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warn less about non-exhaustive in ffi

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Bindgen allows generating `#[non_exhaustive] #[repr(u32)]` enums.
This results in nonintuitive nonlocal `improper_ctypes` warnings,
even when the types are otherwise perfectly valid in C.

Adjust for actual tooling expectations by avoiding warning on
simple enums with only unit variants.
This commit is contained in:
Jubilee Young 2023-10-16 23:56:22 -07:00
parent 749f80ab05
commit e9cf280ef2
4 changed files with 43 additions and 15 deletions
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27
compiler/rustc_lint/src/types.rs
View File

@ -3,6 +3,7 @@ use std::ops::ControlFlow;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::DiagMessage;
use rustc_hir::def::CtorKind;
use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
use rustc_middle::bug;
use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
@ -1386,15 +1387,6 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
// Empty enums are okay... although sort of useless.
return FfiSafe;
}
if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
return FfiUnsafe {
ty,
reason: fluent::lint_improper_ctypes_non_exhaustive,
help: None,
};
}
// Check for a repr() attribute to specify the size of the
// discriminant.
if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
@ -1413,8 +1405,25 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
};
}
// non_exhaustive suggests it is possible that someone might break ABI
// see: https://github.com/rust-lang/rust/issues/44109#issuecomment-537583344
// so warn on complex enums being used outside their crate
let nonexhaustive_nonlocal_ffi =
def.is_variant_list_non_exhaustive() && !def.did().is_local();
// Check the contained variants.
for variant in def.variants() {
// but only warn about really_tagged_union reprs,
// exempt enums with unit ctors like C's (like rust-bindgen)
if nonexhaustive_nonlocal_ffi
&& !matches!(variant.ctor_kind(), Some(CtorKind::Const))
{
return FfiUnsafe {
ty,
reason: fluent::lint_improper_ctypes_non_exhaustive,
help: None,
};
};
let is_non_exhaustive = variant.is_field_list_non_exhaustive();
if is_non_exhaustive && !variant.def_id.is_local() {
return FfiUnsafe {

11
tests/ui/rfcs/rfc-2008-non-exhaustive/improper_ctypes/auxiliary/types.rs
View File

@ -27,3 +27,14 @@ pub enum NonExhaustiveVariants {
#[non_exhaustive] Tuple(u32),
#[non_exhaustive] Struct { field: u32 }
}
// Note the absence of repr(C): it's not necessary, and recent C code can now use repr hints too.
#[repr(u32)]
#[non_exhaustive]
pub enum NonExhaustiveCLikeEnum {
One = 1,
Two = 2,
Three = 3,
Four = 4,
Five = 5,
}

10
tests/ui/rfcs/rfc-2008-non-exhaustive/improper_ctypes/extern_crate_improper.rs
View File

@ -6,7 +6,10 @@ extern crate types;
// This test checks that non-exhaustive types with `#[repr(C)]` from an extern crate are considered
// improper.
use types::{NonExhaustiveEnum, NonExhaustiveVariants, NormalStruct, TupleStruct, UnitStruct};
use types::{
NonExhaustiveCLikeEnum, NonExhaustiveEnum, NonExhaustiveVariants,
NormalStruct, TupleStruct, UnitStruct,
};
extern "C" {
pub fn non_exhaustive_enum(_: NonExhaustiveEnum);
@ -21,4 +24,9 @@ extern "C" {
//~^ ERROR `extern` block uses type `NonExhaustiveVariants`, which is not FFI-safe
}
// These should pass without remark, as they're C-compatible, despite being "non-exhaustive".
extern "C" {
pub fn non_exhaustive_c_compat_enum(_: NonExhaustiveCLikeEnum);
}
fn main() {}

10
tests/ui/rfcs/rfc-2008-non-exhaustive/improper_ctypes/extern_crate_improper.stderr
View File

@ -1,5 +1,5 @@
error: `extern` block uses type `NonExhaustiveEnum`, which is not FFI-safe
--> $DIR/extern_crate_improper.rs:12:35
--> $DIR/extern_crate_improper.rs:15:35
|
LL | pub fn non_exhaustive_enum(_: NonExhaustiveEnum);
| ^^^^^^^^^^^^^^^^^ not FFI-safe
@ -12,7 +12,7 @@ LL | #![deny(improper_ctypes)]
| ^^^^^^^^^^^^^^^
error: `extern` block uses type `NormalStruct`, which is not FFI-safe
--> $DIR/extern_crate_improper.rs:14:44
--> $DIR/extern_crate_improper.rs:17:44
|
LL | pub fn non_exhaustive_normal_struct(_: NormalStruct);
| ^^^^^^^^^^^^ not FFI-safe
@ -20,7 +20,7 @@ LL | pub fn non_exhaustive_normal_struct(_: NormalStruct);
= note: this struct is non-exhaustive
error: `extern` block uses type `UnitStruct`, which is not FFI-safe
--> $DIR/extern_crate_improper.rs:16:42
--> $DIR/extern_crate_improper.rs:19:42
|
LL | pub fn non_exhaustive_unit_struct(_: UnitStruct);
| ^^^^^^^^^^ not FFI-safe
@ -28,7 +28,7 @@ LL | pub fn non_exhaustive_unit_struct(_: UnitStruct);
= note: this struct is non-exhaustive
error: `extern` block uses type `TupleStruct`, which is not FFI-safe
--> $DIR/extern_crate_improper.rs:18:43
--> $DIR/extern_crate_improper.rs:21:43
|
LL | pub fn non_exhaustive_tuple_struct(_: TupleStruct);
| ^^^^^^^^^^^ not FFI-safe
@ -36,7 +36,7 @@ LL | pub fn non_exhaustive_tuple_struct(_: TupleStruct);
= note: this struct is non-exhaustive
error: `extern` block uses type `NonExhaustiveVariants`, which is not FFI-safe
--> $DIR/extern_crate_improper.rs:20:38
--> $DIR/extern_crate_improper.rs:23:38
|
LL | pub fn non_exhaustive_variant(_: NonExhaustiveVariants);
| ^^^^^^^^^^^^^^^^^^^^^ not FFI-safe