use std::assert_matches::assert_matches; use std::convert::TryFrom; use rustc_apfloat::ieee::{Double, Single}; use rustc_apfloat::{Float, FloatConvert}; use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar}; use rustc_middle::mir::CastKind; use rustc_middle::ty::adjustment::PointerCast; use rustc_middle::ty::layout::{IntegerExt, LayoutOf, TyAndLayout}; use rustc_middle::ty::{self, FloatTy, Ty, TypeAndMut}; use rustc_target::abi::Integer; use rustc_type_ir::sty::TyKind::*; use super::{ util::ensure_monomorphic_enough, FnVal, ImmTy, Immediate, InterpCx, Machine, OpTy, PlaceTy, }; impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { pub fn cast( &mut self, src: &OpTy<'tcx, M::Provenance>, cast_kind: CastKind, cast_ty: Ty<'tcx>, dest: &PlaceTy<'tcx, M::Provenance>, ) -> InterpResult<'tcx> { use rustc_middle::mir::CastKind::*; // FIXME: In which cases should we trigger UB when the source is uninit? match cast_kind { Pointer(PointerCast::Unsize) => { let cast_ty = self.layout_of(cast_ty)?; self.unsize_into(src, cast_ty, dest)?; } PointerExposeAddress => { let src = self.read_immediate(src)?; let res = self.pointer_expose_address_cast(&src, cast_ty)?; self.write_immediate(res, dest)?; } PointerFromExposedAddress => { let src = self.read_immediate(src)?; let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?; self.write_immediate(res, dest)?; } Misc => { let src = self.read_immediate(src)?; let res = self.misc_cast(&src, cast_ty)?; self.write_immediate(res, dest)?; } Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer) => { // These are NOPs, but can be wide pointers. let v = self.read_immediate(src)?; self.write_immediate(*v, dest)?; } Pointer(PointerCast::ReifyFnPointer) => { // The src operand does not matter, just its type match *src.layout.ty.kind() { ty::FnDef(def_id, substs) => { // All reifications must be monomorphic, bail out otherwise. ensure_monomorphic_enough(*self.tcx, src.layout.ty)?; let instance = ty::Instance::resolve_for_fn_ptr( *self.tcx, self.param_env, def_id, substs, ) .ok_or_else(|| err_inval!(TooGeneric))?; let fn_ptr = self.create_fn_alloc_ptr(FnVal::Instance(instance)); self.write_pointer(fn_ptr, dest)?; } _ => span_bug!(self.cur_span(), "reify fn pointer on {:?}", src.layout.ty), } } Pointer(PointerCast::UnsafeFnPointer) => { let src = self.read_immediate(src)?; match cast_ty.kind() { ty::FnPtr(_) => { // No change to value self.write_immediate(*src, dest)?; } _ => span_bug!(self.cur_span(), "fn to unsafe fn cast on {:?}", cast_ty), } } Pointer(PointerCast::ClosureFnPointer(_)) => { // The src operand does not matter, just its type match *src.layout.ty.kind() { ty::Closure(def_id, substs) => { // All reifications must be monomorphic, bail out otherwise. ensure_monomorphic_enough(*self.tcx, src.layout.ty)?; let instance = ty::Instance::resolve_closure( *self.tcx, def_id, substs, ty::ClosureKind::FnOnce, ) .ok_or_else(|| err_inval!(TooGeneric))?; let fn_ptr = self.create_fn_alloc_ptr(FnVal::Instance(instance)); self.write_pointer(fn_ptr, dest)?; } _ => span_bug!(self.cur_span(), "closure fn pointer on {:?}", src.layout.ty), } } DynStar => { if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() { // Initial cast from sized to dyn trait let vtable = self.get_vtable_ptr(src.layout.ty, data.principal())?; let vtable = Scalar::from_maybe_pointer(vtable, self); let data = self.read_immediate(src)?.to_scalar(); let _assert_pointer_sized = data.to_pointer(self)?; let val = Immediate::ScalarPair(data, vtable); self.write_immediate(val, dest)?; } else { bug!() } } } Ok(()) } pub fn misc_cast( &mut self, src: &ImmTy<'tcx, M::Provenance>, cast_ty: Ty<'tcx>, ) -> InterpResult<'tcx, Immediate> { use rustc_type_ir::sty::TyKind::*; trace!("Casting {:?}: {:?} to {:?