Listing 7.12 - Undefined behaviour #37
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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)
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Please consider modifying the implicit-boolean
ptrcheck at line 34 toptr->next.ptr.ccia_code_samples/listings/listing_7.12.cpp
Line 34 in 6e7ae1d
ccia_code_samples/listings/listing_7.12.cpp
Line 34 in 16d5077
Even if the stack is empty while calling the destructor,
ptris a valid pointer from the moment we callhead.load()- this leads to undefined behaviour inside one of the atomic fetch operations.Whilst this has been a useful exercise in debugging, please also consider uploading fully-functioning code as a means of verifying that the code published actually functions as intended.
I have attached an example here for anyone coming up against similar issues.