Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #16168

Re: malloc and maximum size

Show all headers | View raw

On 2012-01-25, Tim Rentsch <txr@alumni.caltech.edu> wrote:
> Keith Thompson <kst-u@mib.org> writes:
>
>> James Kuyper <jameskuyper@verizon.net> writes:
>> [...]
>>> Not even sizeof(char[3500000000])? For an implementation where
>>> (size_t)(-1) is 4294967295, what gives that implementation permission to
>>> do anything with that expression other than yield a value of
>>> (size_t)3500000000? The implementation is free to issue a diagnostic, of
>>> course, but not to reject the code.
>>
>> Interesting.  For the following program:
>>
>> #include <stdio.h>
>> int main(void) {
>>     printf("%zu\n", sizeof (char[(size_t)-1]));
>>     return 0;
>> }
>>
>> "gcc -std=c99" rejects it with an error message:
>>
>> c.c: In function 'main':
>> c.c:3:5: error: size of unnamed array is too large
>>
>> Change the array size to (size_t)-1/2 and it compiles and prints
>> "2147483647".  Change it to (size_t)-1/2+1 and it rejects it with the
>> same error message.
>>
>> Does this make "gcc -std=c99" non-conforming?
>
> No, because there is no requirement that this program
> be accepted.

If for every feature of the above program, we can deduce what the behavior
should be (and thus in doing so we must find that it does not violate any
limit, or invoke any UB) then we can deduce that this program must be accepted,
or else it represents a test case that shows the implementation to be
nonconforming.

I don't believe that it violates any limits or invokes any UB, which leads me
to conclude that it does show the above gcc installation to be nonconforming.

This all follows from the software engineering sense of what it means to have a
test case, what requirements are, and what it means for a test case to fail.

It might be a test case that is considered "degenerate", which is a code word
for "something that the users probably won't run into or care about".
Or that it's not a "showstopper bug".

But that sort of negotation or classification of defects is outside of the
standard.

Now if you make a program which stresses each of the limists and gcc chokes on
it, then you have not proven a nonconformity. This is because 5.4.2.1
has the effect of excusing the implementors from handling /all/ such programs.
They have to handle only one, and it can be any program from that set;
not restricted to one that is chosen by the users of the implementation.

If you change your program so that it does not exercise all of the limits
(maybe by scaling back just one of them) and if you can still reproduce the
failure, then you have found a nonconformance.

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

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

csiph-web