src/librustc_mir/interpret/eval_context.rs

   1 use std::collections::HashSet;
   2 use std::fmt::Write;
   3
   4 use rustc::hir::def_id::DefId;
   5 use rustc::hir::map::definitions::DefPathData;
   6 use rustc::middle::const_val::{ConstVal, ErrKind};
   7 use rustc::mir;
   8 use rustc::traits::Reveal;
   9 use rustc::ty::layout::{self, Size, Align, HasDataLayout, LayoutOf, TyLayout};
  10 use rustc::ty::subst::{Subst, Substs};
  11 use rustc::ty::{self, Ty, TyCtxt};
  12 use rustc_data_structures::indexed_vec::Idx;
  13 use rustc::middle::const_val::FrameInfo;
  14 use syntax::codemap::{self, DUMMY_SP, Span};
  15 use syntax::ast::Mutability;
  16 use rustc::mir::interpret::{
  17     GlobalId, Value, Pointer, PrimVal, PrimValKind,
  18     EvalError, EvalResult, EvalErrorKind, MemoryPointer,
  19 };
  20
  21 use super::{Place, PlaceExtra, Memory,
  22             HasMemory, MemoryKind, operator,
  23             Machine};
  24
  25 pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
  26     /// Stores the `Machine` instance.
  27     pub machine: M,
  28
  29     /// The results of the type checker, from rustc.
  30     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
  31
  32     /// Bounds in scope for polymorphic evaluations.
  33     pub param_env: ty::ParamEnv<'tcx>,
  34
  35     /// The virtual memory system.
  36     pub memory: Memory<'a, 'mir, 'tcx, M>,
  37
  38     /// The virtual call stack.
  39     pub(crate) stack: Vec<Frame<'mir, 'tcx>>,
  40
  41     /// The maximum number of stack frames allowed
  42     pub(crate) stack_limit: usize,
  43
  44     /// The maximum number of operations that may be executed.
  45     /// This prevents infinite loops and huge computations from freezing up const eval.
  46     /// Remove once halting problem is solved.
  47     pub(crate) steps_remaining: usize,
  48 }
  49
  50 /// A stack frame.
  51 pub struct Frame<'mir, 'tcx: 'mir> {
  52     ////////////////////////////////////////////////////////////////////////////////
  53     // Function and callsite information
  54     ////////////////////////////////////////////////////////////////////////////////
  55     /// The MIR for the function called on this frame.
  56     pub mir: &'mir mir::Mir<'tcx>,
  57
  58     /// The def_id and substs of the current function
  59     pub instance: ty::Instance<'tcx>,
  60
  61     /// The span of the call site.
  62     pub span: codemap::Span,
  63
  64     ////////////////////////////////////////////////////////////////////////////////
  65     // Return place and locals
  66     ////////////////////////////////////////////////////////////////////////////////
  67     /// The block to return to when returning from the current stack frame
  68     pub return_to_block: StackPopCleanup,
  69
  70     /// The location where the result of the current stack frame should be written to.
  71     pub return_place: Place,
  72
  73     /// The list of locals for this stack frame, stored in order as
  74     /// `[arguments..., variables..., temporaries...]`. The locals are stored as `Option<Value>`s.
  75     /// `None` represents a local that is currently dead, while a live local
  76     /// can either directly contain `PrimVal` or refer to some part of an `Allocation`.
  77     ///
  78     /// Before being initialized, arguments are `Value::ByVal(PrimVal::Undef)` and other locals are `None`.
  79     pub locals: Vec<Option<Value>>,
  80
  81     ////////////////////////////////////////////////////////////////////////////////
  82     // Current position within the function
  83     ////////////////////////////////////////////////////////////////////////////////
  84     /// The block that is currently executed (or will be executed after the above call stacks
  85     /// return).
  86     pub block: mir::BasicBlock,
  87
  88     /// The index of the currently evaluated statement.
  89     pub stmt: usize,
  90 }
  91
  92 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
  93 pub enum StackPopCleanup {
  94     /// The stackframe existed to compute the initial value of a static/constant, make sure it
  95     /// isn't modifyable afterwards in case of constants.
  96     /// In case of `static mut`, mark the memory to ensure it's never marked as immutable through
  97     /// references or deallocated
  98     MarkStatic(Mutability),
  99     /// A regular stackframe added due to a function call will need to get forwarded to the next
 100     /// block
 101     Goto(mir::BasicBlock),
 102     /// The main function and diverging functions have nowhere to return to
 103     None,
 104 }
 105
 106 #[derive(Copy, Clone, Debug)]
 107 pub struct TyAndPacked<'tcx> {
 108     pub ty: Ty<'tcx>,
 109     pub packed: bool,
 110 }
 111
 112 #[derive(Copy, Clone, Debug)]
 113 pub struct ValTy<'tcx> {
 114     pub value: Value,
 115     pub ty: Ty<'tcx>,
 116 }
 117
 118 impl<'tcx> ValTy<'tcx> {
 119     pub fn from(val: &ty::Const<'tcx>) -> Option<Self> {
 120         match val.val {
 121             ConstVal::Value(value) => Some(ValTy { value, ty: val.ty }),
 122             ConstVal::Unevaluated { .. } => None,
 123         }
 124     }
 125 }
 126
 127 impl<'tcx> ::std::ops::Deref for ValTy<'tcx> {
 128     type Target = Value;
 129     fn deref(&self) -> &Value {
 130         &self.value
 131     }
 132 }
 133
 134 impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for &'a EvalContext<'a, 'mir, 'tcx, M> {
 135     #[inline]
 136     fn data_layout(&self) -> &layout::TargetDataLayout {
 137         &self.tcx.data_layout
 138     }
 139 }
 140
 141 impl<'c, 'b, 'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout
 142     for &'c &'b mut EvalContext<'a, 'mir, 'tcx, M> {
 143     #[inline]
 144     fn data_layout(&self) -> &layout::TargetDataLayout {
 145         &self.tcx.data_layout
 146     }
 147 }
 148
 149 impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> layout::HasTyCtxt<'tcx> for &'a EvalContext<'a, 'mir, 'tcx, M> {
 150     #[inline]
 151     fn tcx<'b>(&'b self) -> TyCtxt<'b, 'tcx, 'tcx> {
 152         self.tcx
 153     }
 154 }
 155
 156 impl<'c, 'b, 'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> layout::HasTyCtxt<'tcx>
 157     for &'c &'b mut EvalContext<'a, 'mir, 'tcx, M> {
 158     #[inline]
 159     fn tcx<'d>(&'d self) -> TyCtxt<'d, 'tcx, 'tcx> {
 160         self.tcx
 161     }
 162 }
 163
 164 impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf<Ty<'tcx>> for &'a EvalContext<'a, 'mir, 'tcx, M> {
 165     type TyLayout = EvalResult<'tcx, TyLayout<'tcx>>;
 166
 167     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
 168         self.tcx.layout_of(self.param_env.and(ty))
 169             .map_err(|layout| EvalErrorKind::Layout(layout).into())
 170     }
 171 }
 172
 173 impl<'c, 'b, 'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf<Ty<'tcx>>
 174     for &'c &'b mut EvalContext<'a, 'mir, 'tcx, M> {
 175     type TyLayout = EvalResult<'tcx, TyLayout<'tcx>>;
 176
 177     #[inline]
 178     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
 179         (&**self).layout_of(ty)
 180     }
 181 }
 182
 183 impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
 184     pub fn new(
 185         tcx: TyCtxt<'a, 'tcx, 'tcx>,
 186         param_env: ty::ParamEnv<'tcx>,
 187         machine: M,
 188         memory_data: M::MemoryData,
 189     ) -> Self {
 190         EvalContext {
 191             machine,
 192             tcx,
 193             param_env,
 194             memory: Memory::new(tcx, memory_data),
 195             stack: Vec::new(),
 196             stack_limit: tcx.sess.const_eval_stack_frame_limit.get(),
 197             steps_remaining: tcx.sess.const_eval_step_limit.get(),
 198         }
 199     }
 200
 201     pub fn alloc_ptr(&mut self, ty: Ty<'tcx>) -> EvalResult<'tcx, MemoryPointer> {
 202         let layout = self.layout_of(ty)?;
 203         assert!(!layout.is_unsized(), "cannot alloc memory for unsized type");
 204
 205         let size = layout.size.bytes();
 206         self.memory.allocate(size, layout.align, Some(MemoryKind::Stack))
 207     }
 208
 209     pub fn memory(&self) -> &Memory<'a, 'mir, 'tcx, M> {
 210         &self.memory
 211     }
 212
 213     pub fn memory_mut(&mut self) -> &mut Memory<'a, 'mir, 'tcx, M> {
 214         &mut self.memory
 215     }
 216
 217     pub fn stack(&self) -> &[Frame<'mir, 'tcx>] {
 218         &self.stack
 219     }
 220
 221     #[inline]
 222     pub fn cur_frame(&self) -> usize {
 223         assert!(self.stack.len() > 0);
 224         self.stack.len() - 1
 225     }
 226
 227     pub fn str_to_value(&mut self, s: &str) -> EvalResult<'tcx, Value> {
 228         let ptr = self.memory.allocate_cached(s.as_bytes());
 229         Ok(Value::ByValPair(
 230             PrimVal::Ptr(ptr),
 231             PrimVal::from_u128(s.len() as u128),
 232         ))
 233     }
 234
 235     pub(super) fn const_to_value(&self, const_val: &ConstVal<'tcx>, ty: Ty<'tcx>) -> EvalResult<'tcx, Value> {
 236         match *const_val {
 237             ConstVal::Unevaluated(def_id, substs) => {
 238                 let instance = self.resolve(def_id, substs)?;
