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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: dynamic multithreading
Date: Mon, 18 Nov 2002 14:32:00 +0100
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Date: 2002-11-18T14:32:00+01:00
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On Mon, 18 Nov 2002 13:25:39 +0100, Thierry Lelegard
<thierry.lelegard@canal-plus.fr> wrote:

>> Of course this program _must_ consume all memory.
>> 
>> You explicitly allocate on the heap, but never deallocate. That's what
>> Unchecked_Deallocation is for.
>>
>> Or do you mean even with Free, it consumes all memory?
>
>We agree, that's the whole point. Using Free does not leak.
>
>But, in the previous note, the author seems to think that there should
>be not memory leak, even without unchecked_deallocation:

It should not leak in cases:

1. Stack allocation

   declare
      TV : T;
   begin
      ...
   end;

2. Heap allocation

   TV_Ptr := new T;
   ...
   Free (TV_Ptr);

3. Aggregation

   type Server is ... record
       ...
       TV : T;
   end record;

I don't think he meant GC in the sense of "garbage collection". He
probably meant "elementary collection of the garbage the compiler has
produced to support your tasks". (:-))

1-3 shall not leak. If it does, then it is a compiler bug. The only
case when a task pool could be useful is 3. If Server is controlled,
then Finalize is not called till TV is runing. But it is another
story.

>> > - Second, you must absolutely unchecked_deallocate each task after
>> >   it is terminated (not always trivial to synchronize on actual
>> >   termination of a task). Otherwise, you have a memory leak.
>> 
>> Which means you don't trust the run-time system to do some
>> elementary GC? If you are *that* paranoid (or have a good
>> reason to be) perhaps it's time to abandon Ada and switch
>> back to the good old Assembly language.

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de