Machine in rustc_const_eval::interpret - Rust
Description: Methods of this trait signifies a point where CTFE evaluation would fail and some use case dependent behaviour can instead be applied.

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## Machine

# Trait Machine

Source

    pub trait Machine<'tcx>: Sized {
        type MemoryKind: Debug + Display + MayLeak + Eq + 'static;
        type Provenance: Provenance + Eq + Hash + 'static;
        type ProvenanceExtra: Copy + 'static;
        type ExtraFnVal: Debug + Copy;
        type FrameExtra;
        type AllocExtra: Debug + Clone + 'tcx;
        type Bytes: AllocBytes + 'static;
        type MemoryMap: AllocMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>)> + Default + Clone;

        const GLOBAL_KIND: Option<Self::MemoryKind>;
        const PANIC_ON_ALLOC_FAIL: bool;
        const ALL_CONSTS_ARE_PRECHECKED: bool = true;
    Show 50 methods
        // Required methods
        fn enforce_alignment(ecx: &InterpCx<'tcx, Self>) -> bool;
        fn enforce_validity(
            ecx: &InterpCx<'tcx, Self>,
            layout: TyAndLayout<'tcx>,
        ) -> bool;
        fn ignore_optional_overflow_checks(_ecx: &InterpCx<'tcx, Self>) -> bool;
        fn find_mir_or_eval_fn(
            ecx: &mut InterpCx<'tcx, Self>,
            instance: Instance<'tcx>,
            abi: &FnAbi<'tcx, Ty<'tcx>>,
            args: &[FnArg<'tcx, Self::Provenance>],
            destination: &PlaceTy<'tcx, Self::Provenance>,
            target: Option<BasicBlock>,
            unwind: UnwindAction,
        ) -> InterpResult<'tcx, Option<(&'tcx Body<'tcx>, Instance<'tcx>)>>;
        fn call_extra_fn(
            ecx: &mut InterpCx<'tcx, Self>,
            fn_val: Self::ExtraFnVal,
            abi: &FnAbi<'tcx, Ty<'tcx>>,
            args: &[FnArg<'tcx, Self::Provenance>],
            destination: &PlaceTy<'tcx, Self::Provenance>,
            target: Option<BasicBlock>,
            unwind: UnwindAction,
        ) -> InterpResult<'tcx>;
        fn call_intrinsic(
            ecx: &mut InterpCx<'tcx, Self>,
            instance: Instance<'tcx>,
            args: &[OpTy<'tcx, Self::Provenance>],
            destination: &PlaceTy<'tcx, Self::Provenance>,
            target: Option<BasicBlock>,
            unwind: UnwindAction,
        ) -> InterpResult<'tcx, Option<Instance<'tcx>>>;
        fn check_fn_target_features(
            _ecx: &InterpCx<'tcx, Self>,
            _instance: Instance<'tcx>,
        ) -> InterpResult<'tcx>;
        fn assert_panic(
            ecx: &mut InterpCx<'tcx, Self>,
            msg: &AssertMessage<'tcx>,
            unwind: UnwindAction,
        ) -> InterpResult<'tcx>;
        fn panic_nounwind(
            _ecx: &mut InterpCx<'tcx, Self>,
