+/**
+ * opt_set_alloc - set alloc/realloc/free function for opt to use.
+ * @allocfn: allocator function
+ * @reallocfn: reallocator function, ptr may be NULL, size never 0.
+ * @freefn: free function
+ *
+ * By default opt uses malloc/realloc/free, and simply crashes if they fail.
+ * You can set your own variants here.
+ */
+void opt_set_alloc(void *(*allocfn)(size_t size),
+ void *(*reallocfn)(void *ptr, size_t size),
+ void (*freefn)(void *ptr));
+