Message-Id:	<m0zCOH2-000S4fC@inti.gov.ar>
Comments:	Authenticated sender is <salvador AT natacha DOT inti DOT gov DOT ar>
From:	"Salvador Eduardo Tropea (SET)" <salvador AT inti DOT gov DOT ar>
Organization:	INTI
To:	Endlisnis <s257m AT unb DOT ca>, djgpp AT delorie DOT com
Date:	Fri, 28 Aug 1998 10:10:33 +0000
MIME-Version:	1.0
Subject:	Re: question to malloc and free
In-reply-to:	<35E5EDF2.3DDE5F7D@unb.ca>

Endlisnis <s257m AT unb DOT ca> wrote:

> DJ Delorie wrote:
> 
> > The actual block in memory consists of a few extra words just before
> > what you get your hand on.  That extra bit contains the size of the
> > block, and maybe some other information if you're using a malloc
> > debugger.
> > Why not download the source and see for yourself?
> 
>     I've read that the size of the block allocated by malloc/new is always
> a power of 2, and rounded up to one if it isn't (after adding it's few
> words).  Why does it do this?  This seems (to me) like it would waste about
> 1/2 the RAM allocated.

First: DJ did a new malloc included in v2.02 to solve it.
Now: You waste some *virtual memory* not physical so normally doesn't affect.
The reason malloc works in this way is because is *fast*, the blocks are 
clasified by size, only 32 sizes and to satisfy a malloc request you just 
need to check if one block is available (in linked list of blocks of this 
size) or create a new one, no "heap walks" are needed (like in Borland's 
malloc).
Of course there are better solutions like the one used by DJ in the last 
malloc.

SET
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