https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90192
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Something like this:
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -1153,8 +1153,48 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
void
resize(size_type __new_size, const value_type& __x)
{
- if (__new_size > size())
- _M_fill_insert(end(), __new_size - size(), __x);
+ if (__new_size > capacity())
+ {
+ struct _Guard : _Guard_alloc
+ {
+ // Elements to destroy:
+ pointer _M_first{};
+ pointer _M_last{};
+
+ using _Guard_alloc::_Guard_alloc;
+
+ _GLIBCXX20_CONSTEXPR
+ ~_Guard()
+ {
+ std::_Destroy(this->_M_first, this->_M_last,
+ this->_M_vect._M_get_Tp_allocator());
+ }
+ };
+
+ allocator_type& __a = _M_get_Tp_allocator();
+ const size_type __sz = size();
+ const size_type __n = __new_size - size();
+ const pointer __start = this->_M_allocate(__new_size);
+ _Guard __guard(__start, __new_size, *this);
+ const pointer __mid = __start + __sz;
+ __guard._M_last
+ = std::__uninitialized_fill_n_a(__mid, __n, __x, __a);
+ __guard._M_first = __mid;
+ std::__uninitialized_move_if_noexcept_a(this->_M_impl._M_start,
+ this->_M_impl._M_finish,
+ __start, __a);
+ __guard._M_storage = this->_M_impl._M_start;
+ __guard._M_first = this->_M_impl._M_start;
+ __guard._M_last = this->_M_impl._M_last;
+ this->_M_impl._M_start = __start;
+ this->_M_impl._M_finish = __start + __new_size;
+ this->_M_impl._M_end_of_storage = this->_M_impl._M_finish;
+ }
+ else if (__new_size > size())
+ this->_M_impl._M_finish
+ = std::__uninitialized_fill_n_a(this->_M_impl._M_finish,
+ __new_size - size(),
+ __x, _M_get_Tp_allocator());
else if (__new_size < size())
_M_erase_at_end(this->_M_impl._M_start + __new_size);
}
