compiler/rustc_const_eval/src/interpret/terminator.rs

   1 use std::borrow::Cow;
   2
   3 use rustc_middle::ty::layout::{FnAbiOf, LayoutOf};
   4 use rustc_middle::ty::Instance;
   5 use rustc_middle::{
   6     mir,
   7     ty::{self, Ty},
   8 };
   9 use rustc_target::abi;
  10 use rustc_target::abi::call::{ArgAbi, ArgAttribute, ArgAttributes, FnAbi, PassMode};
  11 use rustc_target::spec::abi::Abi;
  12
  13 use super::{
  14     FnVal, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy, Machine, MemoryKind, OpTy, Operand,
  15     PlaceTy, Scalar, StackPopCleanup, StackPopUnwind,
  16 };
  17
  18 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  19     pub(super) fn eval_terminator(
  20         &mut self,
  21         terminator: &mir::Terminator<'tcx>,
  22     ) -> InterpResult<'tcx> {
  23         use rustc_middle::mir::TerminatorKind::*;
  24         match terminator.kind {
  25             Return => {
  26                 self.pop_stack_frame(/* unwinding */ false)?
  27             }
  28
  29             Goto { target } => self.go_to_block(target),
  30
  31             SwitchInt { ref discr, ref targets, switch_ty } => {
  32                 let discr = self.read_immediate(&self.eval_operand(discr, None)?)?;
  33                 trace!("SwitchInt({:?})", *discr);
  34                 assert_eq!(discr.layout.ty, switch_ty);
  35
  36                 // Branch to the `otherwise` case by default, if no match is found.
  37                 assert!(!targets.iter().is_empty());
  38                 let mut target_block = targets.otherwise();
  39
  40                 for (const_int, target) in targets.iter() {
  41                     // Compare using MIR BinOp::Eq, to also support pointer values.
  42                     // (Avoiding `self.binary_op` as that does some redundant layout computation.)
  43                     let res = self
  44                         .overflowing_binary_op(
  45                             mir::BinOp::Eq,
  46                             &discr,
  47                             &ImmTy::from_uint(const_int, discr.layout),
  48                         )?
  49                         .0;
  50                     if res.to_bool()? {
  51                         target_block = target;
  52                         break;
  53                     }
  54                 }
  55
  56                 self.go_to_block(target_block);
  57             }
  58
  59             Call {
  60                 ref func,
  61                 ref args,
  62                 destination,
  63                 target,
  64                 ref cleanup,
  65                 from_hir_call: _,
  66                 fn_span: _,
  67             } => {
  68                 let old_stack = self.frame_idx();
  69                 let old_loc = self.frame().loc;
  70                 let func = self.eval_operand(func, None)?;
  71                 let args = self.eval_operands(args)?;
  72
  73                 let fn_sig_binder = func.layout.ty.fn_sig(*self.tcx);
  74                 let fn_sig =
  75                     self.tcx.normalize_erasing_late_bound_regions(self.param_env, fn_sig_binder);
  76                 let extra_args = &args[fn_sig.inputs().len()..];
  77                 let extra_args = self.tcx.mk_type_list(extra_args.iter().map(|arg| arg.layout.ty));
  78
  79                 let (fn_val, fn_abi, with_caller_location) = match *func.layout.ty.kind() {
  80                     ty::FnPtr(_sig) => {
  81                         let fn_ptr = self.read_pointer(&func)?;
  82                         let fn_val = self.get_ptr_fn(fn_ptr)?;
  83                         (fn_val, self.fn_abi_of_fn_ptr(fn_sig_binder, extra_args)?, false)
  84                     }
  85                     ty::FnDef(def_id, substs) => {
  86                         let instance =
  87                             self.resolve(ty::WithOptConstParam::unknown(def_id), substs)?;
  88                         (
  89                             FnVal::Instance(instance),
  90                             self.fn_abi_of_instance(instance, extra_args)?,
  91                             instance.def.requires_caller_location(*self.tcx),
  92                         )
  93                     }
  94                     _ => span_bug!(
  95                         terminator.source_info.span,
  96                         "invalid callee of type {:?}",
  97                         func.layout.ty
  98                     ),
  99                 };
 100
 101                 let destination = self.eval_place(destination)?;
 102                 self.eval_fn_call(
 103                     fn_val,
 104                     (fn_sig.abi, fn_abi),
 105                     &args,
 106                     with_caller_location,
 107                     &destination,
 108                     target,
 109                     match (cleanup, fn_abi.can_unwind) {
 110                         (Some(cleanup), true) => StackPopUnwind::Cleanup(*cleanup),
 111                         (None, true) => StackPopUnwind::Skip,
 112                         (_, false) => StackPopUnwind::NotAllowed,
 113                     },
 114                 )?;
 115                 // Sanity-check that `eval_fn_call` either pushed a new frame or
 116                 // did a jump to another block.
