How does a copying garbage collector ensure objects are not accessed while copied?

Question

On collection, the garbage collector copies all live objects into another memory space, thus discarding all garbage objects in the process. A forward pointer to the copied objec

Answer 1

The Loaded Value Barrier implemented in Azul's Generational Pauseless Garbage Collector is an example of a solution to this problem. You can read about it in the article The Azul Garbage Collector posted on InfoQ in early 2011.