keke wrote

Thanks for using this software.

This is a "ftbfs with GCC-10" issue, which is going to be fixed in the near future. The next version of smstools3 has been ready for a while, but it was not released. Because this issue affects to many new distributions on testing, I will release the next version with this ftbfs fixed, and also with lots of new features. This likely will happen during the some next weeks.

While waiting for the next version, you should just disable the warnings. In the src/Makefile, change the line:
CFLAGS += -W -Wall
to
CFLAGS += -fcommon

Hope this helps. At least on Debian 5.7.10-1 (2020-07-26) with GCC 10.1.0-6 the smsd got compiled with the changed flags.