 117                 if self.frame_idx() == old_stack && self.frame().loc == old_loc {
 118                     span_bug!(terminator.source_info.span, "evaluating this call made no progress");
 119                 }
 120             }
 121
 122             Drop { place, target, unwind } => {
 123                 let place = self.eval_place(place)?;
 124                 let ty = place.layout.ty;
 125                 trace!("TerminatorKind::drop: {:?}, type {}", place, ty);
 126
 127                 let instance = Instance::resolve_drop_in_place(*self.tcx, ty);
 128                 self.drop_in_place(&place, instance, target, unwind)?;
 129             }
 130
 131             Assert { ref cond, expected, ref msg, target, cleanup } => {
 132                 let cond_val = self.read_scalar(&self.eval_operand(cond, None)?)?.to_bool()?;
 133                 if expected == cond_val {
 134                     self.go_to_block(target);
 135                 } else {
 136                     M::assert_panic(self, msg, cleanup)?;
 137                 }
 138             }
 139
 140             Abort => {
 141                 M::abort(self, "the program aborted execution".to_owned())?;
 142             }
 143
 144             // When we encounter Resume, we've finished unwinding
 145             // cleanup for the current stack frame. We pop it in order
 146             // to continue unwinding the next frame
 147             Resume => {
 148                 trace!("unwinding: resuming from cleanup");
 149                 // By definition, a Resume terminator means
 150                 // that we're unwinding
 151                 self.pop_stack_frame(/* unwinding */ true)?;
 152                 return Ok(());
 153             }
 154
 155             // It is UB to ever encounter this.
 156             Unreachable => throw_ub!(Unreachable),
 157
 158             // These should never occur for MIR we actually run.
 159             DropAndReplace { .. }
 160             | FalseEdge { .. }
 161             | FalseUnwind { .. }
 162             | Yield { .. }
 163             | GeneratorDrop => span_bug!(
 164                 terminator.source_info.span,
 165                 "{:#?} should have been eliminated by MIR pass",
 166                 terminator.kind
 167             ),
 168
 169             // Inline assembly can't be interpreted.
 170             InlineAsm { .. } => throw_unsup_format!("inline assembly is not supported"),
 171         }
 172
 173         Ok(())
 174     }
 175
 176     fn check_argument_compat(
 177         caller_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 178         callee_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 179     ) -> bool {
 180         // Heuristic for type comparison.
 181         let layout_compat = || {
 182             if caller_abi.layout.ty == callee_abi.layout.ty {
 183                 // No question
 184                 return true;
 185             }
 186             if caller_abi.layout.is_unsized() || callee_abi.layout.is_unsized() {
 187                 // No, no, no. We require the types to *exactly* match for unsized arguments. If
 188                 // these are somehow unsized "in a different way" (say, `dyn Trait` vs `[i32]`),
 189                 // then who knows what happens.
 190                 return false;
 191             }
 192             if caller_abi.layout.size != callee_abi.layout.size
 193                 || caller_abi.layout.align.abi != callee_abi.layout.align.abi
 194             {
 195                 // This cannot go well...
 196                 return false;
 197             }
 198             // The rest *should* be okay, but we are extra conservative.
 199             match (caller_abi.layout.abi, callee_abi.layout.abi) {
 200                 // Different valid ranges are okay (once we enforce validity,
 201                 // that will take care to make it UB to leave the range, just
 202                 // like for transmute).
