Understanding and Using C Pointers

Chapter 8. Odds and Ends

Pointers are vital to almost all aspects of C. Many of these areas are fairly well defined, such as arrays and functions. This chapter examines several topics that do not neatly fit into the previous chapters. Coverage of these topics will round out your knowledge of how pointers work.

In this chapter, we will examine several topics related to pointers:

• Casting pointers

• Accessing hardware devices

• Aliasing and strict aliasing

• Use of the restrict keyword

• Threads

• Object-oriented techniques

With regards to threads, there are two areas of interest. The first deals with the basic problem of sharing data between threads using pointers. The second discusses how pointers are used to support callbacks. An operation may invoke a function to perform a task. When the actual function called changes, this is referred to as a callback function. For example, the sort function used in Chapter 5 is an example of a callback function. A callback is also used to communicate between threads.

We will cover two approaches for providing object-oriented type support within C. The first is the use of an opaque pointer. This technique hides a data structure’s implementation details from users. The second technique will demonstrate how to effect polymorphic type behavior in C.

Casting Pointers

Casting is a basic operator that can be quite useful when used with pointers. Casting pointers are useful for a number of reasons, including:

• Accessing a special purpose address

• Assigning an address to represent ...