 239                 self.read_global_as_value(GlobalId {
 240                     instance,
 241                     promoted: None,
 242                 }, ty)
 243             }
 244             ConstVal::Value(val) => Ok(val),
 245         }
 246     }
 247
 248     pub(super) fn resolve(&self, def_id: DefId, substs: &'tcx Substs<'tcx>) -> EvalResult<'tcx, ty::Instance<'tcx>> {
 249         let substs = self.tcx.trans_apply_param_substs(self.substs(), &substs);
 250         ty::Instance::resolve(
 251             self.tcx,
 252             self.param_env,
 253             def_id,
 254             substs,
 255         ).ok_or(EvalErrorKind::TypeckError.into()) // turn error prop into a panic to expose associated type in const issue
 256     }
 257
 258     pub(super) fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
 259         ty.is_sized(self.tcx.at(DUMMY_SP), self.param_env)
 260     }
 261
 262     pub fn load_mir(
 263         &self,
 264         instance: ty::InstanceDef<'tcx>,
 265     ) -> EvalResult<'tcx, &'tcx mir::Mir<'tcx>> {
 266         // do not continue if typeck errors occurred (can only occur in local crate)
 267         let did = instance.def_id();
 268         if did.is_local() && self.tcx.has_typeck_tables(did) && self.tcx.typeck_tables_of(did).tainted_by_errors {
 269             return err!(TypeckError);
 270         }
 271         trace!("load mir {:?}", instance);
 272         match instance {
 273             ty::InstanceDef::Item(def_id) => {
 274                 self.tcx.maybe_optimized_mir(def_id).ok_or_else(|| {
 275                     EvalErrorKind::NoMirFor(self.tcx.item_path_str(def_id)).into()
 276                 })
 277             }
 278             _ => Ok(self.tcx.instance_mir(instance)),
 279         }
 280     }
 281
 282     pub fn monomorphize(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
 283         // miri doesn't care about lifetimes, and will choke on some crazy ones
 284         // let's simply get rid of them
 285         let without_lifetimes = self.tcx.erase_regions(&ty);
 286         let substituted = without_lifetimes.subst(self.tcx, substs);
 287         let substituted = self.tcx.fully_normalize_monormophic_ty(&substituted);
 288         substituted
 289     }
 290
 291     /// Return the size and aligment of the value at the given type.
 292     /// Note that the value does not matter if the type is sized. For unsized types,
 293     /// the value has to be a fat pointer, and we only care about the "extra" data in it.
 294     pub fn size_and_align_of_dst(
 295         &mut self,
 296         ty: Ty<'tcx>,
 297         value: Value,
 298     ) -> EvalResult<'tcx, (Size, Align)> {
 299         let layout = self.layout_of(ty)?;
 300         if !layout.is_unsized() {
 301             Ok(layout.size_and_align())
 302         } else {
 303             match ty.sty {
 304                 ty::TyAdt(..) | ty::TyTuple(..) => {
 305                     // First get the size of all statically known fields.
 306                     // Don't use type_of::sizing_type_of because that expects t to be sized,
 307                     // and it also rounds up to alignment, which we want to avoid,
 308                     // as the unsized field's alignment could be smaller.
 309                     assert!(!ty.is_simd());
 310                     debug!("DST {} layout: {:?}", ty, layout);
 311
 312                     let sized_size = layout.fields.offset(layout.fields.count() - 1);
 313                     let sized_align = layout.align;
 314                     debug!(
 315                         "DST {} statically sized prefix size: {:?} align: {:?}",
 316                         ty,
 317                         sized_size,
 318                         sized_align
 319                     );
 320
 321                     // Recurse to get the size of the dynamically sized field (must be
 322                     // the last field).
 323                     let field_ty = layout.field(&self, layout.fields.count() - 1)?.ty;
 324                     let (unsized_size, unsized_align) =
 325                         self.size_and_align_of_dst(field_ty, value)?;
 326
 327                     // FIXME (#26403, #27023): We should be adding padding
 328                     // to `sized_size` (to accommodate the `unsized_align`
 329                     // required of the unsized field that follows) before
 330                     // summing it with `sized_size`. (Note that since #26403
 331                     // is unfixed, we do not yet add the necessary padding
 332                     // here. But this is where the add would go.)
 333
 334                     // Return the sum of sizes and max of aligns.
 335                     let size = sized_size + unsized_size;
 336
 337                     // Choose max of two known alignments (combined value must
 338                     // be aligned according to more restrictive of the two).
 339                     let align = sized_align.max(unsized_align);
 340
 341                     // Issue #27023: must add any necessary padding to `size`
 342                     // (to make it a multiple of `align`) before returning it.
 343                     //
 344                     // Namely, the returned size should be, in C notation:
 345                     //
 346                     //   `size + ((size & (align-1)) ? align : 0)`
 347                     //
 348                     // emulated via the semi-standard fast bit trick:
 349                     //
 350                     //   `(size + (align-1)) & -align`
 351
 352                     Ok((size.abi_align(align), align))
 353                 }
 354                 ty::TyDynamic(..) => {
 355                     let (_, vtable) = self.into_ptr_vtable_pair(value)?;
 356                     // the second entry in the vtable is the dynamic size of the object.
 357                     self.read_size_and_align_from_vtable(vtable)
 358                 }
 359
 360                 ty::TySlice(_) | ty::TyStr => {
 361                     let (elem_size, align) = layout.field(&self, 0)?.size_and_align();
 362                     let (_, len) = self.into_slice(value)?;
 363                     Ok((elem_size * len, align))
 364                 }
 365
 366                 _ => bug!("size_of_val::<{:?}>", ty),
 367             }
 368         }
 369     }
 370
 371     pub fn push_stack_frame(
 372         &mut self,
 373         instance: ty::Instance<'tcx>,
 374         span: codemap::Span,
 375         mir: &'mir mir::Mir<'tcx>,
 376         return_place: Place,
 377         return_to_block: StackPopCleanup,
 378     ) -> EvalResult<'tcx> {
 379         ::log_settings::settings().indentation += 1;
 380
 381         /// Return the set of locals that have a storage annotation anywhere
 382         fn collect_storage_annotations<'mir, 'tcx>(mir: &'mir mir::Mir<'tcx>) -> HashSet<mir::Local> {
 383             use rustc::mir::StatementKind::*;
 384
 385             let mut set = HashSet::new();
 386             for block in mir.basic_blocks() {
 387                 for stmt in block.statements.iter() {
 388                     match stmt.kind {
 389                         StorageLive(local) |
 390                         StorageDead(local) => {
 391                             set.insert(local);
 392                         }
 393                         _ => {}
 394                     }
 395                 }
 396             }
 397             set
 398         }
 399
 400         // Subtract 1 because `local_decls` includes the ReturnMemoryPointer, but we don't store a local
 401         // `Value` for that.
 402         let num_locals = mir.local_decls.len() - 1;
 403
 404         let locals = {
 405             let annotated_locals = collect_storage_annotations(mir);
 406             let mut locals = vec![None; num_locals];
 407             for i in 0..num_locals {
 408                 let local = mir::Local::new(i + 1);
 409                 if !annotated_locals.contains(&local) {
 410                     locals[i] = Some(Value::ByVal(PrimVal::Undef));
 411                 }
 412             }
 413             locals
 414         };
 415
 416         self.stack.push(Frame {
 417             mir,
 418             block: mir::START_BLOCK,
 419             return_to_block,
 420             return_place,
 421             locals,
 422             span,
 423             instance,
 424             stmt: 0,
 425         });
 426
 427         self.memory.cur_frame = self.cur_frame();
 428
 429         if self.stack.len() > self.stack_limit {
 430             err!(StackFrameLimitReached)
 431         } else {
 432             Ok(())
 433         }
 434     }
 435
 436     pub(super) fn pop_stack_frame(&mut self) -> EvalResult<'tcx> {
 437         ::log_settings::settings().indentation -= 1;
 438         M::end_region(self, None)?;
 439         let frame = self.stack.pop().expect(
 440             "tried to pop a stack frame, but there were none",
 441         );
 442         if !self.stack.is_empty() {
 443             // TODO: Is this the correct time to start considering these accesses as originating from the returned-to stack frame?
