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some fixes for clashing_extern_declarations lint

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This commit is contained in:
Ralf Jung 2024-09-13 11:13:59 +02:00
parent a5efa01895
commit f362a59c3e
4 changed files with 172 additions and 89 deletions
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74
compiler/rustc_lint/src/foreign_modules.rs
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@ -3,8 +3,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_middle::query::Providers;
use rustc_middle::ty::layout::LayoutError;
use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
use rustc_middle::ty::{self, AdtDef, Instance, Ty, TyCtxt};
use rustc_session::declare_lint;
use rustc_span::{sym, Span, Symbol};
use rustc_target::abi::FIRST_VARIANT;
@ -212,7 +211,17 @@ fn structurally_same_type<'tcx>(
ckind: types::CItemKind,
) -> bool {
let mut seen_types = UnordSet::default();
structurally_same_type_impl(&mut seen_types, tcx, param_env, a, b, ckind)
let result = structurally_same_type_impl(&mut seen_types, tcx, param_env, a, b, ckind);
if cfg!(debug_assertions) && result {
// Sanity-check: must have same ABI, size and alignment.
// `extern` blocks cannot be generic, so we'll always get a layout here.
let a_layout = tcx.layout_of(param_env.and(a)).unwrap();
let b_layout = tcx.layout_of(param_env.and(b)).unwrap();
assert_eq!(a_layout.abi, b_layout.abi);
assert_eq!(a_layout.size, b_layout.size);
assert_eq!(a_layout.align, b_layout.align);
}
result
}
fn structurally_same_type_impl<'tcx>(
@ -266,30 +275,21 @@ fn structurally_same_type_impl<'tcx>(
// Do a full, depth-first comparison between the two.
use rustc_type_ir::TyKind::*;
let compare_layouts = |a, b| -> Result<bool, &'tcx LayoutError<'tcx>> {
debug!("compare_layouts({:?}, {:?})", a, b);
let a_layout = &tcx.layout_of(param_env.and(a))?.layout.abi();
let b_layout = &tcx.layout_of(param_env.and(b))?.layout.abi();
debug!(
"comparing layouts: {:?} == {:?} = {}",
a_layout,
b_layout,
a_layout == b_layout
);
Ok(a_layout == b_layout)
};
let is_primitive_or_pointer =
|ty: Ty<'tcx>| ty.is_primitive() || matches!(ty.kind(), RawPtr(..) | Ref(..));
ensure_sufficient_stack(|| {
match (a.kind(), b.kind()) {
(Adt(a_def, _), Adt(b_def, _)) => {
// We can immediately rule out these types as structurally same if
// their layouts differ.
match compare_layouts(a, b) {
Ok(false) => return false,
_ => (), // otherwise, continue onto the full, fields comparison
(&Adt(a_def, _), &Adt(b_def, _)) => {
// Only `repr(C)` types can be compared structurally.
if !(a_def.repr().c() && b_def.repr().c()) {
return false;
}
// If the types differ in their packed-ness, align, or simd-ness they conflict.
let repr_characteristica =
|def: AdtDef<'tcx>| (def.repr().pack, def.repr().align, def.repr().simd());
if repr_characteristica(a_def) != repr_characteristica(b_def) {
return false;
}
// Grab a flattened representation of all fields.
@ -311,9 +311,9 @@ fn structurally_same_type_impl<'tcx>(
},
)
}
(Array(a_ty, a_const), Array(b_ty, b_const)) => {
// For arrays, we also check the constness of the type.
a_const.kind() == b_const.kind()
(Array(a_ty, a_len), Array(b_ty, b_len)) => {
// For arrays, we also check the length.
a_len == b_len
&& structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
)
@ -357,10 +357,9 @@ fn structurally_same_type_impl<'tcx>(
ckind,
)
}
(Tuple(a_args), Tuple(b_args)) => {
a_args.iter().eq_by(b_args.iter(), |a_ty, b_ty| {
structurally_same_type_impl(seen_types, tcx, param_env, a_ty, b_ty, ckind)
})
(Tuple(..), Tuple(..)) => {
// Tuples are not `repr(C)` so these cannot be compared structurally.
false
}
// For these, it's not quite as easy to define structural-sameness quite so easily.
// For the purposes of this lint, take the conservative approach and mark them as
@ -380,24 +379,21 @@ 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) => {
if let Some(ty) = types::repr_nullable_ptr(tcx, param_env, a, ckind) {
ty == b
if let Some(a_inner) = types::repr_nullable_ptr(tcx, param_env, a, ckind) {
a_inner == b
} else {
compare_layouts(a, b).unwrap_or(false)
false
}
}
(_, Adt(..)) if is_primitive_or_pointer(a) => {
if let Some(ty) = types::repr_nullable_ptr(tcx, param_env, b, ckind) {
ty == a
if let Some(b_inner) = types::repr_nullable_ptr(tcx, param_env, b, ckind) {
b_inner == a
} else {
compare_layouts(a, b).unwrap_or(false)
false
}
}
// Otherwise, just compare the layouts. This may fail to lint for some
// incompatible types, but at the very least, will stop reads into
// uninitialised memory.
_ => compare_layouts(a, b).unwrap_or(false),
_ => false,
}
})
}