diff options
4 files changed, 74 insertions, 8 deletions
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs index 2e51753ede6..7ae8b027e3e 100644 --- a/compiler/rustc_abi/src/lib.rs +++ b/compiler/rustc_abi/src/lib.rs @@ -1215,6 +1215,15 @@ impl Scalar { Scalar::Union { .. } => true, } } + + /// Returns `true` if this is a signed integer scalar + #[inline] + pub fn is_signed(&self) -> bool { + match self.primitive() { + Primitive::Int(_, signed) => signed, + _ => false, + } + } } // NOTE: This struct is generic over the FieldIdx for rust-analyzer usage. @@ -1401,10 +1410,7 @@ impl BackendRepr { #[inline] pub fn is_signed(&self) -> bool { match self { - BackendRepr::Scalar(scal) => match scal.primitive() { - Primitive::Int(_, signed) => signed, - _ => false, - }, + BackendRepr::Scalar(scal) => scal.is_signed(), _ => panic!("`is_signed` on non-scalar ABI {self:?}"), } } @@ -1528,14 +1534,22 @@ pub enum TagEncoding<VariantIdx: Idx> { /// The variant `untagged_variant` contains a niche at an arbitrary /// offset (field `tag_field` of the enum), which for a variant with /// discriminant `d` is set to - /// `(d - niche_variants.start).wrapping_add(niche_start)`. + /// `(d - niche_variants.start).wrapping_add(niche_start)` + /// (this is wrapping arithmetic using the type of the niche field). /// /// For example, `Option<(usize, &T)>` is represented such that /// `None` has a null pointer for the second tuple field, and /// `Some` is the identity function (with a non-null reference). + /// + /// Other variants that are not `untagged_variant` and that are outside the `niche_variants` + /// range cannot be represented; they must be uninhabited. Niche { untagged_variant: VariantIdx, + /// This range *may* contain `untagged_variant`; that is then just a "dead value" and + /// not used to encode anything. niche_variants: RangeInclusive<VariantIdx>, + /// This is inbounds of the type of the niche field + /// (not sign-extended, i.e., all bits beyond the niche field size are 0). niche_start: u128, }, } diff --git a/compiler/rustc_ty_utils/src/layout/invariant.rs b/compiler/rustc_ty_utils/src/layout/invariant.rs index 26ea81daf78..f39b87622f4 100644 --- a/compiler/rustc_ty_utils/src/layout/invariant.rs +++ b/compiler/rustc_ty_utils/src/layout/invariant.rs @@ -1,11 +1,11 @@ use std::assert_matches::assert_matches; -use rustc_abi::{BackendRepr, FieldsShape, Scalar, Size, Variants}; +use rustc_abi::{BackendRepr, FieldsShape, Scalar, Size, TagEncoding, Variants}; use rustc_middle::bug; use rustc_middle::ty::layout::{HasTyCtxt, LayoutCx, TyAndLayout}; /// Enforce some basic invariants on layouts. -pub(super) fn partially_check_layout<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLayout<'tcx>) { +pub(super) fn layout_sanity_check<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLayout<'tcx>) { let tcx = cx.tcx(); // Type-level uninhabitedness should always imply ABI uninhabitedness. @@ -241,7 +241,17 @@ pub(super) fn partially_check_layout<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLa check_layout_abi(cx, layout); - if let Variants::Multiple { variants, .. } = &layout.variants { + if let Variants::Multiple { variants, tag, tag_encoding, .. } = &layout.variants { + if let TagEncoding::Niche { niche_start, untagged_variant, niche_variants } = tag_encoding { + let niche_size = tag.size(cx); + assert!(*niche_start <= niche_size.unsigned_int_max()); + for (idx, variant) in variants.iter_enumerated() { + // Ensure all inhabited variants are accounted for. + if !variant.is_uninhabited() { + assert!(idx == *untagged_variant || niche_variants.contains(&idx)); + } + } + } for variant in variants.iter() { // No nested "multiple". assert_matches!(variant.variants, Variants::Single { .. }); diff --git a/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.rs b/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.rs new file mode 100644 index 00000000000..bd02e7f5fb4 --- /dev/null +++ b/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.rs @@ -0,0 +1,27 @@ +// Validity makes this fail at the wrong place. +//@compile-flags: -Zmiri-disable-validation +use std::mem; + +// This enum has untagged variant idx 1, with niche_variants being 0..=2 +// and niche_start being 2. +// That means the untagged variants is in the niche variant range! +// However, using the corresponding value (2+1 = 3) is not a valid encoding of this variant. +#[derive(Copy, Clone, PartialEq)] +enum Foo { + Var1, + Var2(bool), + Var3, +} + +fn main() { + unsafe { + assert!(Foo::Var2(false) == mem::transmute(0u8)); + assert!(Foo::Var2(true) == mem::transmute(1u8)); + assert!(Foo::Var1 == mem::transmute(2u8)); + assert!(Foo::Var3 == mem::transmute(4u8)); + + let invalid: Foo = mem::transmute(3u8); + assert!(matches!(invalid, Foo::Var2(_))); + //~^ ERROR: invalid tag + } +} diff --git a/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.stderr b/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.stderr new file mode 100644 index 00000000000..759dbc36380 --- /dev/null +++ b/src/tools/miri/tests/fail/enum-untagged-variant-invalid-encoding.stderr @@ -0,0 +1,15 @@ +error: Undefined Behavior: enum value has invalid tag: 0x03 + --> tests/fail/enum-untagged-variant-invalid-encoding.rs:LL:CC + | +LL | assert!(matches!(invalid, Foo::Var2(_))); + | ^^^^^^^ enum value has invalid tag: 0x03 + | + = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior + = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information + = note: BACKTRACE: + = note: inside `main` at tests/fail/enum-untagged-variant-invalid-encoding.rs:LL:CC + +note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace + +error: aborting due to 1 previous error + |