21st Century C, 2nd Edition

Chapter 6. Your Pal the Pointer

He’s the one

Who likes all our pretty songs

And he likes to sing along

And he likes to shoot his gun

But he don’t know what it means.

Nirvana, “In Bloom”

Like a song about music, or a movie about Hollywood, a pointer is data describing other data. It’s certainly easy to get overwhelmed: all at once, you have to deal with getting lost in references to references, aliases, memory management, and malloc. But our outrageous fortune breaks down into separate components. For example, we can use pointers as aliases without bothering with malloc, which doesn’t have to appear nearly as often as the textbooks from the ’90s told us it did. On the one hand, C’s syntax can be confusing with its use of stars; on the other hand, C’s syntax provides us with tools for dealing with especially complicated setups like pointers to functions.

The topics in this chapter address common errors and common points of confusion. If you’ve been writing in C for a long time, these points will seem like second nature to you, and you might want to skip or quickly skim this chapter. It is intended for all those people (and their numbers are legion) who feel a little uneasy when working with pointers.

Automatic, Static, and Manual Memory

C provides three basic models of memory management, which is two more than most languages and two more than you really want to care about. And as a bonus for you, the reader, I’ll even throw in two more memory models later on (thread-local in ...