Re: Is reallocarray() planned to be standardized?

From	cross@spitfire.i.gajendra.net (Dan Cross)
Newsgroups	comp.lang.c
Subject	Re: Is reallocarray() planned to be standardized?
Date	2026-05-17 20:30 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<10ud8hd$lt0$1@reader1.panix.com> (permalink)
References	<10u5a5v$nagc$1@dont-email.me> <10u9du6$rsgq$1@dont-email.me> <hxoOR.793517$o0gf.443538@fx03.iad> <10ud6b2$1tjoi$1@dont-email.me>

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In article <10ud6b2$1tjoi$1@dont-email.me>,
David Brown  <david.brown@hesbynett.no> wrote:
>On 17/05/2026 21:19, Scott Lurndal wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>>> On 16/05/2026 00:12, Scott Lurndal wrote:
>>>> "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:
>>>>> On 5/15/2026 2:50 PM, Dan Cross wrote:
>>>>
>>>>> Iirc, a long time ago I kind of remember reading something about
>>>>> overwrite sensitive data multiple times (e.g., the DoD 5220.22-M
>>>>> standard for storage, though adapted for RAM), sometimes using a pass of
>>>>> random data followed by a pass of fixed characters, or using a fast
>>>>> CSPRNG (like ChaCha20) to generate fast pseudo-random bytes so they
>>>>> don't deplete the physical TRNG.
>>>>
>>>> Yes, that was normal when sanitizing disk platters, to ensure
>>>> no residual analog signal existed on the magnetic media that
>>>> could be teased out with a sillyscope or other analyzers.
>>>>
>>>
>>> The only lab test of recovering zero overwritten data on a hard disk
>>> managed to recover a small handful of bits, after several weeks of work
>>> with a lab full of top-class equipment.  The risk of someone reading
>>> data on a disk that was overwritten with zeros is non-existent - but
>>> that hasn't stopped people making money from selling multi-pass software
>>> to the paranoid.
>> 
>> Al Kossow posted a link to a video describing recovery of the Unix v4
>> data from 9-track that's quite interesting; while the tape hadn't
>> been overwritten, it had degraded to the point where it wasn't
>> readable by a 9-track drive, so they used signal processing on the
>> analog data from each track to recover the data.
>> 
>> https://www.youtube.com/watch?v=-xlq_MPWNKk
>
>Recovering from damaged tape or disk is a different matter than 
>recovering data that has been erased or overwritten with zeros.  I've 
>read of some very impressive recovery of data from hard disks that have 
>been in fires or otherwise physically damaged.

I think one has to make a set of reasonable assumptions about
a particular scenario to actually have a useful discussion.

Let's propose the following scenario: a company's proprietary
payroll information is on a device that is overwritten by a
computer writing zeros to that device.  How much should one
worry about a well-equipped actor recovering data from that
device?

Is it a disk?  Yeah, I'm not gonna lose much sleep over that.

An SSD?  Large chunks of that data is still on the device; I'd
worry.

A tape?  I think somewhere in the middle; probably closer to the
disk, but I'd be worried about echos in between bits and weird
stuff like that.

	- Dan C.

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Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-14 20:09 +0000
  Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-14 21:10 +0000
    Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-14 23:35 +0000
      Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 17:46 -0700
        Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 02:00 +0000
          Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 19:22 -0700
            Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 11:02 +0000
              Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 14:44 -0700
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 21:50 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 14:55 -0700
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 15:02 -0700
                Re: Is reallocarray() planned to be standardized? scott@slp53.sl.home (Scott Lurndal) - 2026-05-15 22:12 +0000
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 11:38 +0200
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-16 13:00 +0200
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 13:58 +0200
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-16 12:34 +0000
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 16:25 +0200
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-16 12:32 -0700
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-17 11:10 +0200
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-17 06:36 +0200
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-16 12:25 -0700
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-17 11:12 +0200
                Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-17 02:26 -0700
                Leader Keith has spoken! (Was: Is reallocarray() planned to be standardized?) gazelle@shell.xmission.com (Kenny McCormack) - 2026-05-17 12:54 +0000
                Re: Is reallocarray() planned to be standardized? scott@slp53.sl.home (Scott Lurndal) - 2026-05-17 19:19 +0000
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-17 21:53 +0200
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-17 20:30 +0000
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-17 20:01 +0000
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 22:32 +0000
            Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 15:23 +0000
              Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 17:28 +0000
              Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 17:40 +0000
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 17:50 +0000
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 18:28 +0000
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 21:35 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 15:05 -0700
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 22:35 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 17:18 -0700
                Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 08:07 +0000
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-16 12:44 +0000
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-15 23:44 +0200
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 21:47 +0000
                Re: Is reallocarray() planned to be standardized? scott@slp53.sl.home (Scott Lurndal) - 2026-05-15 22:10 +0000
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-16 01:13 +0200
                AIX (was Re: Is reallocarray() planned to be standardized?) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 22:30 +0000
                Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 08:04 +0000
    Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-15 07:07 +0000
      Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 13:58 +0000
        Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 00:25 +0000
  Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 17:26 -0700
    Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 02:08 +0000
  Re: Is reallocarray() planned to be standardized? Bonita Montero <Bonita.Montero@gmail.com> - 2026-05-16 11:28 +0200

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