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Groups > comp.lang.c > #385883

Re: "undefined behavior"?

From Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups comp.lang.c
Subject Re: "undefined behavior"?
Date 2024-06-12 15:22 -0700
Organization None to speak of
Message-ID <8734ph7qe5.fsf@nosuchdomain.example.com> (permalink)
References <666a095a$0$952$882e4bbb@reader.netnews.com> <v4d4hm$1rjc5$1@dont-email.me>

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Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
> On 12.06.2024 22:47, DFS wrote:
[...]
>> before: char outliers[100];
>> after : char outliers[100] = "";
[...]
> Seriously; why do you expect [in C] a declaration to initialize that
> stack object? (There are other languages that do initializations as
> the language defines it, but C doesn't; it may help to learn before
> programming in any language?) And why do you think that "" would be
> an appropriate initialization (i.e. a single '\0' character) and not
> all 100 elements set to '\0'? (Someone else might want to access the
> element 'answer[99]'.) And should we pay for initializing 1000000000
> characters in case one declares an appropriate huge array?

This:
    char outliers[100] = "";
initializes all 100 elements to zero.  So does this:
    char outliers[100] = { '\0' };
Any elements or members not specified in an initializer are set to zero.

If you want to set an array's 0th element to 0 and not waste time
initializing the rest, you can assign it separately:
    char outliers[100];
    outliers[0] = '\0';
or
    char outliers[100];
    strcpy(outliers, "");
though the overhead of the function call is likely to outweigh the
cost of initializing the array.

-- 
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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