diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs index 84c6dad1cd3..e2e39399f3a 100644 --- a/compiler/rustc_const_eval/src/interpret/memory.rs +++ b/compiler/rustc_const_eval/src/interpret/memory.rs @@ -884,9 +884,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { throw_ub!(InvalidVTablePointer(Pointer::new(alloc_id, offset))) }; if let Some(expected_trait) = expected_trait { - if vtable_trait != expected_trait.principal() { - throw_ub!(InvalidVTableTrait { expected_trait, vtable_trait }); - } + self.check_vtable_for_type(vtable_trait, expected_trait)?; } Ok(ty) } diff --git a/compiler/rustc_const_eval/src/interpret/traits.rs b/compiler/rustc_const_eval/src/interpret/traits.rs index 44e7244a513..bd2c6519421 100644 --- a/compiler/rustc_const_eval/src/interpret/traits.rs +++ b/compiler/rustc_const_eval/src/interpret/traits.rs @@ -1,11 +1,14 @@ +use rustc_infer::infer::TyCtxtInferExt; +use rustc_infer::traits::ObligationCause; use rustc_middle::mir::interpret::{InterpResult, Pointer}; use rustc_middle::ty::layout::LayoutOf; use rustc_middle::ty::{self, Ty}; use rustc_target::abi::{Align, Size}; +use rustc_trait_selection::traits::ObligationCtxt; use tracing::trace; use super::util::ensure_monomorphic_enough; -use super::{InterpCx, MPlaceTy, Machine, MemPlaceMeta, OffsetMode, Projectable}; +use super::{throw_ub, InterpCx, MPlaceTy, Machine, MemPlaceMeta, OffsetMode, Projectable}; impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { /// Creates a dynamic vtable for the given type and vtable origin. This is used only for @@ -44,6 +47,37 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { Ok((layout.size, layout.align.abi)) } + /// Check that the given vtable trait is valid for a pointer/reference/place with the given + /// expected trait type. + pub(super) fn check_vtable_for_type( + &self, + vtable_trait: Option>, + expected_trait: &'tcx ty::List>, + ) -> InterpResult<'tcx> { + // Fast path: if they are equal, it's all fine. + if expected_trait.principal() == vtable_trait { + return Ok(()); + } + if let (Some(expected_trait), Some(vtable_trait)) = + (expected_trait.principal(), vtable_trait) + { + // Slow path: spin up an inference context to check if these traits are sufficiently equal. + let infcx = self.tcx.infer_ctxt().build(); + let ocx = ObligationCtxt::new(&infcx); + let cause = ObligationCause::dummy_with_span(self.cur_span()); + // equate the two trait refs after normalization + let expected_trait = ocx.normalize(&cause, self.param_env, expected_trait); + let vtable_trait = ocx.normalize(&cause, self.param_env, vtable_trait); + if ocx.eq(&cause, self.param_env, expected_trait, vtable_trait).is_ok() { + if ocx.select_all_or_error().is_empty() { + // All good. + return Ok(()); + } + } + } + throw_ub!(InvalidVTableTrait { expected_trait, vtable_trait }); + } + /// Turn a place with a `dyn Trait` type into a place with the actual dynamic type. pub(super) fn unpack_dyn_trait( &self, diff --git a/src/tools/miri/tests/pass/issues/issue-miri-3541-dyn-vtable-trait-normalization.rs b/src/tools/miri/tests/pass/issues/issue-miri-3541-dyn-vtable-trait-normalization.rs new file mode 100644 index 00000000000..c46031de2d8 --- /dev/null +++ b/src/tools/miri/tests/pass/issues/issue-miri-3541-dyn-vtable-trait-normalization.rs @@ -0,0 +1,40 @@ +#![feature(ptr_metadata)] +// This test is the result of minimizing the `emplacable` crate to reproduce +// . + +use std::{ops::FnMut, ptr::Pointee}; + +pub type EmplacerFn<'a, T> = dyn for<'b> FnMut(::Metadata) + 'a; + +#[repr(transparent)] +pub struct Emplacer<'a, T>(EmplacerFn<'a, T>) +where + T: ?Sized; + +impl<'a, T> Emplacer<'a, T> +where + T: ?Sized, +{ + pub unsafe fn from_fn<'b>(emplacer_fn: &'b mut EmplacerFn<'a, T>) -> &'b mut Self { + // This used to trigger: + // constructing invalid value: wrong trait in wide pointer vtable: expected + // `std::ops::FnMut(<[std::boxed::Box] as std::ptr::Pointee>::Metadata)`, but encountered + // `std::ops::FnMut<(usize,)>`. + unsafe { &mut *((emplacer_fn as *mut EmplacerFn<'a, T>) as *mut Self) } + } +} + +pub fn box_new_with() +where + T: ?Sized, +{ + let emplacer_closure = &mut |_meta| { + unreachable!(); + }; + + unsafe { Emplacer::::from_fn(emplacer_closure) }; +} + +fn main() { + box_new_with::<[Box]>(); +}