https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91531
Bug ID: 91531
Summary: _Rb_tree's copy assignment should respect to POCCA
regardless of is_always_equal
Product: gcc
Version: 9.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: frankhb1989 at gmail dot com
Target Milestone: ---
In <bits/stl_tree.h>:
template<typename _Key, typename _Val, typename _KeyOfValue,
typename _Compare, typename _Alloc>
_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&
_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
operator=(const _Rb_tree& __x)
{
if (this != &__x)
{
// Note that _Key may be a constant type.
#if __cplusplus >= 201103L
if (_Alloc_traits::_S_propagate_on_copy_assign())
{
auto& __this_alloc = this->_M_get_Node_allocator();
auto& __that_alloc = __x._M_get_Node_allocator();
if (!_Alloc_traits::_S_always_equal()
&& __this_alloc != __that_alloc)
{
// Replacement allocator cannot free existing storage, we
need
// to erase nodes first.
clear();
std::__alloc_on_copy(__this_alloc, __that_alloc);
}
}
#endif
_Reuse_or_alloc_node __roan(*this);
_M_impl._M_reset();
_M_impl._M_key_compare = __x._M_impl._M_key_compare;
if (__x._M_root() != 0)
_M_root() = _M_copy(__x, __roan);
}
return *this;
}
As `std::__alloc_on_copy` is called only when
`!_Alloc_traits::_S_always_equal() && __this_alloc != __that_alloc`, so a POCCA
allocator will not be propagated once it is always equal. This is also not
consistent with all sequence/unordered associative standard allocator-aware
containers implemented in libstdc++.
