Listing 7.12 - Undefined behaviour#37
Open
ITHelpDec wants to merge 1 commit intoanthonywilliams:mainfrom
Open
Conversation
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)
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
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.