Re: Initial draft proposal: "Safe arrays and pointers for C"

From	Jens Gustedt <jens.gustedt@loria.fr>
Newsgroups	comp.std.c
Subject	Re: Initial draft proposal: "Safe arrays and pointers for C"
Date	2012-08-16 00:51 +0200
Organization	A noiseless patient Spider
Message-ID	<502C27E7.3010906@loria.fr> (permalink)
References	(12 earlier) <502B95E8.30102@spamsink.net> <502B97D6.6090107@loria.fr> <lnlihgq6j0.fsf@nuthaus.mib.org> <502C1314.8030800@loria.fr> <k0h4s7$67r$1@dont-email.me>

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Am 15.08.2012 23:38, schrieb John Nagle:
> On 8/15/2012 2:22 PM, Jens Gustedt wrote:
>> Am 15.08.2012 21:50, schrieb Keith Thompson:
>>> Or perhaps there's some elegant solution that I'm missing.
>>
>> I think you are missing that the bounds checking can be done at the
>> calling side. The calling side has seen the interface of the function
>> and knows of the restriction.
>>
>> It is not perfect and would not easily work with plain pointers that
>> are passed as arguments, but it could be implement without any
>> additional data if arrays are passed.
>>
>> Jens
> 
>     Exactly.  That's where I'm going with this.  A key concept
> here is to avoid any changes to the ABI, so that old and new
> object files can interoperate.
> 
>     We plug a few more holes, as shown in the paper, and
> offer "strict mode", where only the checkable forms are allowed,
> encourage a move to 100% strict mode code in security-critical
> applications, and, at last, no more buffer overflows.
> 
>     If we can only fix the backwards compatibility problems
> with VLAs...

Perhaps, as a mode of operation, you could just assume that VLA are
part of the language :) And that actually what you are proposing would
make them much more useful and widely adaptable?

A strict mode could require that the visible prototype for a function
with VM types in the argument list (BTW they are never VLA themselves,
but pointers to VLA) should have the same expression as the definition
of the function, and that these expression should be such that their
evaluation could already take place at the point of declaration
without changing the value. Something like it should only contain

- other parameters already declared previously in the list
- integer constant expressions that can be evaluated at declaration of
  the first prototype
- maybe also evaluations of global variables that are known at the
  declaration of the first prototype, but I am less sure for this part

I would claim that this is good style for programming with VM, anyhow.
But since all these requirements would be for strict mode only, so
this wouldn't create incompatibilities with existing code.

Then all the computations for bounds could again be done at the
calling side without changing the ABI, we still would only pass
pointers around.

Jens

Thread

Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-13 11:39 -0700
  Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-13 23:23 +0200
    Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-13 17:04 -0700
    Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-13 20:08 -0700
      Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-13 22:23 -0700
        Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-14 11:20 -0700
          Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 14:54 -0400
            Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-14 21:09 +0200
              Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 16:00 -0400
            Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 18:08 -0400
              Re: Initial draft proposal: "Safe arrays and pointers for C" Philip Lantz <prl@canterey.us> - 2012-08-14 23:05 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-15 06:48 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-15 11:22 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-15 15:13 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-15 13:00 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-15 22:52 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-15 17:18 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-16 19:20 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-16 13:40 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-16 11:04 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-16 14:35 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-16 11:47 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-16 14:52 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-15 14:41 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2012-08-16 12:39 +0100
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-16 09:57 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-16 13:28 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2012-08-16 23:52 +0100
                Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-15 18:56 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 19:23 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Philip Lantz <prl@canterey.us> - 2012-08-15 21:47 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-16 19:14 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-16 20:28 +0200
          Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 15:05 -0400
          Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-14 21:09 +0200
            Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-14 13:24 -0700
              Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 16:39 -0400
              Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 15:23 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Philip Lantz <prl@canterey.us> - 2012-08-14 22:58 -0700
              Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-15 00:37 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 16:42 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-15 22:57 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-15 17:02 -0700
          Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 14:59 -0700
            Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-14 15:35 -0700
              Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 00:51 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 06:43 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 08:31 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 09:14 +0200
              Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 18:58 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 06:45 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Philip Lantz <prl@canterey.us> - 2012-08-14 22:51 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-15 07:18 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 14:15 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 14:28 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 14:36 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 14:54 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 15:08 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-15 12:50 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 23:22 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-15 14:38 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-16 00:51 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-15 16:32 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-16 09:05 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-15 17:22 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-15 20:29 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-15 12:36 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-15 16:09 -0400
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 08:47 +0200
              Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 16:33 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 16:38 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 06:46 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-14 22:28 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-15 08:34 +0200
                Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-15 09:12 +0200
          Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-16 13:09 -0700
            Re: Initial draft proposal: "Safe arrays and pointers for C" Wojtek Lerch <wojtek_l@yahoo.ca> - 2012-08-16 16:21 -0400
              Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-16 14:22 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-16 15:28 -0700
                Re: Initial draft proposal: "Safe arrays and pointers for C" Wojtek Lerch <wojtek_l@yahoo.ca> - 2012-08-16 19:49 -0400
      Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-14 08:56 +0200
      Re: Initial draft proposal: "Safe arrays and pointers for C" James Kuyper <jameskuyper@verizon.net> - 2012-08-14 06:18 -0400
        Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-14 12:42 +0200
          Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-14 09:43 -0700
            Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-14 19:52 +0200
              Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-14 21:03 +0200
            Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-14 21:39 +0200
      Re: Initial draft proposal: "Safe arrays and pointers for C" Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-14 08:26 -0400
  Re: Initial draft proposal: "Safe arrays and pointers for C" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-13 22:44 +0100
    Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-13 18:05 -0700
  Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-14 21:00 +0200
    Re: Initial draft proposal: "Safe arrays and pointers for C" Marc <marc.glisse@gmail.com> - 2012-08-14 21:18 +0000
      Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-14 23:51 +0200
  Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-17 09:40 -0700
    Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-17 21:00 +0200
      Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-17 13:30 -0700
        Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-17 23:14 +0200
        Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-18 01:07 +0200
          Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-19 23:14 -0700
            Re: Initial draft proposal: "Safe arrays and pointers for C" Ike Naar <ike@sverige.freeshell.org> - 2012-08-20 07:16 +0000
              Re: Initial draft proposal: "Safe arrays and pointers for C" John Nagle <nagle@animats.com> - 2012-08-20 00:25 -0700
            Re: Initial draft proposal: "Safe arrays and pointers for C" Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-20 11:49 +0200
            Re: Initial draft proposal: "Safe arrays and pointers for C" Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2012-08-20 22:40 +0200
              Re: Initial draft proposal: "Safe arrays and pointers for C" jacob navia <jacob@spamsink.net> - 2012-08-20 23:08 +0200
    Re: Initial draft proposal: "Safe arrays and pointers for C" Keith Thompson <kst-u@mib.org> - 2012-08-17 15:33 -0700

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