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| From | Stephen Sprunk <stephen@sprunk.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: malloc and maximum size |
| Date | 2011-10-14 13:43 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <j79vs9$euv$1@dont-email.me> (permalink) |
| References | <dc9e20a5-6a6b-4a1c-b2d2-5c8bcc50c812@a12g2000vbz.googlegroups.com> |
On 14-Oct-11 08:31, V.Subramanian, India wrote: > SIZE_MAX, defined in stdint.h, is the largest value that can be > represented in type size_t. However when I pass SIZE_MAX as the > argument to malloc, it is unable to allocate SIZE_MAX bytes of memory. size_t must be capable of representing the size of the largest object the implementation can create. That does _not_ mean the implementation must be capable of creating an object the size of the largest value a size_t can represent. Those are two very different things. > In fact, malloc allocates much much less memory. > > Here is the complete program max_size_to_malloc.c > ... > This program compiles fine with gcc 3.4.3 as > gcc -std=c99 -pedantic -Wall -Wextra max_size_to_malloc.c > > and produces the following output(after quite some time): > 4294967295 - 1365266451 : Allocated 2929700844 bytes of memory > > What is the reason for allocating this much less memory while the > parameter type of malloc is size_t ? Maybe your system didn't have any contiguous blocks of memory larger than 2,929,700,844 bytes available at the time of your test. > Normally what factor drives the maximum size of a single chunk of > memory allocated by malloc ? There are other things in memory (eg. your program, the stack, any objects in the heap, OS services, libraries your program is linked to, etc.), so at least some of it will not be available for you to allocate for your own purposes; how much will vary. Available memory is often fragmented (because those things above are located in different places in memory), so the largest object you can allocate will be limited to the largest _contiguous_ block. Also, there may be administrative policy limiting the amount of memory any program can allocate to below what is technically possible. S -- Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws the K5SSS dice at every possible opportunity." --Stephen Hawking
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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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