Should an empty base class affect the layout of the derived class?

Question

The C++ standard (quoting from draft n3242) says the following about subobjects [intro.object]:

Unless an object is a bit-field or a base class subobj

Answer 1

There are good explanations in this thread. I just wanted to add that to work around this structure bloat issue you can simply make empty class a template, so that instantiating it with a different template argument makes it a different class:

template
struct empty { };
struct member: empty { };
struct derived: empty { member m; };

int main(void)
{
    printf("%d\n", sizeof(derived));
    return 0;
}

Outputs 1.

This is the reason to avoid using boost::noncopyable in large projects.