            msg: &str,
        ) -> InterpResult<'tcx>;
        fn unwind_terminate(
            ecx: &mut InterpCx<'tcx, Self>,
            reason: UnwindTerminateReason,
        ) -> InterpResult<'tcx>;
        fn binary_ptr_op(
            ecx: &InterpCx<'tcx, Self>,
            bin_op: BinOp,
            left: &ImmTy<'tcx, Self::Provenance>,
            right: &ImmTy<'tcx, Self::Provenance>,
        ) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>>;
        fn float_fuse_mul_add(_ecx: &InterpCx<'tcx, Self>) -> bool;
        fn runtime_checks(
            _ecx: &InterpCx<'tcx, Self>,
            r: RuntimeChecks,
        ) -> InterpResult<'tcx, bool>;
        fn extern_static_pointer(
            ecx: &InterpCx<'tcx, Self>,
            def_id: DefId,
        ) -> InterpResult<'tcx, Pointer<Self::Provenance>>;
        fn ptr_from_addr_cast(
            ecx: &InterpCx<'tcx, Self>,
            addr: u64,
        ) -> InterpResult<'tcx, Pointer<Option<Self::Provenance>>>;
        fn expose_provenance(
            ecx: &InterpCx<'tcx, Self>,
            provenance: Self::Provenance,
        ) -> InterpResult<'tcx>;
        fn ptr_get_alloc(
            ecx: &InterpCx<'tcx, Self>,
            ptr: Pointer<Self::Provenance>,
            size: i64,
        ) -> Option<(AllocId, Size, Self::ProvenanceExtra)>;
        fn adjust_alloc_root_pointer(
            ecx: &InterpCx<'tcx, Self>,
            ptr: Pointer,
            kind: Option<MemoryKind<Self::MemoryKind>>,
        ) -> InterpResult<'tcx, Pointer<Self::Provenance>>;
        fn adjust_global_allocation<'b>(
            ecx: &InterpCx<'tcx, Self>,
            id: AllocId,
            alloc: &'b Allocation,
        ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>;
        fn init_local_allocation(
            ecx: &InterpCx<'tcx, Self>,
            id: AllocId,
            kind: MemoryKind<Self::MemoryKind>,
            size: Size,
            align: Align,
        ) -> InterpResult<'tcx, Self::AllocExtra>;
        fn init_frame(
            ecx: &mut InterpCx<'tcx, Self>,
            frame: Frame<'tcx, Self::Provenance>,
        ) -> InterpResult<'tcx, Frame<'tcx, Self::Provenance, Self::FrameExtra>>;
        fn stack<'a>(
            ecx: &'a InterpCx<'tcx, Self>,
        ) -> &'a [Frame<'tcx, Self::Provenance, Self::FrameExtra>];
        fn stack_mut<'a>(
            ecx: &'a mut InterpCx<'tcx, Self>,
        ) -> &'a mut Vec<Frame<'tcx, Self::Provenance, Self::FrameExtra>>;
        fn get_global_alloc_salt(
            ecx: &InterpCx<'tcx, Self>,
            instance: Option<Instance<'tcx>>,
        ) -> usize;
        fn get_default_alloc_params(
            &self,
        ) -> <Self::Bytes as AllocBytes>::AllocParams;

        // Provided methods
        fn alignment_check(
            _ecx: &InterpCx<'tcx, Self>,
            _alloc_id: AllocId,
            _alloc_align: Align,
            _alloc_kind: AllocKind,
            _offset: Size,
            _align: Align,
        ) -> Option<Misalignment> { ... }
        fn enforce_validity_recursively(
            _ecx: &InterpCx<'tcx, Self>,
            _layout: TyAndLayout<'tcx>,
        ) -> bool { ... }
        fn load_mir(
            ecx: &InterpCx<'tcx, Self>,
            instance: InstanceKind<'tcx>,
        ) -> &'tcx Body<'tcx> { ... }
        fn generate_nan<F1: Float + FloatConvert<F2>, F2: Float>(
            _ecx: &InterpCx<'tcx, Self>,
            _inputs: &[F1],
        ) -> F2 { ... }
        fn apply_float_nondet(
            _ecx: &mut InterpCx<'tcx, Self>,
            val: ImmTy<'tcx, Self::Provenance>,
        ) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>> { ... }
        fn equal_float_min_max<F: Float>(
            _ecx: &InterpCx<'tcx, Self>,
            a: F,
            _b: F,
        ) -> F { ... }
        fn before_terminator(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx> { ... }
        fn increment_const_eval_counter(
            _ecx: &mut InterpCx<'tcx, Self>,
        ) -> InterpResult<'tcx> { ... }
        fn before_access_global(
            _tcx: TyCtxtAt<'tcx>,
            _machine: &Self,
            _alloc_id: AllocId,
            _allocation: ConstAllocation<'tcx>,
            _static_def_id: Option<DefId>,
            _is_write: bool,
        ) -> InterpResult<'tcx> { ... }
        fn thread_local_static_pointer(
            _ecx: &mut InterpCx<'tcx, Self>,
            def_id: DefId,
        ) -> InterpResult<'tcx, Pointer<Self::Provenance>> { ... }
        fn before_memory_read(
            _tcx: TyCtxtAt<'tcx>,
            _machine: &Self,
            _alloc_extra: &Self::AllocExtra,
            _ptr: Pointer<Option<Self::Provenance>>,
            _prov: (AllocId, Self::ProvenanceExtra),
            _range: AllocRange,
        ) -> InterpResult<'tcx> { ... }
        fn before_alloc_access(
            _tcx: TyCtxtAt<'tcx>,
            _machine: &Self,
            _alloc_id: AllocId,
        ) -> InterpResult<'tcx> { ... }
        fn before_memory_write(
            _tcx: TyCtxtAt<'tcx>,
            _machine: &mut Self,
            _alloc_extra: &mut Self::AllocExtra,
            _ptr: Pointer<Option<Self::Provenance>>,
            _prov: (AllocId, Self::ProvenanceExtra),
            _range: AllocRange,
        ) -> InterpResult<'tcx> { ... }
        fn before_memory_deallocation(
            _tcx: TyCtxtAt<'tcx>,
            _machine: &mut Self,
            _alloc_extra: &mut Self::AllocExtra,
            _ptr: Pointer<Option<Self::Provenance>>,
            _prov: (AllocId, Self::ProvenanceExtra),
            _size: Size,
            _align: Align,
            _kind: MemoryKind<Self::MemoryKind>,
        ) -> InterpResult<'tcx> { ... }
        fn retag_ptr_value(
            _ecx: &mut InterpCx<'tcx, Self>,
            _val: &ImmTy<'tcx, Self::Provenance>,
            _ty: Ty<'tcx>,
        ) -> InterpResult<'tcx, Option<ImmTy<'tcx, Self::Provenance>>> { ... }
        fn with_retag_mode<T>(
            ecx: &mut InterpCx<'tcx, Self>,
            _mode: RetagMode,
            f: impl FnOnce(&mut InterpCx<'tcx, Self>) -> InterpResult<'tcx, T>,
        ) -> InterpResult<'tcx, T> { ... }
        fn protect_in_place_function_argument(
            ecx: &mut InterpCx<'tcx, Self>,
            mplace: &MPlaceTy<'tcx, Self::Provenance>,
        ) -> InterpResult<'tcx> { ... }
        fn after_stack_push(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx> { ... }
        fn before_stack_pop(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx> { ... }
        fn after_stack_pop(
            _ecx: &mut InterpCx<'tcx, Self>,
            _frame: Frame<'tcx, Self::Provenance, Self::FrameExtra>,
            unwinding: bool,
        ) -> InterpResult<'tcx, ReturnAction> { ... }
        fn after_local_read(
            _ecx: &InterpCx<'tcx, Self>,
            _frame: &Frame<'tcx, Self::Provenance, Self::FrameExtra>,
            _local: Local,
        ) -> InterpResult<'tcx> { ... }
        fn after_local_write(
            _ecx: &mut InterpCx<'tcx, Self>,
            _local: Local,
            _storage_live: bool,
        ) -> InterpResult<'tcx> { ... }
        fn after_local_moved_to_memory(
            _ecx: &mut InterpCx<'tcx, Self>,
            _local: Local,
            _mplace: &MPlaceTy<'tcx, Self::Provenance>,
        ) -> InterpResult<'tcx> { ... }
        fn cached_union_data_range<'e>(
            _ecx: &'e mut InterpCx<'tcx, Self>,
            _ty: Ty<'tcx>,
            compute_range: impl FnOnce() -> RangeSet,
        ) -> Cow<'e, RangeSet> { ... }
        fn enter_trace_span(_span: impl FnOnce() -> Span) -> impl EnteredTraceSpan { ... }
    }

