sbuf_extend
else if (sbuf_extend(s, len > INT_MAX ? INT_MAX : len)
else if (sbuf_extend(s, 1) < 0)
sbuf_extend(s, len - SBUF_FREESPACE(s));
sbuf_extend(s, len);
else if (sbuf_extend(s, len - SBUF_FREESPACE(s)) != 0)