4 use crate::ty::layout::{self, HasDataLayout, Size};
5 use rustc_macros::HashStable;
8 AllocId, EvalResult, CheckInAllocMsg
11 ////////////////////////////////////////////////////////////////////////////////
13 ////////////////////////////////////////////////////////////////////////////////
15 pub trait PointerArithmetic: layout::HasDataLayout {
16 // These are not supposed to be overridden.
19 fn pointer_size(&self) -> Size {
20 self.data_layout().pointer_size
23 /// Helper function: truncate given value-"overflowed flag" pair to pointer size and
24 /// update "overflowed flag" if there was an overflow.
25 /// This should be called by all the other methods before returning!
27 fn truncate_to_ptr(&self, (val, over): (u64, bool)) -> (u64, bool) {
28 let val = val as u128;
29 let max_ptr_plus_1 = 1u128 << self.pointer_size().bits();
30 ((val % max_ptr_plus_1) as u64, over || val >= max_ptr_plus_1)
34 fn overflowing_offset(&self, val: u64, i: u64) -> (u64, bool) {
35 let res = val.overflowing_add(i);
36 self.truncate_to_ptr(res)
39 // Overflow checking only works properly on the range from -u64 to +u64.
41 fn overflowing_signed_offset(&self, val: u64, i: i128) -> (u64, bool) {
42 // FIXME: is it possible to over/underflow here?
44 // Trickery to ensure that i64::min_value() works fine: compute n = -i.
45 // This formula only works for true negative values, it overflows for zero!
46 let n = u64::max_value() - (i as u64) + 1;
47 let res = val.overflowing_sub(n);
48 self.truncate_to_ptr(res)
50 self.overflowing_offset(val, i as u64)
55 fn offset<'tcx>(&self, val: u64, i: u64) -> EvalResult<'tcx, u64> {
56 let (res, over) = self.overflowing_offset(val, i);
57 if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
61 fn signed_offset<'tcx>(&self, val: u64, i: i64) -> EvalResult<'tcx, u64> {
62 let (res, over) = self.overflowing_signed_offset(val, i128::from(i));
63 if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
67 impl<T: layout::HasDataLayout> PointerArithmetic for T {}
70 /// Pointer is generic over the type that represents a reference to Allocations,
71 /// thus making it possible for the most convenient representation to be used in
74 /// Defaults to the index based and loosely coupled AllocId.
76 /// Pointer is also generic over the `Tag` associated with each pointer,
77 /// which is used to do provenance tracking during execution.
78 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd,
79 RustcEncodable, RustcDecodable, Hash, HashStable)]
80 pub struct Pointer<Tag=(),Id=AllocId> {
86 static_assert_size!(Pointer, 16);
88 impl<Tag: fmt::Debug, Id: fmt::Debug> fmt::Debug for Pointer<Tag, Id> {
89 default fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
90 write!(f, "{:?}.{:#x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
93 // Specialization for no tag
94 impl<Id: fmt::Debug> fmt::Debug for Pointer<(), Id> {
95 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
96 write!(f, "{:?}.{:#x}", self.alloc_id, self.offset.bytes())
100 /// Produces a `Pointer` which points to the beginning of the Allocation
101 impl From<AllocId> for Pointer {
103 fn from(alloc_id: AllocId) -> Self {
104 Pointer::new(alloc_id, Size::ZERO)
108 impl<'tcx> Pointer<()> {
110 pub fn new(alloc_id: AllocId, offset: Size) -> Self {
111 Pointer { alloc_id, offset, tag: () }
115 pub fn with_tag<Tag>(self, tag: Tag) -> Pointer<Tag>
117 Pointer::new_with_tag(self.alloc_id, self.offset, tag)
121 impl<'tcx, Tag> Pointer<Tag> {
123 pub fn new_with_tag(alloc_id: AllocId, offset: Size, tag: Tag) -> Self {
124 Pointer { alloc_id, offset, tag }
128 pub fn offset(self, i: Size, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
129 Ok(Pointer::new_with_tag(
131 Size::from_bytes(cx.data_layout().offset(self.offset.bytes(), i.bytes())?),
137 pub fn overflowing_offset(self, i: Size, cx: &impl HasDataLayout) -> (Self, bool) {
138 let (res, over) = cx.data_layout().overflowing_offset(self.offset.bytes(), i.bytes());
139 (Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
143 pub fn wrapping_offset(self, i: Size, cx: &impl HasDataLayout) -> Self {
144 self.overflowing_offset(i, cx).0
148 pub fn signed_offset(self, i: i64, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
149 Ok(Pointer::new_with_tag(
151 Size::from_bytes(cx.data_layout().signed_offset(self.offset.bytes(), i)?),
157 pub fn overflowing_signed_offset(self, i: i128, cx: &impl HasDataLayout) -> (Self, bool) {
158 let (res, over) = cx.data_layout().overflowing_signed_offset(self.offset.bytes(), i);
159 (Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
163 pub fn wrapping_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> Self {
164 self.overflowing_signed_offset(i128::from(i), cx).0
168 pub fn erase_tag(self) -> Pointer {
169 Pointer { alloc_id: self.alloc_id, offset: self.offset, tag: () }
173 pub fn check_in_alloc(
175 allocation_size: Size,
176 msg: CheckInAllocMsg,
177 ) -> EvalResult<'tcx, ()> {
178 if self.offset > allocation_size {
179 err!(PointerOutOfBounds {
180 ptr: self.erase_tag(),