User Jano has found that the compilation instructions for RenumKicadPCB under Linux Mint should include -lm (see https://documenteddesigns.com/2017/03/27/renumkicadpcb-v0203/)
“I just compiled and used your utility successful! Thanks. Just a note to compile I needed to ad -lm at the end of the gcc order: gcc RenumKiCadPCB.c -o RenumKiCadPCB -lm my system is linuxmint 18.3, after that it worked perfectly.”
My understanding is that -lm usually includes a library module (i.e. -lmMingw32) and I’m not a gcc guru so I don’t know what the -lm by itself does, but if you have problems give it a try.