C++ Common Knowledge: Essential Intermediate Programming

Item 11. The Compiler Puts Stuff in Classes

C programmers are used to knowing everything there is to know about the internal structure and layout of their structs, and they have a habit of writing code that depends on a particular layout. Java programmers are used to programming in ignorance of the structural layout of their objects and sometimes assume their days of ignorance are over when they start programming in C++. In fact, safe and portable coding practices in C++ do require a certain level of healthful agnosticism about the structure and layout of class objects.

With a class, it’s not always “what you see is what you get.” For example, most C++ programmers know that if a class declares one or more virtual functions, then the compiler ...