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Rollup merge of #136193 - oli-obk:pattern-type-ffi-checks, r=chenyukang

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Implement pattern type ffi checks

Previously we just rejected pattern types outright in FFI, but that was never meant to be a permanent situation. We'll need them supported to use them as the building block for `NonZero` and `NonNull` after all (both of which are FFI safe).

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Matthias Krüger 2025-02-12 06:07:37 +01:00 • committed by GitHub
commit 2f3f83a4a3
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8 changed files with 180 additions and 90 deletions
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3
compiler/rustc_lint/messages.ftl
View file

@ -390,9 +390,6 @@ lint_improper_ctypes_only_phantomdata = composed only of `PhantomData`
lint_improper_ctypes_opaque = opaque types have no C equivalent
lint_improper_ctypes_pat_help = consider using the base type instead
lint_improper_ctypes_pat_reason = pattern types have no C equivalent
lint_improper_ctypes_slice_help = consider using a raw pointer instead
lint_improper_ctypes_slice_reason = slices have no C equivalent

9
compiler/rustc_lint/src/foreign_modules.rs
View file

@ -241,10 +241,7 @@ fn structurally_same_type_impl<'tcx>(
if let ty::Adt(def, args) = *ty.kind() {
let is_transparent = def.repr().transparent();
let is_non_null = types::nonnull_optimization_guaranteed(tcx, def);
debug!(
"non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
ty, is_transparent, is_non_null
);
debug!(?ty, is_transparent, is_non_null);
if is_transparent && !is_non_null {
debug_assert_eq!(def.variants().len(), 1);
let v = &def.variant(FIRST_VARIANT);
@ -378,14 +375,14 @@ fn structurally_same_type_impl<'tcx>(
// An Adt and a primitive or pointer type. This can be FFI-safe if non-null
// enum layout optimisation is being applied.
(Adt(..), _) if is_primitive_or_pointer(b) => {
(Adt(..) | Pat(..), _) if is_primitive_or_pointer(b) => {
if let Some(a_inner) = types::repr_nullable_ptr(tcx, typing_env, a, ckind) {
a_inner == b
} else {
false
}
}
(_, Adt(..)) if is_primitive_or_pointer(a) => {
(_, Adt(..) | Pat(..)) if is_primitive_or_pointer(a) => {
if let Some(b_inner) = types::repr_nullable_ptr(tcx, typing_env, b, ckind) {
b_inner == a
} else {

1
compiler/rustc_lint/src/lib.rs
View file

@ -33,6 +33,7 @@
#![feature(let_chains)]
#![feature(rustc_attrs)]
#![feature(rustdoc_internals)]
#![feature(try_blocks)]
#![warn(unreachable_pub)]
// tidy-alphabetical-end

