A C++ program that calls a Lua script

Posted 2025-04-21 · Updated 2025-05-01

Alright, so after preparing Lua, here are a few small first step on how to make use of this language within a C++ context

By the way: I haven’t yet used Lua¹ very much, but I’ve read a few tutorials: Well, I don’t think that I will ever fall in love with that language (although I also though that about Powershell many years ago, and that has changed quite a bit in recent years!): Some decisions reading syntax and grammar are pretty… interesting :-/

But I also looked thru the internet for alternatives; any other languages (since 1993, when Lua appeared on the scene), that are similarly small, performant and embeddable in C or C++, resp. for extending C or C++:

And it doesn’t really look that way. There have been a few attempts (mostly based on Lua), but they either were even more niche and/or withered away (after a few years/several years ago).

Something like Python is way more popular and widespread, but looks also to be too big and too powerful.

Setting up the CMake build system

Well, nowadays I have my own helper functions/scripts to quickly set up a prefabricated CMake project for Windows/Visual Studio, by some “boilerplate code” (project template), so I won’t go into the details (this posting is, as many posts here, primarily written for my future self; and explaining that all here in details would just distract from the actual topic).

I only needed to add a few paths in the CMakeLists.txt file, so that the header files and the static library for Lua could be found by the C++ compiler and linker.
(For this test, these are only hardwired paths; don’t pay too much attention.)

target_include_directories (${PROJECT_NAME}
    # ...
	PRIVATE
		"C:/Program Files/Lua/src"
        # ...
)

target_link_libraries (${PROJECT_NAME}
    PRIVATE
        "C:/Program Files/Lua/lua-static-${CPU_ARCHITECTURE}.lib"
)

Source Code

The host program, written in C++, will just call a Lua script that simply prints a line of text:

-- script.lua
print("Hello, world... from a Lua script file!")

The host, the C++ code, sets up the Lua environment (plus a few more necessary steps) and then calls an external Lua script (provided as a path via a command line argument). This is really just a bare “Minimum Viable Product” for now:

#include <iostream>
#include <format>   // I really like the new format strings, but it requires support for the ISO C++ 20 standard! 

extern "C"
{
    #include <lua.h>
    #include <lualib.h>
    #include <lauxlib.h> // The auxiliary library is incuded with Lua and offers a few convenience functions.
}

int main (int argc, char* argv[])
{
    if (argc != 2)
    {        
        std::cout << "Must be called with exactly one argument: The full path to a *.lua file!" << std::endl;
        return 1;
    }
    
    const auto L = luaL_newstate();
        // Set up a new Lua state.

    luaopen_base(L);
        // Open Lua's "base" standard library, to make print() available for the Lua script.

    int status = luaL_dofile (L, argv[1]);
        // Load (and immediately run!) the Lua script from the provided path.
    
    if (status != 0)
        std::cout << std::format("luaL_dofile failed: {0}", lua_tostring(L, -1)) << std::endl;
    
    lua_close(L);
        // Close the Lua state again and clean up.
    
    return 0;
}

Lua 5.4 Reference Manual ↩︎

Feedback: comment@saoe.net · Categories: Development, How To · Tags: EN, C++, Lua, Using C++ with Lua

◀ Building Lua 5.4.7 on Windows 10 with Visual Studio 2022

Mini-Reviews #52 ▶