https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100153
Bug ID: 100153
Summary: Undefined behavior in stl_bvector.h
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: hewillk at gmail dot com
Target Milestone: ---
stl_bvector.h#L505:
_Bit_type*
_M_end_addr() const _GLIBCXX_NOEXCEPT
{
if (this->_M_end_of_storage)
return std::__addressof(this->_M_end_of_storage[-1]) + 1;
return 0;
}
This one will cause UB if _M_end_of_storage is not nullptr and
_M_end_of_storage is equal to _M_start._M_p.
Consider (https://godbolt.org/z/vvrG6KcWP):
std::vector<bool> bv{true, false, true};
bv.clear();
bv.shrink_to_fit();
bv.capacity();
When shrink_to_fit() ends, _M_end_of_storage will be equal to _M_start._M_p and
not nullptr. In capacity():
size_type
capacity() const _GLIBCXX_NOEXCEPT
{ return size_type(const_iterator(this->_M_impl._M_end_addr(), 0)
- begin()); }
we will call _M_end_addr() and perform illegal dereference which cause UB, same
with push_back(), insert() and flip().
