17. Dynamic Loading

An increasingly popular way of adding functionality to a project is to give a program the ability to dynamically load plugins, or modules. By doing this your users can extend your project in new ways, which even you perhaps hadn't envisioned. Dynamic Loading, then, is the process of loading compiled objects into a running program and executing some or all of the code from the loaded objects in the same context as the main executable.

This chapter begins with a discussion of the mechanics of dynamic modules and how they are used, and ends with example code for very simple module loading on GNU/Linux, along with the example code for a complementary dynamically loadable module. Once you have read this chapter and understand the principles of dynamic loading, the next chapter will explain how to use GNU Autotools to write portable dynamic module loading code and address some of the shortcomings of native dynamic loading APIs.