How to export a symbol from an external module?

I am coding outside the kernel source tree. There are two modules, the first one printt have a function printtty() to print string to the current tty, and the second module hello which invokes printtty() during initialization.

I have added EXPORT_SYMBOL(printtty) in module printt, and after insmod ./printt.ko, the information of printtty() can be seen in /proc/kallsyms.

The make process of module hello goes all right. But insmod ./hello.ko will cause an error like:

insmod: ERROR: could not insert module hello.ko: Invalid parameters

and dmesg shows

hello: no symbol version for printttyhello: Unknown symbol printtty (err -22)`.

I've fixed this by

(1) Copy the hello.ko file to a location beneath /lib/modules/version/kernel

(2) Add the exported symbols from hello.ko to /lib/modules/version/build/Module.symvers

But I wonder is there any way to export a symbol just from an external module(without modifying kernel source tree)?