152
compiler/rustc_lint/src/types.rs
View file

@ -877,6 +877,37 @@ fn ty_is_known_nonnull<'tcx>(
.filter_map(|variant| transparent_newtype_field(tcx, variant))
.any(|field| ty_is_known_nonnull(tcx, typing_env, field.ty(tcx, args), mode))
}
ty::Pat(base, pat) => {
ty_is_known_nonnull(tcx, typing_env, *base, mode)
|| Option::unwrap_or_default(
try {
match **pat {
ty::PatternKind::Range { start, end, include_end } => {
match (start, end) {
(Some(start), None) => {
start.try_to_value()?.try_to_bits(tcx, typing_env)? > 0
}
(Some(start), Some(end)) => {
let start =
start.try_to_value()?.try_to_bits(tcx, typing_env)?;
let end =
end.try_to_value()?.try_to_bits(tcx, typing_env)?;
if include_end {
// This also works for negative numbers, as we just need
// to ensure we aren't wrapping over zero.
start > 0 && end >= start
} else {
start > 0 && end > start
}
}
_ => false,
}
}
}
},
)
}
_ => false,
}
}
@ -907,9 +938,8 @@ fn get_nullable_type<'tcx>(
};
return get_nullable_type(tcx, typing_env, inner_field_ty);
}
ty::Int(ty) => Ty::new_int(tcx, ty),
ty::Uint(ty) => Ty::new_uint(tcx, ty),
ty::RawPtr(ty, mutbl) => Ty::new_ptr(tcx, ty, mutbl),
ty::Pat(base, ..) => return get_nullable_type(tcx, typing_env, base),
ty::Int(_) | ty::Uint(_) | ty::RawPtr(..) => ty,
// As these types are always non-null, the nullable equivalent of
// `Option<T>` of these types are their raw pointer counterparts.
ty::Ref(_region, ty, mutbl) => Ty::new_ptr(tcx, ty, mutbl),
@ -965,63 +995,69 @@ pub(crate) fn repr_nullable_ptr<'tcx>(
ckind: CItemKind,
) -> Option<Ty<'tcx>> {
debug!("is_repr_nullable_ptr(tcx, ty = {:?})", ty);
if let ty::Adt(ty_def, args) = ty.kind() {
let field_ty = match &ty_def.variants().raw[..] {
[var_one, var_two] => match (&var_one.fields.raw[..], &var_two.fields.raw[..]) {
([], [field]) | ([field], []) => field.ty(tcx, args),
([field1], [field2]) => {
let ty1 = field1.ty(tcx, args);
let ty2 = field2.ty(tcx, args);
match ty.kind() {
ty::Adt(ty_def, args) => {
let field_ty = match &ty_def.variants().raw[..] {
[var_one, var_two] => match (&var_one.fields.raw[..], &var_two.fields.raw[..]) {
([], [field]) | ([field], []) => field.ty(tcx, args),
([field1], [field2]) => {
let ty1 = field1.ty(tcx, args);
let ty2 = field2.ty(tcx, args);
if is_niche_optimization_candidate(tcx, typing_env, ty1) {
ty2
} else if is_niche_optimization_candidate(tcx, typing_env, ty2) {
ty1
} else {
return None;
if is_niche_optimization_candidate(tcx, typing_env, ty1) {
ty2
} else if is_niche_optimization_candidate(tcx, typing_env, ty2) {
ty1
} else {
return None;
}
}
}
_ => return None,
},
_ => return None,
},
_ => return None,
};
if !ty_is_known_nonnull(tcx, typing_env, field_ty, ckind) {
return None;
}
// At this point, the field's type is known to be nonnull and the parent enum is Option-like.
// If the computed size for the field and the enum are different, the nonnull optimization isn't
// being applied (and we've got a problem somewhere).
let compute_size_skeleton = |t| SizeSkeleton::compute(t, tcx, typing_env).ok();
if !compute_size_skeleton(ty)?.same_size(compute_size_skeleton(field_ty)?) {
bug!("improper_ctypes: Option nonnull optimization not applied?");
}
// Return the nullable type this Option-like enum can be safely represented with.
let field_ty_layout = tcx.layout_of(typing_env.as_query_input(field_ty));
if field_ty_layout.is_err() && !field_ty.has_non_region_param() {
bug!("should be able to compute the layout of non-polymorphic type");
}
let field_ty_abi = &field_ty_layout.ok()?.backend_repr;
if let BackendRepr::Scalar(field_ty_scalar) = field_ty_abi {
match field_ty_scalar.valid_range(&tcx) {
WrappingRange { start: 0, end }
if end == field_ty_scalar.size(&tcx).unsigned_int_max() - 1 =>
{
return Some(get_nullable_type(tcx, typing_env, field_ty).unwrap());
}
WrappingRange { start: 1, .. } => {
return Some(get_nullable_type(tcx, typing_env, field_ty).unwrap());
}
WrappingRange { start, end } => {
unreachable!("Unhandled start and end range: ({}, {})", start, end)
}
};
if !ty_is_known_nonnull(tcx, typing_env, field_ty, ckind) {
return None;
}
// At this point, the field's type is known to be nonnull and the parent enum is Option-like.
// If the computed size for the field and the enum are different, the nonnull optimization isn't
// being applied (and we've got a problem somewhere).
let compute_size_skeleton = |t| SizeSkeleton::compute(t, tcx, typing_env).ok();
if !compute_size_skeleton(ty)?.same_size(compute_size_skeleton(field_ty)?) {
bug!("improper_ctypes: Option nonnull optimization not applied?");
}
// Return the nullable type this Option-like enum can be safely represented with.
let field_ty_layout = tcx.layout_of(typing_env.as_query_input(field_ty));
if field_ty_layout.is_err() && !field_ty.has_non_region_param() {
bug!("should be able to compute the layout of non-polymorphic type");
}
let field_ty_abi = &field_ty_layout.ok()?.backend_repr;
if let BackendRepr::Scalar(field_ty_scalar) = field_ty_abi {
match field_ty_scalar.valid_range(&tcx) {
WrappingRange { start: 0, end }
if end == field_ty_scalar.size(&tcx).unsigned_int_max() - 1 =>
{
return Some(get_nullable_type(tcx, typing_env, field_ty).unwrap());
}
WrappingRange { start: 1, .. } => {
return Some(get_nullable_type(tcx, typing_env, field_ty).unwrap());
}
WrappingRange { start, end } => {
unreachable!("Unhandled start and end range: ({}, {})", start, end)
}
};
}
None
}
ty::Pat(base, pat) => match **pat {
ty::PatternKind::Range { .. } => get_nullable_type(tcx, typing_env, *base),
},
_ => None,
}
None
}
impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
@ -1256,11 +1292,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
help: Some(fluent::lint_improper_ctypes_char_help),
},
ty::Pat(..) => FfiUnsafe {
ty,
reason: fluent::lint_improper_ctypes_pat_reason,
help: Some(fluent::lint_improper_ctypes_pat_help),
},
// It's just extra invariants on the type that you need to uphold,
// but only the base type is relevant for being representable in FFI.
ty::Pat(base, ..) => self.check_type_for_ffi(acc, base),
ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_128bit, help: None }