I believe one of the reasons for adding "class" types in C++ was to break from the C's restrictions on the struct layout. But even then the trouble of breaking binary compatibility was too much to pay for freeing programmers from minding their own data.
No, the same restrictions apply to class as to struct.
The most relevant difference in C++ is that the compiler can reorder data members that are in different visibility specifications (public, protected, private) but not within one of those blocks, to maintain compatibility with C.
Well you only have guaranteed compatibility with C if a class is standard-layout, which requires that all members have the same access control (public, protected, private). So if there is any rule in C++ that mandates ordering within a "block" when there are multiple such "blocks", it's not for compatibility with C.
Oh, putting "class" in the first sentence was a mistake as people hit downvote without reading the rest. I do not say that "class" allows rearranging members (other than C++ access-based rearrangement that applies to structs as well). Really. Please read.