}", *src, src.layout.ty, cast_ty); match src.layout.ty.kind() { // Floating point Float(FloatTy::F32) => { return Ok(self.cast_from_float(src.to_scalar().to_f32()?, cast_ty).into()); } Float(FloatTy::F64) => { return Ok(self.cast_from_float(src.to_scalar().to_f64()?, cast_ty).into()); } // The rest is integer/pointer-"like", including fn ptr casts _ => assert!( src.layout.ty.is_bool() || src.layout.ty.is_char() || src.layout.ty.is_integral() || src.layout.ty.is_any_ptr(), "Unexpected cast from type {:?}", src.layout.ty ), } // # First handle non-scalar source values. // Handle casting any ptr to raw ptr (might be a fat ptr). if src.layout.ty.is_any_ptr() && cast_ty.is_unsafe_ptr() { let dest_layout = self.layout_of(cast_ty)?; if dest_layout.size == src.layout.size { // Thin or fat pointer that just hast the ptr kind of target type changed. return Ok(**src); } else { // Casting the metadata away from a fat ptr. assert_eq!(src.layout.size, 2 * self.pointer_size()); assert_eq!(dest_layout.size, self.pointer_size()); assert!(src.layout.ty.is_unsafe_ptr()); return match **src { Immediate::ScalarPair(data, _) => Ok(data.into()), Immediate::Scalar(..) => span_bug!( self.cur_span(), "{:?} input to a fat-to-thin cast ({:?} -> {:?})", *src, src.layout.ty, cast_ty ), Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)), }; } } // # The remaining source values are scalar and "int-like". let scalar = src.to_scalar(); Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into()) } pub fn pointer_expose_address_cast( &mut self, src: &ImmTy<'tcx, M::Provenance>, cast_ty: Ty<'tcx>, ) -> InterpResult<'tcx, Immediate> { assert_matches!(src.layout.ty.kind(), ty::RawPtr(_) | ty::FnPtr(_)); assert!(cast_ty.is_integral()); let scalar = src.to_scalar(); let ptr = scalar.to_pointer(self)?; match ptr.into_pointer_or_addr() { Ok(ptr) => M::expose_ptr(self, ptr)?, Err(_) => {} // Do nothing, exposing an invalid pointer (`None` provenance) is a NOP. }; Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into()) } pub fn pointer_from_exposed_address_cast( &mut self, src: &ImmTy<'tcx, M::Provenance>, cast_ty: Ty<'tcx>, ) -> InterpResult<'tcx, Immediate> { assert!(src.layout.ty.is_integral()); assert_matches!(cast_ty.kind(), ty::RawPtr(_)); // First cast to usize. let scalar = src.to_scalar(); let addr = self.cast_from_int_like(scalar, src.layout, self.tcx.types.usize)?; let addr = addr.to_machine_usize(self)?; // Then turn address into pointer. let ptr = M::ptr_from_addr_cast(&self, addr)?; Ok(Scalar::from_maybe_pointer(ptr, self).into()) } pub fn cast_from_int_like( &self, scalar: Scalar, // input value (there is no ScalarTy so we separate data+layout) src_layout: TyAndLayout<'tcx>, cast_ty: Ty<'tcx>, ) -> InterpResult<'tcx, Scalar> { // Let's make sure v is sign-extended *if* it has a signed type. let signed = src_layout.abi.is_signed(); // Also asserts that abi is `Scalar`. let v = scalar.to_bits(src_layout.size)?; let v = if signed { self.sign_extend(v, src_layout) } else { v }; trace!("cast_from_scalar: {}, {} -> {}", v, src_layout.ty, cast_ty); Ok(match *cast_ty.kind() { Int(_) | Uint(_) => { let size = match *cast_ty.kind() { Int(t) => Integer::from_int_ty(self, t).size(), Uint(t) => Integer::from_uint_ty(self, t).size(), _ => bug!(), }; let v = size.truncate(v); Scalar::from_uint(v, size) } Float(FloatTy::F32) if signed => Scalar::from_f32(Single::from_i128(v as i128).value), Float(FloatTy::F64) if signed => Scalar::from_f64(Double::from_i128(v as i128).value), Float(FloatTy::F32) => Scalar::from_f32(Single::from_u128(v).value), Float(FloatTy::F64) => Scalar::from_f64(Double::from_u128(v).value), Char => { // `u8` to `char` cast Scalar::from_u32(u8::try_from(v).unwrap().into()) } // Casts to bool are not permitted by rustc, no need to handle them here. _ => span_bug!(self.cur_span(), "invalid int to {:?