If std::allocator_traits::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap. Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined).
wanghenshui
commented
10 months ago
std::allocator_traits::propagate_on_container_swap::value
If std::allocator_traits::propagate_on_container_swap::value is true, then the allocators are exchanged using an unqualified call to non-member swap. Otherwise, they are not swapped (and if get_allocator() != other.get_allocator(), the behavior is undefined).
https://en.cppreference.com/w/cpp/container/vector/swap
https://godbolt.org/z/41Tz1sKdq