From owner-freebsd-questions@FreeBSD.ORG  Thu Aug 18 08:07:55 2005
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: questions@FreeBSD.org
Delivered-To: freebsd-questions@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 797D216A41F
	for <questions@FreeBSD.org>; Thu, 18 Aug 2005 08:07:55 +0000 (GMT)
	(envelope-from sem@FreeBSD.org)
Received: from mail.ciam.ru (mail.ciam.ru [213.147.57.66])
	by mx1.FreeBSD.org (Postfix) with ESMTP id EFB0643D46
	for <questions@FreeBSD.org>; Thu, 18 Aug 2005 08:07:54 +0000 (GMT)
	(envelope-from sem@FreeBSD.org)
Received: from [213.85.81.137] (helo=[192.168.0.3])
	by mail.ciam.ru with esmtpa (Exim 4.x)
	id 1E5fRJ-0004Qb-94; Thu, 18 Aug 2005 12:07:53 +0400
Message-ID: <43044212.20909@FreeBSD.org>
Date: Thu, 18 Aug 2005 12:08:50 +0400
From: Sergey Matveychuk <sem@FreeBSD.org>
User-Agent: Mozilla Thunderbird 1.0.6 (X11/20050813)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: Chuck Swiger <cswiger@mac.com>
References: <4303A632.1000809@FreeBSD.org> <4303B016.3030201@mac.com>
In-Reply-To: <4303B016.3030201@mac.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: questions@FreeBSD.org
Subject: Re: man malloc
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 18 Aug 2005 08:07:55 -0000

Chuck Swiger wrote:

>> What does "suitable aligned for storage of *any* type of object" means?
> 
> 
> On some platforms, it is either desirable or required that, say, a 
> 8-byte double is stored at a memory location which is is also aligned to 
> 8-bytes:

Oh, it was told for different architectures. It's quite clear for me now.

> 
>> What is pointer coercion? I have no pointer before malloc() returns.
> 
> 
> Right.  Well, malloc returns a (void *), but most people want to use the 
> memory malloc returns to hold their own arrays, structs, whatever, which 
> means that you need to be able to coerce the (void *) malloc gave you 
> into whatever pointer type you want to actually use.
> 
> So the memory malloc gives you needs to be aligned so that it's OK to be 
> used for even the most restrictive datatype known to the system, 
> commonly 8, 16, or 32 bytes.
> 

Pointer coercion means a type cast? I see now.
I read it as 'force change of pointer value' before.

Thanks, guys!
--
Sem.