diff options
| -rw-r--r-- | compiler/rustc_lint/messages.ftl | 2 | ||||
| -rw-r--r-- | compiler/rustc_lint/src/types.rs | 47 | ||||
| -rw-r--r-- | tests/ui/repr/repr-transparent-issue-87496.rs | 2 | ||||
| -rw-r--r-- | tests/ui/repr/repr-transparent-issue-87496.stderr | 10 |
4 files changed, 26 insertions, 35 deletions
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl index 2c92277b50d..252177932e4 100644 --- a/compiler/rustc_lint/messages.ftl +++ b/compiler/rustc_lint/messages.ftl @@ -267,8 +267,6 @@ lint_improper_ctypes_char_help = consider using `u32` or `libc::wchar_t` instead lint_improper_ctypes_char_reason = the `char` type has no C equivalent lint_improper_ctypes_dyn = trait objects have no C equivalent -lint_improper_ctypes_enum_phantomdata = this enum contains a PhantomData field - lint_improper_ctypes_enum_repr_help = consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs index bb847578e90..7fef88a5391 100644 --- a/compiler/rustc_lint/src/types.rs +++ b/compiler/rustc_lint/src/types.rs @@ -1009,39 +1009,36 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> { ) -> FfiResult<'tcx> { use FfiResult::*; - let transparent_safety = def.repr().transparent().then(|| { - // Can assume that at most one field is not a ZST, so only check - // that field's type for FFI-safety. + let transparent_with_all_zst_fields = if def.repr().transparent() { + // Transparent newtypes have at most one non-ZST field which needs to be checked.. if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) { return self.check_field_type_for_ffi(cache, field, args); - } else { - // All fields are ZSTs; this means that the type should behave - // like (), which is FFI-unsafe... except if all fields are PhantomData, - // which is tested for below - FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None } } - }); - // We can't completely trust repr(C) markings; make sure the fields are - // actually safe. + + // ..or have only ZST fields, which is FFI-unsafe (unless those fields are all + // `PhantomData`). + true + } else { + false + }; + + // We can't completely trust `repr(C)` markings, so make sure the fields are actually safe. let mut all_phantom = !variant.fields.is_empty(); for field in &variant.fields { - match self.check_field_type_for_ffi(cache, &field, args) { - FfiSafe => { - all_phantom = false; - } - FfiPhantom(..) if !def.repr().transparent() && def.is_enum() => { - return FfiUnsafe { - ty, - reason: fluent::lint_improper_ctypes_enum_phantomdata, - help: None, - }; - } - FfiPhantom(..) => {} - r => return transparent_safety.unwrap_or(r), + all_phantom &= match self.check_field_type_for_ffi(cache, &field, args) { + FfiSafe => false, + FfiPhantom(..) => true, + r @ FfiUnsafe { .. } => return r, } } - if all_phantom { FfiPhantom(ty) } else { transparent_safety.unwrap_or(FfiSafe) } + if all_phantom { + FfiPhantom(ty) + } else if transparent_with_all_zst_fields { + FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None } + } else { + FfiSafe + } } /// Checks if the given type is "ffi-safe" (has a stable, well-defined diff --git a/tests/ui/repr/repr-transparent-issue-87496.rs b/tests/ui/repr/repr-transparent-issue-87496.rs index a4dd45c63f5..0ce6fb2c19f 100644 --- a/tests/ui/repr/repr-transparent-issue-87496.rs +++ b/tests/ui/repr/repr-transparent-issue-87496.rs @@ -6,7 +6,7 @@ struct TransparentCustomZst(()); extern "C" { fn good17(p: TransparentCustomZst); - //~^ WARNING: `extern` block uses type `TransparentCustomZst`, which is not FFI-safe + //~^ WARNING: `extern` block uses type `()`, which is not FFI-safe } fn main() {} diff --git a/tests/ui/repr/repr-transparent-issue-87496.stderr b/tests/ui/repr/repr-transparent-issue-87496.stderr index aee31212b4e..03c62f8514e 100644 --- a/tests/ui/repr/repr-transparent-issue-87496.stderr +++ b/tests/ui/repr/repr-transparent-issue-87496.stderr @@ -1,15 +1,11 @@ -warning: `extern` block uses type `TransparentCustomZst`, which is not FFI-safe +warning: `extern` block uses type `()`, which is not FFI-safe --> $DIR/repr-transparent-issue-87496.rs:8:18 | LL | fn good17(p: TransparentCustomZst); | ^^^^^^^^^^^^^^^^^^^^ not FFI-safe | - = note: this struct contains only zero-sized fields -note: the type is defined here - --> $DIR/repr-transparent-issue-87496.rs:6:1 - | -LL | struct TransparentCustomZst(()); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + = help: consider using a struct instead + = note: tuples have unspecified layout = note: `#[warn(improper_ctypes)]` on by default warning: 1 warning emitted |