To: max AT alcyone DOT com
Cc: djgpp AT delorie DOT com
Subject: Re: Bug in malloc/free ?
Message-ID: <19970306.200419.4511.3.fwec@juno.com>
References: <5fm6r7$6av$1 AT gjallar DOT daimi DOT aau DOT dk>
	<331EF4EF DOT 3788CF9D AT alcyone DOT com>
From: fwec AT juno DOT com (Mark T Logan)
Date: Thu, 06 Mar 1997 20:06:40 EST

On Thu, 06 Mar 1997 08:46:39 -0800 Erik Max Francis <max AT alcyone DOT com>
writes:

>It's possible (though I haven't checked) that memory is becoming too
>fragmented from the allocations and frees, so that eventually it 
>fails.

I think Eric is perfectly right here, but I feel the need to elaborate. 
Fragmented
memory is when you have lots of little memory blocks all over.  What
happens
because of this is that the largest free chunk of memory might be only
10K in
size.  You can have megs and megs of free memory, but you can't allocate
11K
anymore.  

One solution is to write your own memory manager.  The memory
manager must use "garbage collection."  I beleive that Lisp has a manager
like
this built in.  CMIIW.  Anyway, garbage collection simply means that the
manager
will take all the allocated blocks, and smash them all into one contigous
block.
The only catch is that your manager can't give out addresses when you
call its
allocation function.  This is because if it goes and collects the
garbage, all the 
addresses change.  So, you have to give out handles.  A handle is the
address
of a location in memory where you have stored the address of an allocated
block.  This means that your manager has the one and only copy of the
chunks
address, and can change the address when it moves a chunk.

If you want more info, I am working on just such a manager, which will be
part of
a larger package of memory tools, to be distributed under the name
"SuperMem."
I plan to release an alpha version for comments and suggestions later
this month.
I would be happy to mail you the source code, but I don't have an awful
lot written
right now.

Good luck.

||          Fwec AT juno DOT com aka Mark Logan aka Gil Bates
||
|| This message was a work of fiction.  As such, all characters contained
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