1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
//! This module contains everything needed to instantiate an interpreter.
//! This separation exists to ensure that no fancy miri features like
//! interpreting common C functions leak into CTFE.

use std::borrow::{Borrow, Cow};
use std::fmt::Debug;
use std::hash::Hash;

use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
use rustc_middle::mir;
use rustc_middle::ty::layout::TyAndLayout;
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::def_id::DefId;
use rustc_target::abi::{Align, Size};
use rustc_target::spec::abi::Abi as CallAbi;

use crate::const_eval::CheckAlignment;

use super::{
    AllocBytes, AllocId, AllocRange, Allocation, ConstAllocation, FnArg, Frame, ImmTy, InterpCx,
    InterpResult, MPlaceTy, MemoryKind, OpTy, PlaceTy, Pointer, Provenance,
};

/// Data returned by Machine::stack_pop,
/// to provide further control over the popping of the stack frame
#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum StackPopJump {
    /// Indicates that no special handling should be
    /// done - we'll either return normally or unwind
    /// based on the terminator for the function
    /// we're leaving.
    Normal,

    /// Indicates that we should *not* jump to the return/unwind address, as the callback already
    /// took care of everything.
    NoJump,
}

/// Whether this kind of memory is allowed to leak
pub trait MayLeak: Copy {
    fn may_leak(self) -> bool;
}

/// The functionality needed by memory to manage its allocations
pub trait AllocMap<K: Hash + Eq, V> {
    /// Tests if the map contains the given key.
    /// Deliberately takes `&mut` because that is sufficient, and some implementations
    /// can be more efficient then (using `RefCell::get_mut`).
    fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
    where
        K: Borrow<Q>;

    /// Inserts a new entry into the map.
    fn insert(&mut self, k: K, v: V) -> Option<V>;

    /// Removes an entry from the map.
    fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
    where
        K: Borrow<Q>;

    /// Returns data based on the keys and values in the map.
    fn filter_map_collect<T>(&self, f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T>;

    /// Returns a reference to entry `k`. If no such entry exists, call
    /// `vacant` and either forward its error, or add its result to the map
    /// and return a reference to *that*.
    fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E>;

    /// Returns a mutable reference to entry `k`. If no such entry exists, call
    /// `vacant` and either forward its error, or add its result to the map
    /// and return a reference to *that*.
    fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E>;

    /// Read-only lookup.
    fn get(&self, k: K) -> Option<&V> {
        self.get_or(k, || Err(())).ok()
    }

    /// Mutable lookup.
    fn get_mut(&mut self, k: K) -> Option<&mut V> {
        self.get_mut_or(k, || Err(())).ok()
    }
}

/// Methods of this trait signifies a point where CTFE evaluation would fail
/// and some use case dependent behaviour can instead be applied.
pub trait Machine<'mir, 'tcx: 'mir>: Sized {
    /// Additional memory kinds a machine wishes to distinguish from the builtin ones
    type MemoryKind: Debug + std::fmt::Display + MayLeak + Eq + 'static;

    /// Pointers are "tagged" with provenance information; typically the `AllocId` they belong to.
    type Provenance: Provenance + Eq + Hash + 'static;

    /// When getting the AllocId of a pointer, some extra data is also obtained from the provenance
    /// that is passed to memory access hooks so they can do things with it.
    type ProvenanceExtra: Copy + 'static;

    /// Machines can define extra (non-instance) things that represent values of function pointers.
    /// For example, Miri uses this to return a function pointer from `dlsym`
    /// that can later be called to execute the right thing.
    type ExtraFnVal: Debug + Copy;

    /// Extra data stored in every call frame.
    type FrameExtra;

    /// Extra data stored in every allocation.
    type AllocExtra: Debug + Clone + 'tcx;

    /// Type for the bytes of the allocation.
    type Bytes: AllocBytes + 'static;

    /// Memory's allocation map
    type MemoryMap: AllocMap<
            AllocId,
            (
                MemoryKind<Self::MemoryKind>,
                Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>,
            ),
        > + Default
        + Clone;

    /// The memory kind to use for copied global memory (held in `tcx`) --
    /// or None if such memory should not be mutated and thus any such attempt will cause
    /// a `ModifiedStatic` error to be raised.
    /// Statics are copied under two circumstances: When they are mutated, and when
    /// `adjust_allocation` (see below) returns an owned allocation
    /// that is added to the memory so that the work is not done twice.
    const GLOBAL_KIND: Option<Self::MemoryKind>;

    /// Should the machine panic on allocation failures?
    const PANIC_ON_ALLOC_FAIL: bool;

    /// Should post-monomorphization checks be run when a stack frame is pushed?
    const POST_MONO_CHECKS: bool = true;

    /// Whether memory accesses should be alignment-checked.
    fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> CheckAlignment;

    /// Whether, when checking alignment, we should look at the actual address and thus support
    /// custom alignment logic based on whatever the integer address happens to be.
    ///
    /// If this returns true, Provenance::OFFSET_IS_ADDR must be true.
    fn use_addr_for_alignment_check(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;

    fn alignment_check_failed(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        has: Align,
        required: Align,
        check: CheckAlignment,
    ) -> InterpResult<'tcx, ()>;

    /// Whether to enforce the validity invariant for a specific layout.
    fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>, layout: TyAndLayout<'tcx>) -> bool;

    /// Whether function calls should be [ABI](CallAbi)-checked.
    fn enforce_abi(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
        true
    }

    /// Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually
    /// check for overflow.
    fn ignore_optional_overflow_checks(_ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;

    /// Entry point for obtaining the MIR of anything that should get evaluated.
    /// So not just functions and shims, but also const/static initializers, anonymous
    /// constants, ...
    fn load_mir(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        instance: ty::InstanceDef<'tcx>,
    ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
        Ok(ecx.tcx.instance_mir(instance))
    }

    /// Entry point to all function calls.
    ///
    /// Returns either the mir to use for the call, or `None` if execution should
    /// just proceed (which usually means this hook did all the work that the
    /// called function should usually have done). In the latter case, it is
    /// this hook's responsibility to advance the instruction pointer!
    /// (This is to support functions like `__rust_maybe_catch_panic` that neither find a MIR
    /// nor just jump to `ret`, but instead push their own stack frame.)
    /// Passing `dest`and `ret` in the same `Option` proved very annoying when only one of them
    /// was used.
    fn find_mir_or_eval_fn(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        instance: ty::Instance<'tcx>,
        abi: CallAbi,
        args: &[FnArg<'tcx, Self::Provenance>],
        destination: &PlaceTy<'tcx, Self::Provenance>,
        target: Option<mir::BasicBlock>,
        unwind: mir::UnwindAction,
    ) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'tcx>)>>;

    /// Execute `fn_val`. It is the hook's responsibility to advance the instruction
    /// pointer as appropriate.
    fn call_extra_fn(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        fn_val: Self::ExtraFnVal,
        abi: CallAbi,
        args: &[FnArg<'tcx, Self::Provenance>],
        destination: &PlaceTy<'tcx, Self::Provenance>,
        target: Option<mir::BasicBlock>,
        unwind: mir::UnwindAction,
    ) -> InterpResult<'tcx>;

    /// Directly process an intrinsic without pushing a stack frame. It is the hook's
    /// responsibility to advance the instruction pointer as appropriate.
    fn call_intrinsic(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        instance: ty::Instance<'tcx>,
        args: &[OpTy<'tcx, Self::Provenance>],
        destination: &PlaceTy<'tcx, Self::Provenance>,
        target: Option<mir::BasicBlock>,
        unwind: mir::UnwindAction,
    ) -> InterpResult<'tcx>;

    /// Called to evaluate `Assert` MIR terminators that trigger a panic.
    fn assert_panic(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        msg: &mir::AssertMessage<'tcx>,
        unwind: mir::UnwindAction,
    ) -> InterpResult<'tcx>;

    /// Called to trigger a non-unwinding panic.
    fn panic_nounwind(_ecx: &mut InterpCx<'mir, 'tcx, Self>, msg: &str) -> InterpResult<'tcx>;