 444             self.memory.cur_frame = self.cur_frame();
 445         }
 446         match frame.return_to_block {
 447             StackPopCleanup::MarkStatic(mutable) => {
 448                 if let Place::Ptr { ptr, .. } = frame.return_place {
 449                     // FIXME: to_ptr()? might be too extreme here, static zsts might reach this under certain conditions
 450                     self.memory.mark_static_initialized(
 451                         ptr.to_ptr()?.alloc_id,
 452                         mutable,
 453                     )?
 454                 } else {
 455                     bug!("StackPopCleanup::MarkStatic on: {:?}", frame.return_place);
 456                 }
 457             }
 458             StackPopCleanup::Goto(target) => self.goto_block(target),
 459             StackPopCleanup::None => {}
 460         }
 461         // deallocate all locals that are backed by an allocation
 462         for local in frame.locals {
 463             self.deallocate_local(local)?;
 464         }
 465
 466         Ok(())
 467     }
 468
 469     pub fn deallocate_local(&mut self, local: Option<Value>) -> EvalResult<'tcx> {
 470         if let Some(Value::ByRef(ptr, _align)) = local {
 471             trace!("deallocating local");
 472             let ptr = ptr.to_ptr()?;
 473             self.memory.dump_alloc(ptr.alloc_id);
 474             self.memory.deallocate_local(ptr)?;
 475         };
 476         Ok(())
 477     }
 478
 479     /// Evaluate an assignment statement.
 480     ///
 481     /// There is no separate `eval_rvalue` function. Instead, the code for handling each rvalue
 482     /// type writes its results directly into the memory specified by the place.
 483     pub(super) fn eval_rvalue_into_place(
 484         &mut self,
 485         rvalue: &mir::Rvalue<'tcx>,
 486         place: &mir::Place<'tcx>,
 487     ) -> EvalResult<'tcx> {
 488         let dest = self.eval_place(place)?;
 489         let dest_ty = self.place_ty(place);
 490
 491         use rustc::mir::Rvalue::*;
 492         match *rvalue {
 493             Use(ref operand) => {
 494                 let value = self.eval_operand(operand)?.value;
 495                 let valty = ValTy {
 496                     value,
 497                     ty: dest_ty,
 498                 };
 499                 self.write_value(valty, dest)?;
 500             }
 501
 502             BinaryOp(bin_op, ref left, ref right) => {
 503                 let left = self.eval_operand(left)?;
 504                 let right = self.eval_operand(right)?;
 505                 if self.intrinsic_overflowing(
 506                     bin_op,
 507                     left,
 508                     right,
 509                     dest,
 510                     dest_ty,
 511                 )?
 512                 {
 513                     // There was an overflow in an unchecked binop.  Right now, we consider this an error and bail out.
 514                     // The rationale is that the reason rustc emits unchecked binops in release mode (vs. the checked binops
 515                     // it emits in debug mode) is performance, but it doesn't cost us any performance in miri.
 516                     // If, however, the compiler ever starts transforming unchecked intrinsics into unchecked binops,
 517                     // we have to go back to just ignoring the overflow here.
 518                     return err!(OverflowingMath);
 519                 }
 520             }
 521
 522             CheckedBinaryOp(bin_op, ref left, ref right) => {
 523                 let left = self.eval_operand(left)?;
 524                 let right = self.eval_operand(right)?;
 525                 self.intrinsic_with_overflow(
 526                     bin_op,
 527                     left,
 528                     right,
 529                     dest,
 530                     dest_ty,
 531                 )?;
 532             }
 533
 534             UnaryOp(un_op, ref operand) => {
 535                 let val = self.eval_operand_to_primval(operand)?;
 536                 let kind = self.ty_to_primval_kind(dest_ty)?;
 537                 self.write_primval(
 538                     dest,
 539                     operator::unary_op(un_op, val, kind)?,
 540                     dest_ty,
 541                 )?;
 542             }
 543
 544             Aggregate(ref kind, ref operands) => {
 545                 self.inc_step_counter_and_check_limit(operands.len())?;
 546
 547                 let (dest, active_field_index) = match **kind {
 548                     mir::AggregateKind::Adt(adt_def, variant_index, _, active_field_index) => {
 549                         self.write_discriminant_value(dest_ty, dest, variant_index)?;
 550                         if adt_def.is_enum() {
 551                             (self.place_downcast(dest, variant_index)?, active_field_index)
 552                         } else {
 553                             (dest, active_field_index)
 554                         }
 555                     }
 556                     _ => (dest, None)
 557                 };
 558
 559                 let layout = self.layout_of(dest_ty)?;
 560                 for (i, operand) in operands.iter().enumerate() {
 561                     let value = self.eval_operand(operand)?;
 562                     // Ignore zero-sized fields.
 563                     if !self.layout_of(value.ty)?.is_zst() {
 564                         let field_index = active_field_index.unwrap_or(i);
 565                         let (field_dest, _) = self.place_field(dest, mir::Field::new(field_index), layout)?;
 566                         self.write_value(value, field_dest)?;
 567                     }
 568                 }
 569             }
 570
 571             Repeat(ref operand, _) => {
 572                 let (elem_ty, length) = match dest_ty.sty {
 573                     ty::TyArray(elem_ty, n) => (elem_ty, n.val.unwrap_u64()),
 574                     _ => {
 575                         bug!(
 576                             "tried to assign array-repeat to non-array type {:?}",
 577                             dest_ty
 578                         )
 579                     }
 580                 };
 581                 let elem_size = self.layout_of(elem_ty)?.size.bytes();
 582                 let value = self.eval_operand(operand)?.value;
 583
 584                 let (dest, dest_align) = self.force_allocation(dest)?.to_ptr_align();
 585
 586                 // FIXME: speed up repeat filling
 587                 for i in 0..length {
 588                     let elem_dest = dest.offset(i * elem_size, &self)?;
 589                     self.write_value_to_ptr(value, elem_dest, dest_align, elem_ty)?;
 590                 }
 591             }
 592
 593             Len(ref place) => {
 594                 // FIXME(CTFE): don't allow computing the length of arrays in const eval
 595                 let src = self.eval_place(place)?;
 596                 let ty = self.place_ty(place);
 597                 let (_, len) = src.elem_ty_and_len(ty);
 598                 self.write_primval(
 599                     dest,
 600                     PrimVal::from_u128(len as u128),
 601                     dest_ty,
 602                 )?;
 603             }
 604
 605             Ref(_, _, ref place) => {
 606                 let src = self.eval_place(place)?;
 607                 // We ignore the alignment of the place here -- special handling for packed structs ends
 608                 // at the `&` operator.