 203                 (abi::Abi::Scalar(caller), abi::Abi::Scalar(callee)) => {
 204                     caller.primitive() == callee.primitive()
 205                 }
 206                 (
 207                     abi::Abi::ScalarPair(caller1, caller2),
 208                     abi::Abi::ScalarPair(callee1, callee2),
 209                 ) => {
 210                     caller1.primitive() == callee1.primitive()
 211                         && caller2.primitive() == callee2.primitive()
 212                 }
 213                 // Be conservative
 214                 _ => false,
 215             }
 216         };
 217         // When comparing the PassMode, we have to be smart about comparing the attributes.
 218         let arg_attr_compat = |a1: &ArgAttributes, a2: &ArgAttributes| {
 219             // There's only one regular attribute that matters for the call ABI: InReg.
 220             // Everything else is things like noalias, dereferenceable, nonnull, ...
 221             // (This also applies to pointee_size, pointee_align.)
 222             if a1.regular.contains(ArgAttribute::InReg) != a2.regular.contains(ArgAttribute::InReg)
 223             {
 224                 return false;
 225             }
 226             // We also compare the sign extension mode -- this could let the callee make assumptions
 227             // about bits that conceptually were not even passed.
 228             if a1.arg_ext != a2.arg_ext {
 229                 return false;
 230             }
 231             return true;
 232         };
 233         let mode_compat = || match (&caller_abi.mode, &callee_abi.mode) {
 234             (PassMode::Ignore, PassMode::Ignore) => true,
 235             (PassMode::Direct(a1), PassMode::Direct(a2)) => arg_attr_compat(a1, a2),
 236             (PassMode::Pair(a1, b1), PassMode::Pair(a2, b2)) => {
 237                 arg_attr_compat(a1, a2) && arg_attr_compat(b1, b2)
 238             }
 239             (PassMode::Cast(c1, pad1), PassMode::Cast(c2, pad2)) => c1 == c2 && pad1 == pad2,
 240             (
 241                 PassMode::Indirect { attrs: a1, extra_attrs: None, on_stack: s1 },
 242                 PassMode::Indirect { attrs: a2, extra_attrs: None, on_stack: s2 },
 243             ) => arg_attr_compat(a1, a2) && s1 == s2,
 244             (
 245                 PassMode::Indirect { attrs: a1, extra_attrs: Some(e1), on_stack: s1 },
 246                 PassMode::Indirect { attrs: a2, extra_attrs: Some(e2), on_stack: s2 },
 247             ) => arg_attr_compat(a1, a2) && arg_attr_compat(e1, e2) && s1 == s2,
 248             _ => false,
 249         };
 250
 251         if layout_compat() && mode_compat() {
 252             return true;
 253         }
 254         trace!(
 255             "check_argument_compat: incompatible ABIs:\ncaller: {:?}\ncallee: {:?}",
 256             caller_abi,
 257             callee_abi
 258         );
 259         return false;
 260     }
 261
 262     /// Initialize a single callee argument, checking the types for compatibility.
 263     fn pass_argument<'x, 'y>(
 264         &mut self,
 265         caller_args: &mut impl Iterator<
 266             Item = (&'x OpTy<'tcx, M::Provenance>, &'y ArgAbi<'tcx, Ty<'tcx>>),
 267         >,
 268         callee_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 269         callee_arg: &PlaceTy<'tcx, M::Provenance>,
 270     ) -> InterpResult<'tcx>
 271     where
 272         'tcx: 'x,
 273         'tcx: 'y,
 274     {
 275         if matches!(callee_abi.mode, PassMode::Ignore) {
 276             // This one is skipped.
 277             return Ok(());
 278         }
 279         // Find next caller arg.
 280         let (caller_arg, caller_abi) = caller_args.next().ok_or_else(|| {
 281             err_ub_format!("calling a function with fewer arguments than it requires")
 282         })?;
 283         // Now, check
 284         if !Self::check_argument_compat(caller_abi, callee_abi) {
 285             throw_ub_format!(
 286                 "calling a function with argument of type {:?} passing data of type {:?}",
 287                 callee_arg.layout.ty,
 288                 caller_arg.layout.ty
 289             )
 290         }
 291         // Special handling for unsized parameters.
 292         if caller_arg.layout.is_unsized() {
 293             // `check_argument_compat` ensures that both have the same type, so we know they will use the metadata the same way.
 294             assert_eq!(caller_arg.layout.ty, callee_arg.layout.ty);
 295             // We have to properly pre-allocate the memory for the callee.
