} is now dead", local); + + // It is entirely okay for this local to be already dead (at least that's how we currently generate MIR) + let old = mem::replace(&mut self.frame_mut().locals[local].value, LocalValue::Dead); + self.deallocate_local(old)?; + Ok(()) + } + + #[instrument(skip(self), level = "debug")] + fn deallocate_local(&mut self, local: LocalValue<M::Provenance>) -> InterpResult<'tcx> { + if let LocalValue::Live(Operand::Indirect(MemPlace { ptr, .. })) = local { + // All locals have a backing allocation, even if the allocation is empty + // due to the local having ZST type. Hence we can `unwrap`. + trace!( + "deallocating local {:?}: {:?}", + local, + // Locals always have a `alloc_id` (they are never the result of a int2ptr). + self.dump_alloc(ptr.provenance.unwrap().get_alloc_id().unwrap()) + ); + self.deallocate_ptr(ptr, None, MemoryKind::Stack)?; + }; + Ok(()) + } + + pub fn eval_to_allocation( + &self, + gid: GlobalId<'tcx>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> { + // For statics we pick `ParamEnv::reveal_all`, because statics don't have generics + // and thus don't care about the parameter environment. While we could just use + // `self.param_env`, that would mean we invoke the query to evaluate the static + // with different parameter environments, thus causing the static to be evaluated + // multiple times. + let param_env = if self.tcx.is_static(gid.instance.def_id()) { + ty::ParamEnv::reveal_all() + } else { + self.param_env + }; + let param_env = param_env.with_const(); + // Use a precise span for better cycle errors. + let val = self.tcx.at(self.cur_span()).eval_to_allocation_raw(param_env.and(gid))?; + self.raw_const_to_mplace(val) + } + + #[must_use] + pub fn dump_place(&self, place: Place<M::Provenance>) -> PlacePrinter<'_, 'mir, 'tcx, M> { + PlacePrinter { ecx: self, place } + } + + #[must_use] + pub fn generate_stacktrace(&self) -> Vec<FrameInfo<'tcx>> { + let mut frames = Vec::new(); + // This deliberately does *not* honor `requires_caller_location` since it is used for much + // more than just panics. + for frame in self.stack().iter().rev() { + let lint_root = frame.current_source_info().and_then(|source_info| { + match &frame.body.source_scopes[source_info.scope].local_data { + mir::ClearCrossCrate::Set(data) => Some(data.lint_root), + mir::ClearCrossCrate::Clear => None, + } + }); + let span = frame.current_span(); + + frames.push(FrameInfo { span, instance: frame.instance, lint_root }); + } + trace!("generate stacktrace: {:#?}", frames); + frames + } +} + +#[doc(hidden)] +/// Helper struct for the `dump_place` function. +pub struct PlacePrinter<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> { + ecx: &'a InterpCx<'mir, 'tcx, M>, + place: Place<M::Provenance>, +} + +impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> std::fmt::Debug + for PlacePrinter<'a, 'mir, 'tcx, M> +{ + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + match self.place { + Place::Local { frame, local } => { + let mut allocs = Vec::new(); + write!(fmt, "{:?}", local)?; + if frame != self.ecx.frame_idx() { + write!(fmt, " ({} frames up)", self.ecx.frame_idx() - frame)?; + } + write!(fmt, ":")?; + + match self.ecx.stack()[frame].locals[local].value { + LocalValue::Dead => write!(fmt, " is dead")?, + LocalValue::Live(Operand::Immediate(Immediate::Uninit)) => { + write!(fmt, " is uninitialized")? + } + LocalValue::Live(Operand::Indirect(mplace)) => { + write!( + fmt, + " by {} ref {:?}:", + match mplace.meta { + MemPlaceMeta::Meta(meta) => format!(" meta({:?})", meta), + MemPlaceMeta::None => String::new(), + }, + mplace.ptr, + )?; + allocs.extend(mplace.ptr.provenance.map(Provenance::get_alloc_id)); + } + LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => { + write!(fmt, " {:?}", val)?; + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr, _size)) = val { + allocs.push(ptr.provenance.get_alloc_id()); + } + } + LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => { + write!(fmt, " ({:?}, {:?})", val1, val2)?; + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr, _size)) = val1 { + allocs.push(ptr.provenance.get_alloc_id()); + } + if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr, _size)) = val2 { + allocs.push(ptr.provenance.get_alloc_id()); + } + } + } + + write!(fmt, ": {:?}", self.ecx.dump_allocs(allocs.into_iter().flatten().collect())) + } + Place::Ptr(mplace) => match mplace.ptr.provenance.and_then(Provenance::get_alloc_id) { + Some(alloc_id) => { + write!(fmt, "by ref {:?}: {:?}", mplace.ptr, self.ecx.dump_alloc(alloc_id)) + } + ptr => write!(fmt, " integral by ref: {:?}", ptr), + }, + } + } +} |