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Rollup merge of #128277 - RalfJung:offset_from_wildcard, r=oli-obk

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miri: fix offset_from behavior on wildcard pointers

offset_from wouldn't behave correctly when the "end" pointer was a wildcard pointer (result of an int2ptr cast) just at the end of the allocation. Fix that by expressing the "same allocation" check in terms of two `check_ptr_access_signed` instead of something specific to offset_from, which is both more canonical and works better with wildcard pointers.

The second commit just improves diagnostics: I wanted the "pointer is dangling (has no provenance)" message to say how many bytes of memory it expected to see (since if it were 0 bytes, this would actually be legal, so it's good to tell the user that it's not 0 bytes). And then I was annoying that the error looks so different for when you deref a dangling pointer vs an out-of-bounds pointer so I made them more similar.

Fixes https://github.com/rust-lang/miri/issues/3767
This commit is contained in:
Matthias Krüger 2024-07-29 11:42:34 +02:00 • committed by GitHub
commit eb8114bad7
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80 changed files with 301 additions and 239 deletions
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8
compiler/rustc_const_eval/src/interpret/validity.rs
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@ -348,7 +348,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
try_validation!(
self.ecx.get_ptr_vtable_ty(vtable, Some(data)),
self.path,
Ub(DanglingIntPointer(..) | InvalidVTablePointer(..)) =>
Ub(DanglingIntPointer{ .. } | InvalidVTablePointer(..)) =>
InvalidVTablePtr { value: format!("{vtable}") },
Ub(InvalidVTableTrait { expected_trait, vtable_trait }) => {
InvalidMetaWrongTrait { expected_trait, vtable_trait: *vtable_trait }
@ -405,8 +405,8 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
),
self.path,
Ub(DanglingIntPointer(0, _)) => NullPtr { ptr_kind },
Ub(DanglingIntPointer(i, _)) => DanglingPtrNoProvenance {
Ub(DanglingIntPointer { addr: 0, .. }) => NullPtr { ptr_kind },
Ub(DanglingIntPointer { addr: i, .. }) => DanglingPtrNoProvenance {
ptr_kind,
// FIXME this says "null pointer" when null but we need translate
pointer: format!("{}", Pointer::<Option<AllocId>>::from_addr_invalid(*i))
@ -605,7 +605,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
let _fn = try_validation!(
self.ecx.get_ptr_fn(ptr),
self.path,
Ub(DanglingIntPointer(..) | InvalidFunctionPointer(..)) =>
Ub(DanglingIntPointer{ .. } | InvalidFunctionPointer(..)) =>
InvalidFnPtr { value: format!("{ptr}") },
);
// FIXME: Check if the signature matches