__asan_region_is_poisoned takes void *

while heap->obj is a VALUE.  A cast should be there.

transient_heap.c

@@ -807,7 +807,7 @@ transient_heap_block_update_refs(struct transient_heap* theap, struct transient_
 
         unpoison_memory_region(header, sizeof *header, false);
 
-        void *poisoned = __asan_region_is_poisoned(header->obj, SIZEOF_VALUE);
+        void *poisoned = __asan_region_is_poisoned((void *)header->obj, SIZEOF_VALUE);
         unpoison_object(header->obj, false);
 
         header->obj = rb_gc_new_location(header->obj);