Running luajit object file from C

Question

From the documentation: http://luajit.org/running.html

luajit -b test.lua test.obj                 # Generate object file
# Link test.obj with your applicati         


        

Answer 1

The basic usage is as follows:

• Generate the header file using luajit
• #include that header in the source file(s) that's going to be referencing its symbols
• Compile the source into a runnable executable or shared binary module for lua depending on your use-case.

Here's a minimal example to illustrate:

test.lua

return
{
  fooprint = function (s) return print("from foo: "..s) end,
  barprint = function (s) return print("from bar: "..s) end
}

---

test.h

// luajit -b test.lua test.h
#define luaJIT_BC_test_SIZE 155
static const char luaJIT_BC_test[] = {
27,76,74,1,2,44,0,1,4,0,2,0,5,52,1,0,0,37,2,1,0,16,3,0,0,36,2,3,2,64,1,2,0,15,
102,114,111,109,32,102,111,111,58,32,10,112,114,105,110,116,44,0,1,4,0,2,0,5,
52,1,0,0,37,2,1,0,16,3,0,0,36,2,3,2,64,1,2,0,15,102,114,111,109,32,98,97,114,
58,32,10,112,114,105,110,116,58,3,0,2,0,5,0,7,51,0,1,0,49,1,0,0,58,1,2,0,49,1,
3,0,58,1,4,0,48,0,0,128,72,0,2,0,13,98,97,114,112,114,105,110,116,0,13,102,
111,111,112,114,105,110,116,1,0,0,0,0
};

---

runtest.cpp

// g++ -Wall -pedantic -g runtest.cpp -o runtest.exe -llua51
#include 
#include 

#include "lua.hpp"
#include "test.h"

static const char *runtest = 
"test = require 'test'\n"
"test.fooprint('it works!')\n"
"test.barprint('it works!')\n";


int main()
{
  lua_State *L = luaL_newstate();
  luaL_openlibs(L);

  lua_getglobal(L, "package");
  lua_getfield(L, -1, "preload");
  // package, preload, luaJIT_BC_test
  bool err = luaL_loadbuffer(L, luaJIT_BC_test, luaJIT_BC_test_SIZE, NULL);
  assert(!err);

  // package.preload.test = luaJIT_BC_test
  lua_setfield(L, -2, "test");

  // check that 'test' lib is now available; run the embedded test script 
  lua_settop(L, 0);
  err = luaL_dostring(L, runtest);
  assert(!err);

  lua_close(L);
}

This is pretty straight-forward. This example takes the byte-code and places it into the package.preload table for this program's lua environment. Other lua scripts can then use this by doing require 'test'. The embedded lua source in runtest does exactly this and outputs:

from foo: it works!
from bar: it works!