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Simplify clashing_extern_declarations.

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This commit is contained in:
Camille GILLOT 2023-07-15 10:09:36 +00:00
parent 817f45f7bf
commit 56063ff2fb
1 changed files with 280 additions and 287 deletions
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567
compiler/rustc_lint/src/foreign_modules.rs
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@ -1,6 +1,7 @@
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::stack::ensure_sufficient_stack;
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};
@ -22,7 +23,7 @@ pub(crate) fn get_lints() -> LintArray {
fn clashing_extern_declarations(tcx: TyCtxt<'_>, (): ()) {
let mut lint = ClashingExternDeclarations::new();
for id in tcx.hir_crate_items(()).foreign_items() {
lint.check_foreign_item(tcx, tcx.hir().foreign_item(id));
lint.check_foreign_item(tcx, id);
}
}
@ -101,7 +102,7 @@ impl ClashingExternDeclarations {
/// Insert a new foreign item into the seen set. If a symbol with the same name already exists
/// for the item, return its HirId without updating the set.
fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<hir::OwnerId> {
fn insert(&mut self, tcx: TyCtxt<'_>, fi: hir::ForeignItemId) -> Option<hir::OwnerId> {
let did = fi.owner_id.to_def_id();
let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
let name = Symbol::intern(tcx.symbol_name(instance).name);
@ -115,295 +116,287 @@ impl ClashingExternDeclarations {
}
}
/// Get the name of the symbol that's linked against for a given extern declaration. That is,
/// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
/// symbol's name.
fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
if let Some((overridden_link_name, overridden_link_name_span)) =
tcx.codegen_fn_attrs(fi.owner_id).link_name.map(|overridden_link_name| {
// FIXME: Instead of searching through the attributes again to get span
// information, we could have codegen_fn_attrs also give span information back for
// where the attribute was defined. However, until this is found to be a
// bottleneck, this does just fine.
(overridden_link_name, tcx.get_attr(fi.owner_id, sym::link_name).unwrap().span)
})
{
SymbolName::Link(overridden_link_name, overridden_link_name_span)
} else {
SymbolName::Normal(fi.ident.name)
}
}
#[instrument(level = "trace", skip(self, tcx))]
fn check_foreign_item<'tcx>(&mut self, tcx: TyCtxt<'tcx>, this_fi: hir::ForeignItemId) {
let DefKind::Fn = tcx.def_kind(this_fi.owner_id) else { return };
let Some(existing_did) = self.insert(tcx, this_fi) else { return };
/// Checks whether two types are structurally the same enough that the declarations shouldn't
/// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
/// with the same members (as the declarations shouldn't clash).
fn structurally_same_type<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a: Ty<'tcx>,
b: Ty<'tcx>,
ckind: types::CItemKind,
) -> bool {
fn structurally_same_type_impl<'tcx>(
seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a: Ty<'tcx>,
b: Ty<'tcx>,
ckind: types::CItemKind,
) -> bool {
debug!("structurally_same_type_impl(tcx, a = {:?}, b = {:?})", a, b);
let existing_decl_ty = tcx.type_of(existing_did).skip_binder();
let this_decl_ty = tcx.type_of(this_fi.owner_id).instantiate_identity();
debug!(
"ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
existing_did, existing_decl_ty, this_fi.owner_id, this_decl_ty
);
// Given a transparent newtype, reach through and grab the inner
// type unless the newtype makes the type non-null.
let non_transparent_ty = |mut ty: Ty<'tcx>| -> Ty<'tcx> {
loop {
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
);
if is_transparent && !is_non_null {
debug_assert_eq!(def.variants().len(), 1);
let v = &def.variant(FIRST_VARIANT);
// continue with `ty`'s non-ZST field,
// otherwise `ty` is a ZST and we can return
if let Some(field) = types::transparent_newtype_field(tcx, v) {
ty = field.ty(tcx, args);
continue;
}
}
}
debug!("non_transparent_ty -> {:?}", ty);
return ty;
// Check that the declarations match.
