[steventhedev]

The generic version in TFA puts the data type allocated alongside the next pointer - no additional allocation needed. The only functional difference is if the zig compiler is not sufficiently advanced to understand it can reorder the fields (hence the alignment question).

The removal scenario is merely specifying that you are passing in ConnectionListNode instead of a Connection. Although maybe it's a good idea to think about how they compose comparatively.

[whizzter]

Forgot to reply earlier, but there's a difference here.

When the data type is allocated beside the next pointer of the linked structure, the linked structure owns the allocation. So if an object is a member of 2 linked lists, if destruction is allowed through both of the items then destroying the will always involve traversal to locate the outer if destroyed through the inner unless using possibly undefined pointer tricks.

In the intrusive example, since the data-item owns the list pointers, the pointer adjustment is expected but well defined, destruction especially is coherent since the data object is destroyed (extra semantics are easily fixed and the unlinking process is coherent).