Expand description

Methods of this trait signifies a point where CTFE evaluation would fail and some use case dependent behaviour can instead be applied.

## Required Associated Constants§

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#### const GLOBAL_KIND: Option<Self::MemoryKind>

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.

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#### const PANIC_ON_ALLOC_FAIL: bool

Should the machine panic on allocation failures?

## Provided Associated Constants§

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#### const ALL_CONSTS_ARE_PRECHECKED: bool = true

Determines whether `eval_mir_constant` can never fail because all required consts have already been checked before.

## Required Associated Types§

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#### type MemoryKind: Debug + Display + MayLeak + Eq + 'static

Additional memory kinds a machine wishes to distinguish from the builtin ones

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#### type Provenance: Provenance + Eq + Hash + 'static

Pointers are “tagged” with provenance information; typically the `AllocId` they belong to.

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#### type ProvenanceExtra: Copy + '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.

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#### type ExtraFnVal: Debug + Copy

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.

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#### type FrameExtra

Extra data stored in every call frame.

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#### type AllocExtra: Debug + Clone + 'tcx

Extra data stored in every allocation.

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#### type Bytes: AllocBytes + 'static

Type for the bytes of the allocation.

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#### type MemoryMap: AllocMap<AllocId, (MemoryKind<Self::MemoryKind>, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>)> + Default + Clone

Memory’s allocation map

## Required Methods§

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#### fn enforce_alignment(ecx: &InterpCx<'tcx, Self>) -> bool

Whether memory accesses should be alignment-checked.

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#### fn enforce_validity( ecx: &InterpCx<'tcx, Self>, layout: TyAndLayout<'tcx>, ) -> bool

Whether to enforce the validity invariant for a specific layout.

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#### fn ignore_optional_overflow_checks(_ecx: &InterpCx<'tcx, Self>) -> bool

Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually check for overflow.

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#### fn find_mir_or_eval_fn( ecx: &mut InterpCx<'tcx, Self>, instance: Instance<'tcx>, abi: &FnAbi<'tcx, Ty<'tcx>>, args: &[FnArg<'tcx, Self::Provenance>], destination: &PlaceTy<'tcx, Self::Provenance>, target: Option<BasicBlock>, unwind: UnwindAction, ) -> InterpResult<'tcx, Option<(&'tcx Body<'tcx>, Instance<'tcx>)>>

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.

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#### fn call_extra_fn( ecx: &mut InterpCx<'tcx, Self>, fn_val: Self::ExtraFnVal, abi: &FnAbi<'tcx, Ty<'tcx>>, args: &[FnArg<'tcx, Self::Provenance>], destination: &PlaceTy<'tcx, Self::Provenance>, target: Option<BasicBlock>, unwind: UnwindAction, ) -> InterpResult<'tcx>

Execute `fn_val`. It is the hook’s responsibility to advance the instruction pointer as appropriate.

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#### fn call_intrinsic( ecx: &mut InterpCx<'tcx, Self>, instance: Instance<'tcx>, args: &[OpTy<'tcx, Self::Provenance>], destination: &PlaceTy<'tcx, Self::Provenance>, target: Option<BasicBlock>, unwind: UnwindAction, ) -> InterpResult<'tcx, Option<Instance<'tcx>>>

Directly process an intrinsic without pushing a stack frame. It is the hook’s responsibility to advance the instruction pointer as appropriate.

Returns `None` if the intrinsic was fully handled. Otherwise, returns an `Instance` of the function that implements the intrinsic.

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#### fn check_fn_target_features( _ecx: &InterpCx<'tcx, Self>, _instance: Instance<'tcx>, ) -> InterpResult<'tcx>

Check whether the given function may be executed on the current machine, in terms of the target features is requires.

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#### fn assert_panic( ecx: &mut InterpCx<'tcx, Self>, msg: &AssertMessage<'tcx>, unwind: UnwindAction, ) -> InterpResult<'tcx>

Called to evaluate `Assert` MIR terminators that trigger a panic.

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#### fn panic_nounwind( _ecx: &mut InterpCx<'tcx, Self>, msg: &str, ) -> InterpResult<'tcx>

Called to trigger a non-unwinding panic.

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#### fn unwind_terminate( ecx: &mut InterpCx<'tcx, Self>, reason: UnwindTerminateReason, ) -> InterpResult<'tcx>

Called when unwinding reached a state where execution should be terminated.

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#### fn binary_ptr_op( ecx: &InterpCx<'tcx, Self>, bin_op: BinOp, left: &ImmTy<'tcx, Self::Provenance>, right: &ImmTy<'tcx, Self::Provenance>, ) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>>

Called for all binary operations where the LHS has pointer type.

Returns a (value, overflowed) pair if the operation succeeded

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#### fn float_fuse_mul_add(_ecx: &InterpCx<'tcx, Self>) -> bool

Determines whether the `fmuladd` intrinsics fuse the multiply-add or use separate operations.

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#### fn runtime_checks( _ecx: &InterpCx<'tcx, Self>, r: RuntimeChecks, ) -> InterpResult<'tcx, bool>

Determines the result of a `Operand::RuntimeChecks` invocation.

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#### fn extern_static_pointer( ecx: &InterpCx<'tcx, Self>, def_id: DefId, ) -> InterpResult<'tcx, Pointer<Self::Provenance>>

Return the `AllocId` for the given `extern static`.

