This book, The Definitive Guide to GCC, is about how to build, install, customize, use, and troub- shoot GCC version 4.x. GCC has long been available for most major hardware and operating system platforms and is often the preferred family of compilers. As a general-purpose set of compilers, GCC produces high-quality, fast code. Due to its design, GCC is easy to port to different architectures, which contributes to its popularity. GCC, along with GNU Emacs, the Linux operating system, the Apache Web server, the Sendmail mail server, and the BIND DNS server, are showpieces of the free software world and proof that sometimes you can get a free lunch. Why a Book About GCC? I wrote this book, and you should read it, for a variety of reasons: it covers version 4.x; it is the only book that covers general GCC usage; and I would argue that it is better than GCC's own documen- tion. You will not find more complete coverage of GCC's features, quirks, and usage anywhere else in a single volume. There are no other up-to-date sources of information on GCC, excluding GCC's own documentation. GCC usually gets one or two chapters in programming books and only a few pa- graphs in other more general titles.