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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Containers and concurrent modification exception.
Date: Wed, 19 Sep 2018 17:47:08 +0100
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Date: 2018-09-19T17:47:08+01:00
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Jacob Sparre Andersen <jacob@jacob-sparre.dk> writes:

> Simon Wright <simon@pushface.org> writes:
>
>> Jacob Sparre Andersen <jacob@jacob-sparre.dk> writes:
>>
>>> I've posted an executable example here:
>>>
>>> https://bitbucket.org/sparre/ada-2012-examples/src/default/src/container_tampering.adb
>>
>> On macOS this hangs. Also on debian stretch. No assertion failures.
>
> Even built with the project file?  Strange.  I'm running Debian/Stretch
> (9.5) here.

It hadn't even occurred to me that there might be a project file! I
don't use bitbucket (in spite of having relatives working at Atlassian)
and confused it with pastebin ...

OK, building with -gnata to enable assertions does indeed produce
assertion failures:

  $ ./container_tampering 
  ABC
  SYSTEM.ASSERTIONS.ASSERT_FAILURE: Position cursor of Next is bad
  SYSTEM.ASSERTIONS.ASSERT_FAILURE: Position cursor of function Key is bad

But, if I'd been writing the Containers, this would have been a
Program_Error; it's a disaster (and quite legal to reward erroneous code
with PE, too).