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From: "Randy Brukardt" <randy@rrsoftware.com>
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 <1120707674.230510.280700@g47g2000cwa.googlegroups.com>
Subject: Re: GCC 4.0 Ada.Containers Cursor danger.
Date: Thu, 7 Jul 2005 14:18:28 -0500
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Date: 2005-07-07T14:18:28-05:00
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"Dmitriy Anisimkov" <anisimkov@yahoo.com> wrote in message
news:1120707674.230510.280700@g47g2000cwa.googlegroups.com...
> <<You can corrupt memory in Ada 95 with
> address clauses, Unchecked_Conversion, pragma Suppress, >>
>
> The danger of this operations is undersood, at least for me.
>
> <<streams, Sequential_IO, Direct_IO, Storage_IO, >>
>
> I do not know how the streams and IO could broke memory. Could you
> explain a bit more ?

Input of binary data is essentially the same operation as an
Unchecked_Conversion from an array of byte to the output object. If the
output object is composite, what is read in can make the object "abnormal";
any use of an abnormal object afterwards causes erroneous execution and thus
may corrupt memory.

Most problems happen if an object with embedded pointers (explicit or
implicit) is read, because it is never safe to read in pointers. (The memory
that they point at is unlikely to contain the same objects.)

But (almost) any binary input can cause problems if the stream of bytes is
corrupted. And the program really has no control over that, as anything can
happen to the file after it is written and before it is read.

                    Randy.