 296             // So let's tear down some wrappers.
 297             // This all has to be in memory, there are no immediate unsized values.
 298             let src = caller_arg.assert_mem_place();
 299             // The destination cannot be one of these "spread args".
 300             let (dest_frame, dest_local) = callee_arg.assert_local();
 301             // We are just initializing things, so there can't be anything here yet.
 302             assert!(matches!(
 303                 *self.local_to_op(&self.stack()[dest_frame], dest_local, None)?,
 304                 Operand::Immediate(Immediate::Uninit)
 305             ));
 306             // Allocate enough memory to hold `src`.
 307             let Some((size, align)) = self.size_and_align_of_mplace(&src)? else {
 308                 span_bug!(self.cur_span(), "unsized fn arg with `extern` type tail should not be allowed")
 309             };
 310             let ptr = self.allocate_ptr(size, align, MemoryKind::Stack)?;
 311             let dest_place =
 312                 MPlaceTy::from_aligned_ptr_with_meta(ptr.into(), callee_arg.layout, src.meta);
 313             // Update the local to be that new place.
 314             *M::access_local_mut(self, dest_frame, dest_local)? = Operand::Indirect(*dest_place);
 315         }
 316         // We allow some transmutes here.
 317         // FIXME: Depending on the PassMode, this should reset some padding to uninitialized. (This
 318         // is true for all `copy_op`, but there are a lot of special cases for argument passing
 319         // specifically.)
 320         self.copy_op(&caller_arg, callee_arg, /*allow_transmute*/ true)
 321     }
 322
 323     /// Call this function -- pushing the stack frame and initializing the arguments.
 324     ///
 325     /// `caller_fn_abi` is used to determine if all the arguments are passed the proper way.
 326     /// However, we also need `caller_abi` to determine if we need to do untupling of arguments.
 327     ///
 328     /// `with_caller_location` indicates whether the caller passed a caller location. Miri
 329     /// implements caller locations without argument passing, but to match `FnAbi` we need to know
 330     /// when those arguments are present.
 331     pub(crate) fn eval_fn_call(
 332         &mut self,
 333         fn_val: FnVal<'tcx, M::ExtraFnVal>,
 334         (caller_abi, caller_fn_abi): (Abi, &FnAbi<'tcx, Ty<'tcx>>),
 335         args: &[OpTy<'tcx, M::Provenance>],
 336         with_caller_location: bool,
 337         destination: &PlaceTy<'tcx, M::Provenance>,
 338         target: Option<mir::BasicBlock>,
 339         mut unwind: StackPopUnwind,
 340     ) -> InterpResult<'tcx> {
 341         trace!("eval_fn_call: {:#?}", fn_val);
 342
 343         let instance = match fn_val {
 344             FnVal::Instance(instance) => instance,
 345             FnVal::Other(extra) => {
 346                 return M::call_extra_fn(
 347                     self,
 348                     extra,
 349                     caller_abi,
 350                     args,
 351                     destination,
 352                     target,
 353                     unwind,
 354                 );
 355             }
 356         };
 357
 358         match instance.def {
 359             ty::InstanceDef::Intrinsic(def_id) => {
 360                 assert!(self.tcx.is_intrinsic(def_id));
 361                 // caller_fn_abi is not relevant here, we interpret the arguments directly for each intrinsic.
 362                 M::call_intrinsic(self, instance, args, destination, target, unwind)
 363             }
 364             ty::InstanceDef::VTableShim(..)
 365             | ty::InstanceDef::ReifyShim(..)
 366             | ty::InstanceDef::ClosureOnceShim { .. }
 367             | ty::InstanceDef::FnPtrShim(..)
 368             | ty::InstanceDef::DropGlue(..)
 369             | ty::InstanceDef::CloneShim(..)
 370             | ty::InstanceDef::Item(_) => {
 371                 // We need MIR for this fn
 372                 let Some((body, instance)) =
 373                     M::find_mir_or_eval_fn(self, instance, caller_abi, args, destination, target, unwind)? else {
 374                         return Ok(());
 375                     };
 376
 377                 // Compute callee information using the `instance` returned by
 378                 // `find_mir_or_eval_fn`.
