attempt to call global `print' (a nil value)

Question

I have the following C file:

//thing.c
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

#include <stdio.h>

lua_State* L;

int main(){
        L = lua_open();

        lua_dostring(L, "print(\"lua\")");
        printf("hello\n");

        return 0; }

and the following makefile:

default:
        gcc -I/usr/include/lua50 -L/usr/lib -o qwerty thing.c -llua50 -llualib50

the code builds just fine, but when I run it I get the following:

[string "print("lua")"]:1: attempt to call global `print' (a nil value)
hello

Note: I have seen the many other questions on this error, but they all deal with working directly in Lua, as opposed to with the C api. They also seem to imply that the problem is that the print function was never defined. I don't understand this, as I can run both a lua interpreter and a lua script just fine directly from the command line.

EDIT: I am using lua 5.0

Jesse Beder · Accepted Answer · 2012-08-07T16:23:28.660

10

You have to initialize the libraries in Lua. After you call lua_open, call

luaL_openlibs(L);

Edit: for Lua 5.0, I believe you'll have to open the libraries manually. For the print function, you just need the base library:

luaopen_base(L);

edited Aug 07 '12 at 16:23

answered Aug 07 '12 at 16:10

Jesse Beder

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`thing.c:(.text+0x20): undefined reference to 'luaL_openlibs'` Noteworthy: I am using lua 5.0 – ewok Aug 07 '12 at 16:11
@ewok, see edit. However, since you're getting a linking error (and not a compiler error), I think you may be including the 5.1 or 5.2 header, but linking the 5.0 library. I see you're specifying the 5.0 include path, but I wonder if you have the 5.1 or 5.2 headers somewhere in your default include path? – Jesse Beder Aug 07 '12 at 16:26

attempt to call global `print' (a nil value)

1 Answers1