Are these 2 structs layout-compatible?
struct One {
float x, y, z;
};
struct Two {
float c[3];
};
Both contains 3 floats, so in a way, this description can be considered true (from N3797):
16 Two standard-layout struct (Clause 9) types are layout-compatible if they have the same number of non-static data members and corresponding non-static data members (in declaration order) have layout-compatible types (3.9).
N4659 has a different text:
The common initial sequence of two standard-layout struct (Clause 12) types is the longest sequence of non-static data members and bit-fields in declaration order, starting with the first such entity in each of the structs, such that corresponding entities have layout-compatible types and either neither entity is a bit-field or both are bit-fields with the same width.
Two standard-layout struct (Clause 12) types are layout-compatible classes if their common initial sequence comprises all members and bit-fields of both classes (6.9).
If the answer is no, they are not layout-compatible, then: was it the intention of the committee? Maybe they do want One and Two to be layout-compatible (maybe a committee member reads this, and can clarify).
Bonus question: is it guaranteed, that sizeof(One)==sizeof(Two)?