 379                 // FIXME: for variadic support, do we have to somehow determine callee's extra_args?
 380                 let callee_fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
 381
 382                 if callee_fn_abi.c_variadic || caller_fn_abi.c_variadic {
 383                     throw_unsup_format!("calling a c-variadic function is not supported");
 384                 }
 385
 386                 if M::enforce_abi(self) {
 387                     if caller_fn_abi.conv != callee_fn_abi.conv {
 388                         throw_ub_format!(
 389                             "calling a function with calling convention {:?} using calling convention {:?}",
 390                             callee_fn_abi.conv,
 391                             caller_fn_abi.conv
 392                         )
 393                     }
 394                 }
 395
 396                 if !matches!(unwind, StackPopUnwind::NotAllowed) && !callee_fn_abi.can_unwind {
 397                     // The callee cannot unwind.
 398                     unwind = StackPopUnwind::NotAllowed;
 399                 }
 400
 401                 self.push_stack_frame(
 402                     instance,
 403                     body,
 404                     destination,
 405                     StackPopCleanup::Goto { ret: target, unwind },
 406                 )?;
 407
 408                 // If an error is raised here, pop the frame again to get an accurate backtrace.
 409                 // To this end, we wrap it all in a `try` block.
 410                 let res: InterpResult<'tcx> = try {
 411                     trace!(
 412                         "caller ABI: {:?}, args: {:#?}",
 413                         caller_abi,
 414                         args.iter()
 415                             .map(|arg| (arg.layout.ty, format!("{:?}", **arg)))
 416                             .collect::<Vec<_>>()
 417                     );
 418                     trace!(
 419                         "spread_arg: {:?}, locals: {:#?}",
 420                         body.spread_arg,
 421                         body.args_iter()
 422                             .map(|local| (
 423                                 local,
 424                                 self.layout_of_local(self.frame(), local, None).unwrap().ty
 425                             ))
 426                             .collect::<Vec<_>>()
 427                     );
 428
 429                     // In principle, we have two iterators: Where the arguments come from, and where
 430                     // they go to.
 431
 432                     // For where they come from: If the ABI is RustCall, we untuple the
 433                     // last incoming argument.  These two iterators do not have the same type,
 434                     // so to keep the code paths uniform we accept an allocation
 435                     // (for RustCall ABI only).
 436                     let caller_args: Cow<'_, [OpTy<'tcx, M::Provenance>]> =
 437                         if caller_abi == Abi::RustCall && !args.is_empty() {
 438                             // Untuple
 439                             let (untuple_arg, args) = args.split_last().unwrap();
 440                             trace!("eval_fn_call: Will pass last argument by untupling");
 441                             Cow::from(
 442                                 args.iter()
 443                                     .map(|a| Ok(a.clone()))
 444                                     .chain(
 445                                         (0..untuple_arg.layout.fields.count())
 446                                             .map(|i| self.operand_field(untuple_arg, i)),
 447                                     )
 448                                     .collect::<InterpResult<'_, Vec<OpTy<'tcx, M::Provenance>>>>(
 449                                     )?,
 450                             )
 451                         } else {
 452                             // Plain arg passing
 453                             Cow::from(args)
 454                         };
 455                     // If `with_caller_location` is set we pretend there is an extra argument (that
 456                     // we will not pass).
 457                     assert_eq!(
 458                         caller_args.len() + if with_caller_location { 1 } else { 0 },
 459                         caller_fn_abi.args.len(),
 460                         "mismatch between caller ABI and caller arguments",
 461                     );
 462                     let mut caller_args = caller_args
 463                         .iter()
 464                         .zip(caller_fn_abi.args.iter())
 465                         .filter(|arg_and_abi| !matches!(arg_and_abi.1.mode, PassMode::Ignore));
 466
 467                     // Now we have to spread them out across the callee's locals,
 468                     // taking into account the `spread_arg`.  If we could write
 469                     // this is a single iterator (that handles `spread_arg`), then
 470                     // `pass_argument` would be the loop body. It takes care to
 471                     // not advance `caller_iter` for ZSTs.
 472                     let mut callee_args_abis = callee_fn_abi.args.iter();
 473                     for local in body.args_iter() {
 474                         let dest = self.eval_place(mir::Place::from(local))?;
 475                         if Some(local) == body.spread_arg {
 476                             // Must be a tuple
 477                             for i in 0..dest.layout.fields.count() {
 478                                 let dest = self.place_field(&dest, i)?;
 479                                 let callee_abi = callee_args_abis.next().unwrap();
 480                                 self.pass_argument(&mut caller_args, callee_abi, &dest)?;
 481                             }
 482                         } else {
 483                             // Normal argument
 484                             let callee_abi = callee_args_abis.next().unwrap();
 485                             self.pass_argument(&mut caller_args, callee_abi, &dest)?;
 486                         }
 487                     }
 488                     // If the callee needs a caller location, pretend we consume one more argument from the ABI.
 489                     if instance.def.requires_caller_location(*self.tcx) {
 490                         callee_args_abis.next().unwrap();
 491                     }
 492                     // Now we should have no more caller args or callee arg ABIs
 493                     assert!(
 494                         callee_args_abis.next().is_none(),
 495                         "mismatch between callee ABI and callee body arguments"
 496                     );
 497                     if caller_args.next().is_some() {
 498                         throw_ub_format!("calling a function with more arguments than it expected")
 499                     }
 500                     // Don't forget to check the return type!
 501                     if !Self::check_argument_compat(&caller_fn_abi.ret, &callee_fn_abi.ret) {
 502                         throw_ub_format!(
 503                             "calling a function with return type {:?} passing \
 504                                     return place of type {:?}",
 505                             callee_fn_abi.ret.layout.ty,
 506                             caller_fn_abi.ret.layout.ty,
 507                         )
 508                     }
 509                 };
 510                 match res {
 511                     Err(err) => {
 512                         self.stack_mut().pop();
 513                         Err(err)
 514                     }
 515                     Ok(()) => Ok(()),
 516                 }
 517             }
 518             // cannot use the shim here, because that will only result in infinite recursion
 519             ty::InstanceDef::Virtual(def_id, idx) => {
 520                 let mut args = args.to_vec();
 521                 // We have to implement all "object safe receivers". So we have to go search for a
 522                 // pointer or `dyn Trait` type, but it could be wrapped in newtypes. So recursively
 523                 // unwrap those newtypes until we are there.
 524                 let mut receiver = args[0].clone();
 525                 let receiver_place = loop {
 526                     match receiver.layout.ty.kind() {
 527                         ty::Ref(..) | ty::RawPtr(..) => break self.deref_operand(&receiver)?,
 528                         ty::Dynamic(..) => break receiver.assert_mem_place(), // no immediate unsized values
 529                         _ => {
 530                             // Not there yet, search for the only non-ZST field.
 531                             let mut non_zst_field = None;
 532                             for i in 0..receiver.layout.fields.count() {
 533                                 let field = self.operand_field(&receiver, i)?;
 534                                 let zst =
 535                                     field.layout.is_zst() && field.layout.align.abi.bytes() == 1;
 536                                 if !zst {
 537                                     assert!(
 538                                         non_zst_field.is_none(),
 539                                         "multiple non-ZST fields in dyn receiver type {}",
 540                                         receiver.layout.ty
 541                                     );
 542                                     non_zst_field = Some(field);
 543                                 }
 544                             }
 545                             receiver = non_zst_field.unwrap_or_else(|| {
 546                                 panic!(
 547                                     "no non-ZST fields in dyn receiver type {}",
 548                                     receiver.layout.ty
 549                                 )
 550                             });
 551                         }
 552                     }
 553                 };
 554                 // Obtain the underlying trait we are working on.
 555                 let receiver_tail = self
 556                     .tcx
 557                     .struct_tail_erasing_lifetimes(receiver_place.layout.ty, self.param_env);
 558                 let ty::Dynamic(data, ..) = receiver_tail.kind() else {
 559                     span_bug!(self.cur_span(), "dynamic call on non-`dyn` type {}", receiver_tail)
 560                 };
 561
 562                 // Get the required information from the vtable.
 563                 let vptr = receiver_place.meta.unwrap_meta().to_pointer(self)?;
 564                 let (dyn_ty, dyn_trait) = self.get_ptr_vtable(vptr)?;
 565                 if dyn_trait != data.principal() {
 566                     throw_ub_format!(
 567                         "`dyn` call on a pointer whose vtable does not match its type"
 568                     );
 569                 }
 570
 571                 // Now determine the actual method to call. We can do that in two different ways and
 572                 // compare them to ensure everything fits.
