src/librustc_mir/interpret/terminator.rs

   1 use std::borrow::Cow;
   2
   3 use rustc::ty::layout::{self, LayoutOf, TyLayout};
   4 use rustc::ty::Instance;
   5 use rustc::{mir, ty};
   6 use rustc_span::source_map::Span;
   7 use rustc_target::spec::abi::Abi;
   8
   9 use super::{
  10     FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy, StackPopCleanup,
  11 };
  12
  13 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  14     pub(super) fn eval_terminator(
  15         &mut self,
  16         terminator: &mir::Terminator<'tcx>,
  17     ) -> InterpResult<'tcx> {
  18         use rustc::mir::TerminatorKind::*;
  19         match terminator.kind {
  20             Return => {
  21                 self.frame().return_place.map(|r| self.dump_place(*r));
  22                 self.pop_stack_frame(/* unwinding */ false)?
  23             }
  24
  25             Goto { target } => self.go_to_block(target),
  26
  27             SwitchInt { ref discr, ref values, ref targets, .. } => {
  28                 let discr = self.read_immediate(self.eval_operand(discr, None)?)?;
  29                 trace!("SwitchInt({:?})", *discr);
  30
  31                 // Branch to the `otherwise` case by default, if no match is found.
  32                 let mut target_block = targets[targets.len() - 1];
  33
  34                 for (index, &const_int) in values.iter().enumerate() {
  35                     // Compare using binary_op, to also support pointer values
  36                     let res = self
  37                         .overflowing_binary_op(
  38                             mir::BinOp::Eq,
  39                             discr,
  40                             ImmTy::from_uint(const_int, discr.layout),
  41                         )?
  42                         .0;
  43                     if res.to_bool()? {
  44                         target_block = targets[index];
  45                         break;
  46                     }
  47                 }
  48
  49                 self.go_to_block(target_block);
  50             }
  51
  52             Call { ref func, ref args, ref destination, ref cleanup, .. } => {
  53                 let func = self.eval_operand(func, None)?;
  54                 let (fn_val, abi) = match func.layout.ty.kind {
  55                     ty::FnPtr(sig) => {
  56                         let caller_abi = sig.abi();
  57                         let fn_ptr = self.read_scalar(func)?.not_undef()?;
  58                         let fn_val = self.memory.get_fn(fn_ptr)?;
  59                         (fn_val, caller_abi)
  60                     }
  61                     ty::FnDef(def_id, substs) => {
  62                         let sig = func.layout.ty.fn_sig(*self.tcx);
  63                         (FnVal::Instance(self.resolve(def_id, substs)?), sig.abi())
  64                     }
  65                     _ => bug!("invalid callee of type {:?}", func.layout.ty),
  66                 };
  67                 let args = self.eval_operands(args)?;
  68                 let ret = match destination {
  69                     Some((dest, ret)) => Some((self.eval_place(dest)?, *ret)),
  70                     None => None,
  71                 };
  72                 self.eval_fn_call(
  73                     fn_val,
  74                     terminator.source_info.span,
  75                     abi,
  76                     &args[..],
  77                     ret,
  78                     *cleanup,
  79                 )?;
  80             }
  81
  82             Drop { ref location, target, unwind } => {
  83                 // FIXME(CTFE): forbid drop in const eval
  84                 let place = self.eval_place(location)?;
  85                 let ty = place.layout.ty;
  86                 trace!("TerminatorKind::drop: {:?}, type {}", location, ty);
  87
  88                 let instance = Instance::resolve_drop_in_place(*self.tcx, ty);
  89                 self.drop_in_place(place, instance, terminator.source_info.span, target, unwind)?;
  90             }
  91
  92             Assert { ref cond, expected, ref msg, target, cleanup } => {
  93                 let cond_val =
  94                     self.read_immediate(self.eval_operand(cond, None)?)?.to_scalar()?.to_bool()?;
  95                 if expected == cond_val {
  96                     self.go_to_block(target);
  97                 } else {
  98                     M::assert_panic(self, msg, cleanup)?;
  99                 }
 100             }
 101
 102             Abort => {
 103                 M::abort(self)?;
 104             }
 105
 106             // When we encounter Resume, we've finished unwinding
 107             // cleanup for the current stack frame. We pop it in order
 108             // to continue unwinding the next frame
 109             Resume => {
 110                 trace!("unwinding: resuming from cleanup");
 111                 // By definition, a Resume terminator means
 112                 // that we're unwinding
 113                 self.pop_stack_frame(/* unwinding */ true)?;
 114                 return Ok(());
 115             }
 116
 117             // It is UB to ever encounter this.
 118             Unreachable => throw_ub!(Unreachable),
 119
 120             // These should never occur for MIR we actually run.
 121             DropAndReplace { .. }
 122             | FalseEdges { .. }
 123             | FalseUnwind { .. }
 124             | Yield { .. }
 125             | GeneratorDrop => {
 126                 bug!("{:#?} should have been eliminated by MIR pass", terminator.kind)
 127             }
 128         }
 129
 130         Ok(())
 131     }
 132
 133     fn check_argument_compat(
 134         rust_abi: bool,
 135         caller: TyLayout<'tcx>,
 136         callee: TyLayout<'tcx>,
 137     ) -> bool {
 138         if caller.ty == callee.ty {
 139             // No question
 140             return true;
 141         }
 142         if !rust_abi {
 143             // Don't risk anything
 144             return false;
 145         }
 146         // Compare layout
 147         match (&caller.abi, &callee.abi) {
 148             // Different valid ranges are okay (once we enforce validity,
 149             // that will take care to make it UB to leave the range, just
 150             // like for transmute).
 151             (layout::Abi::Scalar(ref caller), layout::Abi::Scalar(ref callee)) => {
 152                 caller.value == callee.value
 153             }
 154             (
 155                 layout::Abi::ScalarPair(ref caller1, ref caller2),
 156                 layout::Abi::ScalarPair(ref callee1, ref callee2),
 157             ) => caller1.value == callee1.value && caller2.value == callee2.value,
 158             // Be conservative
 159             _ => false,
 160         }
 161     }
 162
 163     /// Pass a single argument, checking the types for compatibility.
 164     fn pass_argument(
 165         &mut self,
 166         rust_abi: bool,
 167         caller_arg: &mut impl Iterator<Item = OpTy<'tcx, M::PointerTag>>,
 168         callee_arg: PlaceTy<'tcx, M::PointerTag>,
 169     ) -> InterpResult<'tcx> {
 170         if rust_abi && callee_arg.layout.is_zst() {
 171             // Nothing to do.
 172             trace!("Skipping callee ZST");
 173             return Ok(());
 174         }
 175         let caller_arg = caller_arg.next().ok_or_else(|| {
 176             err_ub_format!("calling a function with fewer arguments than it requires")
 177         })?;
 178         if rust_abi {
 179             assert!(!caller_arg.layout.is_zst(), "ZSTs must have been already filtered out");
 180         }
 181         // Now, check
 182         if !Self::check_argument_compat(rust_abi, caller_arg.layout, callee_arg.layout) {
 183             throw_ub_format!(
 184                 "calling a function with argument of type {:?} passing data of type {:?}",
 185                 callee_arg.layout.ty,
 186                 caller_arg.layout.ty
 187             )
 188         }
 189         // We allow some transmutes here
 190         self.copy_op_transmute(caller_arg, callee_arg)
 191     }
 192
 193     /// Call this function -- pushing the stack frame and initializing the arguments.
 194     fn eval_fn_call(
 195         &mut self,
 196         fn_val: FnVal<'tcx, M::ExtraFnVal>,
 197         span: Span,
 198         caller_abi: Abi,
 199         args: &[OpTy<'tcx, M::PointerTag>],
 200         ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
 201         unwind: Option<mir::BasicBlock>,
 202     ) -> InterpResult<'tcx> {
 203         trace!("eval_fn_call: {:#?}", fn_val);
 204
 205         let instance = match fn_val {
 206             FnVal::Instance(instance) => instance,
 207             FnVal::Other(extra) => {
 208                 return M::call_extra_fn(self, extra, args, ret, unwind);
 209             }
 210         };
 211
 212         // ABI check
 213         {
 214             let callee_abi = {
 215                 let instance_ty = instance.ty_env(*self.tcx, self.param_env);
 216                 match instance_ty.kind {
 217                     ty::FnDef(..) => instance_ty.fn_sig(*self.tcx).abi(),
 218                     ty::Closure(..) => Abi::RustCall,
 219                     ty::Generator(..) => Abi::Rust,
 220                     _ => bug!("unexpected callee ty: {:?}", instance_ty),
 221                 }
 222             };
 223             let normalize_abi = |abi| match abi {
 224                 Abi::Rust | Abi::RustCall | Abi::RustIntrinsic | Abi::PlatformIntrinsic =>
 225                 // These are all the same ABI, really.
