+ /*
+ * 'result' must be a dynamically allocated array of exactly
+ * 'resultsize' chars. The code for actually reading input may
+ * realloc it bigger (and adjust resultsize accordingly) if it has
+ * to. The caller should free it again when finished with it.
+ *
+ * If resultsize==0, then result may be NULL. When setting up a
+ * prompt_t, it's therefore easiest to initialise them this way,
+ * which means all actual allocation is done by the callee. This
+ * is what add_prompt does.
+ */
+ char *result;
+ size_t resultsize;