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#### fn ptr_from_addr_cast( ecx: &InterpCx<'tcx, Self>, addr: u64, ) -> InterpResult<'tcx, Pointer<Option<Self::Provenance>>>

“Int-to-pointer cast”

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#### fn expose_provenance( ecx: &InterpCx<'tcx, Self>, provenance: Self::Provenance, ) -> InterpResult<'tcx>

Marks a pointer as exposed, allowing its provenance to be recovered. “Pointer-to-int cast”

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#### fn ptr_get_alloc( ecx: &InterpCx<'tcx, Self>, ptr: Pointer<Self::Provenance>, size: i64, ) -> Option<(AllocId, Size, Self::ProvenanceExtra)>

Convert a pointer with provenance into an allocation-offset pair and extra provenance info. `size` says how many bytes of memory are expected at that pointer. The sign of `size` can be used to disambiguate situations where a wildcard pointer sits right in between two allocations.

If `ptr.provenance.get_alloc_id()` is `Some(p)`, the returned `AllocId` must be `p`. The resulting `AllocId` will just be used for that one step and the forgotten again (i.e., we’ll never turn the data returned here back into a `Pointer` that might be stored in machine state).

When this fails, that means the pointer does not point to a live allocation.

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#### fn adjust_alloc_root_pointer( ecx: &InterpCx<'tcx, Self>, ptr: Pointer, kind: Option<MemoryKind<Self::MemoryKind>>, ) -> InterpResult<'tcx, Pointer<Self::Provenance>>

Return a “root” 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).

`kind` is the kind of the allocation the pointer points to; it can be `None` when it’s a global and `GLOBAL_KIND` is `None`.

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#### fn adjust_global_allocation<'b>( ecx: &InterpCx<'tcx, Self>, id: AllocId, alloc: &'b Allocation, ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>

Called to adjust global allocations to the Provenance and AllocExtra of this machine.

If `alloc` contains pointers, then they are all pointing to globals.

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.)

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#### fn init_local_allocation( ecx: &InterpCx<'tcx, Self>, id: AllocId, kind: MemoryKind<Self::MemoryKind>, size: Size, align: Align, ) -> InterpResult<'tcx, Self::AllocExtra>

Initialize the extra state of an allocation local to this machine.

This is guaranteed to be called exactly once on all allocations local to this machine. It will not be called automatically for global allocations; `adjust_global_allocation` has to do that itself if that is desired.

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#### fn init_frame( ecx: &mut InterpCx<'tcx, Self>, frame: Frame<'tcx, Self::Provenance>, ) -> InterpResult<'tcx, Frame<'tcx, Self::Provenance, Self::FrameExtra>>

Called immediately before a new stack frame gets pushed.

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#### fn stack<'a>( ecx: &'a InterpCx<'tcx, Self>, ) -> &'a [Frame<'tcx, Self::Provenance, Self::FrameExtra>]

Borrow the current thread’s stack.

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#### fn stack_mut<'a>( ecx: &'a mut InterpCx<'tcx, Self>, ) -> &'a mut Vec<Frame<'tcx, Self::Provenance, Self::FrameExtra>>

Mutably borrow the current thread’s stack.

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#### fn get_global_alloc_salt( ecx: &InterpCx<'tcx, Self>, instance: Option<Instance<'tcx>>, ) -> usize

Returns the salt to be used for a deduplicated global alloation. If the allocation is for a function, the instance is provided as well (this lets Miri ensure unique addresses for some functions).

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#### fn get_default_alloc_params(&self) -> <Self::Bytes as AllocBytes>::AllocParams

Compute the value passed to the constructors of the `AllocBytes` type for abstract machine allocations.

## Provided Methods§

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#### fn alignment_check( _ecx: &InterpCx<'tcx, Self>, _alloc_id: AllocId, _alloc_align: Align, _alloc_kind: AllocKind, _offset: Size, _align: Align, ) -> Option<Misalignment>

Gives the machine a chance to detect more misalignment than the built-in checks would catch.

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#### fn enforce_validity_recursively( _ecx: &InterpCx<'tcx, Self>, _layout: TyAndLayout<'tcx>, ) -> bool

Whether to enforce the validity invariant recursively.