 609                 let (ptr, _align, extra) = self.force_allocation(src)?.to_ptr_align_extra();
 610
 611                 let val = match extra {
 612                     PlaceExtra::None => ptr.to_value(),
 613                     PlaceExtra::Length(len) => ptr.to_value_with_len(len),
 614                     PlaceExtra::Vtable(vtable) => ptr.to_value_with_vtable(vtable),
 615                     PlaceExtra::DowncastVariant(..) => {
 616                         bug!("attempted to take a reference to an enum downcast place")
 617                     }
 618                 };
 619                 let valty = ValTy {
 620                     value: val,
 621                     ty: dest_ty,
 622                 };
 623                 self.write_value(valty, dest)?;
 624             }
 625
 626             NullaryOp(mir::NullOp::Box, ty) => {
 627                 let ty = self.monomorphize(ty, self.substs());
 628                 M::box_alloc(self, ty, dest)?;
 629             }
 630
 631             NullaryOp(mir::NullOp::SizeOf, ty) => {
 632                 let ty = self.monomorphize(ty, self.substs());
 633                 let layout = self.layout_of(ty)?;
 634                 assert!(!layout.is_unsized(),
 635                         "SizeOf nullary MIR operator called for unsized type");
 636                 self.write_primval(
 637                     dest,
 638                     PrimVal::from_u128(layout.size.bytes() as u128),
 639                     dest_ty,
 640                 )?;
 641             }
 642
 643             Cast(kind, ref operand, cast_ty) => {
 644                 debug_assert_eq!(self.monomorphize(cast_ty, self.substs()), dest_ty);
 645                 use rustc::mir::CastKind::*;
 646                 match kind {
 647                     Unsize => {
 648                         let src = self.eval_operand(operand)?;
 649                         let src_layout = self.layout_of(src.ty)?;
 650                         let dst_layout = self.layout_of(dest_ty)?;
 651                         self.unsize_into(src.value, src_layout, dest, dst_layout)?;
 652                     }
 653
 654                     Misc => {
 655                         let src = self.eval_operand(operand)?;
 656                         if self.type_is_fat_ptr(src.ty) {
 657                             match (src.value, self.type_is_fat_ptr(dest_ty)) {
 658                                 (Value::ByRef { .. }, _) |
 659                                 (Value::ByValPair(..), true) => {
 660                                     let valty = ValTy {
 661                                         value: src.value,
 662                                         ty: dest_ty,
 663                                     };
 664                                     self.write_value(valty, dest)?;
 665                                 }
 666                                 (Value::ByValPair(data, _), false) => {
 667                                     let valty = ValTy {
 668                                         value: Value::ByVal(data),
 669                                         ty: dest_ty,
 670                                     };
 671                                     self.write_value(valty, dest)?;
 672                                 }
 673                                 (Value::ByVal(_), _) => bug!("expected fat ptr"),
 674                             }
 675                         } else {
 676                             let src_val = self.value_to_primval(src)?;
 677                             let dest_val = self.cast_primval(src_val, src.ty, dest_ty)?;
 678                             let valty = ValTy {
 679                                 value: Value::ByVal(dest_val),
 680                                 ty: dest_ty,
 681                             };
 682                             self.write_value(valty, dest)?;
 683                         }
 684                     }
 685
 686                     ReifyFnPointer => {
 687                         match self.eval_operand(operand)?.ty.sty {
 688                             ty::TyFnDef(def_id, substs) => {
 689                                 if self.tcx.has_attr(def_id, "rustc_args_required_const") {
 690                                     bug!("reifying a fn ptr that requires \
 691                                           const arguments");
 692                                 }
 693                                 let instance = self.resolve(def_id, substs)?;
 694                                 let fn_ptr = self.memory.create_fn_alloc(instance);
 695                                 let valty = ValTy {
 696                                     value: Value::ByVal(PrimVal::Ptr(fn_ptr)),
 697                                     ty: dest_ty,
 698                                 };
 699                                 self.write_value(valty, dest)?;
 700                             }
 701                             ref other => bug!("reify fn pointer on {:?}", other),
 702                         }
 703                     }
 704
 705                     UnsafeFnPointer => {
 706                         match dest_ty.sty {
 707                             ty::TyFnPtr(_) => {
 708                                 let mut src = self.eval_operand(operand)?;
 709                                 src.ty = dest_ty;
 710                                 self.write_value(src, dest)?;
 711                             }
 712                             ref other => bug!("fn to unsafe fn cast on {:?}", other),
 713                         }
 714                     }
 715
 716                     ClosureFnPointer => {
 717                         match self.eval_operand(operand)?.ty.sty {
 718                             ty::TyClosure(def_id, substs) => {
 719                                 let substs = self.tcx.trans_apply_param_substs(self.substs(), &substs);
 720                                 let instance = ty::Instance::resolve_closure(
 721                                     self.tcx,
 722                                     def_id,
 723                                     substs,
 724                                     ty::ClosureKind::FnOnce,
 725                                 );
 726                                 let fn_ptr = self.memory.create_fn_alloc(instance);
 727                                 let valty = ValTy {
 728                                     value: Value::ByVal(PrimVal::Ptr(fn_ptr)),
 729                                     ty: dest_ty,
 730                                 };
 731                                 self.write_value(valty, dest)?;
 732                             }
 733                             ref other => bug!("closure fn pointer on {:?}", other),
 734                         }
 735                     }
 736                 }
 737             }
 738
 739             Discriminant(ref place) => {
 740                 let ty = self.place_ty(place);
 741                 let place = self.eval_place(place)?;
 742                 let discr_val = self.read_discriminant_value(place, ty)?;
 743                 if let ty::TyAdt(adt_def, _) = ty.sty {
 744                     trace!("Read discriminant {}, valid discriminants {:?}", discr_val, adt_def.discriminants(self.tcx).collect::<Vec<_>>());
 745                     if adt_def.discriminants(self.tcx).all(|v| {
 746                         discr_val != v.val
 747                     })
 748                     {
 749                         return err!(InvalidDiscriminant);
 750                     }
 751                     self.write_primval(dest, PrimVal::Bytes(discr_val), dest_ty)?;
 752                 } else {
 753                     bug!("rustc only generates Rvalue::Discriminant for enums");
 754                 }
 755             }
 756         }
 757
 758         if log_enabled!(::log::Level::Trace) {
 759             self.dump_local(dest);
 760         }
 761
 762         Ok(())
 763     }
 764
 765     pub(super) fn type_is_fat_ptr(&self, ty: Ty<'tcx>) -> bool {
 766         match ty.sty {
 767             ty::TyRawPtr(ref tam) |
 768             ty::TyRef(_, ref tam) => !self.type_is_sized(tam.ty),
 769             ty::TyAdt(def, _) if def.is_box() => !self.type_is_sized(ty.boxed_ty()),
 770             _ => false,
 771         }
 772     }
 773
 774     pub(super) fn eval_operand_to_primval(
 775         &mut self,
 776         op: &mir::Operand<'tcx>,
 777     ) -> EvalResult<'tcx, PrimVal> {
 778         let valty = self.eval_operand(op)?;
 779         self.value_to_primval(valty)
 780     }
 781
 782     pub(crate) fn operands_to_args(
 783         &mut self,
 784         ops: &[mir::Operand<'tcx>],
 785     ) -> EvalResult<'tcx, Vec<ValTy<'tcx>>> {
 786         ops.into_iter()
 787             .map(|op| self.eval_operand(op))
 788             .collect()
 789     }
 790
 791     pub fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<'tcx, ValTy<'tcx>> {
 792         use rustc::mir::Operand::*;
 793         let ty = self.monomorphize(op.ty(self.mir(), self.tcx), self.substs());
 794         match *op {
 795             // FIXME: do some more logic on `move` to invalidate the old location
 796             Copy(ref place) |
 797             Move(ref place) => {
 798                 Ok(ValTy {
 799                     value: self.eval_and_read_place(place)?,
 800                     ty
 801                 })
 802             },
 803
 804             Constant(ref constant) => {
 805                 use rustc::mir::Literal;
 806                 let mir::Constant { ref literal, .. } = **constant;
 807                 let value = match *literal {
 808                     Literal::Value { ref value } => self.const_to_value(&value.val, ty)?,
 809
 810                     Literal::Promoted { index } => {
 811                         self.read_global_as_value(GlobalId {
 812                             instance: self.frame().instance,
 813                             promoted: Some(index),
 814                         }, ty)?
 815                     }
 816                 };
 817
 818                 Ok(ValTy {
 819                     value,
 820                     ty,
 821                 })
 822             }
 823         }
 824     }
 825
 826     pub fn read_discriminant_value(
 827         &mut self,
 828         place: Place,
 829         ty: Ty<'tcx>,
 830     ) -> EvalResult<'tcx, u128> {
 831         let layout = self.layout_of(ty)?;
 832         //trace!("read_discriminant_value {:#?}", layout);
 833
 834         match layout.variants {
 835             layout::Variants::Single { index } => {
 836                 return Ok(index as u128);
 837             }
 838             layout::Variants::Tagged { .. } |
 839             layout::Variants::NicheFilling { .. } => {},
 840         }
 841
 842         let (discr_place, discr) = self.place_field(place, mir::Field::new(0), layout)?;
 843         let raw_discr = self.value_to_primval(ValTy {
 844             value: self.read_place(discr_place)?,
 845             ty: discr.ty
 846         })?;
 847         let discr_val = match layout.variants {
 848             layout::Variants::Single { .. } => bug!(),
 849             layout::Variants::Tagged { .. } => raw_discr.to_bytes()?,
 850             layout::Variants::NicheFilling {
 851                 dataful_variant,
 852                 ref niche_variants,
 853                 niche_start,
 854                 ..
 855             } => {
 856                 let variants_start = niche_variants.start as u128;
 857                 let variants_end = niche_variants.end as u128;
 858                 match raw_discr {
 859                     PrimVal::Ptr(_) => {
 860                         assert!(niche_start == 0);
 861                         assert!(variants_start == variants_end);
 862                         dataful_variant as u128
 863                     },
 864                     PrimVal::Bytes(raw_discr) => {
 865                         let discr = raw_discr.wrapping_sub(niche_start)
 866                             .wrapping_add(variants_start);
 867                         if variants_start <= discr && discr <= variants_end {
 868                             discr
 869                         } else {
 870                             dataful_variant as u128
 871                         }
 872                     },
 873                     PrimVal::Undef => return err!(ReadUndefBytes),
 874                 }
 875             }
 876         };
 877
 878         Ok(discr_val)
 879     }
 880
 881
 882     pub(crate) fn write_discriminant_value(
 883         &mut self,
 884         dest_ty: Ty<'tcx>,
 885         dest: Place,
 886         variant_index: usize,
 887     ) -> EvalResult<'tcx> {
 888         let layout = self.layout_of(dest_ty)?;
 889
 890         match layout.variants {
 891             layout::Variants::Single { index } => {
 892                 if index != variant_index {
 893                     // If the layout of an enum is `Single`, all
 894                     // other variants are necessarily uninhabited.
