A while ago I asked a question on this list: >> 3. When this thread exits (in the example of using BeginThread, when >> the TThreadFunc function passed in to BeginThread terminates) the heap >> for that thread, in addition to the other threadvars, are >> automatically disposed, correct?
To which Jonas replied, helpfully: > Only the already freed blocks that are still around are automatically > disposed, because allocated blocks > may still be referenced by other threads. The memory reserved for holding > threadvars is indeed freed. I need to understand a few more things... I'm still a little confused at how this works. I've read heap.inc and cthreads.pp but I'm still a little fuzzy on a few details... In heap.inc, the "freelists" variable which represents the heap, is a threadvar. So when GetMem is called, it works its way down into SysGetMem_Fixed and uses the heap for that thread to get the memory. This makes sense to me. What I'm still a little unsure on is what happens to the heap when the thread exits. If the heap itself (freelists) is a threadvar, how is the statement "Only the already freed blocks that are still around are automatically disposed, because allocated blocks may still be referenced by other threads" accomplished? Are any still-allocated blocks belonging to that heap relocated to be managed by some other heap so that they can be used and/or tracked (by heaptrc, for example)? I think my reading of FinalizeHeap in heap.inc, called by DoneThread in thread.inc indicates this. So in other words, here's what I *think* is happening, please tell me if I'm correct: - when a thread is started, InitHeapThread in heap.inc is called by InitThread in thread.inc, which initializes that thread's freelists record - the thread runs, all GetMem/FreeMem calls in that thread use that thread's heap - when the thread exists, FinalizeHeap in heap.inc is called by DoneThread in thread.inc. If there are any chunks still allocated on that heap then those blocks are reassigned to the orphaned_freelists heap (which is global across all threads) so that that memory can still be used by other threads and so that something like heaptrc would still work to catch those blocks. - then, once any remaining blocks of freelists are no longer managed by freelists, ReleaseThreadVars is called to actually free the memory associated with the threadvar itself Is that correct? Thanks, -SG -- This email is fiction. Any resemblance to actual events or persons living or dead is purely coincidental. Seth Grover sethdgrover[at]gmail[dot]com _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
