GNU bug report logs - #46796
Cuirass & pointer finalization.

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Message #14 received at 46796 <at> debbugs.gnu.org (full text, mbox):

From: Mathieu Othacehe <othacehe <at> gnu.org>
To: zimoun <zimon.toutoune <at> gmail.com>
Cc: 46796 <at> debbugs.gnu.org
Subject: Re: bug#46796: Cuirass & pointer finalization.
Date: Sat, 27 Feb 2021 13:59:50 +0100

Hello zimoun,

> and why is ’zmq-message-content’ used for?  Since ’message’ is
> initialized with zero, I guess.  Well, I am confused by:
>
>   (let ((content-ptr (zmq_msg_data (message->pointer message)))
> [...]
>         (pointer->bytevector content-ptr size))))
>
> …
>
>         (let ((msg (pointer->message! msg-pointer)))
>           (when content-bv
>             (let ((target (zmq-message-content msg)))
>               (bytevector-copy! content-bv 0 target 0 len)))
>           msg))))
>
> Is ’target’ at the same address than ’msg’?  Maybe ’target’ creates
> somehow a dangling pointer.

No 'target' is not at the same address than 'msg', it's just a field of
'msg' that is allocated internally when "zmq_msg_init_size" is called.

Allocating a message with "zmq_msg_init_size" and filling its content by
memcpy'ing data to the memory region pointed by "zmq_msg_data" is the
example given in "Man 3 zmq_msg_send", to I hope this is a valid
use-case :).

Thanks,

Mathieu

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