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Treat safe target_feature functions as unsafe by default #134317

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Treat safe target_feature functions as unsafe by default #134317

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3a64bef
Also forbid target_feature annotated methods from being lang items
oli-obk Dec 13, 2024
8a4e5d7
Add some convenience helper methods on `hir::Safety`
oli-obk Dec 13, 2024
69bacc5
Treat safe target_feature functions as unsafe by default
oli-obk Dec 13, 2024
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10 changes: 9 additions & 1 deletion compiler/rustc_ast_lowering/src/delegation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
) -> hir::FnSig<'hir> {
let header = if let Some(local_sig_id) = sig_id.as_local() {
match self.resolver.delegation_fn_sigs.get(&local_sig_id) {
Some(sig) => self.lower_fn_header(sig.header, hir::Safety::Safe),
Some(sig) => self.lower_fn_header(
sig.header,
if sig.target_feature && !matches!(sig.header.safety, Safety::Unsafe(_)) {
hir::Safety::Unsafe { target_feature: true }
} else {
hir::Safety::Safe
},
&[],
),
None => self.generate_header_error(),
}
} else {
Expand Down
36 changes: 28 additions & 8 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -231,7 +231,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
});
let sig = hir::FnSig {
decl,
header: this.lower_fn_header(*header, hir::Safety::Safe),
header: this.lower_fn_header(*header, hir::Safety::Safe, attrs),
span: this.lower_span(*fn_sig_span),
};
hir::ItemKind::Fn(sig, generics, body_id)
Expand Down Expand Up @@ -609,7 +609,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
let owner_id = hir_id.expect_owner();
self.lower_attrs(hir_id, &i.attrs);
let attrs = self.lower_attrs(hir_id, &i.attrs);
let item = hir::ForeignItem {
owner_id,
ident: self.lower_ident(i.ident),
Expand All @@ -633,7 +633,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
});

// Unmarked safety in unsafe block defaults to unsafe.
let header = self.lower_fn_header(sig.header, hir::Safety::Unsafe);
let header = self.lower_fn_header(
sig.header,
hir::Safety::Unsafe { target_feature: false },
attrs,
);

hir::ForeignItemKind::Fn(
hir::FnSig { header, decl, span: self.lower_span(sig.span) },
Expand All @@ -644,7 +648,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
ForeignItemKind::Static(box StaticItem { ty, mutability, expr: _, safety }) => {
let ty = self
.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
let safety = self.lower_safety(*safety, hir::Safety::Unsafe);
let safety =
self.lower_safety(*safety, hir::Safety::Unsafe { target_feature: false });

hir::ForeignItemKind::Static(ty, *mutability, safety)
}
Expand Down Expand Up @@ -748,7 +753,7 @@ impl<'hir> LoweringContext<'_, 'hir> {

fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
self.lower_attrs(hir_id, &i.attrs);
let attrs = self.lower_attrs(hir_id, &i.attrs);
let trait_item_def_id = hir_id.expect_owner();

let (generics, kind, has_default) = match &i.kind {
Expand All @@ -775,6 +780,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
attrs,
);
(generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false)
}
Expand All @@ -793,6 +799,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
FnDeclKind::Trait,
sig.header.coroutine_kind,
attrs,
);
(generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true)
}
Expand Down Expand Up @@ -878,7 +885,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
let has_value = true;
let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
self.lower_attrs(hir_id, &i.attrs);
let attrs = self.lower_attrs(hir_id, &i.attrs);

let (generics, kind) = match &i.kind {
AssocItemKind::Const(box ConstItem { generics, ty, expr, .. }) => self.lower_generics(
Expand Down Expand Up @@ -908,6 +915,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
i.id,
if self.is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent },
sig.header.coroutine_kind,
attrs,
);

