| // Not in interpret to make sure we do not use private implementation details |
| |
| use std::fmt; |
| use std::error::Error; |
| use std::borrow::{Borrow, Cow}; |
| use std::hash::Hash; |
| use std::collections::hash_map::Entry; |
| use std::convert::TryInto; |
| |
| use rustc::hir::def::DefKind; |
| use rustc::hir::def_id::DefId; |
| use rustc::middle::lang_items::PanicLocationLangItem; |
| use rustc::mir::interpret::{ConstEvalErr, ErrorHandled, ScalarMaybeUndef}; |
| use rustc::mir; |
| use rustc::ty::{self, Ty, TyCtxt, subst::Subst}; |
| use rustc::ty::layout::{self, LayoutOf, VariantIdx}; |
| use rustc::traits::Reveal; |
| use rustc_data_structures::fx::FxHashMap; |
| use crate::interpret::eval_nullary_intrinsic; |
| |
| use syntax::{source_map::{Span, DUMMY_SP}, symbol::Symbol}; |
| |
| use crate::interpret::{self, |
| PlaceTy, MPlaceTy, OpTy, ImmTy, Immediate, Scalar, Pointer, |
| RawConst, ConstValue, Machine, |
| InterpResult, InterpErrorInfo, GlobalId, InterpCx, StackPopCleanup, |
| Allocation, AllocId, MemoryKind, Memory, |
| snapshot, RefTracking, intern_const_alloc_recursive, |
| }; |
| |
| /// Number of steps until the detector even starts doing anything. |
| /// Also, a warning is shown to the user when this number is reached. |
| const STEPS_UNTIL_DETECTOR_ENABLED: isize = 1_000_000; |
| /// The number of steps between loop detector snapshots. |
| /// Should be a power of two for performance reasons. |
| const DETECTOR_SNAPSHOT_PERIOD: isize = 256; |
| |
| /// The `InterpCx` is only meant to be used to do field and index projections into constants for |
| /// `simd_shuffle` and const patterns in match arms. |
| /// |
| /// The function containing the `match` that is currently being analyzed may have generic bounds |
| /// that inform us about the generic bounds of the constant. E.g., using an associated constant |
| /// of a function's generic parameter will require knowledge about the bounds on the generic |
| /// parameter. These bounds are passed to `mk_eval_cx` via the `ParamEnv` argument. |
| fn mk_eval_cx<'mir, 'tcx>( |
| tcx: TyCtxt<'tcx>, |
| span: Span, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> CompileTimeEvalContext<'mir, 'tcx> { |
| debug!("mk_eval_cx: {:?}", param_env); |
| InterpCx::new(tcx.at(span), param_env, CompileTimeInterpreter::new(), Default::default()) |
| } |
| |
| fn op_to_const<'tcx>( |
| ecx: &CompileTimeEvalContext<'_, 'tcx>, |
| op: OpTy<'tcx>, |
| ) -> &'tcx ty::Const<'tcx> { |
| // We do not have value optimizations for everything. |
| // Only scalars and slices, since they are very common. |
| // Note that further down we turn scalars of undefined bits back to `ByRef`. These can result |
| // from scalar unions that are initialized with one of their zero sized variants. We could |
| // instead allow `ConstValue::Scalar` to store `ScalarMaybeUndef`, but that would affect all |
| // the usual cases of extracting e.g. a `usize`, without there being a real use case for the |
| // `Undef` situation. |
| let try_as_immediate = match op.layout.abi { |
| layout::Abi::Scalar(..) => true, |
| layout::Abi::ScalarPair(..) => match op.layout.ty.kind { |
| ty::Ref(_, inner, _) => match inner.kind { |
| ty::Slice(elem) => elem == ecx.tcx.types.u8, |
| ty::Str => true, |
| _ => false, |
| }, |
| _ => false, |
| }, |
| _ => false, |
| }; |
| let immediate = if try_as_immediate { |
| Err(ecx.read_immediate(op).expect("normalization works on validated constants")) |
| } else { |
| // It is guaranteed that any non-slice scalar pair is actually ByRef here. |
| // When we come back from raw const eval, we are always by-ref. The only way our op here is |
| // by-val is if we are in const_field, i.e., if this is (a field of) something that we |
