Mac OS X For Unix Geeks, 4th Edition

Chapter 11. Libraries, Headers, and Frameworks

In the previous chapter, we gave an overview of the development tools that ship with Mac OS X and emphasized the compilation phase of building executable code. In this chapter, we’ll discuss the linking phase of building Unix-based software under Mac OS X: in particular, header files and libraries.

Header Files

There are two types of header files in Mac OS X:

Ordinary header files

These header files are inserted into source code by a preprocessor prior to compilation. Ordinary header files have an .h extension.

Precompiled header files

These header files have an .h.gch extension.

Header files serve four functions:

• They contain C declarations.

• They contain macro definitions.

• They provide for conditional compilation.

• They provide line control when combining multiple source files into a single file that is subsequently compiled.

Unix developers will find the ordinary header files familiar, since they follow the BSD convention. The C preprocessor directive #include includes a header file in a C source file. There are essentially three forms of this syntax:

#include <headername.h>

This form is used when the header file is located in the directory /usr/include.

#include <directory/headername.h>

This form is used when the header file is located in the directory /usr/include/ directory, where directory is a subdirectory of /usr/include.

#include "headername.h"

This form is used when the header file is located in a user or nonstandard directory. The file should ...