 226                 {
 227                     Abi::Rust
 228                 }
 229                 abi => abi,
 230             };
 231             if normalize_abi(caller_abi) != normalize_abi(callee_abi) {
 232                 throw_ub_format!(
 233                     "calling a function with ABI {:?} using caller ABI {:?}",
 234                     callee_abi,
 235                     caller_abi
 236                 )
 237             }
 238         }
 239
 240         match instance.def {
 241             ty::InstanceDef::Intrinsic(..) => {
 242                 assert!(caller_abi == Abi::RustIntrinsic || caller_abi == Abi::PlatformIntrinsic);
 243                 return M::call_intrinsic(self, span, instance, args, ret, unwind);
 244             }
 245             ty::InstanceDef::VtableShim(..)
 246             | ty::InstanceDef::ReifyShim(..)
 247             | ty::InstanceDef::ClosureOnceShim { .. }
 248             | ty::InstanceDef::FnPtrShim(..)
 249             | ty::InstanceDef::DropGlue(..)
 250             | ty::InstanceDef::CloneShim(..)
 251             | ty::InstanceDef::Item(_) => {
 252                 // We need MIR for this fn
 253                 let body = match M::find_mir_or_eval_fn(self, span, instance, args, ret, unwind)? {
 254                     Some(body) => body,
 255                     None => return Ok(()),
 256                 };
 257
 258                 self.push_stack_frame(
 259                     instance,
 260                     span,
 261                     body,
 262                     ret.map(|p| p.0),
 263                     StackPopCleanup::Goto { ret: ret.map(|p| p.1), unwind },
 264                 )?;
 265
 266                 // If an error is raised here, pop the frame again to get an accurate backtrace.
 267                 // To this end, we wrap it all in a `try` block.
 268                 let res: InterpResult<'tcx> = try {
 269                     trace!(
 270                         "caller ABI: {:?}, args: {:#?}",
 271                         caller_abi,
 272                         args.iter()
 273                             .map(|arg| (arg.layout.ty, format!("{:?}", **arg)))
 274                             .collect::<Vec<_>>()
 275                     );
 276                     trace!(
 277                         "spread_arg: {:?}, locals: {:#?}",
 278                         body.spread_arg,
 279                         body.args_iter()
 280                             .map(|local| (
 281                                 local,
 282                                 self.layout_of_local(self.frame(), local, None).unwrap().ty
 283                             ))
 284                             .collect::<Vec<_>>()
 285                     );
 286
 287                     // Figure out how to pass which arguments.
 288                     // The Rust ABI is special: ZST get skipped.
 289                     let rust_abi = match caller_abi {
 290                         Abi::Rust | Abi::RustCall => true,
 291                         _ => false,
 292                     };
 293                     // We have two iterators: Where the arguments come from,
 294                     // and where they go to.
 295
 296                     // For where they come from: If the ABI is RustCall, we untuple the
 297                     // last incoming argument.  These two iterators do not have the same type,
 298                     // so to keep the code paths uniform we accept an allocation
 299                     // (for RustCall ABI only).
 300                     let caller_args: Cow<'_, [OpTy<'tcx, M::PointerTag>]> =
 301                         if caller_abi == Abi::RustCall && !args.is_empty() {
 302                             // Untuple
 303                             let (&untuple_arg, args) = args.split_last().unwrap();
 304                             trace!("eval_fn_call: Will pass last argument by untupling");
 305                             Cow::from(
 306                                 args.iter()
 307                                     .map(|&a| Ok(a))
 308                                     .chain(
 309                                         (0..untuple_arg.layout.fields.count())
 310                                             .map(|i| self.operand_field(untuple_arg, i as u64)),
 311                                     )
 312                                     .collect::<InterpResult<'_, Vec<OpTy<'tcx, M::PointerTag>>>>(
 313                                     )?,
 314                             )
 315                         } else {
 316                             // Plain arg passing
 317                             Cow::from(args)
 318                         };
 319                     // Skip ZSTs
 320                     let mut caller_iter =
 321                         caller_args.iter().filter(|op| !rust_abi || !op.layout.is_zst()).copied();
 322
 323                     // Now we have to spread them out across the callee's locals,
 324                     // taking into account the `spread_arg`.  If we could write
 325                     // this is a single iterator (that handles `spread_arg`), then
 326                     // `pass_argument` would be the loop body. It takes care to
 327                     // not advance `caller_iter` for ZSTs.
 328                     for local in body.args_iter() {
 329                         let dest = self.eval_place(&mir::Place::from(local))?;
 330                         if Some(local) == body.spread_arg {
 331                             // Must be a tuple
 332                             for i in 0..dest.layout.fields.count() {
 333                                 let dest = self.place_field(dest, i as u64)?;
 334                                 self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 335                             }
 336                         } else {
 337                             // Normal argument
 338                             self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 339                         }
 340                     }
 341                     // Now we should have no more caller args
 342                     if caller_iter.next().is_some() {
 343                         throw_ub_format!("calling a function with more arguments than it expected")
 344                     }
 345                     // Don't forget to check the return type!
