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Fix clashing_extern_declarations stack overflow for recursive types. #75554

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Merged
merged 10 commits into from
Aug 19, 2020
Merged

Fix clashing_extern_declarations stack overflow for recursive types. #75554

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b0eb55a
Add test demonstrating the issue.
jumbatm Aug 15, 2020
db75313
Fix stack overflow for recursive types.
jumbatm Aug 15, 2020
154b74e
Actually introduce a cycle in Reffy test.
jumbatm Aug 16, 2020
a1fa4e0
Remove unnecessary rebinding of def ids.
jumbatm Aug 16, 2020
80c2c80
Remove structural equiv check for Array const.
jumbatm Aug 16, 2020
bca48ad
Reduce indentation by replacing match arm w/ early return.
jumbatm Aug 16, 2020
6c57de1
Don't memoize seen types.
jumbatm Aug 16, 2020
7708abb
Avoid double hashset lookup.
jumbatm Aug 16, 2020
1321a2d
Also accept Refs for is_primitive_or_pointer
jumbatm Aug 16, 2020
bc15dd6
Wrap recursion in `ensure_sufficient_stack`.
jumbatm Aug 17, 2020
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234 changes: 132 additions & 102 deletions src/librustc_lint/builtin.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
use rustc_ast::visit::{FnCtxt, FnKind};
use rustc_ast_pretty::pprust::{self, expr_to_string};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
use rustc_feature::{deprecated_attributes, AttributeGate, AttributeTemplate, AttributeType};
use rustc_feature::{GateIssue, Stability};
Expand Down Expand Up @@ -2153,123 +2154,152 @@ impl ClashingExternDeclarations {
b: Ty<'tcx>,
ckind: CItemKind,
) -> bool {
debug!("structurally_same_type(cx, a = {:?}, b = {:?})", a, b);
let tcx = cx.tcx;
if a == b || rustc_middle::ty::TyS::same_type(a, b) {
// All nominally-same types are structurally same, too.
true
} else {
// Do a full, depth-first comparison between the two.
use rustc_middle::ty::TyKind::*;
let a_kind = &a.kind;
let b_kind = &b.kind;

let compare_layouts = |a, b| -> bool {
let a_layout = &cx.layout_of(a).unwrap().layout.abi;
let b_layout = &cx.layout_of(b).unwrap().layout.abi;
debug!("{:?} == {:?} = {}", a_layout, b_layout, a_layout == b_layout);
a_layout == b_layout
};
fn structurally_same_type_impl<'tcx>(
seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
cx: &LateContext<'tcx>,
a: Ty<'tcx>,
b: Ty<'tcx>,
ckind: CItemKind,
) -> bool {
debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, 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.
return true;
}
let tcx = cx.tcx;
if a == b || rustc_middle::ty::TyS::same_type(a, b) {
// All nominally-same types are structurally same, too.
true
} else {
// Do a full, depth-first comparison between the two.
use rustc_middle::ty::TyKind::*;
let a_kind = &a.kind;
let b_kind = &b.kind;

let compare_layouts = |a, b| -> bool {
let a_layout = &cx.layout_of(a).unwrap().layout.abi;
let b_layout = &cx.layout_of(b).unwrap().layout.abi;
debug!("{:?} == {:?} = {}", a_layout, b_layout, a_layout == b_layout);
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(..))
};

#[allow(rustc::usage_of_ty_tykind)]
let is_primitive_or_pointer =
|kind: &ty::TyKind<'_>| kind.is_primitive() || matches!(kind, RawPtr(..));

match (a_kind, b_kind) {
(Adt(_, a_substs), Adt(_, b_substs)) => {
let a = a.subst(cx.tcx, a_substs);
let b = b.subst(cx.tcx, b_substs);
debug!("Comparing {:?} and {:?}", a, b);

if let (Adt(a_def, ..), Adt(b_def, ..)) = (&a.kind, &b.kind) {
// 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());
compare_layouts(a, b)
ensure_sufficient_stack(|| {
match (a_kind, b_kind) {
(Adt(a_def, a_substs), Adt(b_def, b_substs)) => {
let a = a.subst(cx.tcx, a_substs);
let b = b.subst(cx.tcx, b_substs);
debug!("Comparing {:?} and {:?}", a, b);

// 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());
compare_layouts(a, b)
&& a_fields.eq_by(
b_fields,
|&ty::FieldDef { did: a_did, .. },
&ty::FieldDef { did: b_did, .. }| {
Self::structurally_same_type(
structurally_same_type_impl(
seen_types,
cx,
tcx.type_of(a_did),
tcx.type_of(b_did),
ckind,
)
},
)
} else {
unreachable!()
}
}
(Array(a_ty, a_const), Array(b_ty, b_const)) => {
// For arrays, we also check the constness of the type.
a_const.val == b_const.val
&& Self::structurally_same_type(cx, a_const.ty, b_const.ty, ckind)
&& Self::structurally_same_type(cx, a_ty, b_ty, ckind)
}
(Slice(a_ty), Slice(b_ty)) => Self::structurally_same_type(cx, a_ty, b_ty, ckind),
(RawPtr(a_tymut), RawPtr(b_tymut)) => {
a_tymut.mutbl == b_tymut.mutbl
&& Self::structurally_same_type(cx, &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 && Self::structurally_same_type(cx, a_ty, b_ty, ckind)
}
(FnDef(..), FnDef(..)) => {
let a_poly_sig = a.fn_sig(tcx);
let b_poly_sig = b.fn_sig(tcx);

