Serhiy: "use gc_next/gc_refs for managing a linked list"

I'm not sure that I understand your idea. These fields are already used internally by the garbage collector. If I modify one of these fields, it would corrupt the GC, no?

Serhiy: "You can use a dynamic array of PyObject** instead of a linked list for collecting references to "static variables""

Ah yes, I like the idea of using a single array to track all variables. An array reduces memory fragmentation and is simple to maintain, since the API only needs two operations: list.append(obj) and list.clear(). The API already requires to check for errors, so another memory allocation failure wouldn't be suprising.