    /// Called when unwinding reached a state where execution should be terminated.
    fn unwind_terminate(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        reason: mir::UnwindTerminateReason,
    ) -> InterpResult<'tcx>;

    /// Called for all binary operations where the LHS has pointer type.
    ///
    /// Returns a (value, overflowed) pair if the operation succeeded
    fn binary_ptr_op(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        bin_op: mir::BinOp,
        left: &ImmTy<'tcx, Self::Provenance>,
        right: &ImmTy<'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx, (ImmTy<'tcx, Self::Provenance>, bool)>;

    /// Called before writing the specified `local` of the `frame`.
    /// Since writing a ZST is not actually accessing memory or locals, this is never invoked
    /// for ZST reads.
    ///
    /// Due to borrow checker trouble, we indicate the `frame` as an index rather than an `&mut
    /// Frame`.
    #[inline(always)]
    fn before_access_local_mut<'a>(
        _ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
        _frame: usize,
        _local: mir::Local,
    ) -> InterpResult<'tcx>
    where
        'tcx: 'mir,
    {
        Ok(())
    }

    /// Called before a basic block terminator is executed.
    #[inline]
    fn before_terminator(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Called when the interpreter encounters a `StatementKind::ConstEvalCounter` instruction.
    /// You can use this to detect long or endlessly running programs.
    #[inline]
    fn increment_const_eval_counter(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Called before a global allocation is accessed.
    /// `def_id` is `Some` if this is the "lazy" allocation of a static.
    #[inline]
    fn before_access_global(
        _tcx: TyCtxt<'tcx>,
        _machine: &Self,
        _alloc_id: AllocId,
        _allocation: ConstAllocation<'tcx>,
        _static_def_id: Option<DefId>,
        _is_write: bool,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Return the `AllocId` for the given thread-local static in the current thread.
    fn thread_local_static_base_pointer(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        def_id: DefId,
    ) -> InterpResult<'tcx, Pointer<Self::Provenance>> {
        throw_unsup!(ThreadLocalStatic(def_id))
    }

    /// Return the root pointer for the given `extern static`.
    fn extern_static_base_pointer(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        def_id: DefId,
    ) -> InterpResult<'tcx, Pointer<Self::Provenance>>;

    /// Return a "base" pointer for the given allocation: the one that is used for direct
    /// accesses to this static/const/fn allocation, or the one returned from the heap allocator.
    ///
    /// Not called on `extern` or thread-local statics (those use the methods above).
    fn adjust_alloc_base_pointer(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        ptr: Pointer,
    ) -> InterpResult<'tcx, Pointer<Self::Provenance>>;

    /// "Int-to-pointer cast"
    fn ptr_from_addr_cast(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        addr: u64,
    ) -> InterpResult<'tcx, Pointer<Option<Self::Provenance>>>;

    /// Marks a pointer as exposed, allowing it's provenance
    /// to be recovered. "Pointer-to-int cast"
    fn expose_ptr(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        ptr: Pointer<Self::Provenance>,
    ) -> InterpResult<'tcx>;

    /// Convert a pointer with provenance into an allocation-offset pair
    /// and extra provenance info.
    ///
    /// The returned `AllocId` must be the same as `ptr.provenance.get_alloc_id()`.
    ///
    /// When this fails, that means the pointer does not point to a live allocation.
    fn ptr_get_alloc(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        ptr: Pointer<Self::Provenance>,
    ) -> Option<(AllocId, Size, Self::ProvenanceExtra)>;