 895                     assert_eq!(layout.for_variant(&self, variant_index).abi,
 896                                layout::Abi::Uninhabited);
 897                 }
 898             }
 899             layout::Variants::Tagged { .. } => {
 900                 let discr_val = dest_ty.ty_adt_def().unwrap()
 901                     .discriminant_for_variant(self.tcx, variant_index)
 902                     .val;
 903
 904                 let (discr_dest, discr) = self.place_field(dest, mir::Field::new(0), layout)?;
 905                 self.write_primval(discr_dest, PrimVal::Bytes(discr_val), discr.ty)?;
 906             }
 907             layout::Variants::NicheFilling {
 908                 dataful_variant,
 909                 ref niche_variants,
 910                 niche_start,
 911                 ..
 912             } => {
 913                 if variant_index != dataful_variant {
 914                     let (niche_dest, niche) =
 915                         self.place_field(dest, mir::Field::new(0), layout)?;
 916                     let niche_value = ((variant_index - niche_variants.start) as u128)
 917                         .wrapping_add(niche_start);
 918                     self.write_primval(niche_dest, PrimVal::Bytes(niche_value), niche.ty)?;
 919                 }
 920             }
 921         }
 922
 923         Ok(())
 924     }
 925
 926     pub fn read_global_as_value(&self, gid: GlobalId<'tcx>, ty: Ty<'tcx>) -> EvalResult<'tcx, Value> {
 927         if gid.promoted.is_none() {
 928             let cached = self
 929                 .tcx
 930                 .interpret_interner
 931                 .get_cached(gid.instance.def_id());
 932             if let Some(alloc_id) = cached {
 933                 let layout = self.layout_of(ty)?;
 934                 let ptr = MemoryPointer::new(alloc_id, 0);
 935                 return Ok(Value::ByRef(ptr.into(), layout.align))
 936             }
 937         }
 938         let cv = self.const_eval(gid)?;
 939         self.const_to_value(&cv.val, ty)
 940     }
 941
 942     pub fn const_eval(&self, gid: GlobalId<'tcx>) -> EvalResult<'tcx, &'tcx ty::Const<'tcx>> {
 943         let param_env = if self.tcx.is_static(gid.instance.def_id()).is_some() {
 944             use rustc::traits;
 945             ty::ParamEnv::empty(traits::Reveal::All)
 946         } else {
 947             self.param_env
 948         };
 949         self.tcx.const_eval(param_env.and(gid)).map_err(|err| match *err.kind {
 950             ErrKind::Miri(ref err, _) => match err.kind {
 951                 EvalErrorKind::TypeckError |
 952                 EvalErrorKind::Layout(_) => EvalErrorKind::TypeckError.into(),
 953                 _ => EvalErrorKind::ReferencedConstant.into(),
 954             },
 955             ErrKind::TypeckError => EvalErrorKind::TypeckError.into(),
 956             ref other => bug!("const eval returned {:?}", other),
 957         })
 958     }
 959
 960     pub fn force_allocation(&mut self, place: Place) -> EvalResult<'tcx, Place> {
 961         let new_place = match place {
 962             Place::Local { frame, local } => {
 963                 // -1 since we don't store the return value
 964                 match self.stack[frame].locals[local.index() - 1] {
 965                     None => return err!(DeadLocal),
 966                     Some(Value::ByRef(ptr, align)) => {
 967                         Place::Ptr {
 968                             ptr,
 969                             align,
 970                             extra: PlaceExtra::None,
 971                         }
 972                     }
 973                     Some(val) => {
 974                         let ty = self.stack[frame].mir.local_decls[local].ty;
 975                         let ty = self.monomorphize(ty, self.stack[frame].instance.substs);
 976                         let layout = self.layout_of(ty)?;
 977                         let ptr = self.alloc_ptr(ty)?;
 978                         self.stack[frame].locals[local.index() - 1] =
 979                             Some(Value::ByRef(ptr.into(), layout.align)); // it stays live
 980                         let place = Place::from_ptr(ptr, layout.align);
 981                         self.write_value(ValTy { value: val, ty }, place)?;
 982                         place
 983                     }
 984                 }
 985             }
 986             Place::Ptr { .. } => place,
 987         };
 988         Ok(new_place)
 989     }
 990
 991     /// ensures this Value is not a ByRef
 992     pub fn follow_by_ref_value(
 993         &self,
 994         value: Value,
 995         ty: Ty<'tcx>,
 996     ) -> EvalResult<'tcx, Value> {
 997         match value {
 998             Value::ByRef(ptr, align) => {
 999                 self.read_value(ptr, align, ty)
1000             }
1001             other => Ok(other),
1002         }
1003     }
1004
1005     pub fn value_to_primval(
1006         &self,
1007         ValTy { value, ty } : ValTy<'tcx>,
1008     ) -> EvalResult<'tcx, PrimVal> {
1009         match self.follow_by_ref_value(value, ty)? {
1010             Value::ByRef { .. } => bug!("follow_by_ref_value can't result in `ByRef`"),
1011
1012             Value::ByVal(primval) => {
1013                 // TODO: Do we really want insta-UB here?
1014                 self.ensure_valid_value(primval, ty)?;
1015                 Ok(primval)
1016             }
1017
1018             Value::ByValPair(..) => bug!("value_to_primval can't work with fat pointers"),
1019         }
1020     }
1021
1022     pub fn write_ptr(&mut self, dest: Place, val: Pointer, dest_ty: Ty<'tcx>) -> EvalResult<'tcx> {
1023         let valty = ValTy {
1024             value: val.to_value(),
1025             ty: dest_ty,
1026         };
1027         self.write_value(valty, dest)
1028     }
1029
1030     pub fn write_primval(
1031         &mut self,
1032         dest: Place,
1033         val: PrimVal,
1034         dest_ty: Ty<'tcx>,
1035     ) -> EvalResult<'tcx> {
1036         let valty = ValTy {
1037             value: Value::ByVal(val),
1038             ty: dest_ty,
1039         };
1040         self.write_value(valty, dest)
1041     }
1042
1043     pub fn write_value(
1044         &mut self,
1045         ValTy { value: src_val, ty: dest_ty } : ValTy<'tcx>,
1046         dest: Place,
1047     ) -> EvalResult<'tcx> {
1048         //trace!("Writing {:?} to {:?} at type {:?}", src_val, dest, dest_ty);
1049         // Note that it is really important that the type here is the right one, and matches the type things are read at.
1050         // In case `src_val` is a `ByValPair`, we don't do any magic here to handle padding properly, which is only
1051         // correct if we never look at this data with the wrong type.
1052
1053         match dest {
1054             Place::Ptr { ptr, align, extra } => {
1055                 assert_eq!(extra, PlaceExtra::None);
1056                 self.write_value_to_ptr(src_val, ptr, align, dest_ty)
1057             }
1058
1059             Place::Local { frame, local } => {
1060                 let dest = self.stack[frame].get_local(local)?;
1061                 self.write_value_possibly_by_val(
1062                     src_val,
1063                     |this, val| this.stack[frame].set_local(local, val),
1064                     dest,
1065                     dest_ty,
1066                 )
1067             }
1068         }
1069     }
1070
1071     // The cases here can be a bit subtle. Read carefully!
1072     fn write_value_possibly_by_val<F: FnOnce(&mut Self, Value) -> EvalResult<'tcx>>(
1073         &mut self,
1074         src_val: Value,
1075         write_dest: F,
1076         old_dest_val: Value,
1077         dest_ty: Ty<'tcx>,
1078     ) -> EvalResult<'tcx> {
1079         if let Value::ByRef(dest_ptr, align) = old_dest_val {
1080             // If the value is already `ByRef` (that is, backed by an `Allocation`),
1081             // then we must write the new value into this allocation, because there may be
1082             // other pointers into the allocation. These other pointers are logically
1083             // pointers into the local variable, and must be able to observe the change.
1084             //
1085             // Thus, it would be an error to replace the `ByRef` with a `ByVal`, unless we
1086             // knew for certain that there were no outstanding pointers to this allocation.
1087             self.write_value_to_ptr(src_val, dest_ptr, align, dest_ty)?;
1088         } else if let Value::ByRef(src_ptr, align) = src_val {
1089             // If the value is not `ByRef`, then we know there are no pointers to it
1090             // and we can simply overwrite the `Value` in the locals array directly.
1091             //
1092             // In this specific case, where the source value is `ByRef`, we must duplicate
1093             // the allocation, because this is a by-value operation. It would be incorrect
1094             // if they referred to the same allocation, since then a change to one would
1095             // implicitly change the other.
