std::pmr::polymorphic_allocator<T>:: select_on_container_copy_construction - cppreference.com

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polymorphic_allocatorselect_on_container_copy_construction()const;(since C++17)Returns a default-constructed polymorphic_allocator object.

Parameters

(none)

Return value

A default-constructed polymorphic_allocator object.

Notes

polymorphic_allocators do not propagate on container copy construction.