diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0804.md | 41 | ||||
| -rw-r--r-- | compiler/rustc_error_codes/src/lib.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_hir_typeck/messages.ftl | 9 | ||||
| -rw-r--r-- | compiler/rustc_hir_typeck/src/cast.rs | 28 | ||||
| -rw-r--r-- | compiler/rustc_hir_typeck/src/errors.rs | 9 | ||||
| -rw-r--r-- | compiler/rustc_lint/src/lib.rs | 5 | ||||
| -rw-r--r-- | compiler/rustc_lint_defs/src/builtin.rs | 53 |
7 files changed, 72 insertions, 74 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0804.md b/compiler/rustc_error_codes/src/error_codes/E0804.md new file mode 100644 index 00000000000..9a6937c0b52 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0804.md @@ -0,0 +1,41 @@ +An auto trait cannot be added to the bounds of a `dyn Trait` type via +a pointer cast. + +Erroneous code example: + +```rust,edition2021,compile_fail,E0804 +let ptr: *const dyn core::any::Any = &(); +_ = ptr as *const (dyn core::any::Any + Send); +``` + +Adding an auto trait can make the vtable invalid, potentially causing +UB in safe code afterwards. For example: + +```rust,edition2021,no_run +use core::{mem::transmute, ptr::NonNull}; + +trait Trait { + fn f(&self) + where + Self: Send; +} + +impl Trait for NonNull<()> { + fn f(&self) { + unreachable!() + } +} + +fn main() { + let unsend: &dyn Trait = &NonNull::dangling(); + let bad: &(dyn Trait + Send) = unsafe { transmute(unsend) }; + // This crashes, since the vtable for `NonNull as dyn Trait` does + // not have an entry for `Trait::f`. + bad.f(); +} +``` + +To fix this error, you can use `transmute` rather than pointer casts, +but you must ensure that the vtable is valid for the pointer's type +before calling a method on the trait object or allowing other code to +do so. diff --git a/compiler/rustc_error_codes/src/lib.rs b/compiler/rustc_error_codes/src/lib.rs index 098ca42be2b..d53d5678832 100644 --- a/compiler/rustc_error_codes/src/lib.rs +++ b/compiler/rustc_error_codes/src/lib.rs @@ -547,6 +547,7 @@ E0800: 0800, E0801: 0801, E0802: 0802, E0803: 0803, +E0804: 0804, ); ) } diff --git a/compiler/rustc_hir_typeck/messages.ftl b/compiler/rustc_hir_typeck/messages.ftl index ed80bc3e7be..872861d6289 100644 --- a/compiler/rustc_hir_typeck/messages.ftl +++ b/compiler/rustc_hir_typeck/messages.ftl @@ -171,10 +171,13 @@ hir_typeck_pass_to_variadic_function = can't pass `{$ty}` to variadic function .suggestion = cast the value to `{$cast_ty}` .teach_help = certain types, like `{$ty}`, must be casted before passing them to a variadic function, because of arcane ABI rules dictated by the C standard -hir_typeck_ptr_cast_add_auto_to_object = adding {$traits_len -> - [1] an auto trait {$traits} +hir_typeck_ptr_cast_add_auto_to_object = cannot add {$traits_len -> + [1] auto trait {$traits} *[other] auto traits {$traits} -} to a trait object in a pointer cast may cause UB later on +} to dyn bound via pointer cast + .note = this could allow UB elsewhere + .help = use `transmute` if you're sure this is sound + .label = unsupported cast hir_typeck_remove_semi_for_coerce = you might have meant to return the `match` expression hir_typeck_remove_semi_for_coerce_expr = this could be implicitly returned but it is a statement, not a tail expression diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs index ea4ec345ad0..70b49fea34f 100644 --- a/compiler/rustc_hir_typeck/src/cast.rs +++ b/compiler/rustc_hir_typeck/src/cast.rs @@ -940,23 +940,19 @@ impl<'a, 'tcx> CastCheck<'tcx> { .collect::<Vec<_>>(); if !added.is_empty() { - tcx.emit_node_span_lint( - lint::builtin::PTR_CAST_ADD_AUTO_TO_OBJECT, - self.expr.hir_id, - self.span, - errors::PtrCastAddAutoToObject { - traits_len: added.len(), - traits: { - let mut traits: Vec<_> = added - .into_iter() - .map(|trait_did| tcx.def_path_str(trait_did)) - .collect(); - - traits.sort(); - traits.into() - }, + tcx.dcx().emit_err(errors::PtrCastAddAutoToObject { + span: self.span, + traits_len: added.len(), + traits: { + let mut traits: Vec<_> = added + .into_iter() + .map(|trait_did| tcx.def_path_str(trait_did)) + .collect(); + + traits.sort(); + traits.into() }, - ) + }); } Ok(CastKind::PtrPtrCast) diff --git a/compiler/rustc_hir_typeck/src/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs index 20688a5b949..b73cd26927a 100644 --- a/compiler/rustc_hir_typeck/src/errors.rs +++ b/compiler/rustc_hir_typeck/src/errors.rs @@ -373,9 +373,14 @@ pub(crate) struct LossyProvenanceInt2Ptr<'tcx> { pub sugg: LossyProvenanceInt2PtrSuggestion, } -#[derive(LintDiagnostic)] -#[diag(hir_typeck_ptr_cast_add_auto_to_object)] +#[derive(Diagnostic)] +#[diag(hir_typeck_ptr_cast_add_auto_to_object, code = E0804)] +#[note] +#[help] pub(crate) struct PtrCastAddAutoToObject { + #[primary_span] + #[label] + pub span: Span, pub traits_len: usize, pub traits: DiagSymbolList<String>, } diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs index 5c5b3b350dd..7018774e5c6 100644 --- a/compiler/rustc_lint/src/lib.rs +++ b/compiler/rustc_lint/src/lib.rs @@ -599,6 +599,11 @@ fn register_builtins(store: &mut LintStore) { "converted into hard error, \ see <https://github.com/rust-lang/rust/issues/73333> for more information", ); + store.register_removed( + "ptr_cast_add_auto_to_object", + "converted into hard error, see issue #127323 \ + <https://github.com/rust-lang/rust/issues/127323> for more information", + ); } fn register_internals(store: &mut LintStore) { diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs index 3d63ea82053..10b85be2cfb 100644 --- a/compiler/rustc_lint_defs/src/builtin.rs +++ b/compiler/rustc_lint_defs/src/builtin.rs @@ -80,7 +80,6 @@ declare_lint_pass! { PRIVATE_BOUNDS, PRIVATE_INTERFACES, PROC_MACRO_DERIVE_RESOLUTION_FALLBACK, - PTR_CAST_ADD_AUTO_TO_OBJECT, PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE, REDUNDANT_IMPORTS, @@ -4828,58 +4827,6 @@ declare_lint! { } declare_lint! { - /// The `ptr_cast_add_auto_to_object` lint detects casts of raw pointers to trait - /// objects, which add auto traits. - /// - /// ### Example - /// - /// ```rust,edition2021,compile_fail - /// let ptr: *const dyn core::any::Any = &(); - /// _ = ptr as *const dyn core::any::Any + Send; - /// ``` - /// - /// {{produces}} - /// - /// ### Explanation - /// - /// Adding an auto trait can make the vtable invalid, potentially causing - /// UB in safe code afterwards. For example: - /// - /// ```ignore (causes a warning) - /// #![feature(arbitrary_self_types)] - /// - /// trait Trait { - /// fn f(self: *const Self) - /// where - /// Self: Send; - /// } - /// - /// impl Trait for *const () { - /// fn f(self: *const Self) { - /// unreachable!() - /// } - /// } - /// - /// fn main() { - /// let unsend: *const () = &(); - /// let unsend: *const dyn Trait = &unsend; - /// let send_bad: *const (dyn Trait + Send) = unsend as _; - /// send_bad.f(); // this crashes, since vtable for `*const ()` does not have an entry for `f` - /// } - /// ``` - /// - /// Generally you must ensure that vtable is right for the pointer's type, - /// before passing the pointer to safe code. - pub PTR_CAST_ADD_AUTO_TO_OBJECT, - Warn, - "detects `as` casts from pointers to `dyn Trait` to pointers to `dyn Trait + Auto`", - @future_incompatible = FutureIncompatibleInfo { - reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps, - reference: "issue #127323 <https://github.com/rust-lang/rust/issues/127323>", - }; -} - -declare_lint! { /// The `out_of_scope_macro_calls` lint detects `macro_rules` called when they are not in scope, /// above their definition, which may happen in key-value attributes. /// |