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Re: for-loop mutates to an endless-loop

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From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: for-loop mutates to an endless-loop
Date Sat, 04 Jan 2020 16:39:13 +0000
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Bonita Montero <Bonita.Montero@gmail.com> writes:

>>> Not necessary.
>
>> Not for you, no, but for such a loop to be entirely portable
>> it has to deal with the two problems I pointed out to the OP.
>
> The loop is terminated before the wrap-around.

The increment is done on every loop execution.  When int is wider than
short the effect of the last (unnecessary) increment is implementation
defined and hence the code is not 100% portable (for example, an
implementation may choose to raise a signal).  When int is the same
width as short the behaviour of that last increment is undefined (so,
technically, all bets are off).

The code is portable only to systems that meet the hidden assumptions
behind it.  Which is fine, by the way.  There's lots of code like that,
and a good living to be made fixing it when is has to be ported to other
systems that were not even in existence when the original was written.

-- 
Ben.

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Thread

for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-03 13:27 +0100
  Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-03 14:01 +0100
  Re: for-loop mutates to an endless-loop Dan Purgert <dan@djph.net> - 2020-01-03 13:18 +0000
    Re: for-loop mutates to an endless-loop James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-03 08:28 -0500
      Re: for-loop mutates to an endless-loop Dan Purgert <dan@djph.net> - 2020-01-03 13:33 +0000
        Re: for-loop mutates to an endless-loop James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-03 21:10 -0500
    Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-03 15:34 +0100
  Re: for-loop mutates to an endless-loop James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-03 08:26 -0500
    Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-04 16:15 +0100
      Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-04 17:17 +0100
      Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 16:20 +0000
        Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-04 18:43 +0100
          Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-04 19:28 +0100
            Re: for-loop mutates to an endless-loop Bart <bc@freeuk.com> - 2020-01-04 18:59 +0000
              Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-05 14:24 +0100
            Re: for-loop mutates to an endless-loop Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-04 13:47 -0800
              Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-05 14:26 +0100
              Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-06 20:31 +0100
          Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 22:25 +0000
      Re: for-loop mutates to an endless-loop Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-01-04 14:08 -0800
      Re: for-loop mutates to an endless-loop James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-04 21:32 -0500
        Re: for-loop mutates to an endless-loop scott@slp53.sl.home (Scott Lurndal) - 2020-01-05 21:48 +0000
      Re: for-loop mutates to an endless-loop James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-01-04 21:43 -0500
  Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-03 14:47 +0100
    Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 14:39 +0000
      Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-03 15:42 +0100
        Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 15:07 +0000
          Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-03 16:18 +0100
            Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-03 16:47 +0100
              Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 20:41 +0000
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 01:05 +0100
            Re: for-loop mutates to an endless-loop gazelle@shell.xmission.com (Kenny McCormack) - 2020-01-03 18:30 +0000
        Re: for-loop mutates to an endless-loop Robert Wessel <robertwessel2@yahoo.com> - 2020-01-04 00:23 -0600
          Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 08:10 +0100
            Re: for-loop mutates to an endless-loop scott@slp53.sl.home (Scott Lurndal) - 2020-01-04 16:41 +0000
              Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 17:44 +0100
          Re: for-loop mutates to an endless-loop Bart <bc@freeuk.com> - 2020-01-04 11:15 +0000
            Re: for-loop mutates to an endless-loop Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-04 12:33 +0000
              Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-04 15:59 +0100
              Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 16:01 +0100
                Re: for-loop mutates to an endless-loop Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-01-04 16:04 +0000
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 17:06 +0100
                Re: for-loop mutates to an endless-loop scott@slp53.sl.home (Scott Lurndal) - 2020-01-04 16:42 +0000
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 17:44 +0100
            Re: for-loop mutates to an endless-loop Robert Wessel <robertwessel2@yahoo.com> - 2020-01-04 17:55 -0600
              Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-06 20:43 +0100
                Re: for-loop mutates to an endless-loop scott@slp53.sl.home (Scott Lurndal) - 2020-01-06 19:50 +0000
                Re: for-loop mutates to an endless-loop Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-01-06 15:37 -0500
                Re: for-loop mutates to an endless-loop scott@slp53.sl.home (Scott Lurndal) - 2020-01-06 21:59 +0000
                Re: for-loop mutates to an endless-loop Robert Wessel <robertwessel2@yahoo.com> - 2020-01-06 17:33 -0600
      Re: for-loop mutates to an endless-loop gazelle@shell.xmission.com (Kenny McCormack) - 2020-01-03 18:31 +0000
        Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 01:06 +0100
          Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 01:38 +0000
            Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 08:10 +0100
              Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 16:39 +0000
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 17:41 +0100
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-04 17:49 +0100
                Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 22:49 +0000
                Re: for-loop mutates to an endless-loop Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-05 03:44 +0100
            Re: for-loop mutates to an endless-loop David Brown <david.brown@hesbynett.no> - 2020-01-04 13:09 +0100
  Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-03 14:28 +0000
    Re: for-loop mutates to an endless-loop jak <nospam@please.ty> - 2020-01-05 00:40 +0100
    Re: for-loop mutates to an endless-loop "Walter H." <Walter.H-Nntp@mathemainzel.info> - 2020-01-06 20:50 +0100
      Re: for-loop mutates to an endless-loop Manfred <noname@add.invalid> - 2020-01-06 21:28 +0100
    Re: for-loop mutates to an endless-loop Manfred <noname@add.invalid> - 2020-01-06 21:02 +0100
    Re: for-loop mutates to an endless-loop Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-11 10:01 -0800
  Re: for-loop mutates to an endless-loop Richard Damon <Richard@Damon-Family.org> - 2020-01-04 16:21 -0500
    Re: for-loop mutates to an endless-loop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-01-04 22:17 +0000

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