    /// Called to adjust allocations to the Provenance and AllocExtra of this machine.
    ///
    /// The way we construct allocations is to always first construct it without extra and then add
    /// the extra. This keeps uniform code paths for handling both allocations created by CTFE for
    /// globals, and allocations created by Miri during evaluation.
    ///
    /// `kind` is the kind of the allocation being adjusted; it can be `None` when
    /// it's a global and `GLOBAL_KIND` is `None`.
    ///
    /// This should avoid copying if no work has to be done! If this returns an owned
    /// allocation (because a copy had to be done to adjust things), machine memory will
    /// cache the result. (This relies on `AllocMap::get_or` being able to add the
    /// owned allocation to the map even when the map is shared.)
    ///
    /// This must only fail if `alloc` contains provenance.
    fn adjust_allocation<'b>(
        ecx: &InterpCx<'mir, 'tcx, Self>,
        id: AllocId,
        alloc: Cow<'b, Allocation>,
        kind: Option<MemoryKind<Self::MemoryKind>>,
    ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>;

    fn eval_inline_asm(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        _template: &'tcx [InlineAsmTemplatePiece],
        _operands: &[mir::InlineAsmOperand<'tcx>],
        _options: InlineAsmOptions,
    ) -> InterpResult<'tcx> {
        throw_unsup_format!("inline assembly is not supported")
    }

    /// Hook for performing extra checks on a memory read access.
    ///
    /// Takes read-only access to the allocation so we can keep all the memory read
    /// operations take `&self`. Use a `RefCell` in `AllocExtra` if you
    /// need to mutate.
    #[inline(always)]
    fn before_memory_read(
        _tcx: TyCtxt<'tcx>,
        _machine: &Self,
        _alloc_extra: &Self::AllocExtra,
        _prov: (AllocId, Self::ProvenanceExtra),
        _range: AllocRange,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Hook for performing extra checks on a memory write access.
    #[inline(always)]
    fn before_memory_write(
        _tcx: TyCtxt<'tcx>,
        _machine: &mut Self,
        _alloc_extra: &mut Self::AllocExtra,
        _prov: (AllocId, Self::ProvenanceExtra),
        _range: AllocRange,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Hook for performing extra operations on a memory deallocation.
    #[inline(always)]
    fn before_memory_deallocation(
        _tcx: TyCtxt<'tcx>,
        _machine: &mut Self,
        _alloc_extra: &mut Self::AllocExtra,
        _prov: (AllocId, Self::ProvenanceExtra),
        _range: AllocRange,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Executes a retagging operation for a single pointer.
    /// Returns the possibly adjusted pointer.
    #[inline]
    fn retag_ptr_value(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        _kind: mir::RetagKind,
        val: &ImmTy<'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>> {
        Ok(val.clone())
    }

    /// Executes a retagging operation on a compound value.
    /// Replaces all pointers stored in the given place.
    #[inline]
    fn retag_place_contents(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        _kind: mir::RetagKind,
        _place: &PlaceTy<'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Called on places used for in-place function argument and return value handling.
    ///
    /// These places need to be protected to make sure the program cannot tell whether the
    /// argument/return value was actually copied or passed in-place..
    fn protect_in_place_function_argument(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        place: &PlaceTy<'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx> {
        // Without an aliasing model, all we can do is put `Uninit` into the place.
        ecx.write_uninit(place)
    }

    /// Called immediately before a new stack frame gets pushed.
    fn init_frame_extra(
        ecx: &mut InterpCx<'mir, 'tcx, Self>,
        frame: Frame<'mir, 'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx, Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>>;

    /// Borrow the current thread's stack.
    fn stack<'a>(
        ecx: &'a InterpCx<'mir, 'tcx, Self>,
    ) -> &'a [Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>];

    /// Mutably borrow the current thread's stack.
    fn stack_mut<'a>(
        ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
    ) -> &'a mut Vec<Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>>;

    /// Called immediately after a stack frame got pushed and its locals got initialized.
    fn after_stack_push(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Called just before the return value is copied to the caller-provided return place.
    fn before_stack_pop(
        _ecx: &InterpCx<'mir, 'tcx, Self>,
        _frame: &Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>,
    ) -> InterpResult<'tcx> {
        Ok(())
    }

    /// Called immediately after a stack frame got popped, but before jumping back to the caller.
    /// The `locals` have already been destroyed!
    #[inline(always)]
    fn after_stack_pop(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        _frame: Frame<'mir, 'tcx, Self::Provenance, Self::FrameExtra>,
        unwinding: bool,
    ) -> InterpResult<'tcx, StackPopJump> {
        // By default, we do not support unwinding from panics
        assert!(!unwinding);
        Ok(StackPopJump::Normal)
    }

