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Comment by eska | Hacker News Reader

Respectfully, you do not seem to understand this topic well. If the C++ standard library design abstracted memory allocation correctly, you’d still be able to use containers and algorithms and not even notice that their allocation strategy uses the heap, stack, a bump allocator, a pool, etc

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Would that even work? If you use std::vector within an arena, you allocate twice as much memory as you need to, since the old arrays can't be deallocated. You might want to use std::deque instead. Memory management is not independent from data structures - std allocators smell to me like another failed experiment, like auto_ptr mentioned in another comment.

Also, with allocators you can replace new and delete, but you can't implement anything that doesn't fit into the new/delete paradigm, like any allocation strategy that requires moving objects.

I understand how C++ standard containers are designed. They are designed in such a way, so that they don't store a pointer to an allocator instance inside. This allows to save memory in the most cases (where the standard allocator is used). Overriding an allocator is possible, but only with some another global allocator (via a template argument), with no possibility to specify a per-object allocator.

As I know in newer C++ standards there is something which allows to workaround this issue. Or at least there are proposals for this.

Each container stores an allocator instance inside, not a pointer to one. If you need shared state, it's up to you to make each allocator instance contain a pointer to the shared state.

Respectfully, your way out of date with your understanding of this topic.

C++ added polymorphic memory allocators in C++17 along with polymorphic versions of all standard library containers under the std::pmr namespace, so that you have std::pmr::vector, std::pmr::map, etc... all of which fully abstract out the details of memory allocation.

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