Re: What's new in C?

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: What's new in C?
Date	2012-12-04 18:48 -0800
Organization	None to speak of
Message-ID	<ln624hqkmv.fsf@nuthaus.mib.org> (permalink)
References	(7 earlier) <0.7b0242de075459b63082.20121204125043GMT.874nk20yn0.fsf@bsb.me.uk> <k9lnp9$i6m$1@speranza.aioe.org> <0.300b02743c2991662518.20121204214531GMT.87y5hdze2s.fsf@bsb.me.uk> <k9m745$lg2$1@speranza.aioe.org> <k9m8eq$vqa$1@dont-email.me>

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James Kuyper <jameskuyper@verizon.net> writes:
[...
> Objects defined inside of a block have a lifetime that starts at the
> point of definition, and ends upon exiting the block. If the block is
> entered and exited multiple times, for example a block associated with a
> while() statement, objects defined inside the block have a separate
> lifetime during each pass through the block. Does that correspond to
> your concept of an allocation level?
> I believe that this has been true for at least as long as C has had a
> standard, and probably as far back as K&R C, but I can only be sure
> about C99 and later.

Actually, the lifetime of a non-VLA object defined inside a block
extends from entry into the block until execution of the block
ends in any way.  So an object can exist for some time before its
declaration is reached.  (You can write some ugly code using gotos
for which the distinction matters.)

VLAs exist only from the declaration of the object (since the size
isn't necessarily known before that).

And of course this is all subject to the as-if rule.  It's not
uncommon, I think, for everything to be allocated on function entry,
even if some objects in the function have a narrower lifetime.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-11-28 19:41 -0700
  Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-11-28 19:15 -0800
    Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-06 02:43 -0700
      Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-06 07:45 -0500
  Re: What's new in C? Noob <root@127.0.0.1> - 2012-11-29 10:36 +0100
    Re: What's new in C? Weland <weland@sdf.lonestar.org> - 2012-11-29 10:17 +0000
    Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-04 01:45 -0700
  Re: What's new in C? Weland <weland@sdf.lonestar.org> - 2012-11-29 09:48 +0000
    Re: What's new in C? David Brown <david@westcontrol.removethisbit.com> - 2012-11-29 13:50 +0100
  Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-11-29 05:55 -0800
    Re: What's new in C? Les Cargill <lcargill99@comcast.com> - 2012-11-29 12:48 -0600
      Re: What's new in C? Rui Maciel <rui.maciel@gmail.com> - 2012-11-30 10:46 +0000
        Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-11-30 05:31 -0800
          Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-11-30 14:22 +0000
          Re: What's new in C? Rui Maciel <rui.maciel@gmail.com> - 2012-11-30 15:04 +0000
            Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-11-30 16:41 +0000
              Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-11-30 11:49 -0500
              Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-11-30 10:12 -0800
              Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-11-30 11:12 -0800
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-11-30 22:26 +0000
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-11-30 22:36 +0000
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-11-30 23:27 +0000
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-04 01:39 -0700
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-04 00:43 -0800
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-04 03:14 -0700
                Re: What's new in C? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-04 12:50 +0000
                Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-12-04 05:54 -0800
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-04 20:51 +0000
                Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-04 16:09 -0500
                Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-04 16:19 -0500
                Re: What's new in C? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-04 21:45 +0000
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-05 01:13 +0000
                Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-04 20:36 -0500
                Re: What's new in C? Robert Wessel <robertwessel2@yahoo.com> - 2012-12-04 20:26 -0600
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-04 18:48 -0800
                Re: What's new in C? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-05 02:57 +0000
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-05 01:42 +0000
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-06 02:06 -0700
                Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-06 07:50 -0500
                Re: What's new in C? JohnF <john@please.see.sig.for.email.com> - 2012-12-06 13:46 +0000
                Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-06 09:39 -0500
              Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-11-30 15:52 -0500
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-04 01:53 -0700
                Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-04 08:16 -0500
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-04 21:18 +0000
                Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-04 18:04 -0500
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-05 01:19 +0000
                Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-04 21:05 -0500
                Re: What's new in C? Noob <root@127.0.0.1> - 2012-12-05 16:45 +0100
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-06 01:45 -0700
                Re: What's new in C? James Kuyper <jameskuyper@verizon.net> - 2012-12-06 08:12 -0500
                Re: What's new in C? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-06 21:13 +0000
                Re: What's new in C? Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-06 09:15 -0500
                Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-12 18:28 -0700
        Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-11-30 11:22 -0800
          Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-04 03:04 -0700
  Re: What's new in C? Rui Maciel <rui.maciel@gmail.com> - 2012-11-29 18:19 +0000
    Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-11-29 11:41 -0800
  Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-11-30 20:50 +0000
    Re: What's new in C? Jens Gustedt <jens.gustedt@loria.fr> - 2012-11-30 23:35 +0100
      Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-12-05 03:26 +0000
        Re: What's new in C? gwowen <gwowen@gmail.com> - 2012-12-05 23:49 -0800
          Re: What's new in C? Cal Dershowitz <cal@example.invalid> - 2012-12-06 01:49 -0700
          Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-12-08 07:55 +0000
            Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 13:29 +0000
              Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-12-08 15:23 +0000
                Re: What's new in C? Martin Shobe <martin.shobe@yahoo.com> - 2012-12-08 17:46 +0000
                Re: What's new in C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-12-08 10:45 -0800
                Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-12-08 19:32 +0000
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 18:55 +0000
                Re: What's new in C? Ian Collins <ian-news@hotmail.com> - 2012-12-09 08:26 +1300
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 20:12 +0000
                Re: What's new in C? Ian Collins <ian-news@hotmail.com> - 2012-12-09 09:18 +1300
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 21:21 +0000
                Re: What's new in C? Ian Collins <ian-news@hotmail.com> - 2012-12-09 10:27 +1300
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-08 13:36 -0800
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-08 12:59 -0800
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 22:10 +0000
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-08 16:15 -0800
                Re: What's new in C? Ian Collins <ian-news@hotmail.com> - 2012-12-09 14:23 +1300
                Re: What's new in C? Ian Collins <ian-news@hotmail.com> - 2012-12-09 14:20 +1300
                Re: What's new in C? Keith Thompson <kst-u@mib.org> - 2012-12-08 11:32 -0800
                Re: What's new in C? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-09 02:52 +0000
                Re: What's new in C? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-09 02:53 +0000
                Re: What's new in C? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-12-08 20:08 +0000
                Re: What's new in C? "BartC" <bc@freeuk.com> - 2012-12-08 20:25 +0000

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