This allows types like Option<NonZeroU8> to be used in FFI without triggering the improper_ctypes lint. This works by changing the is_repr_nullable_ptr function to consider an enum E to be FFI-safe if:
- E has no explicit #[repr(...)].
- It only has two variants.
- One of those variants is empty (meaning it has no fields).
- The other variant has only one field.
- That field is one of the following:
- &T
- &mut T
- extern "C" fn
- core::num::NonZero*
- core::ptr::NonNull<T>
- #[repr(transparent)] struct wrapper around one of the types in this list.
- The size of E and its field are both known and are both the same size (implying E is participating in the nonnull optimization).
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
#[repr(transparent)]
#[rustc_layout_scalar_valid_range_start(1)]
+ #[cfg_attr(not(stage0), rustc_nonnull_optimization_guaranteed)]
pub struct $Ty($Int);
}
#[stable(feature = "nonnull", since = "1.25.0")]
#[repr(transparent)]
#[rustc_layout_scalar_valid_range_start(1)]
+#[cfg_attr(not(stage0), rustc_nonnull_optimization_guaranteed)]
pub struct NonNull<T: ?Sized> {
pointer: *const T,
}
#![allow(non_snake_case)]
use rustc::hir::{ExprKind, Node};
+use crate::hir::def_id::DefId;
use rustc::hir::lowering::is_range_literal;
use rustc::ty::subst::SubstsRef;
use rustc::ty::{self, AdtKind, ParamEnv, Ty, TyCtxt};
-use rustc::ty::layout::{self, IntegerExt, LayoutOf, VariantIdx};
+use rustc::ty::layout::{self, IntegerExt, LayoutOf, VariantIdx, SizeSkeleton};
use rustc::{lint, util};
use rustc_data_structures::indexed_vec::Idx;
use util::nodemap::FxHashSet;
use std::cmp;
use std::{i8, i16, i32, i64, u8, u16, u32, u64, f32, f64};
-use syntax::{ast, attr};
+use syntax::{ast, attr, source_map};
use syntax::errors::Applicability;
+use syntax::symbol::sym;
use rustc_target::spec::abi::Abi;
use syntax_pos::Span;
-use syntax::source_map;
use rustc::hir;
},
}
+fn is_zst<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, did: DefId, ty: Ty<'tcx>) -> bool {
+ tcx.layout_of(tcx.param_env(did).and(ty)).map(|layout| layout.is_zst()).unwrap_or(false)
+}
+
+fn ty_is_known_nonnull<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> bool {
+ match ty.sty {
+ ty::FnPtr(_) => true,
+ ty::Ref(..) => true,
+ ty::Adt(field_def, substs) if field_def.repr.transparent() && field_def.is_struct() => {
+ for field in &field_def.non_enum_variant().fields {
+ let field_ty = tcx.normalize_erasing_regions(
+ ParamEnv::reveal_all(),
+ field.ty(tcx, substs),
+ );
+ if is_zst(tcx, field.did, field_ty) {
+ continue;
+ }
+
+ let attrs = tcx.get_attrs(field_def.did);
+ if attrs.iter().any(|a| a.check_name(sym::rustc_nonnull_optimization_guaranteed)) ||
+ ty_is_known_nonnull(tcx, field_ty) {
+ return true;
+ }
+ }
+
+ false
+ }
+ _ => false,
+ }
+}
+
/// Check if this enum can be safely exported based on the
/// "nullable pointer optimization". Currently restricted
-/// to function pointers and references, but could be
-/// expanded to cover NonZero raw pointers and newtypes.
+/// to function pointers, references, core::num::NonZero*,
+/// core::ptr::NonNull, and #[repr(transparent)] newtypes.
/// FIXME: This duplicates code in codegen.
fn is_repr_nullable_ptr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
- def: &'tcx ty::AdtDef,
+ ty: Ty<'tcx>,
+ ty_def: &'tcx ty::AdtDef,
substs: SubstsRef<'tcx>)
-> bool {
- if def.variants.len() == 2 {
- let data_idx;
+ if ty_def.variants.len() != 2 {
+ return false;
+ }
- let zero = VariantIdx::new(0);
- let one = VariantIdx::new(1);
+ let get_variant_fields = |index| &ty_def.variants[VariantIdx::new(index)].fields;
+ let variant_fields = [get_variant_fields(0), get_variant_fields(1)];
+ let fields = if variant_fields[0].is_empty() {
+ &variant_fields[1]
+ } else if variant_fields[1].is_empty() {
+ &variant_fields[0]
+ } else {
+ return false;
+ };
- if def.variants[zero].fields.is_empty() {
- data_idx = one;
- } else if def.variants[one].fields.is_empty() {
- data_idx = zero;
- } else {
- return false;
- }
+ if fields.len() != 1 {
+ return false;
+ }
- if def.variants[data_idx].fields.len() == 1 {
- match def.variants[data_idx].fields[0].ty(tcx, substs).sty {
- ty::FnPtr(_) => {
- return true;
- }
- ty::Ref(..) => {
- return true;
- }
- _ => {}
- }
- }
+ let field_ty = fields[0].ty(tcx, substs);
+ if !ty_is_known_nonnull(tcx, field_ty) {
+ return false;
}
- false
+
+ // 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, ParamEnv::reveal_all()).unwrap();
+ if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
+ bug!("improper_ctypes: Option nonnull optimization not applied?");
+ }
+
+ true
}
impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
);
// repr(transparent) types are allowed to have arbitrary ZSTs, not just
// PhantomData -- skip checking all ZST fields
- if def.repr.transparent() {
- let is_zst = cx
- .layout_of(cx.param_env(field.did).and(field_ty))
- .map(|layout| layout.is_zst())
- .unwrap_or(false);
- if is_zst {
- continue;
- }
+ if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
+ continue;
}
let r = self.check_type_for_ffi(cache, field_ty);
match r {
// discriminant.
if !def.repr.c() && def.repr.int.is_none() {
// Special-case types like `Option<extern fn()>`.
- if !is_repr_nullable_ptr(cx, def, substs) {
+ if !is_repr_nullable_ptr(cx, ty, def, substs) {
return FfiUnsafe {
ty: ty,
reason: "enum has no representation hint",
is just used to enable niche optimizations in libcore \
and will never be stable",
cfg_fn!(rustc_attrs))),
+ (sym::rustc_nonnull_optimization_guaranteed, Whitelisted, template!(Word),
+ Gated(Stability::Unstable,
+ sym::rustc_attrs,
+ "the `#[rustc_nonnull_optimization_guaranteed]` attribute \
+ is just used to enable niche optimizations in libcore \
+ and will never be stable",
+ cfg_fn!(rustc_attrs))),
(sym::rustc_regions, Normal, template!(Word), Gated(Stability::Unstable,
sym::rustc_attrs,
"the `#[rustc_regions]` attribute \
rustc_layout_scalar_valid_range_end,
rustc_layout_scalar_valid_range_start,
rustc_mir,
+ rustc_nonnull_optimization_guaranteed,
rustc_object_lifetime_default,
rustc_on_unimplemented,
rustc_outlives,
#[rustc_variance] //~ ERROR the `#[rustc_variance]` attribute is just used for rustc unit tests and will never be stable
#[rustc_error] //~ ERROR the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
+#[rustc_nonnull_optimization_guaranteed] //~ ERROR the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
fn main() {}
= note: for more information, see https://github.com/rust-lang/rust/issues/29642
= help: add #![feature(rustc_attrs)] to the crate attributes to enable
-error: aborting due to 2 previous errors
+error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
+ --> $DIR/feature-gate-rustc-attrs-1.rs:7:1
+ |
+LL | #[rustc_nonnull_optimization_guaranteed]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: for more information, see https://github.com/rust-lang/rust/issues/29642
+ = help: add #![feature(rustc_attrs)] to the crate attributes to enable
+
+error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0658`.
#![deny(improper_ctypes)]
#![allow(dead_code)]
+use std::num;
+
enum Z { }
enum U { A }
enum B { C, D }
#[repr(isize)]
enum Isize { A, B, C }
+#[repr(transparent)]
+struct Transparent<T>(T, std::marker::PhantomData<Z>);
+
+struct Rust<T>(T);
+
extern {
fn zf(x: Z);
fn uf(x: U); //~ ERROR enum has no representation hint
fn bf(x: B); //~ ERROR enum has no representation hint
fn tf(x: T); //~ ERROR enum has no representation hint
- fn reprc(x: ReprC);
- fn u8(x: U8);
- fn isize(x: Isize);
+ fn repr_c(x: ReprC);
+ fn repr_u8(x: U8);
+ fn repr_isize(x: Isize);
+ fn option_ref(x: Option<&'static u8>);
+ fn option_fn(x: Option<extern "C" fn()>);
+ fn nonnull(x: Option<std::ptr::NonNull<u8>>);
+ fn nonzero_u8(x: Option<num::NonZeroU8>);
+ fn nonzero_u16(x: Option<num::NonZeroU16>);
+ fn nonzero_u32(x: Option<num::NonZeroU32>);
+ fn nonzero_u64(x: Option<num::NonZeroU64>);
+ fn nonzero_u128(x: Option<num::NonZeroU128>);
+ //~^ ERROR 128-bit integers don't currently have a known stable ABI
+ fn nonzero_usize(x: Option<num::NonZeroUsize>);
+ fn nonzero_i8(x: Option<num::NonZeroI8>);
+ fn nonzero_i16(x: Option<num::NonZeroI16>);
+ fn nonzero_i32(x: Option<num::NonZeroI32>);
+ fn nonzero_i64(x: Option<num::NonZeroI64>);
+ fn nonzero_i128(x: Option<num::NonZeroI128>);
+ //~^ ERROR 128-bit integers don't currently have a known stable ABI
+ fn nonzero_isize(x: Option<num::NonZeroIsize>);
+ fn repr_transparent(x: Option<Transparent<num::NonZeroU8>>);
+ fn repr_rust(x: Option<Rust<num::NonZeroU8>>); //~ ERROR enum has no representation hint
+ fn no_result(x: Result<(), num::NonZeroI32>); //~ ERROR enum has no representation hint
}
pub fn main() { }
error: `extern` block uses type `U` which is not FFI-safe: enum has no representation hint
- --> $DIR/lint-ctypes-enum.rs:20:13
+ --> $DIR/lint-ctypes-enum.rs:27:13
|
LL | fn uf(x: U);
| ^
| ^^^^^^^^^^^^^^^
= help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
- --> $DIR/lint-ctypes-enum.rs:5:1
+ --> $DIR/lint-ctypes-enum.rs:7:1
|
LL | enum U { A }
| ^^^^^^^^^^^^
error: `extern` block uses type `B` which is not FFI-safe: enum has no representation hint
- --> $DIR/lint-ctypes-enum.rs:21:13
+ --> $DIR/lint-ctypes-enum.rs:28:13
|
LL | fn bf(x: B);
| ^
|
= help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
- --> $DIR/lint-ctypes-enum.rs:6:1
+ --> $DIR/lint-ctypes-enum.rs:8:1
|
LL | enum B { C, D }
| ^^^^^^^^^^^^^^^
error: `extern` block uses type `T` which is not FFI-safe: enum has no representation hint
- --> $DIR/lint-ctypes-enum.rs:22:13
+ --> $DIR/lint-ctypes-enum.rs:29:13
|
LL | fn tf(x: T);
| ^
|
= help: consider adding a #[repr(...)] attribute to this enum
note: type defined here
- --> $DIR/lint-ctypes-enum.rs:7:1
+ --> $DIR/lint-ctypes-enum.rs:9:1
|
LL | enum T { E, F, G }
| ^^^^^^^^^^^^^^^^^^
-error: aborting due to 3 previous errors
+error: `extern` block uses type `u128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
+ --> $DIR/lint-ctypes-enum.rs:40:23
+ |
+LL | fn nonzero_u128(x: Option<num::NonZeroU128>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `extern` block uses type `i128` which is not FFI-safe: 128-bit integers don't currently have a known stable ABI
+ --> $DIR/lint-ctypes-enum.rs:47:23
+ |
+LL | fn nonzero_i128(x: Option<num::NonZeroI128>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `extern` block uses type `std::option::Option<Rust<std::num::NonZeroU8>>` which is not FFI-safe: enum has no representation hint
+ --> $DIR/lint-ctypes-enum.rs:51:20
+ |
+LL | fn repr_rust(x: Option<Rust<num::NonZeroU8>>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = help: consider adding a #[repr(...)] attribute to this enum
+
+error: `extern` block uses type `std::result::Result<(), std::num::NonZeroI32>` which is not FFI-safe: enum has no representation hint
+ --> $DIR/lint-ctypes-enum.rs:52:20
+ |
+LL | fn no_result(x: Result<(), num::NonZeroI32>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = help: consider adding a #[repr(...)] attribute to this enum
+
+error: aborting due to 7 previous errors
projects / rust.git / commitdiff