py/gc: Update comment now that gc_drain_stack is called gc_mark_subtree.
@@ -341,10 +341,9 @@ void gc_collect_root(void **ptrs, size_t len) {
for (size_t i = 0; i < len; i++) {
void *ptr = ptrs[i];
if (VERIFY_PTR(ptr)) {
- // Mark and push this pointer
size_t block = BLOCK_FROM_PTR(ptr);
if (ATB_GET_KIND(block) == AT_HEAD) {
- // an unmarked head, mark it, and push it on gc stack
+ // An unmarked head: mark it, and mark all its children
TRACE_MARK(block, ptr);
ATB_HEAD_TO_MARK(block);
gc_mark_subtree(block);