(generics, hir::ImplItemKind::Fn(sig, body_id))
Expand Down Expand Up @@ -1322,8 +1330,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
id: NodeId,
kind: FnDeclKind,
coroutine_kind: Option<CoroutineKind>,
attrs: &[Attribute],
) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
let header = self.lower_fn_header(sig.header, hir::Safety::Safe);
let header = self.lower_fn_header(sig.header, hir::Safety::Safe, attrs);
let itctx = ImplTraitContext::Universal;
let (generics, decl) = self.lower_generics(generics, id, itctx, |this| {
this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
Expand All @@ -1335,12 +1344,23 @@ impl<'hir> LoweringContext<'_, 'hir> {
&mut self,
h: FnHeader,
default_safety: hir::Safety,
attrs: &[Attribute],
) -> hir::FnHeader {
let asyncness = if let Some(CoroutineKind::Async { span, .. }) = h.coroutine_kind {
hir::IsAsync::Async(span)
} else {
hir::IsAsync::NotAsync
};

let default_safety = if attrs.iter().any(|attr| attr.has_name(sym::target_feature))
&& !matches!(h.safety, Safety::Unsafe(_))
&& default_safety.is_safe()
{
hir::Safety::Unsafe { target_feature: true }
} else {
default_safety
};

hir::FnHeader {
safety: self.lower_safety(h.safety, default_safety),
asyncness,
Expand Down Expand Up @@ -1394,7 +1414,7 @@ impl<'hir> LoweringContext<'_, 'hir> {

pub(super) fn lower_safety(&mut self, s: Safety, default: hir::Safety) -> hir::Safety {
match s {
Safety::Unsafe(_) => hir::Safety::Unsafe,
Safety::Unsafe(_) => hir::Safety::Unsafe { target_feature: false },
Safety::Default => default,
Safety::Safe(_) => hir::Safety::Safe,
}
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1222,7 +1222,7 @@ fn get_rust_try_fn<'a, 'gcc, 'tcx>(
iter::once(i8p),
tcx.types.unit,
false,
rustc_hir::Safety::Unsafe,
rustc_hir::Safety::Unsafe { target_feature: false },
Abi::Rust,
)),
);
Expand All @@ -1233,7 +1233,7 @@ fn get_rust_try_fn<'a, 'gcc, 'tcx>(
[i8p, i8p].iter().cloned(),
tcx.types.unit,
false,
rustc_hir::Safety::Unsafe,
rustc_hir::Safety::Unsafe { target_feature: false },
Abi::Rust,
)),
);
Expand All @@ -1242,7 +1242,7 @@ fn get_rust_try_fn<'a, 'gcc, 'tcx>(
[try_fn_ty, i8p, catch_fn_ty],
tcx.types.i32,
false,
rustc_hir::Safety::Unsafe,
rustc_hir::Safety::Unsafe { target_feature: false },
Abi::Rust,
));
let rust_try = gen_fn(cx, "__rust_try", rust_fn_sig, codegen);
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_codegen_llvm/src/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1091,7 +1091,7 @@ fn get_rust_try_fn<'ll, 'tcx>(
[i8p],
tcx.types.unit,
false,
hir::Safety::Unsafe,
hir::Safety::Unsafe { target_feature: false },
ExternAbi::Rust,
)),
);
Expand All @@ -1102,7 +1102,7 @@ fn get_rust_try_fn<'ll, 'tcx>(
[i8p, i8p],
tcx.types.unit,
false,
hir::Safety::Unsafe,
hir::Safety::Unsafe { target_feature: false },
ExternAbi::Rust,
)),
);
Expand All @@ -1111,7 +1111,7 @@ fn get_rust_try_fn<'ll, 'tcx>(
[try_fn_ty, i8p, catch_fn_ty],
tcx.types.i32,
false,
hir::Safety::Unsafe,
hir::Safety::Unsafe { target_feature: false },
ExternAbi::Rust,
));
let rust_try = gen_fn(cx, "__rust_try", rust_fn_sig, codegen);
Expand Down
4 changes: 3 additions & 1 deletion compiler/rustc_codegen_ssa/src/codegen_attrs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,7 +251,9 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
sym::target_feature => {
if !tcx.is_closure_like(did.to_def_id())
&& let Some(fn_sig) = fn_sig()
&& fn_sig.skip_binder().safety() == hir::Safety::Safe
&& matches!(fn_sig.skip_binder().safety(), hir::Safety::Unsafe {
target_feature: true
})
{
if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
// The `#[target_feature]` attribute is allowed on
Expand Down
5 changes: 2 additions & 3 deletions compiler/rustc_const_eval/src/const_eval/fn_queries.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -53,9 +53,8 @@ fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
Some(stab) => {
if cfg!(debug_assertions) && stab.promotable {
let sig = tcx.fn_sig(def_id);
assert_eq!(
sig.skip_binder().safety(),
hir::Safety::Safe,
assert!(
sig.skip_binder().safety().is_safe(),
"don't mark const unsafe fns as promotable",
// https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
);
Expand Down
29 changes: 25 additions & 4 deletions compiler/rustc_hir/src/hir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3390,23 +3390,44 @@ impl<'hir> Item<'hir> {
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
#[derive(Encodable, Decodable, HashStable_Generic)]
pub enum Safety {
Unsafe,
Unsafe {
/// Whether this is a safe target_feature function.
/// We treat those as unsafe almost everywhere, but in unsafeck,
/// which allows calling them from other target_feature functions
/// without an `unsafe` block.
target_feature: bool,
},
Safe,
}

impl Safety {
pub fn prefix_str(self) -> &'static str {
match self {
Self::Unsafe => "unsafe ",
Self::Unsafe { target_feature: false } => "unsafe ",
Self::Unsafe { target_feature: true } => "#[target_feature] ",
Self::Safe => "",
}
}

#[inline]
pub fn is_unsafe(self) -> bool {
!self.is_safe()
}

#[inline]
pub fn is_safe(self) -> bool {
match self {
Self::Unsafe { .. } => false,
Self::Safe => true,
}
}
}

impl fmt::Display for Safety {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(match *self {
Self::Unsafe => "unsafe",
Self::Unsafe { target_feature: false } => "unsafe",
Self::Unsafe { target_feature: true } => "#[target_feature] safe",
Self::Safe => "safe",
})
}
Expand Down Expand Up @@ -3445,7 +3466,7 @@ impl FnHeader {
}

pub fn is_unsafe(&self) -> bool {
matches!(&self.safety, Safety::Unsafe)
self.safety.is_unsafe()
}
}

Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_hir_analysis/src/check/check.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
use rustc_errors::MultiSpan;
use rustc_errors::codes::*;
use rustc_hir::def::{CtorKind, DefKind};
use rustc_hir::{Node, Safety, intravisit};
use rustc_hir::{Node, intravisit};
use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
use rustc_infer::traits::{Obligation, ObligationCauseCode};
use rustc_lint_defs::builtin::{
Expand Down Expand Up @@ -161,7 +161,7 @@ fn check_unsafe_fields(tcx: TyCtxt<'_>, item_def_id: LocalDefId) {
};
let typing_env = ty::TypingEnv::non_body_analysis(tcx, item_def_id);
for field in def.all_fields() {
if field.safety != Safety::Unsafe {
if !field.safety.is_unsafe() {
continue;
}
let Ok(field_ty) = tcx.try_normalize_erasing_regions(typing_env, field.ty(tcx, args))
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_hir_analysis/src/check/intrinsic.rs
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Expand Up @@ -76,7 +76,7 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
tcx.fn_sig(intrinsic_id).skip_binder().safety()
} else {
// Old-style intrinsics are never safe
Safety::Unsafe
Safety::Unsafe { target_feature: false }
};
let is_in_list = match tcx.item_name(intrinsic_id.into()) {
// When adding a new intrinsic to this list,
Expand Down Expand Up @@ -137,7 +137,7 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
| sym::fdiv_algebraic
| sym::frem_algebraic
| sym::const_eval_select => hir::Safety::Safe,
_ => hir::Safety::Unsafe,
_ => hir::Safety::Unsafe { target_feature: false },
};

