Re: "undefined behavior"?

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: "undefined behavior"?
Date	2024-06-12 15:30 -0700
Organization	None to speak of
Message-ID	<87y1796bfn.fsf@nosuchdomain.example.com> (permalink)
References	<666a095a$0$952$882e4bbb@reader.netnews.com> <8t3k6j5ikf5mvimvksv2t91gbt11ljdfgb@4ax.com> <666a18de$0$958$882e4bbb@reader.netnews.com>

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DFS <nospam@dfs.com> writes:
> On 6/12/2024 5:30 PM, Barry Schwarz wrote:
>> On Wed, 12 Jun 2024 16:47:23 -0400, DFS <nospam@dfs.com> wrote:
>> 
>>> Wrote a C program to mimic the stats shown on:
>>>
>>> https://www.calculatorsoup.com/calculators/statistics/descriptivestatistics.php
>>>
>>> My code compiles and works fine - every stat matches - except for one
>>> anomaly: when using a dataset of consecutive numbers 1 to N, all values
>>>> 40 are flagged as outliers.  Up to 40, no problem.  Random numbers
>>> dataset of any size: no problem.
>>>
>>> And values 41+ definitely don't meet the conditions for outliers (using
>>> the IQR * 1.5 rule).
>>>
>>> Very strange.
>>>
>>> Edit: I just noticed I didn't initialize a char:
>>> before: char outliers[100];
>>> after : char outliers[100] = "";
>>>
>>> And the problem went away.  Reset it to before and problem came back.
>>>
>>> Makes no sense.  What could cause the program to go FUBAR at data point
>>> 41+ only when the dataset is consecutive numbers?

>>> Also, why doesn't gcc just do you a solid and initialize to "" for you?
>> Makes perfect sense.  The first rule of undefined behavior is
>> "Whatever happens is exactly correct."  You are not entitled to any
>> expectations and none of the behavior (or perhaps all of the behavior)
>> can be called unexpected.
>
> I HATE bogus answers like this.
>
> Aren't you embarrassed to say things like that?

He has nothing to be embarrassed about.  What he wrote is correct.

The C standard's definition of "undefined behavior" is "behavior, upon
use of a nonportable or erroneous program construct or of erroneous
data, for which this International Standard imposes no requirements".

If you don't like the way C deals with undefined behavior, that's
perfectly valid, and a lot of people are likely to agree with you.
But I advise against lashing out at people who are correctly explaining
what the C standard says.

DFS, since you've been posting in comp.lang.c for at least ten years,
I'm surprised you're having difficulties with this.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */

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"undefined behavior"? DFS <nospam@dfs.com> - 2024-06-12 16:47 -0400
  Re: "undefined behavior"? Barry Schwarz <schwarzb@delq.com> - 2024-06-12 14:30 -0700
    Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-12 17:53 -0400
      Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-12 15:30 -0700
        Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-12 19:07 -0400
          Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-12 17:33 -0700
            Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-13 05:47 +0100
              Re: "undefined behavior"? scott@slp53.sl.home (Scott Lurndal) - 2024-06-13 15:39 +0000
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-13 18:08 +0100
                Re: "undefined behavior"? bart <bc@freeuk.com> - 2024-06-13 19:01 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-13 19:54 +0100
                Re: "undefined behavior"? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-13 12:34 -0700
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 00:32 +0100
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-14 00:55 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 02:48 +0100
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-14 12:44 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 15:30 +0100
                Re: "undefined behavior"? Richard Harnden <richard.nospam@gmail.invalid> - 2024-06-14 16:32 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 19:06 +0100
                Re: "undefined behavior"? bart <bc@freeuk.com> - 2024-06-14 19:31 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 20:13 +0100
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-14 22:29 +0100
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 23:35 +0100
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-15 00:14 +0100
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-15 20:57 +0200
                Re: "undefined behavior"? Richard Harnden <richard.nospam@gmail.invalid> - 2024-06-15 20:27 +0100
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-15 23:13 +0100
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-16 12:53 +0200
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-16 14:44 +0100
                Re: "undefined behavior"? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-14 11:49 -0700
                Re: "undefined behavior"? Ben Bacarisse <ben@bsb.me.uk> - 2024-06-14 22:32 +0100
                Re: "undefined behavior"? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-15 00:56 -0700
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-13 15:58 -0700
                Re: "undefined behavior"? bart <bc@freeuk.com> - 2024-06-14 02:18 +0100
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-14 19:08 +0200
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-14 12:34 -0700
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-15 22:13 +0200
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-14 13:43 -0700
              Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-13 14:47 -0700
                Re: "undefined behavior"? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2024-06-14 00:41 +0100
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-13 17:09 -0700
  Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-12 23:38 +0200
    Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-12 15:18 -0700
      Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-13 14:42 +0200
        Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-13 16:39 -0700
      Re: "undefined behavior"? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-18 17:23 -0700
        Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-18 17:42 -0700
          Re: "undefined behavior"? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-06-22 09:28 -0700
    Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-12 18:29 -0400
      Re: "undefined behavior"? Ike Naar <ike@sdf.org> - 2024-06-13 07:25 +0000
        Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-13 11:13 -0400
          Re: "undefined behavior"? scott@slp53.sl.home (Scott Lurndal) - 2024-06-13 15:40 +0000
          Re: "undefined behavior"? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2024-06-13 15:49 +0000
            Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-13 13:05 -0400
      Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-13 15:15 +0200
        Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-13 16:47 -0700
          Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-14 19:13 +0200
  Re: "undefined behavior"? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-12 23:38 +0200
    Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-12 15:22 -0700
      Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-12 18:34 -0400
        Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-13 15:21 +0200
          Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-13 10:38 -0400
            Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-14 19:18 +0200
              Re: "undefined behavior"? scott@slp53.sl.home (Scott Lurndal) - 2024-06-14 17:36 +0000
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-15 22:15 +0200
              Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-14 19:05 -0400
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-14 18:39 -0700
                Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-14 23:49 -0400
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-14 20:56 -0700
                Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-15 00:45 -0400
                Re: "undefined behavior"? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-15 07:03 +0200
                Re: "undefined behavior"? DFS <nospam@dfs.com> - 2024-06-15 07:39 -0400
                Re: "undefined behavior"? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-15 01:05 -0400
                Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-14 22:20 -0700
                Re: "undefined behavior"? bart <bc@freeuk.com> - 2024-06-15 09:37 +0100
                Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-15 22:22 +0200
      Re: "undefined behavior"? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-06-13 02:19 +0200
        Re: "undefined behavior"? David Brown <david.brown@hesbynett.no> - 2024-06-13 15:28 +0200
  Re: "undefined behavior"? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-12 14:57 -0700
  Re: "undefined behavior"? bart <bc@freeuk.com> - 2024-06-13 10:43 +0100
  Re: "undefined behavior"? Bonita Montero <Bonita.Montero@gmail.com> - 2024-06-13 11:45 +0200

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