Lua Binding Generator Tutorial

A Lua binding is the interface between the Lua virtual machine and a native C function or C++ method. It is the glue code that makes it possible to call native code from within a Lua script.

The idea is to extend Lua with your own functions and methods, such as device management APIs. Lua bindings can be designed manually or generated automatically. This web application helps new users expose proprietary C or C++ APIs to Lua without first learning how to construct Lua bindings by hand.

Automatically Generated vs. Manually Designed Bindings

Automatically generated bindings provide a fast and convenient way to get started. By supplying your header files, this tool can generate the glue code required to expose many C/C++ functions to Lua with minimal effort.

This approach is especially useful for quick prototypes or large APIs where writing bindings manually would be time-consuming. However, generated bindings are usually generic and may not provide the most natural or efficient Lua interface.

For production systems, particularly in embedded environments, manually designed bindings are usually recommended because they let you:

Create a cleaner and more intuitive Lua API
Reduce code size and memory usage
Implement advanced patterns such as asynchronous callbacks and object-oriented interfaces

See the following resources for more information:

Introduction to Lua bindings and how to write Lua bindings using C code and load the bindings dynamically at runtime.
Manual Lua binding creation using the C++ framework SOL2, including how to statically include the bindings in the Mako Server at compile time.
C/C++ to Lua asynchronous binding tutorial for sending events, such as real-time interrupt messages, from C/C++ code to Lua.

How to Generate Lua Bindings for C or C++

Create a text file named functions.txt.
Copy the function declarations you want to expose from your header file(s) and paste them into functions.txt.
Navigate to the online Lua Binding Generator.
Select a module name for your functions.
Select C or C++ and click Continue.
Use a browser that supports drag and drop, such as Firefox or Chrome, and drop functions.txt into the browser window.
Download the generated C or C++ file.
Integrate the generated C or C++ file with your build.

Note: Function declarations in functions.txt may depend on defines, types, enumerations, and other declarations. Do not paste those supporting declarations into functions.txt. Instead, include the header files where they are defined when you drag files into the browser. You can drag and drop multiple files at the same time. For example, select functions.txt and the required header files, then drop them into the browser together. You cannot drop files multiple times; all required files must be dropped simultaneously.

Note: If you drag header files into the browser without functions.txt, the generator creates bindings for all functions found in those headers. Use functions.txt to limit the generated bindings to only the functions you want to make available to Lua.

Note: When generating C++ bindings, functions.txt must include the class declarations and class methods you want to expose.

Note: If your browser does not support drag and drop, you can ZIP all required files into one archive and upload the archive using the traditional upload button.

Simplified Wrapper Generator (SWIG)

This service, the Lua Binding Generator Web Application, uses SWIG under the hood. Use it as an initial stepping stone. We recommend learning how to manually create Lua bindings, but SWIG is useful when you need a quick starting point or have a large set of C/C++ functions to expose to Lua.

SWIG can be installed on Linux with sudo apt install swig.
Windows binaries can be downloaded from the SWIG web site.

Recommended reading:

C++ Tutorial: Binding C++ to Lua Using Swig
Linux Tutorial: Embedded Linux Web Interface Design
Documentation: SWIG and Lua
Documentation: The complete SWIG documentation

Note: The module interface file used by SWIG is automatically created by the Lua Binding Generator Web Application. The file is assembled as follows:

%module your-selected-module-name %{ The optional header files are included here %} The content of functions.txt is injected here. If you do not include functions.txt, then all header files are included here.

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