On Tue, 19 Jan 2010, Henning Thielemann wrote:
The documentation of System.Mem.Weak.addFinalizer suggests to me, that this function is very fragile, because the object we track, might be optimized away. ...
After even more web search I found the bytestring-mmap package that brought my attention to the module Foreign.Concurrent. This actually solves my problem! I would like to have pointers in System.Mem.Weak and Foreign.ForeignPtr to this module, otherwise it is very hard to find! The function names in this module are so similar to Foreign.ForeignPtr that it is likely that you do not even recognize easily that it is actually different functionality, not only the same functionality for concurrent applications. I would also like to read about examples, where System.Mem.Weak.addFinalizer can be actually used and does not interfer unexpectedly with unboxing. If there is no such example there might be a warning like "addFinalizer is certainly not, what you are looking for" or a DEPRECATED flag.