In the public APIs, always add new struct members to the end of the struct. This allows us to maintain backward API/ABI compatibility (as long as the application being linked allocates structs via API functions).

This generally applies to enum values as well, as the compiler will define enum values to 0, 1, etc., in the order given, so inserting a value in the middle will change the numerical values of all later values, making them backward-incompatible. However, if enum numerical values are explicitly specified rather than left to the compiler, new values can be added anywhere.