| // "tried to make immediate" before. We wouldn't do that for non-slice scalar pairs or |
| // structs containing such. |
| op.try_as_mplace() |
| }; |
| let val = match immediate { |
| Ok(mplace) => { |
| let ptr = mplace.ptr.to_ptr().unwrap(); |
| let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); |
| ConstValue::ByRef { alloc, offset: ptr.offset } |
| }, |
| // see comment on `let try_as_immediate` above |
| Err(ImmTy { imm: Immediate::Scalar(x), .. }) => match x { |
| ScalarMaybeUndef::Scalar(s) => ConstValue::Scalar(s), |
| ScalarMaybeUndef::Undef => { |
| // When coming out of "normal CTFE", we'll always have an `Indirect` operand as |
| // argument and we will not need this. The only way we can already have an |
| // `Immediate` is when we are called from `const_field`, and that `Immediate` |
| // comes from a constant so it can happen have `Undef`, because the indirect |
| // memory that was read had undefined bytes. |
| let mplace = op.assert_mem_place(); |
| let ptr = mplace.ptr.to_ptr().unwrap(); |
| let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); |
| ConstValue::ByRef { alloc, offset: ptr.offset } |
| }, |
| }, |
| Err(ImmTy { imm: Immediate::ScalarPair(a, b), .. }) => { |
| let (data, start) = match a.not_undef().unwrap() { |
| Scalar::Ptr(ptr) => ( |
| ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id), |
| ptr.offset.bytes(), |
| ), |
| Scalar::Raw { .. } => ( |
| ecx.tcx.intern_const_alloc(Allocation::from_byte_aligned_bytes( |
| b"" as &[u8], |
| )), |
| 0, |
| ), |
| }; |
| let len = b.to_machine_usize(&ecx.tcx.tcx).unwrap(); |
| let start = start.try_into().unwrap(); |
| let len: usize = len.try_into().unwrap(); |
| ConstValue::Slice { |
| data, |
| start, |
| end: start + len, |
| } |
| }, |
| }; |
| ecx.tcx.mk_const(ty::Const { val: ty::ConstKind::Value(val), ty: op.layout.ty }) |
| } |
| |
| // Returns a pointer to where the result lives |
| fn eval_body_using_ecx<'mir, 'tcx>( |
| ecx: &mut CompileTimeEvalContext<'mir, 'tcx>, |
| cid: GlobalId<'tcx>, |
| body: &'mir mir::Body<'tcx>, |
| ) -> InterpResult<'tcx, MPlaceTy<'tcx>> { |
| debug!("eval_body_using_ecx: {:?}, {:?}", cid, ecx.param_env); |
| let tcx = ecx.tcx.tcx; |
| let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?; |
| assert!(!layout.is_unsized()); |
| let ret = ecx.allocate(layout, MemoryKind::Stack); |
| |
| let name = ty::tls::with(|tcx| tcx.def_path_str(cid.instance.def_id())); |
| let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p)); |
| trace!("eval_body_using_ecx: pushing stack frame for global: {}{}", name, prom); |
| |
| // Assert all args (if any) are zero-sized types; `eval_body_using_ecx` doesn't |
| // make sense if the body is expecting nontrivial arguments. |
| // (The alternative would be to use `eval_fn_call` with an args slice.) |
| for arg in body.args_iter() { |
| let decl = body.local_decls.get(arg).expect("arg missing from local_decls"); |
| let layout = ecx.layout_of(decl.ty.subst(tcx, cid.instance.substs))?; |
| assert!(layout.is_zst()) |
| }; |
| |
| ecx.push_stack_frame( |
| cid.instance, |
| body.span, |
| body, |
| Some(ret.into()), |
| StackPopCleanup::None { cleanup: false }, |
| )?; |
| |
| // The main interpreter loop. |
| ecx.run()?; |
| |
| // Intern the result |
| intern_const_alloc_recursive(ecx, tcx.static_mutability(cid.instance.def_id()), ret)?; |
| |
| debug!("eval_body_using_ecx done: {:?}", *ret); |
| Ok(ret) |
| } |
| |
| #[derive(Clone, Debug)] |
| pub enum ConstEvalError { |
| NeedsRfc(String), |
| } |
| |
| impl<'tcx> Into<InterpErrorInfo<'tcx>> for ConstEvalError { |
| fn into(self) -> InterpErrorInfo<'tcx> { |
| err_unsup!(Unsupported(self.to_string())).into() |
| } |
