diff options
Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_middle/src/mir/interpret/pointer.rs | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/compiler/rustc_middle/src/mir/interpret/pointer.rs b/compiler/rustc_middle/src/mir/interpret/pointer.rs index 384954cbb..95e52e391 100644 --- a/compiler/rustc_middle/src/mir/interpret/pointer.rs +++ b/compiler/rustc_middle/src/mir/interpret/pointer.rs @@ -107,8 +107,12 @@ impl<T: HasDataLayout> PointerArithmetic for T {} /// pointer), but `derive` adds some unnecessary bounds. pub trait Provenance: Copy + fmt::Debug { /// Says whether the `offset` field of `Pointer`s with this provenance is the actual physical address. - /// If `true, ptr-to-int casts work by simply discarding the provenance. - /// If `false`, ptr-to-int casts are not supported. The offset *must* be relative in that case. + /// - If `false`, the offset *must* be relative. This means the bytes representing a pointer are + /// different from what the Abstract Machine prescribes, so the interpreter must prevent any + /// operation that would inspect the underlying bytes of a pointer, such as ptr-to-int + /// transmutation. A `ReadPointerAsBytes` error will be raised in such situations. + /// - If `true`, the interpreter will permit operations to inspect the underlying bytes of a + /// pointer, and implement ptr-to-int transmutation by stripping provenance. const OFFSET_IS_ADDR: bool; /// We also use this trait to control whether to abort execution when a pointer is being partially overwritten @@ -125,6 +129,9 @@ pub trait Provenance: Copy + fmt::Debug { /// Otherwise this function is best-effort (but must agree with `Machine::ptr_get_alloc`). /// (Identifying the offset in that allocation, however, is harder -- use `Memory::ptr_get_alloc` for that.) fn get_alloc_id(self) -> Option<AllocId>; + + /// Defines the 'join' of provenance: what happens when doing a pointer load and different bytes have different provenance. + fn join(left: Option<Self>, right: Option<Self>) -> Option<Self>; } impl Provenance for AllocId { @@ -152,6 +159,10 @@ impl Provenance for AllocId { fn get_alloc_id(self) -> Option<AllocId> { Some(self) } + + fn join(_left: Option<Self>, _right: Option<Self>) -> Option<Self> { + panic!("merging provenance is not supported when `OFFSET_IS_ADDR` is false") + } } /// Represents a pointer in the Miri engine. |