3file.c

// ********************************************************************************
// samplelib.h
#ifndef INCLUDED_SAMPLELIB_H 
#define INCLUDED_SAMPLELIB_H

void some_func(void);

#endif//INCLUDED_SAMPLELIB_H

// ********************************************************************************
// samplelib.c
// system
#include <stdio.h>

// local
#include "samplelib.h"

//
void some_func(void)
{
    printf("samplelib: some_func is called\n");
}

void _init(void)
{
    printf("samplelib: _init is called\n");
}

void _fini(void)
{
    printf("samplelib: _fini is called\n");
}

// ********************************************************************************
// main.c
// system
#include <stdio.h>

//
#include "samplelib.h"

//
int main(void)
{
    //
    printf("main: main is called\n");

    //
    some_func();

    //
    return 0;
}