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From: jgk@panix.com (Joe keane)
Newsgroups: comp.compilers
Subject: Re: Question about inter-thread stack references
Date: Tue, 27 Jan 2015 02:53:48 +0000 (UTC)
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Xref: csiph.com comp.compilers:1501

Kaz Kylheku  <kaz@kylheku.com> wrote:
>  message_t request, reply;
>
>  init_request(&request, ... args);
>
>  if (send_request(other_thread, &request, &reply) == SEND_OK) {
>    /* reply object contains reply */
>  }

It is more like:

    struct my_request request;
    struct my_reply reply;

    /* request is dead, reply is dead */

    put_stuff_into_request(&request, args);

    /* request is live, reply is dead */

    do_some_bullshit_with_request(&request, args);

    /* request is live, reply is dead */

    err = enqueue_request_and_reply(queue, args, &request, &reply);

    /* request is live, reply is live */

    do_some_bullshit();

    /* request is live, reply is live */

    err = dequeue_request_and_reply(queue, args, &request, &reply);

    /* request is dead, reply is live */

    do_some_bullshit_with_reply(&reply, args);

    /* request is dead, reply is live */

    get_stuff_out_of_reply(&reply, args);

    /* request is dead, reply is dead */

It is OK if both threads are in one function, but it is easy to make a
benign change that breaks things, or worse, usually works.