1096             //
1097             // It is a valid optimization to attempt reading a primitive value out of the
1098             // source and write that into the destination without making an allocation, so
1099             // we do so here.
1100             if let Ok(Some(src_val)) = self.try_read_value(src_ptr, align, dest_ty) {
1101                 write_dest(self, src_val)?;
1102             } else {
1103                 let dest_ptr = self.alloc_ptr(dest_ty)?.into();
1104                 let layout = self.layout_of(dest_ty)?;
1105                 self.memory.copy(src_ptr, align.min(layout.align), dest_ptr, layout.align, layout.size.bytes(), false)?;
1106                 write_dest(self, Value::ByRef(dest_ptr, layout.align))?;
1107             }
1108         } else {
1109             // Finally, we have the simple case where neither source nor destination are
1110             // `ByRef`. We may simply copy the source value over the the destintion.
1111             write_dest(self, src_val)?;
1112         }
1113         Ok(())
1114     }
1115
1116     pub fn write_value_to_ptr(
1117         &mut self,
1118         value: Value,
1119         dest: Pointer,
1120         dest_align: Align,
1121         dest_ty: Ty<'tcx>,
1122     ) -> EvalResult<'tcx> {
1123         trace!("write_value_to_ptr: {:#?}", value);
1124         let layout = self.layout_of(dest_ty)?;
1125         match value {
1126             Value::ByRef(ptr, align) => {
1127                 self.memory.copy(ptr, align.min(layout.align), dest, dest_align.min(layout.align), layout.size.bytes(), false)
1128             }
1129             Value::ByVal(primval) => {
1130                 match layout.abi {
1131                     layout::Abi::Scalar(_) => {}
1132                     _ if primval.is_undef() => {}
1133                     _ => bug!("write_value_to_ptr: invalid ByVal layout: {:#?}", layout)
1134                 }
1135                 // TODO: Do we need signedness?
1136                 self.memory.write_primval(dest.to_ptr()?, dest_align, primval, layout.size.bytes(), false)
1137             }
1138             Value::ByValPair(a_val, b_val) => {
1139                 let ptr = dest.to_ptr()?;
1140                 trace!("write_value_to_ptr valpair: {:#?}", layout);
1141                 let (a, b) = match layout.abi {
1142                     layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
1143                     _ => bug!("write_value_to_ptr: invalid ByValPair layout: {:#?}", layout)
1144                 };
1145                 let (a_size, b_size) = (a.size(&self), b.size(&self));
1146                 let a_ptr = ptr;
1147                 let b_offset = a_size.abi_align(b.align(&self));
1148                 let b_ptr = ptr.offset(b_offset.bytes(), &self)?.into();
1149                 // TODO: What about signedess?
1150                 self.memory.write_primval(a_ptr, dest_align, a_val, a_size.bytes(), false)?;
1151                 self.memory.write_primval(b_ptr, dest_align, b_val, b_size.bytes(), false)
1152             }
1153         }
1154     }
1155
1156     pub fn ty_to_primval_kind(&self, ty: Ty<'tcx>) -> EvalResult<'tcx, PrimValKind> {
1157         use syntax::ast::FloatTy;
1158
1159         let kind = match ty.sty {
1160             ty::TyBool => PrimValKind::Bool,
1161             ty::TyChar => PrimValKind::Char,
1162
1163             ty::TyInt(int_ty) => {
1164                 use syntax::ast::IntTy::*;
1165                 let size = match int_ty {
1166                     I8 => 1,
1167                     I16 => 2,
1168                     I32 => 4,
1169                     I64 => 8,
1170                     I128 => 16,
1171                     Isize => self.memory.pointer_size(),
1172                 };
1173                 PrimValKind::from_int_size(size)
1174             }
1175
1176             ty::TyUint(uint_ty) => {
1177                 use syntax::ast::UintTy::*;
1178                 let size = match uint_ty {
1179                     U8 => 1,
1180                     U16 => 2,
1181                     U32 => 4,
1182                     U64 => 8,
1183                     U128 => 16,
1184                     Usize => self.memory.pointer_size(),
1185                 };
1186                 PrimValKind::from_uint_size(size)
1187             }
1188
1189             ty::TyFloat(FloatTy::F32) => PrimValKind::F32,
1190             ty::TyFloat(FloatTy::F64) => PrimValKind::F64,
1191
1192             ty::TyFnPtr(_) => PrimValKind::FnPtr,
1193
1194             ty::TyRef(_, ref tam) |
1195             ty::TyRawPtr(ref tam) if self.type_is_sized(tam.ty) => PrimValKind::Ptr,
1196
1197             ty::TyAdt(def, _) if def.is_box() => PrimValKind::Ptr,
1198
1199             ty::TyAdt(..) => {
1200                 match self.layout_of(ty)?.abi {
1201                     layout::Abi::Scalar(ref scalar) => {
1202                         use rustc::ty::layout::Primitive::*;
1203                         match scalar.value {
1204                             Int(i, false) => PrimValKind::from_uint_size(i.size().bytes()),
1205                             Int(i, true) => PrimValKind::from_int_size(i.size().bytes()),
1206                             F32 => PrimValKind::F32,
1207                             F64 => PrimValKind::F64,
1208                             Pointer => PrimValKind::Ptr,
1209                         }
1210                     }
1211
1212                     _ => return err!(TypeNotPrimitive(ty)),
1213                 }
1214             }
1215
1216             _ => return err!(TypeNotPrimitive(ty)),
1217         };
1218
1219         Ok(kind)
1220     }
1221
1222     fn ensure_valid_value(&self, val: PrimVal, ty: Ty<'tcx>) -> EvalResult<'tcx> {
1223         match ty.sty {
1224             ty::TyBool if val.to_bytes()? > 1 => err!(InvalidBool),
1225
1226             ty::TyChar if ::std::char::from_u32(val.to_bytes()? as u32).is_none() => {
1227                 err!(InvalidChar(val.to_bytes()? as u32 as u128))
1228             }
1229
1230             _ => Ok(()),
1231         }
1232     }
1233
1234     pub fn read_value(&self, ptr: Pointer, align: Align, ty: Ty<'tcx>) -> EvalResult<'tcx, Value> {
1235         if let Some(val) = self.try_read_value(ptr, align, ty)? {
1236             Ok(val)
1237         } else {
1238             bug!("primitive read failed for type: {:?}", ty);
1239         }
1240     }
1241
1242     pub(crate) fn read_ptr(
1243         &self,
1244         ptr: MemoryPointer,
1245         ptr_align: Align,
1246         pointee_ty: Ty<'tcx>,
1247     ) -> EvalResult<'tcx, Value> {
1248         let ptr_size = self.memory.pointer_size();
1249         let p: Pointer = self.memory.read_ptr_sized_unsigned(ptr, ptr_align)?.into();
1250         if self.type_is_sized(pointee_ty) {
1251             Ok(p.to_value())
1252         } else {
1253             trace!("reading fat pointer extra of type {}", pointee_ty);
1254             let extra = ptr.offset(ptr_size, self)?;
1255             match self.tcx.struct_tail(pointee_ty).sty {
1256                 ty::TyDynamic(..) => Ok(p.to_value_with_vtable(
1257                     self.memory.read_ptr_sized_unsigned(extra, ptr_align)?.to_ptr()?,
1258                 )),
1259                 ty::TySlice(..) | ty::TyStr => {
1260                     let len = self
1261                         .memory
1262                         .read_ptr_sized_unsigned(extra, ptr_align)?
1263                         .to_bytes()?;
1264                     Ok(p.to_value_with_len(len as u64))
1265                 },
1266                 _ => bug!("unsized primval ptr read from {:?}", pointee_ty),
1267             }
1268         }
1269     }
1270
1271     pub fn try_read_value(&self, ptr: Pointer, ptr_align: Align, ty: Ty<'tcx>) -> EvalResult<'tcx, Option<Value>> {
1272         use syntax::ast::FloatTy;
1273
1274         let ptr = ptr.to_ptr()?;
1275         let val = match ty.sty {
1276             ty::TyBool => {
1277                 let val = self.memory.read_primval(ptr, ptr_align, 1, false)?;
1278                 let val = match val {
1279                     PrimVal::Bytes(0) => false,
1280                     PrimVal::Bytes(1) => true,
1281                     // TODO: This seems a little overeager, should reading at bool type already be insta-UB?
