How to write C module

[Tristan Kohl <tristankohl@...>]

Hello everybody,

I am trying to create bindings for a C++ library so I can use it in my
Lua project. However I seem to miss something. Maybe one of you could
help me. The module builds without errors but when I try to require the
.so file from Lua I get an error.

Lua version: 5.3.5
OS: Voidlinux


> g++ -fPIC -I/usr/include/lua5.3 -shared -Wall -o test.so test.cpp


> lua
>> require("test")
error loading module 'test' from file './test.so':
	./test.so: undefined symbol: luaopen_test


> nm -g test.so
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable
00000000000011ac T _Z12luaopen_testP9lua_State
                 w __cxa_finalize@@GLIBC_2.2.5
                 w __gmon_start__
                 U luaL_checknumber
                 U luaL_checkversion_
                 U luaL_setfuncs
                 U lua_createtable
                 U lua_pushnumber


test.cpp:
#include <lua.hpp>

static int l_test(lua_State *L) {
    double num1 = luaL_checknumber(L, 1);
    double num2 = luaL_checknumber(L, 2);
    lua_pushnumber(L, num1 + num2);
    return 1;
}

static luaL_Reg mylib [] = {
    {"test", l_test},
    {NULL, NULL}
};

int luaopen_test(lua_State *L) {
    luaL_newlib(L, mylib);
    return 1;
}


lua.hpp:
extern "C" {
#include "lua.h"
#include "lualib.h"
#include "lauxlib.h"
}


Thank you in advance.