if !structurally_same_type(
tcx,
tcx.param_env(this_fi.owner_id),
existing_decl_ty,
this_decl_ty,
types::CItemKind::Declaration,
) {
let orig = name_of_extern_decl(tcx, existing_did);
// Finally, emit the diagnostic.
let this = tcx.item_name(this_fi.owner_id.to_def_id());
let orig = orig.get_name();
let previous_decl_label = get_relevant_span(tcx, existing_did);
let mismatch_label = get_relevant_span(tcx, this_fi.owner_id);
let sub =
BuiltinClashingExternSub { tcx, expected: existing_decl_ty, found: this_decl_ty };
let decorator = if orig == this {
BuiltinClashingExtern::SameName {
this,
orig,
previous_decl_label,
mismatch_label,
sub,
}
} else {
BuiltinClashingExtern::DiffName {
this,
orig,
previous_decl_label,
mismatch_label,
sub,
}
};
let a = non_transparent_ty(a);
let b = non_transparent_ty(b);
if !seen_types.insert((a, b)) {
// We've encountered a cycle. There's no point going any further -- the types are
// structurally the same.
true
} else if a == b {
// All nominally-same types are structurally same, too.
true
} else {
// Do a full, depth-first comparison between the two.
use rustc_type_ir::sty::TyKind::*;
let a_kind = a.kind();
let b_kind = b.kind();
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)
};
#[allow(rustc::usage_of_ty_tykind)]
let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
kind.is_primitive() || matches!(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
}
// Grab a flattened representation of all fields.
let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
// Perform a structural comparison for each field.
a_fields.eq_by(
b_fields,
|&ty::FieldDef { did: a_did, .. },
&ty::FieldDef { did: b_did, .. }| {
structurally_same_type_impl(
seen_types,
tcx,
param_env,
tcx.type_of(a_did).instantiate_identity(),
tcx.type_of(b_did).instantiate_identity(),
ckind,
)
},
)
}
(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()
&& structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
)
}
(Slice(a_ty), Slice(b_ty)) => structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
),
(RawPtr(a_tymut), RawPtr(b_tymut)) => {
a_tymut.mutbl == b_tymut.mutbl
&& structurally_same_type_impl(
seen_types, tcx, param_env, a_tymut.ty, b_tymut.ty, ckind,
)
}
(Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
// For structural sameness, we don't need the region to be same.
a_mut == b_mut
&& structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
)
}
(FnDef(..), FnDef(..)) => {
let a_poly_sig = a.fn_sig(tcx);
let b_poly_sig = b.fn_sig(tcx);
// We don't compare regions, but leaving bound regions around ICEs, so
// we erase them.
let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
(a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
== (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
&& a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
structurally_same_type_impl(
seen_types, tcx, param_env, *a, *b, ckind,
)
})
&& structurally_same_type_impl(
seen_types,
tcx,
param_env,
a_sig.output(),
b_sig.output(),
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,
)
})
}
// 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
// not structurally same.
(Dynamic(..), Dynamic(..))
| (Error(..), Error(..))
| (Closure(..), Closure(..))
| (Generator(..), Generator(..))
| (GeneratorWitness(..), GeneratorWitness(..))
| (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
| (Alias(ty::Inherent, ..), Alias(ty::Inherent, ..))
| (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
// These definitely should have been caught above.
(Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
// An Adt and a primitive or pointer type. This can be FFI-safe if non-null
// enum layout optimisation is being applied.
(Adt(..), other_kind) | (other_kind, Adt(..))
if is_primitive_or_pointer(other_kind) =>
{
let (primitive, adt) =
if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
if let Some(ty) = types::repr_nullable_ptr(tcx, param_env, adt, ckind) {
ty == primitive
} else {
compare_layouts(a, b).unwrap_or(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),
}
})
}
}
let mut seen_types = FxHashSet::default();
structurally_same_type_impl(&mut seen_types, tcx, param_env, a, b, ckind)
}
#[instrument(level = "trace", skip(self, tcx))]
fn check_foreign_item<'tcx>(&mut self, tcx: TyCtxt<'tcx>, this_fi: &hir::ForeignItem<'_>) {
if let hir::ForeignItemKind::Fn(..) = this_fi.kind {
if let Some(existing_did) = self.insert(tcx, this_fi) {
let existing_decl_ty = tcx.type_of(existing_did).skip_binder();
let this_decl_ty = tcx.type_of(this_fi.owner_id).instantiate_identity();
debug!(
"ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
existing_did, existing_decl_ty, this_fi.owner_id, this_decl_ty
);
// Check that the declarations match.
if !Self::structurally_same_type(
tcx,
tcx.param_env(this_fi.owner_id),
existing_decl_ty,
this_decl_ty,
types::CItemKind::Declaration,
) {
let orig_fi = tcx.hir().expect_foreign_item(existing_did);
let orig = Self::name_of_extern_decl(tcx, orig_fi);
// We want to ensure that we use spans for both decls that include where the
// name was defined, whether that was from the link_name attribute or not.
let get_relevant_span =
|fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
SymbolName::Normal(_) => fi.span,
SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
};
// Finally, emit the diagnostic.
let this = this_fi.ident.name;
let orig = orig.get_name();
let previous_decl_label = get_relevant_span(orig_fi);
let mismatch_label = get_relevant_span(this_fi);
let sub = BuiltinClashingExternSub {
tcx,
expected: existing_decl_ty,
found: this_decl_ty,
};
let decorator = if orig == this {
BuiltinClashingExtern::SameName {
this,
orig,
previous_decl_label,
mismatch_label,
sub,
}
} else {
BuiltinClashingExtern::DiffName {
this,
orig,
previous_decl_label,
mismatch_label,
sub,
}
};
tcx.emit_spanned_lint(
CLASHING_EXTERN_DECLARATIONS,
this_fi.hir_id(),
get_relevant_span(this_fi),
decorator,
);
}
}
tcx.emit_spanned_lint(
CLASHING_EXTERN_DECLARATIONS,
this_fi.hir_id(),
mismatch_label,
decorator,
);
}
}
}
/// Get the name of the symbol that's linked against for a given extern declaration. That is,
/// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
/// symbol's name.
fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: hir::OwnerId) -> SymbolName {
if let Some((overridden_link_name, overridden_link_name_span)) =
tcx.codegen_fn_attrs(fi).link_name.map(|overridden_link_name| {
// FIXME: Instead of searching through the attributes again to get span
// information, we could have codegen_fn_attrs also give span information back for
// where the attribute was defined. However, until this is found to be a
// bottleneck, this does just fine.
(overridden_link_name, tcx.get_attr(fi, sym::link_name).unwrap().span)
})
{
SymbolName::Link(overridden_link_name, overridden_link_name_span)
} else {
SymbolName::Normal(tcx.item_name(fi.to_def_id()))
}
}
/// We want to ensure that we use spans for both decls that include where the
/// name was defined, whether that was from the link_name attribute or not.
fn get_relevant_span(tcx: TyCtxt<'_>, fi: hir::OwnerId) -> Span {
match name_of_extern_decl(tcx, fi) {
SymbolName::Normal(_) => tcx.def_span(fi),
SymbolName::Link(_, annot_span) => annot_span,
}
}
/// Checks whether two types are structurally the same enough that the declarations shouldn't
/// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
/// with the same members (as the declarations shouldn't clash).
fn structurally_same_type<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a: Ty<'tcx>,
b: Ty<'tcx>,
ckind: types::CItemKind,
) -> bool {
let mut seen_types = FxHashSet::default();
structurally_same_type_impl(&mut seen_types, tcx, param_env, a, b, ckind)
}
fn structurally_same_type_impl<'tcx>(
seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a: Ty<'tcx>,
b: Ty<'tcx>,
ckind: types::CItemKind,
) -> bool {
debug!("structurally_same_type_impl(tcx, a = {:?}, b = {:?})", a, b);
// Given a transparent newtype, reach through and grab the inner
// type unless the newtype makes the type non-null.
