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| From | Lowell Gilbert <lgusenet@be-well.ilk.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: malloc and maximum size |
| References | (1 earlier) <c4Kdnddfxr6_1gXTnZ2dnUVZ_jmdnZ2d@posted.internetamerica> <44zkh37goi.fsf@be-well.ilk.org> <4E985803.8070300@verizon.net> <44r52f760i.fsf@be-well.ilk.org> <4E988AC3.6050701@verizon.net> |
| Date | 2011-10-14 15:46 -0400 |
| Message-ID | <44mxd373wl.fsf@be-well.ilk.org> (permalink) |
James Kuyper <jameskuyper@verizon.net> writes: > On 10/14/2011 03:00 PM, Lowell Gilbert wrote: >> James Kuyper <jameskuyper@verizon.net> writes: >> >>> On 10/14/2011 11:10 AM, Lowell Gilbert wrote: >>> ... >>>> Does SIZE_MAX have to be the largest value representable in a size_t? >>>> The standard just says that it's the "maximum value" for the type, >>> >>> What distinction do you see between "largest value representable" if a >>> type and "maximum value" for a type? The phrases seem synonymous to me. >> >> Certainly there's no difference in *most* cases. >> >> For size_t, the type is just defined as the output type for sizeof, >> which is defined in turn as yielding the size of its operand. So I can >> see an argument that the "maximum value" of a size_t could be viewed as >> the largest value that sizeof could possibly yield on the particular >> implementation. > > Well, the maximum value returnable by sizeof has to be the same as the > maximum value representable by size_t: > > sizeof(char[(size_t)-1]) == (size_t)(-1) Assuming I understand what you're getting at, you're begging the question here. [But the expression doesn't make sense to me, so the assumption may well be wrong.] > It has been argued that, since it's not possible for the standard's > specifications for the value and type of sizeof(char[SIZE_MAX][2]) to be > simultaneously satisfied, an implementation is free, among other > possibilities, to treat it as having a value that is larger than > SIZE_MAX. Personally, I think such code should be rejected, but it's not > clear that the standard requires, or even allows, it to be rejected. Right; this argument has gone around a few times, and I don't think there's a definitive answer either. > However, there's no possible basis that I'm aware of for rejecting > sizeof(char[(size_t)-1]). I assume you mean SIZE_MAX rather than (size_t), in which case I agree. But that doesn't mean SIZE_MAX has to be the largest value a size_t can hold, if there are other limits on how big an object can be. >> ... Of course, that can be (and, indeed, often is) smaller >> than a size_t could represent. > > With respect to your claim "often is" - can you cite any implementation > where the equality expression given above is NOT true? I think you're misreading my claim. There certainly are systems with architectural limitations on how big an object can be, well short of what fits in a size_t. For example, the machine I'm posting from has 32-bit words, from which it gets a 4-gigabyte range for its size_t. However, the operating system reserves some of the address space, so no program can ever have more than 3 gigabytes. As a result, sizeof can *never* return more than 3 gigabytes. This prompted me to wonder whether it would be legitimate for the system's SIZE_MAX to be 3 gigabytes. Am I making more sense now? -- Lowell Gilbert, embedded/networking software engineer http://be-well.ilk.org/~lowell/
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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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