CompileTimeMachine in rustc_const_eval::const_eval - Rust
Description: Extra machine state for CTFE, and the Machine instance.

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## CompileTimeMachine

# Struct CompileTimeMachine

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    pub struct CompileTimeMachine<'tcx> {
        pub(super) num_evaluated_steps: usize,
        pub(super) stack: Vec<Frame<'tcx>>,
        pub(super) can_access_mut_global: CanAccessMutGlobal,
        pub(super) check_alignment: CheckAlignment,
        pub(crate) static_root_ids: Option<(AllocId, LocalDefId)>,
        union_data_ranges: FxHashMap<Ty<'tcx>, RangeSet>,
        retag_mode: RetagMode,
    }

Expand description

Extra machine state for CTFE, and the Machine instance.

## Fields§

§`num_evaluated_steps: usize`

The number of terminators that have been evaluated.

This is used to produce lints informing the user that the compiler is not stuck. Set to `usize::MAX` to never report anything.

§`stack: Vec<Frame<'tcx>>`

The virtual call stack.

§`can_access_mut_global: CanAccessMutGlobal`

Pattern matching on consts with references would be unsound if those references could point to anything mutable. Therefore, when evaluating consts and when constructing valtrees, we ensure that only immutable global memory can be accessed.

§`check_alignment: CheckAlignment`

Whether to check alignment during evaluation.

§`static_root_ids: Option<(AllocId, LocalDefId)>`

If `Some`, we are evaluating the initializer of the static with the given `LocalDefId`, storing the result in the given `AllocId`. Used to prevent accesses to a static’s base allocation, as that may allow for self-initialization loops.

§`union_data_ranges: FxHashMap<Ty<'tcx>, RangeSet>`

A cache of “data range” computations for unions (i.e., the offsets of non-padding bytes).

§`retag_mode: RetagMode`

The current retag mode.

## Implementations§

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### impl<'tcx> CompileTimeMachine<'tcx>

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#### pub(crate) fn new( can_access_mut_global: CanAccessMutGlobal, check_alignment: CheckAlignment, ) -> Self

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### impl<'tcx> CompileTimeMachine<'tcx>

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#### pub fn best_lint_scope(&self, tcx: TyCtxt<'tcx>) -> HirId

Find the first stack frame that is within the current crate, if any. Otherwise, return the crate’s HirId

## Trait Implementations§

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### impl HasStaticRootDefId for CompileTimeMachine<'_>

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#### fn static_def_id(&self) -> Option<LocalDefId>

Returns the `DefId` of the static item that is currently being evaluated. Used for interning to be able to handle nested allocations.
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### impl<'tcx> Machine<'tcx> for CompileTimeMachine<'tcx>

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

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 = false

Should the machine panic on allocation failures?
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#### type Provenance = CtfeProvenance

Pointers are “tagged” with provenance information; typically the `AllocId` they belong to.
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#### type ProvenanceExtra = bool

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 = !

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 MemoryKind = MemoryKind

Additional memory kinds a machine wishes to distinguish from the builtin ones
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#### type MemoryMap = IndexMap<AllocId, (MemoryKind<MemoryKind>, Allocation), FxBuildHasher>

Memory’s allocation map
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#### type AllocExtra = ()

Extra data stored in every allocation.
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#### type FrameExtra = ()

Extra data stored in every call frame.
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#### type Bytes = Box<[u8]>

Type for the bytes of the allocation.
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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 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 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 call_extra_fn( _ecx: &mut InterpCx<'tcx, Self>, fn_val: !, _abi: &FnAbi<'tcx, Ty<'tcx>>, _args: &[FnArg<'tcx>], _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 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 adjust_global_allocation<'b>( _ecx: &InterpCx<'tcx, Self>, _id: AllocId, alloc: &'b Allocation, ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance>>>

Called to adjust global allocations to the Provenance and AllocExtra of this machine. Read more
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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. Read more
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#### fn extern_static_pointer( ecx: &InterpCx<'tcx, Self>, def_id: DefId, ) -> InterpResult<'tcx, Pointer>

Return the `AllocId` for the given `extern static`.
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#### fn adjust_alloc_root_pointer( _ecx: &InterpCx<'tcx, Self>, ptr: Pointer<CtfeProvenance>, _kind: Option<MemoryKind<Self::MemoryKind>>, ) -> InterpResult<'tcx, Pointer<CtfeProvenance>>

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. Read more
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#### fn ptr_from_addr_cast( _ecx: &InterpCx<'tcx, Self>, addr: u64, ) -> InterpResult<'tcx, Pointer<Option<CtfeProvenance>>>

“Int-to-pointer cast”
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#### fn ptr_get_alloc( _ecx: &InterpCx<'tcx, Self>, ptr: Pointer<CtfeProvenance>, _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. Read more
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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 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 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 find_mir_or_eval_fn( ecx: &mut InterpCx<'tcx, Self>, orig_instance: Instance<'tcx>, _abi: &FnAbi<'tcx, Ty<'tcx>>, args: &[FnArg<'tcx>], dest: &PlaceTy<'tcx>, ret: Option<BasicBlock>, _unwind: UnwindAction, ) -> InterpResult<'tcx, Option<(&'tcx Body<'tcx>, Instance<'tcx>)>>

Entry point to all function calls. Read more
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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 call_intrinsic( ecx: &mut InterpCx<'tcx, Self>, instance: Instance<'tcx>, args: &[OpTy<'tcx>], dest: &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. Read more
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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 runtime_checks( _ecx: &InterpCx<'tcx, Self>, _r: RuntimeChecks, ) -> InterpResult<'tcx, bool>

Determines the result of a `Operand::RuntimeChecks` invocation.
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#### fn binary_ptr_op( _ecx: &InterpCx<'tcx, Self>, _bin_op: BinOp, _left: &ImmTy<'tcx>, _right: &ImmTy<'tcx>, ) -> InterpResult<'tcx, ImmTy<'tcx>>

Called for all binary operations where the LHS has pointer type. Read more
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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 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 init_frame( ecx: &mut InterpCx<'tcx, Self>, frame: Frame<'tcx>, ) -> InterpResult<'tcx, Frame<'tcx>>

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 before_access_global( _tcx: TyCtxtAt<'tcx>, machine: &Self, alloc_id: AllocId, alloc: 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 retag_ptr_value( ecx: &mut InterpCx<'tcx, Self>, val: &ImmTy<'tcx, CtfeProvenance>, _ty: Ty<'tcx>, ) -> InterpResult<'tcx, Option<ImmTy<'tcx, CtfeProvenance>>>

Executes a retagging operation for a single pointer. Returns the possibly adjusted pointer. Return `None` if the pointer was left unchanged. Read more
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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 before_memory_write( _tcx: TyCtxtAt<'tcx>, _machine: &mut Self, _alloc_extra: &mut Self::AllocExtra, _ptr: Pointer<Option<Self::Provenance>>, (_alloc_id, immutable): (AllocId, bool), 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_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. Read more
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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 get_default_alloc_params(&self)

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

## Auto Trait Implementations§

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### impl<'tcx> !DynSend for CompileTimeMachine<'tcx>

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### impl<'tcx> !DynSync for CompileTimeMachine<'tcx>

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### impl<'tcx> !RefUnwindSafe for CompileTimeMachine<'tcx>

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### impl<'tcx> !Send for CompileTimeMachine<'tcx>

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### impl<'tcx> !Sync for CompileTimeMachine<'tcx>

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### impl<'tcx> !UnwindSafe for CompileTimeMachine<'tcx>

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

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

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

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment

Alignment of `Self`.
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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T, R> CollectAndApply<T, R> for T

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#### fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to `f(&iter.collect::<Vec<_>>())`.

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#### type Output = R

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### impl<T> ErasedDestructor for T
where T: 'static,

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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<K> IntoQueryKey<K> for K

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#### fn into_query_key(self) -> K

Argument conversion from `Self` to `K`. This should always be a very cheap conversion, e.g. `LocalDefId::to_def_id`.
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### impl<T> MaybeResult<T> for T

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#### type Error = !

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#### fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

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#### fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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#### fn upcast(self, interner: I) -> U

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### impl<I, T> UpcastFrom<I, T> for T

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#### fn upcast_from(from: T, _tcx: I) -> T

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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 88 bytes