let non_transparent_ty = |mut ty: Ty<'tcx>| -> Ty<'tcx> {
loop {
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
);
if is_transparent && !is_non_null {
debug_assert_eq!(def.variants().len(), 1);
let v = &def.variant(FIRST_VARIANT);
// continue with `ty`'s non-ZST field,
// otherwise `ty` is a ZST and we can return
if let Some(field) = types::transparent_newtype_field(tcx, v) {
ty = field.ty(tcx, args);
continue;
}
}
}
debug!("non_transparent_ty -> {:?}", ty);
return ty;
}
};
let a = non_transparent_ty(a);
let b = non_transparent_ty(b);
if !seen_types.insert((a, b)) {
// We've encountered a cycle. There's no point going any further -- the types are
// structurally the same.
true
} else if a == b {
// All nominally-same types are structurally same, too.
true
} else {
// Do a full, depth-first comparison between the two.
use rustc_type_ir::sty::TyKind::*;
let a_kind = a.kind();
let b_kind = b.kind();
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)
};
#[allow(rustc::usage_of_ty_tykind)]
let is_primitive_or_pointer =
|kind: &ty::TyKind<'_>| kind.is_primitive() || matches!(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
}
// Grab a flattened representation of all fields.
let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
// Perform a structural comparison for each field.
a_fields.eq_by(
b_fields,
|&ty::FieldDef { did: a_did, .. }, &ty::FieldDef { did: b_did, .. }| {
structurally_same_type_impl(
seen_types,
tcx,
param_env,
tcx.type_of(a_did).instantiate_identity(),
tcx.type_of(b_did).instantiate_identity(),
ckind,
)
},
)
}
(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()
&& structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
)
}
(Slice(a_ty), Slice(b_ty)) => {
structurally_same_type_impl(seen_types, tcx, param_env, *a_ty, *b_ty, ckind)
}
(RawPtr(a_tymut), RawPtr(b_tymut)) => {
a_tymut.mutbl == b_tymut.mutbl
&& structurally_same_type_impl(
seen_types, tcx, param_env, a_tymut.ty, b_tymut.ty, ckind,
)
}
(Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
// For structural sameness, we don't need the region to be same.
a_mut == b_mut
&& structurally_same_type_impl(
seen_types, tcx, param_env, *a_ty, *b_ty, ckind,
)
}
(FnDef(..), FnDef(..)) => {
let a_poly_sig = a.fn_sig(tcx);
let b_poly_sig = b.fn_sig(tcx);
// We don't compare regions, but leaving bound regions around ICEs, so
// we erase them.
let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
(a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
== (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
&& a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
structurally_same_type_impl(seen_types, tcx, param_env, *a, *b, ckind)
})
&& structurally_same_type_impl(
seen_types,
tcx,
param_env,
a_sig.output(),
b_sig.output(),
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)
})
}
// 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
// not structurally same.
(Dynamic(..), Dynamic(..))
| (Error(..), Error(..))
| (Closure(..), Closure(..))
| (Generator(..), Generator(..))
| (GeneratorWitness(..), GeneratorWitness(..))
| (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
| (Alias(ty::Inherent, ..), Alias(ty::Inherent, ..))
| (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
// These definitely should have been caught above.
(Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
// An Adt and a primitive or pointer type. This can be FFI-safe if non-null
// enum layout optimisation is being applied.
(Adt(..), other_kind) | (other_kind, Adt(..))
if is_primitive_or_pointer(other_kind) =>
{
let (primitive, adt) =
if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
if let Some(ty) = types::repr_nullable_ptr(tcx, param_env, adt, ckind) {
ty == primitive
} else {
compare_layouts(a, b).unwrap_or(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),
}
})
}
}