Re: Typecasting Pointers on a 64 bit System

From	blmblm@myrealbox.com <blmblm.myrealbox@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Typecasting Pointers on a 64 bit System
Date	2011-11-18 14:48 +0000
Organization	None
Message-ID	<9in9hvFkg4U2@mid.individual.net> (permalink)
References	<j9hbnp$13g$1@speranza.aioe.org> <slrnjc38ub.r7s.usenet-nospam@guild.seebs.net> <9ikojfF3p7U2@mid.individual.net> <slrnjcakol.11i2.usenet-nospam@guild.seebs.net>

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In article <slrnjcakol.11i2.usenet-nospam@guild.seebs.net>,
Seebs  <usenet-nospam@seebs.net> wrote:
> On 2011-11-17, blmblm  myrealbox.com <blmblm.myrealbox@gmail.com> wrote:
> > In article <slrnjc38ub.r7s.usenet-nospam@guild.seebs.net>,
> > Seebs  <usenet-nospam@seebs.net> wrote:
> >> It is very easy for people who have finally been taught that it's not okay
> >> to return the address of a local variable to conclude that it's fine to
> >> pass the address of a local variable to a function you call.  And you're
> >> *calling* pthread_create(), see.  So that's fine.
> 
> > Well, now *I*'m the one who's confused ....  Are you saying
> > it's not fine?
> 
> Yes.
> 
> > I suppose if the function you call creates an
> > independent thread, and that thread persists longer than the one
> > that created it, yes, there could be a problem ....  Was that
> > your point?
> 
> Yes.
> 
> But it's "fine" according to the simple rule people learn if they don't
> really *get* threaded programming.  In the absence of threads, passing the
> address of a local variable to a function you call is generally safe.
> (Not, of course, if that function stashes the pointer for later use...)

Good heavens.  That way lies madness .... though maybe not, since
is it paranoia if they really *are* out to get you?  

I'd have put myself in the group that claims to "get" threaded
programming, but I'll admit I never thought about this particular
potential pitfall.  Then again, I tend to write the kind of
threaded programs in which there's a "master" thread that creates
the other threads and doesn't terminate until all the others do,
and in that case surely passing addresses of local variables in the
master thread to the other threads is okay, no?  (At least in the
sense that the memory will still be there for the other threads,
though if multiple threads have access to the same location, well,
there are the usual potential problems with that.)

-- 
B. L. Massingill
ObDisclaimer:  I don't speak for my employers; they return the favor.

Thread

Typecasting Pointers on a 64 bit System Quentin Pope <qp19433@hotmail.NOSPAM.com> - 2011-11-10 20:21 +0000
  Re: Typecasting Pointers on a 64 bit System Lauri Alanko <la@iki.fi> - 2011-11-10 20:29 +0000
    Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 20:51 +0000
      Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 20:58 +0000
      Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-10 16:08 -0500
        Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 21:35 +0000
          Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-10 17:18 -0500
            Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 23:14 +0000
              Re: Typecasting Pointers on a 64 bit System Richard Damon <news.x.richarddamon@xoxy.net> - 2011-11-10 19:36 -0500
  Re: Typecasting Pointers on a 64 bit System Ben Pfaff <blp@cs.stanford.edu> - 2011-11-10 12:32 -0800
    Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-10 15:44 -0500
    Re: Typecasting Pointers on a 64 bit System Keith Thompson <kst-u@mib.org> - 2011-11-10 12:58 -0800
      Re: Typecasting Pointers on a 64 bit System blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-11-17 15:53 +0000
  Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 20:45 +0000
    Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 21:00 +0000
  Re: Typecasting Pointers on a 64 bit System Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-11-10 15:14 -0700
  Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-11 11:22 +1300
    Re: Typecasting Pointers on a 64 bit System William Ahern <william@wilbur.25thandClement.com> - 2011-11-14 11:10 -0800
      Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 08:28 +1300
        Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-14 14:48 -0500
          Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 10:15 +1300
            Re: Typecasting Pointers on a 64 bit System jacob navia <jacob@spamsink.net> - 2011-11-14 22:18 +0100
              Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 10:26 +1300
            Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-14 16:46 -0500
              Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 10:58 +1300
                Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-14 17:15 -0500
                Re: Typecasting Pointers on a 64 bit System blp@cs.stanford.edu (Ben Pfaff) - 2011-11-14 14:18 -0800
                Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 11:29 +1300
                Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-14 18:14 -0500
                Re: Typecasting Pointers on a 64 bit System Seebs <usenet-nospam@seebs.net> - 2011-11-14 23:01 +0000
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-16 10:39 +0200
                Re: Typecasting Pointers on a 64 bit System Seebs <usenet-nospam@seebs.net> - 2011-11-16 20:18 +0000
                Re: Typecasting Pointers on a 64 bit System Fritz Wuehler <fritz@spamexpire-201111.rodent.frell.theremailer.net> - 2011-11-17 02:54 +0100
                Re: Typecasting Pointers on a 64 bit System pete <pfiland@mindspring.com> - 2011-11-16 21:29 -0500
                Re: Typecasting Pointers on a 64 bit System Seebs <usenet-nospam@seebs.net> - 2011-11-17 02:31 +0000
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-18 14:31 +0200
                Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-17 02:44 +0000
                Re: Typecasting Pointers on a 64 bit System Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-11-16 21:33 -0700
                Re: Typecasting Pointers on a 64 bit System "io_x" <a@b.c.invalid> - 2011-11-17 04:01 +0100
                Re: Typecasting Pointers on a 64 bit System blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-11-17 15:46 +0000
                Re: Typecasting Pointers on a 64 bit System Seebs <usenet-nospam@seebs.net> - 2011-11-17 18:48 +0000
                Re: Typecasting Pointers on a 64 bit System blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-11-18 14:48 +0000
                Re: Typecasting Pointers on a 64 bit System Ian Collins <ian-news@hotmail.com> - 2011-11-15 14:37 +1300
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-16 10:23 +0200
                Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-16 06:53 -0500
                Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-16 11:15 -0500
                Re: Typecasting Pointers on a 64 bit System Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-16 17:08 +0000
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-18 15:09 +0200
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-18 14:24 +0200
                Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-18 10:08 -0500
                Re: Typecasting Pointers on a 64 bit System Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-18 17:52 +0200
            Re: Typecasting Pointers on a 64 bit System Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-11-14 15:45 -0700
  Re: Typecasting Pointers on a 64 bit System "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2011-11-10 15:19 -0800
    Re: Typecasting Pointers on a 64 bit System Kaz Kylheku <kaz@kylheku.com> - 2011-11-10 23:41 +0000
      Re: Typecasting Pointers on a 64 bit System Keith Thompson <kst-u@mib.org> - 2011-11-10 20:48 -0800
      Re: Typecasting Pointers on a 64 bit System "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2011-11-14 03:39 -0800
        Re: Typecasting Pointers on a 64 bit System Lauri Alanko <la@iki.fi> - 2011-11-14 13:08 +0000
          Re: Typecasting Pointers on a 64 bit System James Kuyper <jameskuyper@verizon.net> - 2011-11-14 09:21 -0500
        Re: Typecasting Pointers on a 64 bit System Keith Thompson <kst-u@mib.org> - 2011-11-14 12:54 -0800

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