 346                     if let Some((caller_ret, _)) = ret {
 347                         let callee_ret = self.eval_place(&mir::Place::return_place())?;
 348                         if !Self::check_argument_compat(
 349                             rust_abi,
 350                             caller_ret.layout,
 351                             callee_ret.layout,
 352                         ) {
 353                             throw_ub_format!(
 354                                 "calling a function with return type {:?} passing \
 355                                      return place of type {:?}",
 356                                 callee_ret.layout.ty,
 357                                 caller_ret.layout.ty
 358                             )
 359                         }
 360                     } else {
 361                         let local = mir::RETURN_PLACE;
 362                         let callee_layout = self.layout_of_local(self.frame(), local, None)?;
 363                         if !callee_layout.abi.is_uninhabited() {
 364                             throw_ub_format!("calling a returning function without a return place")
 365                         }
 366                     }
 367                 };
 368                 match res {
 369                     Err(err) => {
 370                         self.stack.pop();
 371                         Err(err)
 372                     }
 373                     Ok(v) => Ok(v),
 374                 }
 375             }
 376             // cannot use the shim here, because that will only result in infinite recursion
 377             ty::InstanceDef::Virtual(_, idx) => {
 378                 let mut args = args.to_vec();
 379                 // We have to implement all "object safe receivers".  Currently we
 380                 // support built-in pointers (&, &mut, Box) as well as unsized-self.  We do
 381                 // not yet support custom self types.
 382                 // Also see librustc_codegen_llvm/abi.rs and librustc_codegen_llvm/mir/block.rs.
 383                 let receiver_place = match args[0].layout.ty.builtin_deref(true) {
 384                     Some(_) => {
 385                         // Built-in pointer.
 386                         self.deref_operand(args[0])?
 387                     }
 388                     None => {
 389                         // Unsized self.
 390                         args[0].assert_mem_place(self)
 391                     }
 392                 };
 393                 // Find and consult vtable
 394                 let vtable = receiver_place.vtable();
 395                 let drop_fn = self.get_vtable_slot(vtable, idx)?;
 396
 397                 // `*mut receiver_place.layout.ty` is almost the layout that we
 398                 // want for args[0]: We have to project to field 0 because we want
 399                 // a thin pointer.
 400                 assert!(receiver_place.layout.is_unsized());
 401                 let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
 402                 let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0)?;
 403                 // Adjust receiver argument.
 404                 args[0] =
 405                     OpTy::from(ImmTy { layout: this_receiver_ptr, imm: receiver_place.ptr.into() });
 406                 trace!("Patched self operand to {:#?}", args[0]);
 407                 // recurse with concrete function
 408                 self.eval_fn_call(drop_fn, span, caller_abi, &args, ret, unwind)
 409             }
 410         }
 411     }
 412
 413     fn drop_in_place(
 414         &mut self,
 415         place: PlaceTy<'tcx, M::PointerTag>,
 416         instance: ty::Instance<'tcx>,
 417         span: Span,
 418         target: mir::BasicBlock,
 419         unwind: Option<mir::BasicBlock>,
 420     ) -> InterpResult<'tcx> {
 421         trace!("drop_in_place: {:?},\n  {:?}, {:?}", *place, place.layout.ty, instance);
 422         // We take the address of the object.  This may well be unaligned, which is fine
 423         // for us here.  However, unaligned accesses will probably make the actual drop
 424         // implementation fail -- a problem shared by rustc.
 425         let place = self.force_allocation(place)?;
 426
 427         let (instance, place) = match place.layout.ty.kind {
 428             ty::Dynamic(..) => {
 429                 // Dropping a trait object.
 430                 self.unpack_dyn_trait(place)?
 431             }
 432             _ => (instance, place),
 433         };
 434
 435         let arg = ImmTy {
 436             imm: place.to_ref(),
 437             layout: self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
 438         };
 439
 440         let ty = self.tcx.mk_unit(); // return type is ()
 441         let dest = MPlaceTy::dangling(self.layout_of(ty)?, self);
 442
 443         self.eval_fn_call(
 444             FnVal::Instance(instance),
 445             span,
 446             Abi::Rust,
 447             &[arg.into()],
 448             Some((dest.into(), target)),
 449             unwind,
 450         )
 451     }
 452 }