    /// Called immediately after actual memory was allocated for a local
    /// but before the local's stack frame is updated to point to that memory.
    #[inline(always)]
    fn after_local_allocated(
        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
        _frame: usize,
        _local: mir::Local,
        _mplace: &MPlaceTy<'tcx, Self::Provenance>,
    ) -> InterpResult<'tcx> {
        Ok(())
    }
}

/// A lot of the flexibility above is just needed for `Miri`, but all "compile-time" machines
/// (CTFE and ConstProp) use the same instance. Here, we share that code.
pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
    type Provenance = AllocId;
    type ProvenanceExtra = ();

    type ExtraFnVal = !;

    type MemoryMap =
        rustc_data_structures::fx::FxIndexMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation)>;
    const GLOBAL_KIND: Option<Self::MemoryKind> = None; // no copying of globals from `tcx` to machine memory

    type AllocExtra = ();
    type FrameExtra = ();
    type Bytes = Box<[u8]>;

    #[inline(always)]
    fn use_addr_for_alignment_check(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
        // We do not support `use_addr`.
        false
    }

    #[inline(always)]
    fn ignore_optional_overflow_checks(_ecx: &InterpCx<$mir, $tcx, Self>) -> bool {
        false
    }

    #[inline(always)]
    fn unwind_terminate(
        _ecx: &mut InterpCx<$mir, $tcx, Self>,
        _reason: mir::UnwindTerminateReason,
    ) -> InterpResult<$tcx> {
        unreachable!("unwinding cannot happen during compile-time evaluation")
    }

    #[inline(always)]
    fn call_extra_fn(
        _ecx: &mut InterpCx<$mir, $tcx, Self>,
        fn_val: !,
        _abi: CallAbi,
        _args: &[FnArg<$tcx>],
        _destination: &PlaceTy<$tcx, Self::Provenance>,
        _target: Option<mir::BasicBlock>,
        _unwind: mir::UnwindAction,
    ) -> InterpResult<$tcx> {
        match fn_val {}
    }

    #[inline(always)]
    fn adjust_allocation<'b>(
        _ecx: &InterpCx<$mir, $tcx, Self>,
        _id: AllocId,
        alloc: Cow<'b, Allocation>,
        _kind: Option<MemoryKind<Self::MemoryKind>>,
    ) -> InterpResult<$tcx, Cow<'b, Allocation<Self::Provenance>>> {
        Ok(alloc)
    }

    fn extern_static_base_pointer(
        ecx: &InterpCx<$mir, $tcx, Self>,
        def_id: DefId,
    ) -> InterpResult<$tcx, Pointer> {
        // Use the `AllocId` associated with the `DefId`. Any actual *access* will fail.
        Ok(Pointer::new(ecx.tcx.reserve_and_set_static_alloc(def_id), Size::ZERO))
    }

    #[inline(always)]
    fn adjust_alloc_base_pointer(
        _ecx: &InterpCx<$mir, $tcx, Self>,
        ptr: Pointer<AllocId>,
    ) -> InterpResult<$tcx, Pointer<AllocId>> {
        Ok(ptr)
    }

    #[inline(always)]
    fn ptr_from_addr_cast(
        _ecx: &InterpCx<$mir, $tcx, Self>,
        addr: u64,
    ) -> InterpResult<$tcx, Pointer<Option<AllocId>>> {
        // Allow these casts, but make the pointer not dereferenceable.
        // (I.e., they behave like transmutation.)
        // This is correct because no pointers can ever be exposed in compile-time evaluation.
        Ok(Pointer::from_addr_invalid(addr))
    }

    #[inline(always)]
    fn ptr_get_alloc(
        _ecx: &InterpCx<$mir, $tcx, Self>,
        ptr: Pointer<AllocId>,
    ) -> Option<(AllocId, Size, Self::ProvenanceExtra)> {
        // We know `offset` is relative to the allocation, so we can use `into_parts`.
        let (alloc_id, offset) = ptr.into_parts();
        Some((alloc_id, offset, ()))
    }
}