What is the C++ memory layout of objects/structs etc?

Question

In C++ I presume the C++ standard has nothing to do with how data members are arranged within a class, in terms of memory layout? Would I be right in thinking this is down t

Answer 1

Yes, the standard doesn't say how the objects are to be represented in memory. To get an idea how normall C++ objects are represented read this book: inside C++ object model.

Answer 2

The C++ standard does specify a few things, but far from everything.

The main rules are these:

• objects in an array are laid out contiguously, with no padding between them.
• class member objects not separated by an access specifier (public:/private:/protected:) are laid out in memory in the order in which they're declared, but there may be an unspecified amount of padding between member objects.
• for certain types (standard-layout structs, in standardese terminology), the first base class, or if none exists, the first member, is laid out at the same address that the class itself.

There are a few more bits and pieces specified by the standard, but on the whole, the remaining details are really down to the compiler.