RTS linker: unloadObj() does not actually unload the code
We've known about this for a long time, but it hasn't been a pressing issue in GHCi. The problem with actually unloading code is that there might be pointers into it from the heap or other RTS data structures, so we need to do a full heap traversal to discover whether it is safe to unload code or not.
This is an issue for a project at Facebook that needs to have long running processes that regularly unload and load code using the RTS linker, and right now the process grows over time.
This ticket is to track the issue, and I'm also working on a fix. The same problem affects the dynamic linker, although I'm not planning to fix that (yet).