| } |
| |
| impl fmt::Display for ConstEvalError { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| use self::ConstEvalError::*; |
| match *self { |
| NeedsRfc(ref msg) => { |
| write!( |
| f, |
| "\"{}\" needs an rfc before being allowed inside constants", |
| msg |
| ) |
| } |
| } |
| } |
| } |
| |
| impl Error for ConstEvalError { |
| fn description(&self) -> &str { |
| use self::ConstEvalError::*; |
| match *self { |
| NeedsRfc(_) => "this feature needs an rfc before being allowed inside constants", |
| } |
| } |
| |
| fn cause(&self) -> Option<&dyn Error> { |
| None |
| } |
| } |
| |
| // Extra machine state for CTFE, and the Machine instance |
| pub struct CompileTimeInterpreter<'mir, 'tcx> { |
| /// When this value is negative, it indicates the number of interpreter |
| /// steps *until* the loop detector is enabled. When it is positive, it is |
| /// the number of steps after the detector has been enabled modulo the loop |
| /// detector period. |
| pub(super) steps_since_detector_enabled: isize, |
| |
| /// Extra state to detect loops. |
| pub(super) loop_detector: snapshot::InfiniteLoopDetector<'mir, 'tcx>, |
| } |
| |
| impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> { |
| fn new() -> Self { |
| CompileTimeInterpreter { |
| loop_detector: Default::default(), |
| steps_since_detector_enabled: -STEPS_UNTIL_DETECTOR_ENABLED, |
| } |
| } |
| } |
| |
| impl<K: Hash + Eq, V> interpret::AllocMap<K, V> for FxHashMap<K, V> { |
| #[inline(always)] |
| fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool |
| where K: Borrow<Q> |
| { |
| FxHashMap::contains_key(self, k) |
| } |
| |
| #[inline(always)] |
| fn insert(&mut self, k: K, v: V) -> Option<V> |
| { |
| FxHashMap::insert(self, k, v) |
| } |
| |
| #[inline(always)] |
| fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V> |
| where K: Borrow<Q> |
| { |
| FxHashMap::remove(self, k) |
| } |
| |
| #[inline(always)] |
| fn filter_map_collect<T>(&self, mut f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T> { |
| self.iter() |
| .filter_map(move |(k, v)| f(k, &*v)) |
| .collect() |
| } |
| |
| #[inline(always)] |
| fn get_or<E>( |
| &self, |
| k: K, |
| vacant: impl FnOnce() -> Result<V, E> |
| ) -> Result<&V, E> |
| { |
| match self.get(&k) { |
| Some(v) => Ok(v), |
| None => { |
| vacant()?; |
| bug!("The CTFE machine shouldn't ever need to extend the alloc_map when reading") |
| } |
| } |
| } |
| |
| #[inline(always)] |
| fn get_mut_or<E>( |
| &mut self, |
| k: K, |
| vacant: impl FnOnce() -> Result<V, E> |
| ) -> Result<&mut V, E> |
| { |
| match self.entry(k) { |
| Entry::Occupied(e) => Ok(e.into_mut()), |
| Entry::Vacant(e) => { |
| let v = vacant()?; |
| Ok(e.insert(v)) |
| } |
| } |
| } |
| } |
| |
| crate type CompileTimeEvalContext<'mir, 'tcx> = |
| InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>; |
| |
| impl interpret::MayLeak for ! { |
| #[inline(always)] |
| fn may_leak(self) -> bool { |
| // `self` is uninhabited |
| self |
| } |
| } |
| |
| impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, 'tcx> { |
| type MemoryKinds = !; |
| type PointerTag = (); |
| type ExtraFnVal = !; |
| |
| type FrameExtra = (); |
| type MemoryExtra = (); |
| type AllocExtra = (); |
| |
| type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation)>; |
| |
| const STATIC_KIND: Option<!> = None; // no copying of statics allowed |
| |
| // We do not check for alignment to avoid having to carry an `Align` |
| // in `ConstValue::ByRef`. |
| const CHECK_ALIGN: bool = false; |
| |
| #[inline(always)] |
| fn enforce_validity(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool { |
| false // for now, we don't enforce validity |
| } |
| |
| fn find_fn( |
| ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx>], |
| ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock> // unwinding is not supported in consts |
| ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> { |
| debug!("eval_fn_call: {:?}", instance); |
| // Only check non-glue functions |
| if let ty::InstanceDef::Item(def_id) = instance.def { |
| // Execution might have wandered off into other crates, so we cannot do a stability- |
| // sensitive check here. But we can at least rule out functions that are not const |
| // at all. |
| if !ecx.tcx.is_const_fn_raw(def_id) { |
| // Some functions we support even if they are non-const -- but avoid testing |
| // that for const fn! We certainly do *not* want to actually call the fn |
| // though, so be sure we return here. |
| return if ecx.hook_panic_fn(instance, args, ret)? { |
| Ok(None) |
| } else { |
| throw_unsup_format!("calling non-const function `{}`", instance) |
| }; |
| } |
| } |
| // This is a const fn. Call it. |
| Ok(Some(match ecx.load_mir(instance.def, None) { |
| Ok(body) => body, |
| Err(err) => { |
| if let err_unsup!(NoMirFor(ref path)) = err.kind { |
| return Err( |
| ConstEvalError::NeedsRfc(format!("calling extern function `{}`", path)) |
| .into(), |
| ); |
| } |
| return Err(err); |
| } |
| })) |
| } |
| |
| fn call_extra_fn( |
| _ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| fn_val: !, |
| _args: &[OpTy<'tcx>], |
| _ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock> |
| ) -> InterpResult<'tcx> { |
| match fn_val {} |
| } |
| |
| fn call_intrinsic( |
| ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| span: Span, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx>], |
| ret: Option<(PlaceTy<'tcx>, mir::BasicBlock)>, |
| _unwind: Option<mir::BasicBlock> |
| ) -> InterpResult<'tcx> { |
| if ecx.emulate_intrinsic(span, instance, args, ret)? { |
| return Ok(()); |
| } |
| // An intrinsic that we do not support |
| let intrinsic_name = ecx.tcx.item_name(instance.def_id()); |
| Err( |
| ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", intrinsic_name)).into() |
| ) |
| } |
| |
| fn ptr_to_int( |
| _mem: &Memory<'mir, 'tcx, Self>, |
| _ptr: Pointer, |
| ) -> InterpResult<'tcx, u64> { |
| Err( |
| ConstEvalError::NeedsRfc("pointer-to-integer cast".to_string()).into(), |
| ) |
| } |
| |
| fn binary_ptr_op( |
| _ecx: &InterpCx<'mir, 'tcx, Self>, |
| _bin_op: mir::BinOp, |
| _left: ImmTy<'tcx>, |
| _right: ImmTy<'tcx>, |
| ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> { |
| Err( |
| ConstEvalError::NeedsRfc("pointer arithmetic or comparison".to_string()).into(), |
| ) |
| } |
| |
| fn find_foreign_static( |
| _tcx: TyCtxt<'tcx>, |
| _def_id: DefId, |
| ) -> InterpResult<'tcx, Cow<'tcx, Allocation<Self::PointerTag>>> { |
| throw_unsup!(ReadForeignStatic) |
| } |
| |
| #[inline(always)] |
| fn tag_allocation<'b>( |
| _memory_extra: &(), |
| _id: AllocId, |
| alloc: Cow<'b, Allocation>, |
| _kind: Option<MemoryKind<!>>, |
| ) -> (Cow<'b, Allocation<Self::PointerTag>>, Self::PointerTag) { |
| // We do not use a tag so we can just cheaply forward the allocation |
| (alloc, ()) |
| } |
| |
| #[inline(always)] |
| fn tag_static_base_pointer( |
| _memory_extra: &(), |
| _id: AllocId, |
| ) -> Self::PointerTag { |
| () |
| } |
| |
| fn box_alloc( |
| _ecx: &mut InterpCx<'mir, 'tcx, Self>, |
| _dest: PlaceTy<'tcx>, |
| ) -> InterpResult<'tcx> { |
| Err( |
| ConstEvalError::NeedsRfc("heap allocations via `box` keyword".to_string()).into(), |
| ) |
| } |
| |
| fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> { |
| { |
| let steps = &mut ecx.machine.steps_since_detector_enabled; |
| |
| *steps += 1; |
| if *steps < 0 { |
| return Ok(()); |
| } |
| |
| *steps %= DETECTOR_SNAPSHOT_PERIOD; |
