Re: Buffer contents well-defined after fgets() reaches EOF ?

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Buffer contents well-defined after fgets() reaches EOF ?
Date	2025-02-11 13:59 -0800
Organization	None to speak of
Message-ID	<87msesnnwa.fsf@nosuchdomain.example.com> (permalink)
References	(8 earlier) <vodi7t$1b6at$1@dont-email.me> <voe7kp$1f0us$3@dont-email.me> <voegdf$1hbn6$1@dont-email.me> <voel5v$1kp3m$1@dont-email.me> <vog3lp$1sd7k$1@dont-email.me>

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James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> On 2/10/25 23:54, Lawrence D'Oliveiro wrote:
>> On Mon, 10 Feb 2025 22:33:03 -0500, James Kuyper wrote:
> ...
>>> "The fgets function reads at most one less than the number of characters
>>> specified by n from the stream pointed to by stream into the array
>>> pointed to by s." (7.32.7.2p2)
>>>
>>> If the buffer length is 1, "at most one less than the number ...
>>> specified" is 0. Therefore, fgets() cannot read any characters into the
>>> buffer, no matter what the contents of the input stream are. Again,
>>> since there is no "last byte read into the array", there is no location
>>> where a null byte should be written.
>> 
>> Have you tried it? I have.
>
> I just tried it, using gcc  and found that fgets() does set the first
> byte of the buffer to a null character. Therefore, it doesn't conform to
> the requirements of the standard. That's not particularly surprising -
> calling fgets with useless arguments isn't something that I'd expect to
> be a high priority on their pre-delivery tests.

As you know, gcc doesn't implement fgets().  Were you using GNU libc?

-- 
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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Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 06:59 +0100
  Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-09 06:23 +0000
  Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-08 22:23 -0800
    Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-08 23:12 -0800
      Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-09 23:52 +0000
        Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 17:06 -0800
          Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 17:22 -0800
            Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-10 12:49 +0200
              Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-13 07:14 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-14 16:51 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 15:10 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-14 17:23 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 16:46 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 17:28 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 17:22 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-14 11:03 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-14 19:34 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:06 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-14 20:01 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 20:51 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:02 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:29 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:29 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-16 01:04 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-16 07:37 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 18:59 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-16 10:48 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:14 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-17 11:54 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-16 07:32 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-16 11:05 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:25 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 19:21 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-16 20:26 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:41 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:29 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:33 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 20:23 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-14 14:38 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-14 21:02 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 19:53 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-16 04:48 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-15 08:37 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-15 20:08 +0200
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-18 20:17 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-21 05:58 +0000
            Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-15 08:12 -0800
          Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:44 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-10 03:28 +0000
            Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 20:11 -0800
              Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-10 07:21 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? scott@slp53.sl.home (Scott Lurndal) - 2025-02-10 16:39 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-10 13:58 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 01:03 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-10 22:33 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 03:42 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 04:54 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 13:07 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-11 21:47 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 17:44 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-12 06:16 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-11 13:59 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-02-11 17:58 -0500
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-11 15:40 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-17 21:11 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-10 22:32 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-10 22:38 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 12:04 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-02-13 07:29 -0800
    Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 08:13 +0100
      Re: Buffer contents well-defined after fgets() reaches EOF ? Michael S <already5chosen@yahoo.com> - 2025-02-09 12:50 +0200
        Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 18:29 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 21:57 +0000
      Re: Buffer contents well-defined after fgets() reaches EOF ? Andrey Tarasevich <noone@noone.net> - 2025-02-09 07:27 -0800
        Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-09 18:34 +0100
          Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 16:57 -0800
            Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:35 +0100
              Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 20:37 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 07:08 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-02-09 22:41 -0800
                Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 07:54 +0100
                Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 23:22 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Kaz Kylheku <643-408-1753@kylheku.com> - 2025-02-11 00:59 +0000
                Re: Buffer contents well-defined after fgets() reaches EOF ? Lawrence D'Oliveiro <ldo@nz.invalid> - 2025-02-17 02:50 +0000
      Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 22:57 +0000
        Re: Buffer contents well-defined after fgets() reaches EOF ? Mark Bourne <nntp.mbourne@spamgourmet.com> - 2025-02-10 23:24 +0000
  Re: Buffer contents well-defined after fgets() reaches EOF ? Ben Bacarisse <ben@bsb.me.uk> - 2025-02-10 01:32 +0000
    Re: Buffer contents well-defined after fgets() reaches EOF ? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-02-10 02:40 +0100

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