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#### fn load_mir( ecx: &InterpCx<'tcx, Self>, instance: InstanceKind<'tcx>, ) -> &'tcx Body<'tcx>

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, …

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#### fn generate_nan<F1: Float + FloatConvert<F2>, F2: Float>( _ecx: &InterpCx<'tcx, Self>, _inputs: &[F1], ) -> F2

Generate the NaN returned by a float operation, given the list of inputs. (This is all inputs, not just NaN inputs!)

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#### fn apply_float_nondet( _ecx: &mut InterpCx<'tcx, Self>, val: ImmTy<'tcx, Self::Provenance>, ) -> InterpResult<'tcx, ImmTy<'tcx, Self::Provenance>>

Apply non-determinism to float operations that do not return a precise result.

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#### fn equal_float_min_max<F: Float>(_ecx: &InterpCx<'tcx, Self>, a: F, _b: F) -> F

Determines the result of `min`/`max` on floats when the arguments are equal.

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#### fn before_terminator(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx>

Called before a basic block terminator is executed.

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#### fn increment_const_eval_counter( _ecx: &mut InterpCx<'tcx, Self>, ) -> InterpResult<'tcx>

Called when the interpreter encounters a `StatementKind::ConstEvalCounter` instruction. You can use this to detect long or endlessly running programs.

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#### fn before_access_global( _tcx: TyCtxtAt<'tcx>, _machine: &Self, _alloc_id: AllocId, _allocation: ConstAllocation<'tcx>, _static_def_id: Option<DefId>, _is_write: bool, ) -> InterpResult<'tcx>

Called before a global allocation is accessed. `def_id` is `Some` if this is the “lazy” allocation of a static.

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#### fn thread_local_static_pointer( _ecx: &mut InterpCx<'tcx, Self>, def_id: DefId, ) -> InterpResult<'tcx, Pointer<Self::Provenance>>

Return the `AllocId` for the given thread-local static in the current thread.

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#### fn before_memory_read( _tcx: TyCtxtAt<'tcx>, _machine: &Self, _alloc_extra: &Self::AllocExtra, _ptr: Pointer<Option<Self::Provenance>>, _prov: (AllocId, Self::ProvenanceExtra), _range: AllocRange, ) -> InterpResult<'tcx>

Hook for performing extra checks on a memory read access. `ptr` will always be a pointer with the provenance in `prov` pointing to the beginning of `range`.

This will not be called during validation!

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.

This is not invoked for ZST accesses, as no read actually happens.

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#### fn before_alloc_access( _tcx: TyCtxtAt<'tcx>, _machine: &Self, _alloc_id: AllocId, ) -> InterpResult<'tcx>

Hook for performing extra checks on any memory read access, that involves an allocation, even ZST reads.

This will not be called during validation!

Used to prevent statics from self-initializing by reading from their own memory as it is being initialized.

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#### fn before_memory_write( _tcx: TyCtxtAt<'tcx>, _machine: &mut Self, _alloc_extra: &mut Self::AllocExtra, _ptr: Pointer<Option<Self::Provenance>>, _prov: (AllocId, Self::ProvenanceExtra), _range: AllocRange, ) -> InterpResult<'tcx>

Hook for performing extra checks on a memory write access. This is not invoked for ZST accesses, as no write actually happens. `ptr` will always be a pointer with the provenance in `prov` pointing to the beginning of `range`.

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#### fn before_memory_deallocation( _tcx: TyCtxtAt<'tcx>, _machine: &mut Self, _alloc_extra: &mut Self::AllocExtra, _ptr: Pointer<Option<Self::Provenance>>, _prov: (AllocId, Self::ProvenanceExtra), _size: Size, _align: Align, _kind: MemoryKind<Self::MemoryKind>, ) -> InterpResult<'tcx>

Hook for performing extra operations on a memory deallocation. `ptr` will always be a pointer with the provenance in `prov` pointing to the beginning of the allocation.

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#### fn retag_ptr_value( _ecx: &mut InterpCx<'tcx, Self>, _val: &ImmTy<'tcx, Self::Provenance>, _ty: Ty<'tcx>, ) -> InterpResult<'tcx, Option<ImmTy<'tcx, Self::Provenance>>>

Executes a retagging operation for a single pointer. Returns the possibly adjusted pointer. Return `None` if the pointer was left unchanged.

`ty` is the full type of the pointer. This is not the same as `val.layout.ty` for boxes where `val` is just the inner raw pointer, but `ty` is the entire `Box` type.

