src/librustc_mir/interpret/machine.rs - third_party/rust - Git at Google

 //! 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::hash::Hash;

 use rustc::hir::def_id::DefId;
 use rustc::mir;
 use rustc::ty::{self, Ty, TyCtxt};
 use syntax_pos::Span;

 use super::{
     Allocation, AllocId, InterpResult, Scalar, AllocationExtra, AssertMessage,
     InterpCx, PlaceTy, OpTy, ImmTy, MemoryKind, Pointer, Memory,
     Frame, Operand,
 };

 /// 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 StackPopInfo {
     /// 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 stop unwinding,
     /// as we've reached a catch frame
     StopUnwinding
 }

 /// 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 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>: Sized {
     /// Additional memory kinds a machine wishes to distinguish from the builtin ones
     type MemoryKinds: ::std::fmt::Debug + MayLeak + Eq + 'static;

     /// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
     /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
     /// The `default()` is used for pointers to consts, statics, vtables and functions.
     type PointerTag: ::std::fmt::Debug + Copy + Eq + Hash + '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: ::std::fmt::Debug + Copy;

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

     /// Extra data stored in memory. A reference to this is available when `AllocExtra`
     /// gets initialized, so you can e.g., have an `Rc` here if there is global state you
     /// need access to in the `AllocExtra` hooks.
     type MemoryExtra;

     /// Extra data stored in every allocation.
     type AllocExtra: AllocationExtra<Self::PointerTag> + 'static;

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

     /// The memory kind to use for copied statics -- or None if statics 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
     /// `tag_allocation` or `find_foreign_static` (see below) returns an owned allocation
     /// that is added to the memory so that the work is not done twice.
     const STATIC_KIND: Option<Self::MemoryKinds>;

     /// Whether memory accesses should be alignment-checked.
     const CHECK_ALIGN: bool;

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

     /// Called before a basic block terminator is executed.
     /// You can use this to detect endlessly running programs.
     fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'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.
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx, Self::PointerTag>],
         ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
         unwind: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx, Option<&'mir mir::Body<'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,
         args: &[OpTy<'tcx, Self::PointerTag>],
         ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
         unwind: Option<mir::BasicBlock>,
     ) -> 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>,
         span: Span,
         instance: ty::Instance<'tcx>,
         args: &[OpTy<'tcx, Self::PointerTag>],
         ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
         unwind: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx>;

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

     /// Called for read access to a foreign static item.
     ///
     /// This will only be called once per static and machine; the result is cached in
     /// the machine memory. (This relies on `AllocMap::get_or` being able to add the
     /// owned allocation to the map even when the map is shared.)
     ///
     /// This allocation will then be fed to `tag_allocation` to initialize the "extra" state.
     fn find_foreign_static(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
     ) -> InterpResult<'tcx, Cow<'tcx, Allocation>>;

     /// 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::PointerTag>,
         right: ImmTy<'tcx, Self::PointerTag>,
     ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;

     /// Heap allocations via the `box` keyword.
     fn box_alloc(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
         dest: PlaceTy<'tcx, Self::PointerTag>,
     ) -> InterpResult<'tcx>;

     /// Called to read the specified `local` from the `frame`.
     fn access_local(
         _ecx: &InterpCx<'mir, 'tcx, Self>,
         frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
         local: mir::Local,
     ) -> InterpResult<'tcx, Operand<Self::PointerTag>> {
         frame.locals[local].access()
     }

     /// Called before a `StaticKind::Static` value is accessed.
     fn before_access_static(
         _allocation: &Allocation,
     ) -> InterpResult<'tcx> {
         Ok(())
     }

     /// Called to initialize the "extra" state of an allocation and make the pointers
     /// it contains (in relocations) tagged.  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 statics, and allocations ceated by Miri during evaluation.
     ///
     /// `kind` is the kind of the allocation being tagged; it can be `None` when
     /// it's a static and `STATIC_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 add tags or metadata), 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.)
     ///
     /// Also return the "base" tag to use for this allocation: the one that is used for direct
     /// accesses to this allocation. If `kind == STATIC_KIND`, this tag must be consistent
     /// with `tag_static_base_pointer`.
     fn init_allocation_extra<'b>(
         memory_extra: &Self::MemoryExtra,
         id: AllocId,
         alloc: Cow<'b, Allocation>,
         kind: Option<MemoryKind<Self::MemoryKinds>>,
     ) -> (Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>, Self::PointerTag);

     /// Return the "base" tag for the given *static* allocation: the one that is used for direct
     /// accesses to this static/const/fn allocation. If `id` is not a static allocation,
     /// this will return an unusable tag (i.e., accesses will be UB)!
     fn tag_static_base_pointer(
         memory_extra: &Self::MemoryExtra,
         id: AllocId,
     ) -> Self::PointerTag;

     /// Executes a retagging operation
     #[inline]
     fn retag(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,
         _kind: mir::RetagKind,
         _place: PlaceTy<'tcx, Self::PointerTag>,
     ) -> InterpResult<'tcx> {
         Ok(())
     }

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

     /// Called immediately after a stack frame gets popped
     fn stack_pop(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,
         _extra: Self::FrameExtra,
         _unwinding: bool
     ) -> InterpResult<'tcx, StackPopInfo> {
         // By default, we do not support unwinding from panics
         Ok(StackPopInfo::Normal)
     }

     fn int_to_ptr(
         _mem: &Memory<'mir, 'tcx, Self>,
         int: u64,
     ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
         Err((if int == 0 {
             err_unsup!(InvalidNullPointerUsage)
         } else {
             err_unsup!(ReadBytesAsPointer)
         }).into())
     }

     fn ptr_to_int(
         _mem: &Memory<'mir, 'tcx, Self>,
         _ptr: Pointer<Self::PointerTag>,
     ) -> InterpResult<'tcx, u64>;
 }
	//! 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::hash::Hash;

	use rustc::hir::def_id::DefId;
	use rustc::mir;
	use rustc::ty::{self, Ty, TyCtxt};
	use syntax_pos::Span;

	use super::{
	Allocation, AllocId, InterpResult, Scalar, AllocationExtra, AssertMessage,
	InterpCx, PlaceTy, OpTy, ImmTy, MemoryKind, Pointer, Memory,
	Frame, Operand,
	};

	/// 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 StackPopInfo {
	/// 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 stop unwinding,
	/// as we've reached a catch frame
	StopUnwinding
	}

	/// 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 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>: Sized {
	/// Additional memory kinds a machine wishes to distinguish from the builtin ones
	type MemoryKinds: ::std::fmt::Debug + MayLeak + Eq + 'static;

	/// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
	/// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
	/// The `default()` is used for pointers to consts, statics, vtables and functions.
	type PointerTag: ::std::fmt::Debug + Copy + Eq + Hash + '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: ::std::fmt::Debug + Copy;

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

	/// Extra data stored in memory. A reference to this is available when `AllocExtra`
	/// gets initialized, so you can e.g., have an `Rc` here if there is global state you
	/// need access to in the `AllocExtra` hooks.
	type MemoryExtra;

	/// Extra data stored in every allocation.
	type AllocExtra: AllocationExtra<Self::PointerTag> + 'static;

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

	/// The memory kind to use for copied statics -- or None if statics 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
	/// `tag_allocation` or `find_foreign_static` (see below) returns an owned allocation
	/// that is added to the memory so that the work is not done twice.
	const STATIC_KIND: Option<Self::MemoryKinds>;

	/// Whether memory accesses should be alignment-checked.
	const CHECK_ALIGN: bool;

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

	/// Called before a basic block terminator is executed.
	/// You can use this to detect endlessly running programs.
	fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'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.
	fn find_mir_or_eval_fn(
	ecx: &mut InterpCx<'mir, 'tcx, Self>,
	instance: ty::Instance<'tcx>,
	args: &[OpTy<'tcx, Self::PointerTag>],
	ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
	unwind: Option<mir::BasicBlock>,
	) -> InterpResult<'tcx, Option<&'mir mir::Body<'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,
	args: &[OpTy<'tcx, Self::PointerTag>],
	ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
	unwind: Option<mir::BasicBlock>,
	) -> 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>,
	span: Span,
	instance: ty::Instance<'tcx>,
	args: &[OpTy<'tcx, Self::PointerTag>],
	ret: Option<(PlaceTy<'tcx, Self::PointerTag>, mir::BasicBlock)>,
	unwind: Option<mir::BasicBlock>,
	) -> InterpResult<'tcx>;

