problems embedding lua in c++

Question

I am attempting to embed lua code in C++, and I'm getting a strange compiler error. Here's my code:

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

int main() {
    lua_State *luaVM = luaL_newstate();
    if (luaVM == NULL) {
        printf("Error initializing lua!\n");
        return -1;
    }

    luaL_openlibs(luaVM);

    luaL_dofile(luaVM, "test.lua");

    lua_close(luaVM);

    return 0;
}

compiled with:

g++ -Wall -o embed -llua embed.cpp

and the error is:

g++ -Wall -o embed -llua embed.cpp
/tmp/ccMGuzal.o: In function `main':
embed.cpp:(.text+0x47): undefined reference to `luaL_loadfilex'
embed.cpp:(.text+0x72): undefined reference to `lua_pcallk'
collect2: error: ld returned 1 exit status

I am not calling luaL_loadfilex or lua_pcallk from my code, which lends itself to the assumption that the problem is not in my code, but in lua itself. does anyone have any ideas here?

UPDATE

Here is my version info:

$ lua -v
Lua 5.2.0  Copyright (C) 1994-2011 Lua.org, PUC-Rio

@MartinSchröder note that that also was my question. I decided that, having figured out what was causing that problem (lualib doesnt exist), it was better to ask this as a new question that keep editing that one. — ewok
– ewok, Commented Jul 31, 2012 at 17:43

yuri kilochek · Accepted Answer · 2012-07-31 14:40:37Z

2

In in lua 5.2.1 luaL_dofile is a macro that is declared like so:

#define luaL_dofile(L, fn) \
    (luaL_loadfile(L, fn) || lua_pcall(L, 0, LUA_MULTRET, 0))

in your version of lua it might very well be implemented with luaL_loadfilex and lua_pcallk, and you get undefined references like @Shahbaz said.

answered Jul 31, 2012 at 14:40

yuri kilochek

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Comments

Shahbaz · Accepted Answer · 2012-07-31 15:01:58Z

2

Pre 5.1 answer: According to this website, you need to add -llualib after -llua if you include lauxlib.h and lualib.h:

g++ -Wall -o embed embed.cpp -llua -llualib

Update

Silly me, you should always link files/libs in the order they use the other. If A uses B, you should mention A before B.

In your case, since embed.cpp uses lua, then you should write:

g++ -Wall -o embed embed.cpp -llua

edited Jul 31, 2012 at 15:01

answered Jul 31, 2012 at 14:36

Shahbaz

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8 Comments

ewok Over a year ago

according to this answer, there is no lualib in lua >5.1. when I add -llualib, i get a new error, backing this up: /usr/bin/ld: cannot find -llualib

Shahbaz Over a year ago

@ewok, what is your lua version?

ewok Over a year ago

@Shabaz, I have moved the links, but to no avail.

Shahbaz Over a year ago

@ewok, do you get the exact same error?! Try nm on the lib file of lua and check if those symbols exist in it.

Shahbaz Over a year ago

@ewok, did you nm on lua's lib file?

|

ewok · Accepted Answer · 2012-09-12 12:58:19Z

2

Ultimately the problem was that the libraries are named differently by version. When installed from the repository, the libraries are called liblua5.x and liblualib5.x, and therefore the following command was required:

g++ -Wall -o embed embed.cpp -llua5.2 -llualib5.2

answered Sep 12, 2012 at 12:58

ewok

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Comments

Zoe - Save the data dump · Accepted Answer · 2019-02-17 19:22:27Z

0

You can use:

cc embed.cpp -o embed -llua -L../lua -I../lua -lm -ldl

edited Feb 17, 2019 at 19:22

Zoe - Save the data dump

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answered Feb 17, 2019 at 19:11

Andres Riofrio

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