Use NULL instead of END_X_QUEUE closures?
Currently we sometimes use special closures to mark end of lists of different objects. Some examples: - END_TSO_QUEUE - END_STM_WATCH_QUEUE - END_STM_CHUNK_LIST But we also use NULL for the same thing, e.g. in weak pointer lists (old_weak_ptr_list, weak_ptr_list). I'm wondering why we need special marker objects (which are actual closures with info tables) instead of using NULL consistently. Current approach causes a minor problem when working on the RTS because every time I traverse a list I need to remember how the list is terminated (e.g. NULL when traversing weak pointer lists, END_TSO_QUEUE when traversing TSO lists). Ömer
Hi Ömer,
These are pointed to by objects traversed by GC. They have info tables
like any other heap object that GC can understand. I think this is a much
simpler invariant to hold then to have some heap objects point to NULL.
Ryan
On Mon, May 7, 2018 at 3:34 PM, Ömer Sinan Ağacan
Currently we sometimes use special closures to mark end of lists of different objects. Some examples:
- END_TSO_QUEUE - END_STM_WATCH_QUEUE - END_STM_CHUNK_LIST
But we also use NULL for the same thing, e.g. in weak pointer lists (old_weak_ptr_list, weak_ptr_list).
I'm wondering why we need special marker objects (which are actual closures with info tables) instead of using NULL consistently. Current approach causes a minor problem when working on the RTS because every time I traverse a list I need to remember how the list is terminated (e.g. NULL when traversing weak pointer lists, END_TSO_QUEUE when traversing TSO lists).
Ömer _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
participants (2)
-
Ryan Yates -
Ömer Sinan Ağacan