Re: malloc and maximum size

From	Richard Damon <news.x.richarddamon@xoxy.net>
Newsgroups	comp.lang.c
Subject	Re: malloc and maximum size
Date	2011-10-15 11:50 -0400
Organization	A noiseless patient Spider
Message-ID	<j7ca3q$u1a$1@dont-email.me> (permalink)
References	(6 earlier) <44mxd373wl.fsf@be-well.ilk.org> <4E989DDC.8040900@verizon.net> <44pqhztcty.fsf@lowell-desk.lan> <lnaa93rw5t.fsf@nuthaus.mib.org> <j7asgb$nmk$1@dont-email.me>

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On 10/14/11 10:51 PM, James Kuyper wrote:
> On 10/14/2011 07:27 PM, Keith Thompson wrote:
> ...
>> C99 5.2.4.1 discusses translation limits (127 nesting levels of blocks,
>> 63 nesting levels of conditional inclusion, etc.).  It requires an
>> implementation to accept 65535 bytes in an object, but that doesn't
>> apply to the above expression, since it doesn't refer to an object.
>>
>> On the other hand, 5.2.4.1 doesn't even say that an implementation
>> must always accept 65535 bytes in an object.  It says:
>>
>>      The implementation shall be able to translate and execute at least
>>      one program that contains at least one instance of every one of the
>>      following limits:
>>
>> followed by a list of limits.  By rejecting "sizeof(char[3500000000])",
>> gcc isn't violating any requirement in 5.2.4.1; presumably it does
>> translate and execute that one program (which doesn't include an
>> instance of "sizeof(char[3500000000])".
>>
>> Presumably an implementation may legitimately reject a program violating
>> some limit not listed in 5.2.4.1, such as a trillion-line translation
>> unit.  So I *think* that rejecting any program referring to a type
>> bigger than 2**31 bytes is permitted.  But I'm not 100% certain.
>
> As I'm sure you're already aware, 5.2.4.1 is one of my least favorite
> clauses in the standard. Taking it's words literally, what it fails to
> promise renders virtually the entire rest of the standard meaningless;
> this is just one example of that fact. Except when I'm arguing against
> someone who disagrees on that point, I generally prefer to pretend that
> 5.2.4.1 says something that allows the rest of the standard to be
> meaningful.
>

One interesting thing to note, is that in reading 5.2.4.1, the standard 
does NOT give the implementation any right to fail to translate a 
program that exceeds the limits. It can NOT be claimed to be undefined 
or unspecified behavior, as the standard's definition of conformance is 
NOT limited to these limits (the only restriction I find is that a 
strictly conforming program can not violate those limits). The standard 
requires that the compiler must be able to succeed on one given program, 
but grants no permission to fail.

I suppose that this is really a defect in the standard, and the standard 
needs some language to allow the implementation to establish limits, and 
to generate a diagnostic and reject a program that exceeds these limits.

Exceeding implementation limits must NOT be considered undefined 
behavior, (unless the definition of implementation limits is vastly 
improved) as currently you can not know if a given program exceeds the 
implementation limits, so considering it undefined behavior, and not 
requiring a diagnostic, means it is impossible to show any given 
implementation as "non-conforming", as any non-conforming behavior can 
be blamed on exceeding some implementation limit.

Thread

malloc and maximum size "V.Subramanian, India" <subramanian100in@yahoo.com> - 2011-10-14 06:31 -0700
  Re: malloc and maximum size gordonb.pey1d@burditt.org (Gordon Burditt) - 2011-10-14 09:45 -0500
    Re: malloc and maximum size Lowell Gilbert <lgusenet@be-well.ilk.org> - 2011-10-14 11:10 -0400
      Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 11:40 -0400
        Re: malloc and maximum size Lowell Gilbert <lgusenet@be-well.ilk.org> - 2011-10-14 15:00 -0400
          Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 15:17 -0400
            Re: malloc and maximum size Lowell Gilbert <lgusenet@be-well.ilk.org> - 2011-10-14 15:46 -0400
              Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 16:38 -0400
                Re: malloc and maximum size Ike Naar <ike@iceland.freeshell.org> - 2011-10-14 21:59 +0000
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 18:26 -0400
                Re: malloc and maximum size Lowell Gilbert <lgusenet@be-well.ilk.org> - 2011-10-14 18:42 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 16:27 -0700
                Re: malloc and maximum size Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-14 20:41 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 18:31 -0700
                Re: malloc and maximum size Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-15 02:58 +0100
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 22:11 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 22:59 -0400
                Re: malloc and maximum size Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-14 23:44 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 22:56 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-15 07:52 -0400
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:54 -0800
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:51 -0800
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 22:51 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 22:48 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-15 07:54 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-15 11:25 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-15 21:21 -0400
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 17:41 -0800
                Re: malloc and maximum size Kaz Kylheku <kaz@kylheku.com> - 2012-01-25 02:11 +0000
                Re: malloc and maximum size Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-15 11:50 -0400
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-15 21:38 -0400
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 17:33 -0800
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 17:06 -0800
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:58 -0800
                Re: malloc and maximum size Kaz Kylheku <kaz@kylheku.com> - 2012-01-25 01:23 +0000
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 16:31 -0800
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 22:20 -0400
                Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 16:03 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 23:01 -0400
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 17:35 -0800
                Re: malloc and maximum size Kaz Kylheku <kaz@kylheku.com> - 2012-01-25 02:33 +0000
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 17:14 -0800
              Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:45 -0800
            Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:32 -0800
              Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2012-01-25 02:40 -0800
                Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 17:27 -0800
          Re: malloc and maximum size Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-14 16:17 -0400
            Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 16:52 -0400
              Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 16:12 -0700
                Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 23:04 -0400
          Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:36 -0800
    Re: malloc and maximum size Ike Naar <ike@iceland.freeshell.org> - 2011-10-14 16:49 +0000
  Re: malloc and maximum size James Kuyper <jameskuyper@verizon.net> - 2011-10-14 11:05 -0400
  Re: malloc and maximum size Nobody <nobody@nowhere.com> - 2011-10-14 16:11 +0100
  Re: malloc and maximum size Kenneth Brody <kenbrody@spamcop.net> - 2011-10-14 12:24 -0400
  Re: malloc and maximum size jt@toerring.de (Jens Thoms Toerring) - 2011-10-14 17:10 +0000
  Re: malloc and maximum size Stephen Sprunk <stephen@sprunk.org> - 2011-10-14 13:43 -0500
    Re: malloc and maximum size Keith Thompson <kst-u@mib.org> - 2011-10-14 12:03 -0700
      Re: malloc and maximum size jt@toerring.de (Jens Thoms Toerring) - 2011-10-14 20:36 +0000
    Re: malloc and maximum size Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 16:26 -0800
  Re: malloc and maximum size Seebs <usenet-nospam@seebs.net> - 2011-10-17 17:21 +0000
  Re: malloc and maximum size Shao Miller <sha0.miller@gmail.com> - 2012-01-24 23:49 -0500
    Re: malloc and maximum size Shao Miller <sha0.miller@gmail.com> - 2012-01-24 23:55 -0500

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