how to use custom functions in easyc pro

If I create a source file and create a function, such as

#include "Main.h"
int something() { return 5; }

inside of a Source File, how can I access this function inside the main block diagram? Is that possible?

By the way, I went to the Main blog diagram and added a code block that was simply


something();

But when I compiled it said “Warning[2058] Main.c line# 5: call of function without prototype.”

See link: https://vexforum.com/t/answered-g11-entanglement/25220/1