- * adns__alloc_interim_{only,fail}(qu,0) will not return 0,
- * but it will not necessarily return a distinct pointer each time.
+ * The memory from _preserved is is kept and transferred into the
+ * larger buffer - unless we run out of memory, in which case it too
+ * is freed. When you use _preserved you have to add code to the
+ * x_nomem error exit case in adns__makefinal_query to clear out the
+ * pointers you made to those allocations, because that's when they're
+ * thrown away; you should also make a note in the declaration of
+ * those pointer variables, to note that they are _preserved rather
+ * than _interim. If they're in the answer, note it here:
+ * answer->cname and answer->owner are _preserved.
+ */
+
+void adns__transfer_interim(adns_query from, adns_query to, void *block, size_t sz);
+/* Transfers an interim allocation from one query to another, so that
+ * the `to' query will have room for the data when we get to makefinal
+ * and so that the free will happen when the `to' query is freed
+ * rather than the `from' query.
+ *
+ * It is legal to call adns__transfer_interim with a null pointer; this
+ * has no effect.
+ *
+ * _transfer_interim also ensures that the expiry time of the `to' query
+ * is no later than that of the `from' query, so that child queries'
+ * TTLs get inherited by their parents.