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

	/// Called for read access to a foreign static item.
	///
	/// This will only be called once per static and machine; the result is cached in
	/// the machine memory. (This relies on `AllocMap::get_or` being able to add the
	/// owned allocation to the map even when the map is shared.)
	///
	/// This allocation will then be fed to `tag_allocation` to initialize the "extra" state.
	fn find_foreign_static(
	tcx: TyCtxt<'tcx>,
	def_id: DefId,
	) -> InterpResult<'tcx, Cow<'tcx, Allocation>>;

	/// 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::PointerTag>,
	right: ImmTy<'tcx, Self::PointerTag>,
	) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;

	/// Heap allocations via the `box` keyword.
	fn box_alloc(
	ecx: &mut InterpCx<'mir, 'tcx, Self>,
	dest: PlaceTy<'tcx, Self::PointerTag>,
	) -> InterpResult<'tcx>;

	/// Called to read the specified `local` from the `frame`.
	fn access_local(
	_ecx: &InterpCx<'mir, 'tcx, Self>,
	frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
	local: mir::Local,
	) -> InterpResult<'tcx, Operand<Self::PointerTag>> {
	frame.locals[local].access()
	}

	/// Called before a `StaticKind::Static` value is accessed.
	fn before_access_static(
	_allocation: &Allocation,
	) -> InterpResult<'tcx> {
	Ok(())
	}

	/// Called to initialize the "extra" state of an allocation and make the pointers
	/// it contains (in relocations) tagged. 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 statics, and allocations ceated by Miri during evaluation.
	///
	/// `kind` is the kind of the allocation being tagged; it can be `None` when
	/// it's a static and `STATIC_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 add tags or metadata), 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.)
	///
	/// Also return the "base" tag to use for this allocation: the one that is used for direct
	/// accesses to this allocation. If `kind == STATIC_KIND`, this tag must be consistent
	/// with `tag_static_base_pointer`.
	fn init_allocation_extra<'b>(
	memory_extra: &Self::MemoryExtra,
	id: AllocId,
	alloc: Cow<'b, Allocation>,
	kind: Option<MemoryKind<Self::MemoryKinds>>,
	) -> (Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>, Self::PointerTag);

	/// Return the "base" tag for the given static allocation: the one that is used for direct
	/// accesses to this static/const/fn allocation. If `id` is not a static allocation,
	/// this will return an unusable tag (i.e., accesses will be UB)!
	fn tag_static_base_pointer(
	memory_extra: &Self::MemoryExtra,
	id: AllocId,
	) -> Self::PointerTag;

	/// Executes a retagging operation
	#[inline]
	fn retag(
	_ecx: &mut InterpCx<'mir, 'tcx, Self>,
	_kind: mir::RetagKind,
	_place: PlaceTy<'tcx, Self::PointerTag>,
	) -> InterpResult<'tcx> {
	Ok(())
	}

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

	/// Called immediately after a stack frame gets popped
	fn stack_pop(
	_ecx: &mut InterpCx<'mir, 'tcx, Self>,
	_extra: Self::FrameExtra,
	_unwinding: bool
	) -> InterpResult<'tcx, StackPopInfo> {
	// By default, we do not support unwinding from panics
	Ok(StackPopInfo::Normal)
	}

	fn int_to_ptr(
	_mem: &Memory<'mir, 'tcx, Self>,
	int: u64,
	) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
	Err((if int == 0 {
	err_unsup!(InvalidNullPointerUsage)
	} else {
	err_unsup!(ReadBytesAsPointer)
	}).into())
	}

	fn ptr_to_int(
	_mem: &Memory<'mir, 'tcx, Self>,
	_ptr: Pointer<Self::PointerTag>,
	) -> InterpResult<'tcx, u64>;
	}