Question

I am attempting to redefine the print function as described in this question. Here is my code:

extern "C"{
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>
}

#include <iostream>

using namespace std;

lua_State* L;

static int l_my_print(lua_State* L) {
    int nargs = lua_gettop(L);

    for (int i=1; i <= nargs; i++) {
        if (lua_isstring(L, i)) {
            cout << "!!!" << lua_tostring(L, i) << "!!!" << endl;
        }
    }

    return 0;
}

static const struct luaL_Reg printlib [] = {
  {"print", l_my_print},
  {NULL, NULL} /* end of array */
};

extern int luaopen_luamylib(lua_State *L)
{
  lua_getglobal(L, "_G");
  luaL_register(L, NULL, printlib);
  lua_pop(L, 1);
}


int main(){
    L = luaL_newstate();
    luaL_openlibs(L);
    luaopen_luamylib(L);

    luaL_dostring(L, "print(\"hello\")");

    lua_close(L);

    return 0;
}

When I attempt to compile the code, I get:

$ g++ -I/usr/include/lua5.2 -o embed test.cpp -Wall -Wextra -llua5.2
test.cpp:28:1: error: elements of array ‘const luaL_reg printlib []’ have incomplete type
test.cpp:28:1: error: storage size of ‘printlib’ isn’t known
test.cpp: In function ‘int luaopen_luamylib(lua_State*)’:
test.cpp:33:34: error: ‘luaL_register’ was not declared in this scope
test.cpp:35:1: warning: no return statement in function returning non-void [-Wreturn-type]

Can anyone explain what is occurring here? am I missing a library or something?

UPDATE

It was pointed out that the struct is called luaL_Reg, not luaL_reg. This solved my first problem:

$ g++ -I/usr/include/lua5.2 -o embed test.cpp -Wall -Wextra -llua5.2
test.cpp: In function ‘int luaopen_luamylib(lua_State*)’:
test.cpp:33:34: error: ‘luaL_register’ was not declared in this scope
test.cpp:35:1: warning: no return statement in function returning non-void [-Wreturn-type]

Answer 1

First error: It’s luaL_Reg, not luaL_reg.

Second error:
luaL_register is deprecated (in Lua 5.2), and is only available if LUA_COMPAT_MODULE is defined before you include the Lua headers. You should use luaL_setfuncs instead.