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Re: obscure bug "extern void free (void *__ptr) __attribute__ ((__nothro

From: Mathias Steiger
Subject: Re: obscure bug "extern void free (void *__ptr) __attribute__ ((__nothrow__ , __leaf__));"
Date: Fri, 22 Jan 2021 05:05:31 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1

Here is the strace output.


It is very excessive due to the nature of Autoconf and I couldn't make a lot of sense of it.

When I downgraded the package from bash-5.1.004-1 to bash-5.0.018-2 the bug disappeared.

On 1/22/21 12:27 AM, Eduardo Bustamante wrote:
On Thu, Jan 21, 2021 at 2:07 PM Mathias Steiger
<mathias.steiger@googlemail.com> wrote:

As such bugs are likely related to buffer issues, maybe even in
underlying APIs, and since they only surface after very lengthy
mysterious sequences of commands - often just on single specific system
installations - I wouldn't know how you can reproduce this in a test.

Maybe you have specific testing frameworks for this, that would reduce
the whole script to more basic components and which schematically remove
or add complexity until the nature of the bug becomes more apparent?

This seems to call for a specialist who is able to follow the problem
into a far lower level of abstraction.

As it stands now, I don't see how there is no way how this kind of
execution can make any sense from a scripting POV.

Of course in a giant script, all sorts of random things might happen.
But this is not one of them.
You could run the script through "strace" or a similar command to see
what's writing that output and when. We could use that log output to
confirm that it is indeed Bash that is writing this out-of-order and
to a file descriptor that it shouldn't.

Greg pointed out earlier that the construct you're trying to use
doesn't work well when the shell is not Bash. Are you 100% confident
that it is /bin/bash that is running the script and not /bin/sh (and
thus maybe something like Dash?). And keep in mind that even Bash
running as /bin/sh is not quite the same as Bash running as /bin/bash.

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