// As we don't compare regions, skip_binder is fine.
let a_sig = a_poly_sig.skip_binder();
let b_sig = b_poly_sig.skip_binder();

(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| {
Self::structurally_same_type(cx, a, b, ckind)
})
&& Self::structurally_same_type(cx, a_sig.output(), b_sig.output(), ckind)
}
(Tuple(a_substs), Tuple(b_substs)) => {
a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
Self::structurally_same_type(cx, 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(..))
| (Projection(..), Projection(..))
| (Opaque(..), Opaque(..)) => false,

// These definitely should have been caught above.
(Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),

// An Adt and a primitive type. This can be FFI-safe is the ADT is an enum with a
// non-null field.
(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) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
ty == primitive
} else {
compare_layouts(a, b)
}
(Array(a_ty, a_const), Array(b_ty, b_const)) => {
// For arrays, we also check the constness of the type.
a_const.val == b_const.val
&& structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
}
(Slice(a_ty), Slice(b_ty)) => {
structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
}
(RawPtr(a_tymut), RawPtr(b_tymut)) => {
a_tymut.mutbl == b_tymut.mutbl
&& structurally_same_type_impl(
seen_types,
cx,
&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, cx, a_ty, b_ty, ckind)
}
(FnDef(..), FnDef(..)) => {
let a_poly_sig = a.fn_sig(tcx);
let b_poly_sig = b.fn_sig(tcx);

// As we don't compare regions, skip_binder is fine.
let a_sig = a_poly_sig.skip_binder();
let b_sig = b_poly_sig.skip_binder();

(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, cx, a, b, ckind)
})
&& structurally_same_type_impl(
seen_types,
cx,
a_sig.output(),
b_sig.output(),
ckind,
)
}
(Tuple(a_substs), Tuple(b_substs)) => {
a_substs.types().eq_by(b_substs.types(), |a_ty, b_ty| {
structurally_same_type_impl(seen_types, cx, 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(..))
| (Projection(..), Projection(..))
| (Opaque(..), 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) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
ty == primitive
} else {
compare_layouts(a, b)
}
}
// 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),
}
}
// 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),
})
}
}
let mut seen_types = FxHashSet::default();
structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
}
}

Expand Down
119 changes: 119 additions & 0 deletions src/test/ui/lint/clashing-extern-fn-recursion.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,119 @@
// check-pass
//
// This tests checks that clashing_extern_declarations handles types that are recursive through a
// pointer or ref argument. See #75512.

#![crate_type = "lib"]

mod raw_ptr_recursion {
mod a {
#[repr(C)]
struct Pointy {
pointy: *const Pointy,
}

extern "C" {
fn run_pointy(pointy: Pointy);
}
}
mod b {
#[repr(C)]
struct Pointy {
pointy: *const Pointy,
}

extern "C" {
fn run_pointy(pointy: Pointy);
}
}
}

mod raw_ptr_recursion_once_removed {
mod a {
#[repr(C)]
struct Pointy1 {
pointy_two: *const Pointy2,
}

#[repr(C)]
struct Pointy2 {
pointy_one: *const Pointy1,
}

extern "C" {
fn run_pointy2(pointy: Pointy2);
}
}

mod b {
#[repr(C)]
struct Pointy1 {
pointy_two: *const Pointy2,
}

#[repr(C)]
struct Pointy2 {
pointy_one: *const Pointy1,
}

extern "C" {
fn run_pointy2(pointy: Pointy2);
}
}
}

mod ref_recursion {
mod a {
#[repr(C)]
struct Reffy<'a> {
reffy: &'a Reffy<'a>,
}

extern "C" {
fn reffy_recursion(reffy: Reffy);
}
}
mod b {
#[repr(C)]
struct Reffy<'a> {
reffy: &'a Reffy<'a>,
}

extern "C" {
fn reffy_recursion(reffy: Reffy);
}
}
}

mod ref_recursion_once_removed {
mod a {
#[repr(C)]
struct Reffy1<'a> {
reffy: &'a Reffy2<'a>,
}

struct Reffy2<'a> {
reffy: &'a Reffy1<'a>,
}

extern "C" {
#[allow(improper_ctypes)]
fn reffy_once_removed(reffy: Reffy1);
}
}
mod b {
#[repr(C)]
struct Reffy1<'a> {
reffy: &'a Reffy2<'a>,
}

struct Reffy2<'a> {
reffy: &'a Reffy1<'a>,
}

extern "C" {
#[allow(improper_ctypes)]
fn reffy_once_removed(reffy: Reffy1);
}
}
}