 573                 let Some(ty::VtblEntry::Method(fn_inst)) = self.get_vtable_entries(vptr)?.get(idx).copied() else {
 574                     throw_ub_format!("`dyn` call trying to call something that is not a method")
 575                 };
 576                 if cfg!(debug_assertions) {
 577                     let tcx = *self.tcx;
 578
 579                     let trait_def_id = tcx.trait_of_item(def_id).unwrap();
 580                     let virtual_trait_ref =
 581                         ty::TraitRef::from_method(tcx, trait_def_id, instance.substs);
 582                     assert_eq!(
 583                         receiver_tail,
 584                         virtual_trait_ref.self_ty(),
 585                         "mismatch in underlying dyn trait computation within Miri and MIR building",
 586                     );
 587                     let existential_trait_ref =
 588                         ty::ExistentialTraitRef::erase_self_ty(tcx, virtual_trait_ref);
 589                     let concrete_trait_ref = existential_trait_ref.with_self_ty(tcx, dyn_ty);
 590
 591                     let concrete_method = Instance::resolve_for_vtable(
 592                         tcx,
 593                         self.param_env,
 594                         def_id,
 595                         instance.substs.rebase_onto(tcx, trait_def_id, concrete_trait_ref.substs),
 596                     )
 597                     .unwrap();
 598                     assert_eq!(fn_inst, concrete_method);
 599                 }
 600
 601                 // `*mut receiver_place.layout.ty` is almost the layout that we
 602                 // want for args[0]: We have to project to field 0 because we want
 603                 // a thin pointer.
 604                 assert!(receiver_place.layout.is_unsized());
 605                 let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
 606                 let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0);
 607                 // Adjust receiver argument.
 608                 args[0] = OpTy::from(ImmTy::from_immediate(
 609                     Scalar::from_maybe_pointer(receiver_place.ptr, self).into(),
 610                     this_receiver_ptr,
 611                 ));
 612                 trace!("Patched receiver operand to {:#?}", args[0]);
 613                 // recurse with concrete function
 614                 self.eval_fn_call(
 615                     FnVal::Instance(fn_inst),
 616                     (caller_abi, caller_fn_abi),
 617                     &args,
 618                     with_caller_location,
 619                     destination,
 620                     target,
 621                     unwind,
 622                 )
 623             }
 624         }
 625     }
 626
 627     fn drop_in_place(
 628         &mut self,
 629         place: &PlaceTy<'tcx, M::Provenance>,
 630         instance: ty::Instance<'tcx>,
 631         target: mir::BasicBlock,
 632         unwind: Option<mir::BasicBlock>,
 633     ) -> InterpResult<'tcx> {
 634         trace!("drop_in_place: {:?},\n  {:?}, {:?}", *place, place.layout.ty, instance);
 635         // We take the address of the object.  This may well be unaligned, which is fine
 636         // for us here.  However, unaligned accesses will probably make the actual drop
 637         // implementation fail -- a problem shared by rustc.
 638         let place = self.force_allocation(place)?;
 639
 640         let (instance, place) = match place.layout.ty.kind() {
 641             ty::Dynamic(..) => {
 642                 // Dropping a trait object. Need to find actual drop fn.
 643                 let place = self.unpack_dyn_trait(&place)?;
 644                 let instance = ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
 645                 (instance, place)
 646             }
 647             _ => (instance, place),
 648         };
 649         let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
 650
 651         let arg = ImmTy::from_immediate(
 652             place.to_ref(self),
 653             self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
 654         );
 655         let ret = MPlaceTy::fake_alloc_zst(self.layout_of(self.tcx.types.unit)?);
 656
 657         self.eval_fn_call(
 658             FnVal::Instance(instance),
 659             (Abi::Rust, fn_abi),
 660             &[arg.into()],
 661             false,
 662             &ret.into(),
 663             Some(target),
 664             match unwind {
 665                 Some(cleanup) => StackPopUnwind::Cleanup(cleanup),
 666                 None => StackPopUnwind::Skip,
 667             },
 668         )
 669     }
 670 }