dylib_test.c

#include "lua.h"
#include "lauxlib.h"

#include <stdio.h>

int
dylib_add(lua_State* L) {
    int a = lua_tonumber(L,1);
    int b = lua_tonumber(L,2);
    int c = a+b;
    lua_pop(L,2);
    lua_pushnumber(L,c);
    return 1;
}

int dylib2_test(lua_State* L);
int start(lua_State* L) {
    luaL_requiref(L, "dylib2.test", dylib2_test, 0);
    return 0;
}

int
luaopen_dylib_test(lua_State* L) {
    luaL_Reg l[] = {
       { "add", dylib_add },
       { "start", start },
       { NULL, NULL },
    };
    luaL_checkversion(L);
    luaL_newlib(L,l);

    return 1;
}

int
dylib2_test(lua_State* L) {
    luaL_Reg l[] = {
       { "add", dylib_add },
       { NULL, NULL },
    };
    luaL_checkversion(L);
    luaL_newlib(L,l);

    return 1;
}

test.lua

dylib = require "dylib.test"

local c = dylib.add(1,2)
print(c)

dylib.start()

dylib = require "dylib2.test"

local c = dylib.add(1,2)
print(c)