1282                     _ => return err!(InvalidBool),
1283                 };
1284                 PrimVal::from_bool(val)
1285             }
1286             ty::TyChar => {
1287                 let c = self.memory.read_primval(ptr, ptr_align, 4, false)?.to_bytes()? as u32;
1288                 match ::std::char::from_u32(c) {
1289                     Some(ch) => PrimVal::from_char(ch),
1290                     None => return err!(InvalidChar(c as u128)),
1291                 }
1292             }
1293
1294             ty::TyInt(int_ty) => {
1295                 use syntax::ast::IntTy::*;
1296                 let size = match int_ty {
1297                     I8 => 1,
1298                     I16 => 2,
1299                     I32 => 4,
1300                     I64 => 8,
1301                     I128 => 16,
1302                     Isize => self.memory.pointer_size(),
1303                 };
1304                 self.memory.read_primval(ptr, ptr_align, size, true)?
1305             }
1306
1307             ty::TyUint(uint_ty) => {
1308                 use syntax::ast::UintTy::*;
1309                 let size = match uint_ty {
1310                     U8 => 1,
1311                     U16 => 2,
1312                     U32 => 4,
1313                     U64 => 8,
1314                     U128 => 16,
1315                     Usize => self.memory.pointer_size(),
1316                 };
1317                 self.memory.read_primval(ptr, ptr_align, size, false)?
1318             }
1319
1320             ty::TyFloat(FloatTy::F32) => {
1321                 PrimVal::Bytes(self.memory.read_primval(ptr, ptr_align, 4, false)?.to_bytes()?)
1322             }
1323             ty::TyFloat(FloatTy::F64) => {
1324                 PrimVal::Bytes(self.memory.read_primval(ptr, ptr_align, 8, false)?.to_bytes()?)
1325             }
1326
1327             ty::TyFnPtr(_) => self.memory.read_ptr_sized_unsigned(ptr, ptr_align)?,
1328             ty::TyRef(_, ref tam) |
1329             ty::TyRawPtr(ref tam) => return self.read_ptr(ptr, ptr_align, tam.ty).map(Some),
1330
1331             ty::TyAdt(def, _) => {
1332                 if def.is_box() {
1333                     return self.read_ptr(ptr, ptr_align, ty.boxed_ty()).map(Some);
1334                 }
1335
1336                 if let layout::Abi::Scalar(ref scalar) = self.layout_of(ty)?.abi {
1337                     let mut signed = false;
1338                     if let layout::Int(_, s) = scalar.value {
1339                         signed = s;
1340                     }
1341                     let size = scalar.value.size(self).bytes();
1342                     self.memory.read_primval(ptr, ptr_align, size, signed)?
1343                 } else {
1344                     return Ok(None);
1345                 }
1346             }
1347
1348             _ => return Ok(None),
1349         };
1350
1351         Ok(Some(Value::ByVal(val)))
1352     }
1353
1354     pub fn frame(&self) -> &Frame<'mir, 'tcx> {
1355         self.stack.last().expect("no call frames exist")
1356     }
1357
1358     pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1359         self.stack.last_mut().expect("no call frames exist")
1360     }
1361
1362     pub(super) fn mir(&self) -> &'mir mir::Mir<'tcx> {
1363         self.frame().mir
1364     }
1365
1366     pub fn substs(&self) -> &'tcx Substs<'tcx> {
1367         if let Some(frame) = self.stack.last() {
1368             frame.instance.substs
1369         } else {
1370             Substs::empty()
1371         }
1372     }
1373
1374     fn unsize_into_ptr(
1375         &mut self,
1376         src: Value,
1377         src_ty: Ty<'tcx>,
1378         dest: Place,
1379         dest_ty: Ty<'tcx>,
1380         sty: Ty<'tcx>,
1381         dty: Ty<'tcx>,
1382     ) -> EvalResult<'tcx> {
1383         // A<Struct> -> A<Trait> conversion
1384         let (src_pointee_ty, dest_pointee_ty) = self.tcx.struct_lockstep_tails(sty, dty);
1385
1386         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
1387             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
1388                 let ptr = self.into_ptr(src)?;
1389                 // u64 cast is from usize to u64, which is always good
1390                 let valty = ValTy {
1391                     value: ptr.to_value_with_len(length.val.unwrap_u64() ),
1392                     ty: dest_ty,
1393                 };
1394                 self.write_value(valty, dest)
1395             }
1396             (&ty::TyDynamic(..), &ty::TyDynamic(..)) => {
1397                 // For now, upcasts are limited to changes in marker
1398                 // traits, and hence never actually require an actual
1399                 // change to the vtable.
1400                 let valty = ValTy {
1401                     value: src,
1402                     ty: dest_ty,
1403                 };
1404                 self.write_value(valty, dest)
1405             }
1406             (_, &ty::TyDynamic(ref data, _)) => {
1407                 let trait_ref = data.principal().unwrap().with_self_ty(
1408                     self.tcx,
1409                     src_pointee_ty,
1410                 );
1411                 let trait_ref = self.tcx.erase_regions(&trait_ref);
1412                 let vtable = self.get_vtable(src_pointee_ty, trait_ref)?;
1413                 let ptr = self.into_ptr(src)?;
1414                 let valty = ValTy {
1415                     value: ptr.to_value_with_vtable(vtable),
1416                     ty: dest_ty,
1417                 };
1418                 self.write_value(valty, dest)
1419             }
1420
1421             _ => bug!("invalid unsizing {:?} -> {:?}", src_ty, dest_ty),
1422         }
1423     }
1424
1425     fn unsize_into(
1426         &mut self,
1427         src: Value,
1428         src_layout: TyLayout<'tcx>,
1429         dst: Place,
1430         dst_layout: TyLayout<'tcx>,
1431     ) -> EvalResult<'tcx> {
1432         match (&src_layout.ty.sty, &dst_layout.ty.sty) {
1433             (&ty::TyRef(_, ref s), &ty::TyRef(_, ref d)) |
1434             (&ty::TyRef(_, ref s), &ty::TyRawPtr(ref d)) |
1435             (&ty::TyRawPtr(ref s), &ty::TyRawPtr(ref d)) => {
1436                 self.unsize_into_ptr(src, src_layout.ty, dst, dst_layout.ty, s.ty, d.ty)
1437             }
1438             (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) => {
1439                 assert_eq!(def_a, def_b);
1440                 if def_a.is_box() || def_b.is_box() {
1441                     if !def_a.is_box() || !def_b.is_box() {
1442                         bug!("invalid unsizing between {:?} -> {:?}", src_layout, dst_layout);
1443                     }
1444                     return self.unsize_into_ptr(
1445                         src,
1446                         src_layout.ty,
1447                         dst,
1448                         dst_layout.ty,
1449                         src_layout.ty.boxed_ty(),
1450                         dst_layout.ty.boxed_ty(),
1451                     );
1452                 }
1453
1454                 // unsizing of generic struct with pointer fields
1455                 // Example: `Arc<T>` -> `Arc<Trait>`
1456                 // here we need to increase the size of every &T thin ptr field to a fat ptr
1457                 for i in 0..src_layout.fields.count() {
1458                     let (dst_f_place, dst_field) =
1459                         self.place_field(dst, mir::Field::new(i), dst_layout)?;
1460                     if dst_field.is_zst() {
1461                         continue;
1462                     }
1463                     let (src_f_value, src_field) = match src {
1464                         Value::ByRef(ptr, align) => {
1465                             let src_place = Place::from_primval_ptr(ptr, align);
1466                             let (src_f_place, src_field) =
1467                                 self.place_field(src_place, mir::Field::new(i), src_layout)?;
1468                             (self.read_place(src_f_place)?, src_field)
1469                         }
1470                         Value::ByVal(_) | Value::ByValPair(..) => {
1471                             let src_field = src_layout.field(&self, i)?;
1472                             assert_eq!(src_layout.fields.offset(i).bytes(), 0);
1473                             assert_eq!(src_field.size, src_layout.size);
1474                             (src, src_field)
1475                         }
1476                     };
1477                     if src_field.ty == dst_field.ty {
1478                         self.write_value(ValTy {
1479                             value: src_f_value,
1480                             ty: src_field.ty,
1481                         }, dst_f_place)?;
1482                     } else {
1483                         self.unsize_into(src_f_value, src_field, dst_f_place, dst_field)?;
1484                     }
1485                 }
1486                 Ok(())
1487             }
1488             _ => {
1489                 bug!(
1490                     "unsize_into: invalid conversion: {:?} -> {:?}",
1491                     src_layout,
1492                     dst_layout
1493                 )
1494             }
1495         }
1496     }
1497
1498     pub fn dump_local(&self, place: Place) {
1499         // Debug output
1500         match place {
1501             Place::Local { frame, local } => {
1502                 let mut allocs = Vec::new();
1503                 let mut msg = format!("{:?}", local);
1504                 if frame != self.cur_frame() {
1505                     write!(msg, " ({} frames up)", self.cur_frame() - frame).unwrap();
1506                 }
1507                 write!(msg, ":").unwrap();
1508
1509                 match self.stack[frame].get_local(local) {
1510                     Err(err) => {
1511                         if let EvalErrorKind::DeadLocal = err.kind {
1512                             write!(msg, " is dead").unwrap();
1513                         } else {
1514                             panic!("Failed to access local: {:?}", err);
1515                         }
1516                     }
1517                     Ok(Value::ByRef(ptr, align)) => {
1518                         match ptr.into_inner_primval() {
1519                             PrimVal::Ptr(ptr) => {
1520                                 write!(msg, " by align({}) ref:", align.abi()).unwrap();
1521                                 allocs.push(ptr.alloc_id);
1522                             }
1523                             ptr => write!(msg, " integral by ref: {:?}", ptr).unwrap(),
1524                         }
1525                     }
1526                     Ok(Value::ByVal(val)) => {
1527                         write!(msg, " {:?}", val).unwrap();
1528                         if let PrimVal::Ptr(ptr) = val {
1529                             allocs.push(ptr.alloc_id);
1530                         }
1531                     }
1532                     Ok(Value::ByValPair(val1, val2)) => {
1533                         write!(msg, " ({:?}, {:?})", val1, val2).unwrap();
1534                         if let PrimVal::Ptr(ptr) = val1 {
1535                             allocs.push(ptr.alloc_id);
1536                         }
1537                         if let PrimVal::Ptr(ptr) = val2 {
1538                             allocs.push(ptr.alloc_id);
1539                         }
1540                     }
1541                 }
1542
1543                 trace!("{}", msg);
1544                 self.memory.dump_allocs(allocs);
1545             }
1546             Place::Ptr { ptr, align, .. } => {
1547                 match ptr.into_inner_primval() {
1548                     PrimVal::Ptr(ptr) => {
1549                         trace!("by align({}) ref:", align.abi());
1550                         self.memory.dump_alloc(ptr.alloc_id);
1551                     }
1552                     ptr => trace!(" integral by ref: {:?}", ptr),
1553                 }
1554             }
1555         }
1556     }
1557
1558     /// Convenience function to ensure correct usage of locals
1559     pub fn modify_local<F>(&mut self, frame: usize, local: mir::Local, f: F) -> EvalResult<'tcx>
1560     where
1561         F: FnOnce(&mut Self, Value) -> EvalResult<'tcx, Value>,
1562     {
1563         let val = self.stack[frame].get_local(local)?;
1564         let new_val = f(self, val)?;
1565         self.stack[frame].set_local(local, new_val)?;
1566         // FIXME(solson): Run this when setting to Undef? (See previous version of this code.)
