From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Simon Content-Type: multipart/alternative; boundary=Apple-Mail-F20ADDC2-E7BB-4841-B85C-A29C6064E318 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) Message-Id: Date: Thu, 26 Nov 2015 23:14:55 +0000 References: <20151125160347.GN20646@sigint.cs.purdue.edu> <79F2255E-5E76-43E8-83B3-0DFB2CD34AC7@bitblocks.com> <3175949A-26D0-4C4A-BB7D-4E5A3EA7F8B7@me.com> In-Reply-To: To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Subject: Re: [9fans] Undefined Behaviour in C Topicbox-Message-UUID: 78a28f82-ead9-11e9-9d60-3106f5b1d025 --Apple-Mail-F20ADDC2-E7BB-4841-B85C-A29C6064E318 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable I don't know about the PDP but the VAX allowed access to address zero. Even more insidious, it allowed you to dereference a null pointer and guaran= teed it would contain a zero, which resulted in many tiresome portability is= sues - I used Interdatas at the time, which faulted on a read at address zer= o. -Steve > On 26 Nov 2015, at 17:48, Bakul Shah wrote: >=20 > Good points! Though 0 was a valid address on pdp11, right?=20 --Apple-Mail-F20ADDC2-E7BB-4841-B85C-A29C6064E318 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 7bit

I don't know about the PDP but the VAX allowed access to address zero.

Even more insidious, it allowed you to dereference a null pointer and guaranteed it would contain a zero, which resulted in many tiresome portability issues - I used Interdatas at the time, which faulted on a read at address zero.

-Steve


On 26 Nov 2015, at 17:48, Bakul Shah <bakul@bitblocks.com> wrote:

Good points! Though 0 was a valid address on pdp11, right? 
 
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