Lua Integration 101

So you want to use Lua to script your C program?

Here's a basic C code skeleton (hosting the Lua runtime) that allows you to run a Lua script via host lua_script.lua with the Lua script able to directly call the say_something function defined in the C host program.

Assuming you have a C/C++ compiler such as the DevKit installed on your Windows box as well as the Lua headers and library, build the executable using something like:

C:\>gcc -Wall -O3 -s -o host.exe -Ic:/lua/include -Lc:/lua/bin -llua51 host.c


More details and examples in future posts.

/* file: host.c */

#include <stdio.h>
#include <stdlib.h>

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"

/* Variable arg function callable from a Lua script as:
 *   say_something('A', 'gaggle', 'of', 5, 'args')
static int
say_something(lua_State* luaVM) {
    int n = lua_gettop(luaVM);
    int i;

    if (n == 0) {
        printf("no arguments");
        return 0;

    for (i = 1; i <= n; i++) {
        if (!lua_isstring(luaVM, i)) {
            lua_pushstring(luaVM, "[ERROR] argument must be a string or a number");
        printf("%s\n", lua_tostring(luaVM, i));

    return 0;

static void
print_usage(void) {
    fprintf(stderr, "usage: %s lua_script\n", "main");

static int
check_args(int arg_count, char** arg_strings) {
    if (arg_count != 2) {
    } else {

static void
err_message(const char* msg) {
    fprintf(stderr, "%s\n", msg);

main(int argc, char** argv) {
    if (!check_args(argc, argv)) return(EXIT_FAILURE);

    /* Initialize Lua */
    lua_State* luaVM = luaL_newstate();
    if (luaVM == NULL) {
        err_message("Cannot initialize Lua; exiting...");
        return EXIT_FAILURE;

    /* Stop the GC during Lua library (all std) initialization and function
     * registrations. C functions that are callable from a Lua script must be
     * registered with Lua.
    lua_gc(luaVM, LUA_GCSTOP, 0);
    lua_register(luaVM, "say_something", say_something);
    lua_gc(luaVM, LUA_GCRESTART, 0);

    /* Execute the Lua script */
    if (luaL_dofile(luaVM, argv[1])) err_message("Problem running script.");

    /* Lua cleanup */

    return EXIT_SUCCESS;
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