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Re: addresses of variables

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Hello,

Am 03/22/2012 11:22 AM, schrieb James Kuyper:
> Note: I'm winging it on that last statement. I've not had time to
> assimilate C's new support for multi-threaded code. If there's some way
> to guarantee that a scanf() call followed by a dereference in some other
> part of the program will be executed between the printf() and the return
> in quux(), then I'm wrong.

has nothing to do with threads. printf is a library function, yes, but
there is no guarantee, I think that it has no right to at least
inspect the contents that the argument is pointing to.


> But I'd expect that the ability to guarantee
> such sequencing would require executing a call to one of the new
> thread-related functions between the printf() and the return. Code where
> such sequencing is merely possible, but not guaranteed, has undefined
> behavior if it doesn't execute in that sequence, thereby allowing the
> optimization.

No. The other thread could know by some other magic when doing this
if the thread here still is alive and thus the pointer is still
valid. (E.g all threads might be serialized and the other thread can
inspect a table of all running threads.)

As a side note, in C11 it is implementation specific if a thread has
the right to poke into memory that resides on the stack of another
thread.

Jens

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addresses of variables Zero <chefmuetze@web.de> - 2012-03-18 03:56 -0700
  Re: addresses of variables "BartC" <bc@freeuk.com> - 2012-03-18 11:18 +0000
  Re: addresses of variables jt@toerring.de (Jens Thoms Toerring) - 2012-03-18 11:18 +0000
  Re: addresses of variables pete <pfiland@mindspring.com> - 2012-03-18 07:30 -0500
    Re: addresses of variables Zero <chefmuetze@web.de> - 2012-03-18 04:42 -0700
      Re: addresses of variables Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-19 10:52 -0400
        Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-19 12:55 -0500
          Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-19 14:30 -0400
            Re: addresses of variables jacob navia <jacob@spamsink.net> - 2012-03-19 20:11 +0100
              Re: addresses of variables hoganlong@gmail.com - 2012-03-19 12:17 -0700
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-19 16:15 -0400
                Re: addresses of variables hoganlong@gmail.com - 2012-03-19 14:18 -0700
                Re: addresses of variables "io_x" <a@b.c.invalid> - 2012-03-19 23:26 +0100
            Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-20 03:52 -0500
              Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-20 06:00 -0400
                Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-20 16:47 -0500
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-20 18:37 -0400
                Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-21 17:58 -0500
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-21 20:24 -0400
                Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-21 23:53 -0500
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-22 06:22 -0400
                Re: addresses of variables Kenneth Brody <kenbrody@spamcop.net> - 2012-03-22 12:01 -0400
                Re: addresses of variables Stephen Sprunk <stephen@sprunk.org> - 2012-03-24 16:09 -0500
                Re: addresses of variables Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-23 13:41 +0100
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-23 09:06 -0400
                Re: addresses of variables Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-23 19:47 +0100
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-23 16:04 -0400
                Re: addresses of variables Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-24 00:19 +0100
                Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-23 22:20 -0400
                Re: addresses of variables Jens Gustedt <jens.gustedt@loria.fr> - 2012-03-24 09:39 +0100
            Re: addresses of variables Anders Wegge Keller <wegge@wegge.dk> - 2012-03-20 20:02 +0100
              Re: addresses of variables James Kuyper <jameskuyper@verizon.net> - 2012-03-20 15:18 -0400
                Re: addresses of variables Anders Wegge Keller <wegge@wegge.dk> - 2012-03-21 21:37 +0100
          Re: addresses of variables Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-20 11:52 -0400
            Re: addresses of variables Kenneth Brody <kenbrody@spamcop.net> - 2012-03-21 11:04 -0400

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