Per-type vtable shared by every IoObject of a given primitive class. An IoTag carries the type's name, a set of function pointers (clone, free, mark, activate, compare, perform, write/read, notification, cleanup) and is reference-counted across the proto and all its clones. Each IoObject_new... constructor attaches exactly one tag (installed by the corresponding IoXxx_newTag helper) and the collector calls markFunc / freeFunc through the tag rather than switching on type. Keeping the dispatch here lets IoObject stay a fixed-size marker regardless of how many primitive subtypes the VM defines.
Reference-counted release. Decrements referenceCount and returns early while any object still holds the tag; on the final release it invokes the optional tagCleanupFunc (for per-type bookkeeping like freeing interned pools), frees the duplicated name, and io_frees the tag itself. Called by IoObject's free path through each primitive's tag registration.
Collector hook for per-tag GC roots. Currently a no-op because the recyclableInstances stack is disabled; kept as a seam so future per-type caches (e.g. instance freelists) can participate in marking without touching the collector core.
Copies name into the tag's own heap buffer via io_realloc, so the caller's string need not remain live. Called by IoTag_newWithName_ and whenever a tag is renamed (rare — mostly during bootstrap).
Allocates a zeroed tag with referenceCount 1 and a default performFunc. When IOMESSAGE_INLINE_PERFORM is defined the performFunc is left NULL so IoMessage can inline the dispatch; otherwise it points at IoObject_perform. All other slots (clone/free/mark/activate/compare/ write/read/notification/cleanup) start NULL and must be filled in by the caller before the tag is attached to any object.
Convenience constructor used by every IoXxx_newTag helper: allocate a fresh tag, then set its name. The name is duplicated into the tag's own heap buffer (see IoTag_name_) so the caller's string literal need not remain live.
Bumps referenceCount. Used when the same tag is shared across multiple owners (e.g. CFunction instances of a particular class) so that IoTag_free only actually releases on the last drop.