http://www.lispworks.com/documentation/HyperSpec/Body/f_upda_1.htm#update-instance-for-redefined-class http://www.lispworks.com/documentation/HyperSpec/Body/f_u

http://www.lispworks.com/documentation/HyperSpec/Body/f_upda_1.htm#update-instance-for-redefined-class http://www.lispworks.com/documentation/HyperSpec/Body/f_upda... That's how you'd handle it in Lisp. Smalltalk has something similar, but I'm less familiar with the internals for it. No restart needed, but it requires a runtime that is able to track data instances by type. You could build that onto C, though. Probably with a custom allocator that was passed some symbol indicating the structure type so it could report on instances for executing an update. Would be hard, though, to do this without invalidating pointers when the size changes. You'd probably end up with an extra level of indirection as a consequence to make it simpler (for the runtime author, not for the end user).