| if *steps != 0 { |
| return Ok(()); |
| } |
| } |
| |
| let span = ecx.frame().span; |
| ecx.machine.loop_detector.observe_and_analyze( |
| *ecx.tcx, |
| span, |
| &ecx.memory, |
| &ecx.stack[..], |
| ) |
| } |
| |
| #[inline(always)] |
| fn stack_push(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> { |
| Ok(()) |
| } |
| } |
| |
| /// Extracts a field of a (variant of a) const. |
| // this function uses `unwrap` copiously, because an already validated constant must have valid |
| // fields and can thus never fail outside of compiler bugs |
| pub fn const_field<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| variant: Option<VariantIdx>, |
| field: mir::Field, |
| value: &'tcx ty::Const<'tcx>, |
| ) -> &'tcx ty::Const<'tcx> { |
| trace!("const_field: {:?}, {:?}", field, value); |
| let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env); |
| // get the operand again |
| let op = ecx.eval_const_to_op(value, None).unwrap(); |
| // downcast |
| let down = match variant { |
| None => op, |
| Some(variant) => ecx.operand_downcast(op, variant).unwrap(), |
| }; |
| // then project |
| let field = ecx.operand_field(down, field.index() as u64).unwrap(); |
| // and finally move back to the const world, always normalizing because |
| // this is not called for statics. |
| op_to_const(&ecx, field) |
| } |
| |
| pub fn const_caller_location<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| (file, line, col): (Symbol, u32, u32), |
| ) -> &'tcx ty::Const<'tcx> { |
| trace!("const_caller_location: {}:{}:{}", file, line, col); |
| let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all()); |
| |
| let loc_ty = tcx.mk_imm_ref( |
| tcx.lifetimes.re_static, |
| tcx.type_of(tcx.require_lang_item(PanicLocationLangItem, None)) |
| .subst(tcx, tcx.mk_substs([tcx.lifetimes.re_static.into()].iter())), |
| ); |
| let loc_place = ecx.alloc_caller_location(file, line, col).unwrap(); |
| intern_const_alloc_recursive(&mut ecx, None, loc_place).unwrap(); |
| let loc_const = ty::Const { |
| ty: loc_ty, |
| val: ty::ConstKind::Value(ConstValue::Scalar(loc_place.ptr.into())), |
| }; |
| |
| tcx.mk_const(loc_const) |
| } |
| |
| // this function uses `unwrap` copiously, because an already validated constant must have valid |
| // fields and can thus never fail outside of compiler bugs |
| pub fn const_variant_index<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| val: &'tcx ty::Const<'tcx>, |
| ) -> VariantIdx { |
| trace!("const_variant_index: {:?}", val); |
| let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env); |
| let op = ecx.eval_const_to_op(val, None).unwrap(); |
| ecx.read_discriminant(op).unwrap().1 |
| } |
| |
| /// Turn an interpreter error into something to report to the user. |
| /// As a side-effect, if RUSTC_CTFE_BACKTRACE is set, this prints the backtrace. |
| /// Should be called only if the error is actually going to to be reported! |
| pub fn error_to_const_error<'mir, 'tcx, M: Machine<'mir, 'tcx>>( |
| ecx: &InterpCx<'mir, 'tcx, M>, |
| mut error: InterpErrorInfo<'tcx>, |
| ) -> ConstEvalErr<'tcx> { |
| error.print_backtrace(); |
| let stacktrace = ecx.generate_stacktrace(None); |
| ConstEvalErr { error: error.kind, stacktrace, span: ecx.tcx.span } |
| } |
| |
| pub fn note_on_undefined_behavior_error() -> &'static str { |
| "The rules on what exactly is undefined behavior aren't clear, \ |
| so this check might be overzealous. Please open an issue on the rustc \ |
| repository if you believe it should not be considered undefined behavior." |
| } |
| |
| fn validate_and_turn_into_const<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| constant: RawConst<'tcx>, |
| key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>, |
| ) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> { |
| let cid = key.value; |
| let ecx = mk_eval_cx(tcx, tcx.def_span(key.value.instance.def_id()), key.param_env); |
| let val = (|| { |
| let mplace = ecx.raw_const_to_mplace(constant)?; |
| let mut ref_tracking = RefTracking::new(mplace); |
| while let Some((mplace, path)) = ref_tracking.todo.pop() { |
| ecx.validate_operand( |
| mplace.into(), |
| path, |
| Some(&mut ref_tracking), |
| )?; |
| } |
| // Now that we validated, turn this into a proper constant. |
| // Statics/promoteds are always `ByRef`, for the rest `op_to_const` decides |
| // whether they become immediates. |
| let def_id = cid.instance.def.def_id(); |
| if tcx.is_static(def_id) || cid.promoted.is_some() { |
| let ptr = mplace.ptr.to_ptr()?; |
| Ok(tcx.mk_const(ty::Const { |
| val: ty::ConstKind::Value(ConstValue::ByRef { |
| alloc: ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id), |
| offset: ptr.offset, |
| }), |
| ty: mplace.layout.ty, |
| })) |
| } else { |
| Ok(op_to_const(&ecx, mplace.into())) |
| } |
| })(); |
| |
| val.map_err(|error| { |
| let err = error_to_const_error(&ecx, error); |
| match err.struct_error(ecx.tcx, "it is undefined behavior to use this value") { |
| Ok(mut diag) => { |
| diag.note(note_on_undefined_behavior_error()); |
| diag.emit(); |
| ErrorHandled::Reported |
| } |
| Err(err) => err, |
| } |
| }) |
| } |
| |
| pub fn const_eval_provider<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>, |
| ) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> { |
| // see comment in const_eval_raw_provider for what we're doing here |
| if key.param_env.reveal == Reveal::All { |
| let mut key = key.clone(); |
| key.param_env.reveal = Reveal::UserFacing; |
| match tcx.const_eval(key) { |
| // try again with reveal all as requested |
| Err(ErrorHandled::TooGeneric) => { |
| // Promoteds should never be "too generic" when getting evaluated. |
| // They either don't get evaluated, or we are in a monomorphic context |
| assert!(key.value.promoted.is_none()); |
| }, |
| // dedupliate calls |
| other => return other, |
| } |
| } |
| |
| // We call `const_eval` for zero arg intrinsics, too, in order to cache their value. |
| // Catch such calls and evaluate them instead of trying to load a constant's MIR. |
| if let ty::InstanceDef::Intrinsic(def_id) = key.value.instance.def { |
| let ty = key.value.instance.ty(tcx); |
| let substs = match ty.kind { |
| ty::FnDef(_, substs) => substs, |
| _ => bug!("intrinsic with type {:?}", ty), |
| }; |
| return eval_nullary_intrinsic(tcx, key.param_env, def_id, substs) |
| .map_err(|error| { |
| let span = tcx.def_span(def_id); |
| let error = ConstEvalErr { error: error.kind, stacktrace: vec![], span }; |
| error.report_as_error(tcx.at(span), "could not evaluate nullary intrinsic") |
| }) |
| } |
| |
| tcx.const_eval_raw(key).and_then(|val| { |
| validate_and_turn_into_const(tcx, val, key) |
| }) |
| } |
| |
| pub fn const_eval_raw_provider<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>, |
| ) -> ::rustc::mir::interpret::ConstEvalRawResult<'tcx> { |
| // Because the constant is computed twice (once per value of `Reveal`), we are at risk of |
| // reporting the same error twice here. To resolve this, we check whether we can evaluate the |
| // constant in the more restrictive `Reveal::UserFacing`, which most likely already was |
| // computed. For a large percentage of constants that will already have succeeded. Only |
| // associated constants of generic functions will fail due to not enough monomorphization |
| // information being available. |
| |
| // In case we fail in the `UserFacing` variant, we just do the real computation. |