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#### fn with_retag_mode<T>( ecx: &mut InterpCx<'tcx, Self>, _mode: RetagMode, f: impl FnOnce(&mut InterpCx<'tcx, Self>) -> InterpResult<'tcx, T>, ) -> InterpResult<'tcx, T>

Invoke `f` in a state where calls to `retag_ptr_value` will use the given retag mode.

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#### fn protect_in_place_function_argument( ecx: &mut InterpCx<'tcx, Self>, mplace: &MPlaceTy<'tcx, Self::Provenance>, ) -> InterpResult<'tcx>

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..

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#### fn after_stack_push(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx>

Called immediately after a stack frame got pushed and its locals got initialized.

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#### fn before_stack_pop(_ecx: &mut InterpCx<'tcx, Self>) -> InterpResult<'tcx>

Called just before the frame is removed from the stack (followed by return value copy and local cleanup).

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#### fn after_stack_pop( _ecx: &mut InterpCx<'tcx, Self>, _frame: Frame<'tcx, Self::Provenance, Self::FrameExtra>, unwinding: bool, ) -> InterpResult<'tcx, ReturnAction>

Called immediately after a stack frame got popped, but before jumping back to the caller. The `locals` have already been destroyed!

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#### fn after_local_read( _ecx: &InterpCx<'tcx, Self>, _frame: &Frame<'tcx, Self::Provenance, Self::FrameExtra>, _local: Local, ) -> InterpResult<'tcx>

Called immediately after an “immediate” local variable is read in a given frame (i.e., this is called for reads that do not end up accessing addressable memory).

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#### fn after_local_write( _ecx: &mut InterpCx<'tcx, Self>, _local: Local, _storage_live: bool, ) -> InterpResult<'tcx>

Called immediately after an “immediate” local variable is assigned a new value (i.e., this is called for writes that do not end up in memory). `storage_live` indicates whether this is the initial write upon `StorageLive`.

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#### fn after_local_moved_to_memory( _ecx: &mut InterpCx<'tcx, Self>, _local: Local, _mplace: &MPlaceTy<'tcx, Self::Provenance>, ) -> InterpResult<'tcx>

Called immediately after actual memory was allocated for a local but before the local’s stack frame is updated to point to that memory.

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#### fn cached_union_data_range<'e>( _ecx: &'e mut InterpCx<'tcx, Self>, _ty: Ty<'tcx>, compute_range: impl FnOnce() -> RangeSet, ) -> Cow<'e, RangeSet>

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#### fn enter_trace_span(_span: impl FnOnce() -> Span) -> impl EnteredTraceSpan

Allows enabling/disabling tracing calls from within `rustc_const_eval` at compile time, by delegating the entering of tracing::Spans to implementors of the Machine trait. The default implementation corresponds to tracing being disabled, meaning the tracing calls will supposedly be optimized out completely. To enable tracing, override this trait method and return `span.entered()`. Also see crate::enter_trace_span.

## Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

## Implementors§

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### impl<'tcx> Machine<'tcx> for CompileTimeMachine<'tcx>

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#### const GLOBAL_KIND: Option<Self::MemoryKind> = None

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#### const PANIC_ON_ALLOC_FAIL: bool = false

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#### type Provenance = CtfeProvenance

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#### type ProvenanceExtra = bool

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#### type ExtraFnVal = !

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#### type MemoryKind = MemoryKind

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#### type MemoryMap = IndexMap<AllocId, (MemoryKind<MemoryKind>, Allocation), FxBuildHasher>

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#### type AllocExtra = ()

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#### type FrameExtra = ()

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#### type Bytes = Box<[u8]>

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### impl<'tcx> Machine<'tcx> for DummyMachine

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#### const GLOBAL_KIND: Option<Self::MemoryKind> = None

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#### const PANIC_ON_ALLOC_FAIL: bool = true

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#### const ALL_CONSTS_ARE_PRECHECKED: bool = false

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#### type Provenance = CtfeProvenance

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#### type ProvenanceExtra = bool

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#### type ExtraFnVal = !

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#### type MemoryKind = MemoryKind

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#### type MemoryMap = IndexMap<AllocId, (MemoryKind<MemoryKind>, Allocation), FxBuildHasher>

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#### type AllocExtra = ()

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#### type FrameExtra = ()

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#### type Bytes = Box<[u8]>