Jakub Jablonski escribió:

Hi, I was trying out some examples of using multi_index_container with custom allocator. I found out that even an empty container, on creation, allocates memory for a single node (but no element is stored inside). In other words, if I store N elements, the container allocates memory for N+1 elements.

Is it a fault?

No, your appreciaton is correct, an empty multi_index_container allocates one node.

If not, what is this memory used for?

This node is known as a header node and simplifies the handling of the internal data structures such as rb-trees. For instance, end iterators point to this header node.

Is there any way to avoid this allocation?

Not from the user's side, I'm afraid. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo