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AK: Fix crash during teardown of self-owning objects

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We now null out smart pointers *before* calling unref on the pointee.
This ensures that the same smart pointer can't be used to acquire a new
reference to the pointee after its destruction has begun.

I ran into this when destroying a non-empty IntrusiveList of RefPtrs,
but the problem was more general so this fixes it for all of RefPtr,
NonnullRefPtr, OwnPtr and NonnullOwnPtr.
This commit is contained in:
Andreas Kling 2023-04-21 13:36:32 +02:00
parent 66bd7cdb28
commit b7e847e58b
10 changed files with 102 additions and 14 deletions
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27
Tests/AK/TestNonnullRefPtr.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -8,6 +8,7 @@
#include <AK/DeprecatedString.h>
#include <AK/NonnullRefPtr.h>
#include <AK/OwnPtr.h>
struct Object : public RefCounted<Object> {
int x;
@ -58,3 +59,27 @@ TEST_CASE(swap_with_self)
swap(object, object);
EXPECT_EQ(object->ref_count(), 1u);
}
TEST_CASE(destroy_self_owning_refcounted_object)
{
// This test is a little convoluted because SelfOwningRefCounted can't own itself
// through a NonnullRefPtr directly. We have to use an intermediate object ("Inner").
struct SelfOwningRefCounted : public RefCounted<SelfOwningRefCounted> {
SelfOwningRefCounted()
: inner(make<Inner>(*this))
{
}
struct Inner {
explicit Inner(SelfOwningRefCounted& self)
: self(self)
{
}
NonnullRefPtr<SelfOwningRefCounted> self;
};
OwnPtr<Inner> inner;
};
RefPtr object = make_ref_counted<SelfOwningRefCounted>();
auto* object_ptr = object.ptr();
object = nullptr;
object_ptr->inner = nullptr;
}