d->config = xrealloc(d->config, d->config_bufsize);
d->present = xrealloc(d->present, d->config_bufsize);
memset(d->present + orig_size, 0, d->config_bufsize - orig_size);
d->config = xrealloc(d->config, d->config_bufsize);
d->present = xrealloc(d->present, d->config_bufsize);
memset(d->present + orig_size, 0, d->config_bufsize - orig_size);