| if key.param_env.reveal == Reveal::All { |
| let mut key = key.clone(); |
| key.param_env.reveal = Reveal::UserFacing; |
| match tcx.const_eval_raw(key) { |
| // try again with reveal all as requested |
| Err(ErrorHandled::TooGeneric) => {}, |
| // dedupliate calls |
| other => return other, |
| } |
| } |
| if cfg!(debug_assertions) { |
| // Make sure we format the instance even if we do not print it. |
| // This serves as a regression test against an ICE on printing. |
| // The next two lines concatenated contain some discussion: |
| // https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/ |
| // subject/anon_const_instance_printing/near/135980032 |
| let instance = key.value.instance.to_string(); |
| trace!("const eval: {:?} ({})", key, instance); |
| } |
| |
| let cid = key.value; |
| let def_id = cid.instance.def.def_id(); |
| |
| if def_id.is_local() && tcx.typeck_tables_of(def_id).tainted_by_errors { |
| return Err(ErrorHandled::Reported); |
| } |
| |
| let span = tcx.def_span(cid.instance.def_id()); |
| let mut ecx = InterpCx::new( |
| tcx.at(span), |
| key.param_env, |
| CompileTimeInterpreter::new(), |
| Default::default() |
| ); |
| |
| let res = ecx.load_mir(cid.instance.def, cid.promoted); |
| res.and_then( |
| |body| eval_body_using_ecx(&mut ecx, cid, body) |
| ).and_then(|place| { |
| Ok(RawConst { |
| alloc_id: place.ptr.assert_ptr().alloc_id, |
| ty: place.layout.ty |
| }) |
| }).map_err(|error| { |
| let err = error_to_const_error(&ecx, error); |
| // errors in statics are always emitted as fatal errors |
| if tcx.is_static(def_id) { |
| // Ensure that if the above error was either `TooGeneric` or `Reported` |
| // an error must be reported. |
| let v = err.report_as_error(ecx.tcx, "could not evaluate static initializer"); |
| tcx.sess.delay_span_bug( |
| err.span, |
| &format!("static eval failure did not emit an error: {:#?}", v) |
| ); |
| v |
| } else if def_id.is_local() { |
| // constant defined in this crate, we can figure out a lint level! |
| match tcx.def_kind(def_id) { |
| // constants never produce a hard error at the definition site. Anything else is |
| // a backwards compatibility hazard (and will break old versions of winapi for sure) |
| // |
| // note that validation may still cause a hard error on this very same constant, |
| // because any code that existed before validation could not have failed validation |
| // thus preventing such a hard error from being a backwards compatibility hazard |
| Some(DefKind::Const) | Some(DefKind::AssocConst) => { |
| let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap(); |
| err.report_as_lint( |
| tcx.at(tcx.def_span(def_id)), |
| "any use of this value will cause an error", |
| hir_id, |
| Some(err.span), |
| ) |
| }, |
| // promoting runtime code is only allowed to error if it references broken constants |
| // any other kind of error will be reported to the user as a deny-by-default lint |
| _ => if let Some(p) = cid.promoted { |
| let span = tcx.promoted_mir(def_id)[p].span; |
| if let err_inval!(ReferencedConstant) = err.error { |
| err.report_as_error( |
| tcx.at(span), |
| "evaluation of constant expression failed", |
| ) |
| } else { |
| err.report_as_lint( |
| tcx.at(span), |
| "reaching this expression at runtime will panic or abort", |
| tcx.hir().as_local_hir_id(def_id).unwrap(), |
| Some(err.span), |
| ) |
| } |
| // anything else (array lengths, enum initializers, constant patterns) are reported |
| // as hard errors |
| } else { |
| err.report_as_error( |
| ecx.tcx, |
| "evaluation of constant value failed", |
| ) |
| }, |
| } |
| } else { |
| // use of broken constant from other crate |
| err.report_as_error(ecx.tcx, "could not evaluate constant") |
| } |
| }) |
| } |
