compile.sh

#!/bin/bash
# located in root

# cd into project directory
cd ${0%/*}

# compile library
clang++ -Wall -dynamiclib lib_src/myprint.cpp -o myprint.dylib

# compile main object file
clang++ -Wall -c main_src/main.cpp -I ./lib_src -o main.o

# link main object file and dylib
clang++ -Wall main.o myprint.dylib -o main

main.cpp

// Located in root/main_src
#include "../lib_src/print_lib.h"

int main(int argc, char **argv)
{
    lib_print("HELLO WORLD");
}

print_lib.cpp

// Located in root/lib_src
#include <iostream>
#include "print_lib.h"

void lib_print(const char *input)
{
    std::cout << "lib_print: " << input << std::endl;
}

print_lib.h

// Located in root/lib_src
#pragma once

void lib_print(const char *input);