1567         // if let Value::ByRef(ptr) = self.stack[frame].get_local(local) {
1568         //     self.memory.deallocate(ptr)?;
1569         // }
1570         Ok(())
1571     }
1572
1573     pub fn generate_stacktrace(&self, explicit_span: Option<Span>) -> Vec<FrameInfo> {
1574         let mut last_span = None;
1575         let mut frames = Vec::new();
1576         // skip 1 because the last frame is just the environment of the constant
1577         for &Frame { instance, span, .. } in self.stack().iter().skip(1).rev() {
1578             // make sure we don't emit frames that are duplicates of the previous
1579             if explicit_span == Some(span) {
1580                 last_span = Some(span);
1581                 continue;
1582             }
1583             if let Some(last) = last_span {
1584                 if last == span {
1585                     continue;
1586                 }
1587             } else {
1588                 last_span = Some(span);
1589             }
1590             let location = if self.tcx.def_key(instance.def_id()).disambiguated_data.data == DefPathData::ClosureExpr {
1591                 "closure".to_owned()
1592             } else {
1593                 instance.to_string()
1594             };
1595             frames.push(FrameInfo { span, location });
1596         }
1597         frames
1598     }
1599
1600     pub fn report(&self, e: &mut EvalError, as_err: bool, explicit_span: Option<Span>) {
1601         match e.kind {
1602             EvalErrorKind::Layout(_) |
1603             EvalErrorKind::TypeckError => return,
1604             _ => {},
1605         }
1606         if let Some(ref mut backtrace) = e.backtrace {
1607             let mut trace_text = "\n\nAn error occurred in miri:\n".to_string();
1608             backtrace.resolve();
1609             write!(trace_text, "backtrace frames: {}\n", backtrace.frames().len()).unwrap();
1610             'frames: for (i, frame) in backtrace.frames().iter().enumerate() {
1611                 if frame.symbols().is_empty() {
1612                     write!(trace_text, "{}: no symbols\n", i).unwrap();
1613                 }
1614                 for symbol in frame.symbols() {
1615                     write!(trace_text, "{}: ", i).unwrap();
1616                     if let Some(name) = symbol.name() {
1617                         write!(trace_text, "{}\n", name).unwrap();
1618                     } else {
1619                         write!(trace_text, "<unknown>\n").unwrap();
1620                     }
1621                     write!(trace_text, "\tat ").unwrap();
1622                     if let Some(file_path) = symbol.filename() {
1623                         write!(trace_text, "{}", file_path.display()).unwrap();
1624                     } else {
1625                         write!(trace_text, "<unknown_file>").unwrap();
1626                     }
1627                     if let Some(line) = symbol.lineno() {
1628                         write!(trace_text, ":{}\n", line).unwrap();
1629                     } else {
1630                         write!(trace_text, "\n").unwrap();
1631                     }
1632                 }
1633             }
1634             error!("{}", trace_text);
1635         }
1636         if let Some(frame) = self.stack().last() {
1637             let block = &frame.mir.basic_blocks()[frame.block];
1638             let span = explicit_span.unwrap_or_else(|| if frame.stmt < block.statements.len() {
1639                 block.statements[frame.stmt].source_info.span
1640             } else {
1641                 block.terminator().source_info.span
1642             });
1643             trace!("reporting const eval failure at {:?}", span);
1644             let mut err = if as_err {
1645                 ::rustc::middle::const_val::struct_error(self.tcx, span, "constant evaluation error")
1646             } else {
1647                 let node_id = self
1648                     .stack()
1649                     .iter()
1650                     .rev()
1651                     .filter_map(|frame| self.tcx.hir.as_local_node_id(frame.instance.def_id()))
1652                     .next()
1653                     .expect("some part of a failing const eval must be local");
1654                 self.tcx.struct_span_lint_node(
1655                     ::rustc::lint::builtin::CONST_ERR,
1656                     node_id,
1657                     span,
1658                     "constant evaluation error",
1659                 )
1660             };
1661             err.span_label(span, e.to_string());
1662             for FrameInfo { span, location } in self.generate_stacktrace(explicit_span) {
1663                 err.span_note(span, &format!("inside call to {}", location));
1664             }
1665             err.emit();
1666         } else {
1667             self.tcx.sess.err(&e.to_string());
1668         }
1669     }
1670 }
1671
1672 impl<'mir, 'tcx> Frame<'mir, 'tcx> {
1673     pub fn get_local(&self, local: mir::Local) -> EvalResult<'tcx, Value> {
1674         // Subtract 1 because we don't store a value for the ReturnPointer, the local with index 0.
1675         self.locals[local.index() - 1].ok_or(EvalErrorKind::DeadLocal.into())
1676     }
1677
1678     fn set_local(&mut self, local: mir::Local, value: Value) -> EvalResult<'tcx> {
1679         // Subtract 1 because we don't store a value for the ReturnPointer, the local with index 0.
1680         match self.locals[local.index() - 1] {
1681             None => err!(DeadLocal),
1682             Some(ref mut local) => {
1683                 *local = value;
1684                 Ok(())
1685             }
1686         }
1687     }
1688
1689     pub fn storage_live(&mut self, local: mir::Local) -> EvalResult<'tcx, Option<Value>> {
1690         trace!("{:?} is now live", local);
1691
1692         let old = self.locals[local.index() - 1];
1693         self.locals[local.index() - 1] = Some(Value::ByVal(PrimVal::Undef)); // StorageLive *always* kills the value that's currently stored
1694         return Ok(old);
1695     }
1696
1697     /// Returns the old value of the local
1698     pub fn storage_dead(&mut self, local: mir::Local) -> EvalResult<'tcx, Option<Value>> {
1699         trace!("{:?} is now dead", local);
1700
1701         let old = self.locals[local.index() - 1];
1702         self.locals[local.index() - 1] = None;
1703         return Ok(old);
1704     }
1705 }
1706
1707 // TODO(solson): Upstream these methods into rustc::ty::layout.
1708
1709 pub fn resolve_drop_in_place<'a, 'tcx>(
1710     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1711     ty: Ty<'tcx>,
1712 ) -> ty::Instance<'tcx> {
1713     let def_id = tcx.require_lang_item(::rustc::middle::lang_items::DropInPlaceFnLangItem);
1714     let substs = tcx.intern_substs(&[ty.into()]);
1715     ty::Instance::resolve(tcx, ty::ParamEnv::empty(Reveal::All), def_id, substs).unwrap()
1716 }