Book Image

Integrate Lua with C++

By : Wenhuan Li
Book Image

Integrate Lua with C++

By: Wenhuan Li

Overview of this book

C++ is a popular choice in the developer community for building complex and large-scale performant applications and systems. Often a need arises to extend the system at runtime, without recompiling the whole C++ program. Using a scripting language like Lua can help achieve this goal efficiently. Integrate Lua to C++ is a comprehensive guide to integrating Lua to C++ and will enable you to achieve the goal of extending C++ programs at runtime. You’ll learn, in sequence, how to get and compile the Lua library, the Lua programming language, calling Lua code from C++, and calling C++ code from Lua. In each topic, you’ll practice with code examples, and learn the in-depth mechanisms for smooth working. Throughout the book, the latter examples build on the earlier ones while also acting as a standalone. You’ll learn to implement Lua executor and Lua binding generator, which you can use in your projects directly with further customizations. By the end of this book, you’ll have mastered integrating Lua into C++ and using Lua in your C++ project efficiently, gained the skills to extend your applications at runtime, and achieved dynamic and adaptable C++ development.
Table of Contents (18 chapters)
Free Chapter
1
Part 1 – Lua Basics
4
Part 2 – Calling Lua from C++
8
Part 3 – Calling C++ from Lua
12
Part 4 – Advanced Topics

Storing state in Lua

There are two ways to store state in Lua for lua_CFunction: upvalues and the registry. Let’s recap them and dig deeper into upvalues.

Upvalues

To introduce the complete definition for upvalues, we need to introduce Lua C closures at the same time. To quote the Lua reference manual:

When a C function is created, it is possible to associate some values with it, thus creating a C closure; these values are called upvalues and are accessible to the function whenever it is called.

To put it simply, the closure is still our old friend lua_CFunction. When you associate some values with it, it becomes a closure, and the values become upvalues.

It is important to note that Lua C closures and upvalues are inseparable.

To create a closure, use the following library function:

void lua_pushcclosure(
    lua_State *L, lua_CFunction fn, int n);

This creates a closure from lua_CFunction and associates n values with it.

To see...