} cast", cast_ty), }) } fn cast_from_float(&self, f: F, dest_ty: Ty<'tcx>) -> Scalar where F: Float + Into> + FloatConvert + FloatConvert, { use rustc_type_ir::sty::TyKind::*; match *dest_ty.kind() { // float -> uint Uint(t) => { let size = Integer::from_uint_ty(self, t).size(); // `to_u128` is a saturating cast, which is what we need // (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r). let v = f.to_u128(size.bits_usize()).value; // This should already fit the bit width Scalar::from_uint(v, size) } // float -> int Int(t) => { let size = Integer::from_int_ty(self, t).size(); // `to_i128` is a saturating cast, which is what we need // (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r). let v = f.to_i128(size.bits_usize()).value; Scalar::from_int(v, size) } // float -> f32 Float(FloatTy::F32) => Scalar::from_f32(f.convert(&mut false).value), // float -> f64 Float(FloatTy::F64) => Scalar::from_f64(f.convert(&mut false).value), // That's it. _ => span_bug!(self.cur_span(), "invalid float to {:?} cast", dest_ty), } } fn unsize_into_ptr( &mut self, src: &OpTy<'tcx, M::Provenance>, dest: &PlaceTy<'tcx, M::Provenance>, // The pointee types source_ty: Ty<'tcx>, cast_ty: Ty<'tcx>, ) -> InterpResult<'tcx> { // A -> A conversion let (src_pointee_ty, dest_pointee_ty) = self.tcx.struct_lockstep_tails_erasing_lifetimes(source_ty, cast_ty, self.param_env); match (&src_pointee_ty.kind(), &dest_pointee_ty.kind()) { (&ty::Array(_, length), &ty::Slice(_)) => { let ptr = self.read_scalar(src)?; // u64 cast is from usize to u64, which is always good let val = Immediate::new_slice(ptr, length.eval_usize(*self.tcx, self.param_env), self); self.write_immediate(val, dest) } (&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => { let val = self.read_immediate(src)?; if data_a.principal() == data_b.principal() { // A NOP cast that doesn't actually change anything, should be allowed even with mismatching vtables. return self.write_immediate(*val, dest); } let (old_data, old_vptr) = val.to_scalar_pair(); let old_vptr = old_vptr.to_pointer(self)?; let (ty, old_trait) = self.get_ptr_vtable(old_vptr)?; if old_trait != data_a.principal() { throw_ub_format!("upcast on a pointer whose vtable does not match its type"); } let new_vptr = self.get_vtable_ptr(ty, data_b.principal())?; self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest) } (_, &ty::Dynamic(ref data, _, ty::Dyn)) => { // Initial cast from sized to dyn trait let vtable = self.get_vtable_ptr(src_pointee_ty, data.principal())?; let ptr = self.read_scalar(src)?; let val = Immediate::new_dyn_trait(ptr, vtable, &*self.tcx); self.write_immediate(val, dest) } _ => { span_bug!(self.cur_span(), "invalid unsizing {:?} -> {:?}", src.layout.ty, cast_ty) } } } fn unsize_into( &mut self, src: &OpTy<'tcx, M::Provenance>, cast_ty: TyAndLayout<'tcx>, dest: &PlaceTy<'tcx, M::Provenance>, ) -> InterpResult<'tcx> { trace!("Unsizing {:?} of type {} into {:?}", *src, src.layout.ty, cast_ty.ty); match (&src.layout.ty.kind(), &cast_ty.ty.kind()) { (&ty::Ref(_, s, _), &ty::Ref(_, c, _) | &ty::RawPtr(TypeAndMut { ty: c, .. })) | (&ty::RawPtr(TypeAndMut { ty: s, .. }), &ty::RawPtr(TypeAndMut { ty: c, .. })) => { self.unsize_into_ptr(src, dest, *s, *c) } (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => { assert_eq!(def_a, def_b); // unsizing of generic struct with pointer fields // Example: `Arc` -> `Arc` // here we need to increase the size of every &T thin ptr field to a fat ptr for i in 0..src.layout.fields.count() { let cast_ty_field = cast_ty.field(self, i); if cast_ty_field.is_zst() { continue; } let src_field = self.operand_field(src, i)?; let dst_field = self.place_field(dest, i)?; if src_field.layout.ty == cast_ty_field.ty { self.copy_op(&src_field, &dst_field, /*allow_transmute*/ false)?; } else { self.unsize_into(&src_field, cast_ty_field, &dst_field)?; } } Ok(()) } _ => span_bug!( self.cur_span(), "unsize_into: invalid conversion: {:?} -> {:?}", src.layout, dest.layout ), } } }