Mailing-List: contact dev-help@stdcxx.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@stdcxx.apache.org
Received-SPF: pass (athena.apache.org: domain of msebor@gmail.com designates
 209.85.200.172 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=message-id:date:from:organization:user-agent:mime-version:to:subject:references:in-reply-to:content-type:content-transfer-encoding:sender;
        b=ShBUW+WfKHt+9gSzozv+ULQ842ognHwAGyeJxSQ6WFzLvIdXxNXlHXdYGARVONhTkhAZAnDrff2jqp/znCgpk8uiat18ijgqu/k1gG0jL04doiJZpz53OfloCvcHgCvsOEx/icenFMywk3ZGfwRgZ28gcUyebxrUOQOO/6Gzkho=
Message-ID: <47FEBCEC.20609@roguewave.com>
Date: Thu, 10 Apr 2008 19:20:44 -0600
From: Martin Sebor <sebor@roguewave.com>
Organization: Rogue Wave Software, Inc.
User-Agent: Thunderbird 2.0.0.12 (X11/20080226)
MIME-Version: 1.0
To: dev@stdcxx.apache.org
Subject: Re: Null src pointer in memcpy?
References: 
 <CFFDD219128FD94FB4F92B99F52D0A49010A36F0@exchmail01.Blue.Roguewave.Com>
In-Reply-To: 
 <CFFDD219128FD94FB4F92B99F52D0A49010A36F0@exchmail01.Blue.Roguewave.Com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: Martin Sebor <msebor@gmail.com>

Eric Lemings wrote:
>  
> Is it safe to pass a null pointer as the 2nd argument to memcpy()?  Or
> undefined?

Assuming the third argument is 0. Strictly speaking I believe it's
undefined because memcpy(s1, s2, n) is specified to "copy n bytes
from the object pointed to by s2 into the object pointed to by s1"
and a null pointer doesn't point to an object. An object is defined
as "a region of storage in the execution environment, the contents
of which can represent values."

AFAIK, most implementations allow null pointers for no-op calls to
memcpy() but gcc issues a warning when it detects at compile time
that a null pointer is passed as the first or second argument to
memcpy().

Martin