#8199: Get rid of HEAP_ALLOCED ----------------------------+---------------------------------------------- Reporter: ezyang | Owner: ezyang Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.7 Component: | Keywords: Compiler | Architecture: Unknown/Multiple Resolution: | Difficulty: Project (more than a week) Operating System: | Blocked By: 5435 Unknown/Multiple | Related Tickets: Type of failure: | None/Unknown | Test Case: | Blocking: | ----------------------------+---------------------------------------------- Comment (by ezyang): As it turns out, removing HEAP_ALLOCED has a bad interaction with object unloading. The immediate failure is that the unload-object code thinks that all objects are unreferenced when checking static closures, because the static closure doesn't live in the object image but in the dynamic heap. One way to fix this is to add some extra data to all static closures saying where their indirection lives and use that to determine if a static closure is associated an unloaded object. Then when we dynamically load an object, we place all of its static closures in a block allocated specifically for that object (this would only work for GHC's linker, but as it so happens, at the moment we only support unloading static objects and not dynamic libraries); once we conclude the object is dead we free the block back to the memory manager. Here's an alternative scheme. Since the static closures no longer live in the object image, we can treat them as normal closures and just check if their info tables are keeping an object live. However, we still need to make sure that space in the static blocks ends up getting freed; the most reliable way to do that is to actually GC static closures the same we GC normal objects. (But of course, if we do that, we still need pointers to the static indirections to update them when the static object moves somewhere else.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8199#comment:26 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler