Professional C++, 6th Edition

11Modules, Header Files, and Miscellaneous Topics

WHAT'S IN THIS CHAPTER?

• What modules are and how to author and consume them
• Details of preprocessor directives
• What preprocessor macros are and why they are dangerous
• What linkage is and how it affects accessibility of named entities
• The meaning of the one definition rule, ODR
• Details of header files
• What feature-test macros for core language features are
• The different uses of the static keyword
• C-style variable-length argument lists

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This chapter starts with a detailed discussion on how modules allow you to write reusable components and contrasts this against old-style header files. It also explains what preprocessor directives are and gives some examples of why C-style preprocessor macros are dangerous. The chapter then explains the concept of linkage, which specifies where named entities can be accessed from, and explains the one definition rule. The final part of the chapter discusses the different uses of the static and extern keywords, as well as C-style variable-length argument lists.

MODULES

Modules are introduced in Chapter 1, “A Crash Course in C++ and the Standard Library,” and you have already authored and consumed your own simple modules in previous chapters. However, there ...