From 16d50777974df5e8d5c94ba23f914726f06fe36e Mon Sep 17 00:00:00 2001
From: ITHelpDec <34002836+ITHelpDec@users.noreply.github.com>
Date: Sun, 4 Jun 2023 15:05:31 +0100
Subject: [PATCH] Change `ptr` to `ptr->next.ptr`

Inside <shared_ptr>

- Current implementation exhibits undefined behaviour

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _Tp
__libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT
{
#if defined(_LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT) && !defined(_LIBCPP_HAS_NO_THREADS)
    return __atomic_add_fetch(&__t, -1, __ATOMIC_ACQ_REL); <<<<<
//...

- Thread 1: EXC_BAD_ACCESS (code=2, address=0x7ff80feda427)
---
 listings/listing_7.12.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/listings/listing_7.12.cpp b/listings/listing_7.12.cpp
index b271612..b86d979 100644
--- a/listings/listing_7.12.cpp
+++ b/listings/listing_7.12.cpp
@@ -31,7 +31,7 @@ class lock_free_stack
         {
             increase_head_count(old_head);
             node* const ptr=old_head.ptr;
-            if(!ptr)
+            if(!ptr->next.ptr)
             {
                 return std::shared_ptr<T>();
             }