Groups | Search | Server Info | Keyboard shortcuts | Login | Register

Groups > comp.lang.c > #399006

Re: Is reallocarray() planned to be standardized?

From cross@spitfire.i.gajendra.net (Dan Cross)
Newsgroups comp.lang.c
Subject Re: Is reallocarray() planned to be standardized?
Date 2026-05-15 11:02 +0000
Organization PANIX Public Access Internet and UNIX, NYC
Message-ID <10u6ufo$nd7$2@reader1.panix.com> (permalink)
References <10u5a5v$nagc$1@dont-email.me> <10u5qch$uo0d$8@kst.eternal-september.org> <10u5uoc$k88$2@reader1.panix.com> <10u601c$uo0d$12@kst.eternal-september.org>

Show all headers | View raw

In article <10u601c$uo0d$12@kst.eternal-september.org>,
Keith Thompson  <Keith.S.Thompson+u@gmail.com> wrote:
>cross@spitfire.i.gajendra.net (Dan Cross) writes:
>> In article <10u5qch$uo0d$8@kst.eternal-september.org>,
>> Keith Thompson  <Keith.S.Thompson+u@gmail.com> wrote:
>>>cross@spitfire.i.gajendra.net (Dan Cross) writes:
>>>[...]
>>>> `reallocarray` is, indeed, in POSIX-2024, but has yet to make it
>>>> into C.  `recallocarray` is not yet in POSIX, however.
>>>
>>>I don't think that's what you meant to say.
>>
>> I mean that `reallocarray` is in POSIX-2024, but not in ISO C.
>>
>> There is a related function, `recallocarray`, that is not in
>> POSIX.
>
>Ah, I completely missed that "reallocarray" and "recallocarray"
>("re" vs. "rec") are distinct.
>
>"recallocarray" is apparently BSD-specific, and is not implemented
>in glibc.  "recallocarray" differs from "reallocarray" in that
>freed memory is cleared with explicit_bzero().

And newly allocated memory is cleared, a la `calloc`.

>>>I'm unaware of any proposal to add reallocarray to ISO C.
>>
>> I'm mildly surprised it hasn't been proposed.
>
>As far as I can tell, reallocarray() differs from realloc() only
>in that it takes two arguments to specify the size, and fails
>if the multiplication would overflow (um, I mean wrap around).
>realloc(p, n*size) does the same thing in the absence of overflow.
>Obviously somebody thought it was worthwhile.

It's a security thing, similar to `explicit_bzero` or
`memset_explicit`.  I believe that when it was introduced into
OpenBSD, it actually found a number of overflow bugs; whether
those were exploitable or not, I don't know.  The OpenBSD people
are known to be zealous when it comes to security.

	- Dan C.

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-14 20:09 +0000
  Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-14 21:10 +0000
    Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-14 23:35 +0000
      Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 17:46 -0700
        Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 02:00 +0000
          Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 19:22 -0700
            Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 11:02 +0000
              Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 14:44 -0700
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 21:50 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 14:55 -0700
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 15:02 -0700
                Re: Is reallocarray() planned to be standardized? scott@slp53.sl.home (Scott Lurndal) - 2026-05-15 22:12 +0000
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 11:38 +0200
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-16 13:00 +0200
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 13:58 +0200
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-16 12:34 +0000
                Re: Is reallocarray() planned to be standardized? David Brown <david.brown@hesbynett.no> - 2026-05-16 16:25 +0200
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 22:32 +0000
            Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 15:23 +0000
              Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 17:28 +0000
              Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 17:40 +0000
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 17:50 +0000
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 18:28 +0000
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 21:35 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 15:05 -0700
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 22:35 +0000
                Re: Is reallocarray() planned to be standardized? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-15 17:18 -0700
                Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 08:07 +0000
                Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-16 12:44 +0000
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-15 23:44 +0200
                Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 21:47 +0000
                Re: Is reallocarray() planned to be standardized? scott@slp53.sl.home (Scott Lurndal) - 2026-05-15 22:10 +0000
                Re: Is reallocarray() planned to be standardized? Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-16 01:13 +0200
                AIX (was Re: Is reallocarray() planned to be standardized?) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 22:30 +0000
                Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 08:04 +0000
    Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-15 07:07 +0000
      Re: Is reallocarray() planned to be standardized? kalevi@kolttonen.fi (Kalevi Kolttonen) - 2026-05-15 13:58 +0000
        Re: Is reallocarray() planned to be standardized? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-16 00:25 +0000
  Re: Is reallocarray() planned to be standardized? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-14 17:26 -0700
    Re: Is reallocarray() planned to be standardized? cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-15 02:08 +0000
  Re: Is reallocarray() planned to be standardized? Bonita Montero <Bonita.Montero@gmail.com> - 2026-05-16 11:28 +0200

csiph-web