NSXMLNode ivar type

[David Chisnall]

Hello the list,

I am working on the new ObjC ABI and one of the changes I have made is to 
include the type encoding in the ivar offset variable.  This protects against 
type confusion by causing linker failures when an instance variable is 
referenced with the wrong type (which can happen if it’s in a library that 
changes and someone forgets to bump the SONAME).

Unfortunately, I have found that -base doesn’t build because it uses some 
complex preprocessor logic to change the type of NSXMLNode’s node ivar 
depending on which subclass you are using.  This is quite dangerous because, 
although the types have a common prefix, the version used in the root is not a 
prefix of the others and so it’s possible for type confusion if someone 
modifies NSXMLNode without realising how the subclasses use this.

Does anyone object if I commit a patch that turns this into a union?

David