if has_safe_attr != is_in_list {
Expand Down Expand Up @@ -216,7 +216,7 @@ pub fn check_intrinsic_type(
return;
}
};
(n_tps, 0, 0, inputs, output, hir::Safety::Unsafe)
(n_tps, 0, 0, inputs, output, hir::Safety::Unsafe { target_feature: false })
} else {
let safety = intrinsic_operation_unsafety(tcx, intrinsic_id);
let (n_tps, n_cts, inputs, output) = match intrinsic_name {
Expand Down
12 changes: 6 additions & 6 deletions compiler/rustc_hir_analysis/src/coherence/unsafety.rs
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Expand Up @@ -24,7 +24,7 @@ pub(super) fn check_item(
let trait_def_safety = if is_copy {
// If `Self` has unsafe fields, `Copy` is unsafe to implement.
if trait_header.trait_ref.skip_binder().self_ty().has_unsafe_fields() {
rustc_hir::Safety::Unsafe
rustc_hir::Safety::Unsafe { target_feature: false }
} else {
rustc_hir::Safety::Safe
}
Expand All @@ -33,7 +33,7 @@ pub(super) fn check_item(
};

match (trait_def_safety, unsafe_attr, trait_header.safety, trait_header.polarity) {
(Safety::Safe, None, Safety::Unsafe, Positive | Reservation) => {
(Safety::Safe, None, Safety::Unsafe { .. }, Positive | Reservation) => {
let span = tcx.def_span(def_id);
return Err(struct_span_code_err!(
tcx.dcx(),
Expand All @@ -51,7 +51,7 @@ pub(super) fn check_item(
.emit());
}

(Safety::Unsafe, _, Safety::Safe, Positive | Reservation) => {
(Safety::Unsafe { .. }, _, Safety::Safe, Positive | Reservation) => {
let span = tcx.def_span(def_id);
return Err(struct_span_code_err!(
tcx.dcx(),
Expand Down Expand Up @@ -109,14 +109,14 @@ pub(super) fn check_item(
.emit());
}

(_, _, Safety::Unsafe, Negative) => {
(_, _, Safety::Unsafe { .. }, Negative) => {
// Reported in AST validation
assert!(tcx.dcx().has_errors().is_some(), "unsafe negative impl");
Ok(())
}
(_, _, Safety::Safe, Negative)
| (Safety::Unsafe, _, Safety::Unsafe, Positive | Reservation)
| (Safety::Safe, Some(_), Safety::Unsafe, Positive | Reservation)
| (Safety::Unsafe { .. }, _, Safety::Unsafe { .. }, Positive | Reservation)
| (Safety::Safe, Some(_), Safety::Unsafe { .. }, Positive | Reservation)
| (Safety::Safe, None, Safety::Safe, _) => Ok(()),
}
}
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/collect.rs
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Expand Up @@ -1371,7 +1371,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
// constructors for structs with `layout_scalar_valid_range` are unsafe to call
let safety = match tcx.layout_scalar_valid_range(adt_def_id) {
(Bound::Unbounded, Bound::Unbounded) => hir::Safety::Safe,
_ => hir::Safety::Unsafe,
_ => hir::Safety::Unsafe { target_feature: false },
};
ty::Binder::dummy(tcx.mk_fn_sig(inputs, ty, false, safety, ExternAbi::Rust))
}
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_hir_pretty/src/lib.rs
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Expand Up @@ -2293,8 +2293,8 @@ impl<'a> State<'a> {

fn print_safety(&mut self, s: hir::Safety) {
match s {
hir::Safety::Safe => {}
hir::Safety::Unsafe => self.word_nbsp("unsafe"),
hir::Safety::Unsafe { target_feature: true } | hir::Safety::Safe => {}
hir::Safety::Unsafe { target_feature: false } => self.word_nbsp("unsafe"),
}
}

Expand Down
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