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| From | Kaz Kylheku <kaz@kylheku.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: zero up memory |
| Date | 2012-01-23 20:14 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <20120123120939.71@kylheku.com> (permalink) |
| References | <jfjvmb$sod$1@speranza.aioe.org> <4f1d9169$0$18698$91cee783@newsreader03.highway.telekom.at> <7edb6549-55af-4c5a-91b7-5633b6215246@n6g2000vbz.googlegroups.com> <ln4nvmwcz1.fsf@nuthaus.mib.org> |
On 2012-01-23, Keith Thompson <kst-u@mib.org> wrote: > Malcolm McLean <malcolm.mclean5@btinternet.com> writes: >> On Jan 23, 4:57 pm, Johann Klammer <klamm...@NOSPAM.a1.net> wrote: >>> >>> calloc implicitly zeroes the allocated memory(all the struct fields). >>> >> Yes. Calloc() was specified before the C standard was worked out. >> >> All bits zero isn't necessarily a floating point zero, and it isn't >> necessarily a null pointer. Which makes calloc() pretty useless. > > It's useful if the allocated memory doesn't contain any floating-point > or pointer subobjects. It's useful even if it isn't, just no portable. Nonportable and useless are different things. I can think of a lot of code that will never need to run on a machine where null pointers or 0.0 aren't all zero bits. All-zero memory can be very efficiently procured on a virtual memory OS: you can alias all of the pages to the same physical frame of memory. This is very useful for, for instance, large sparse matrices. An architecture where zero bits don't make a 0.0 floating point value is plain stupid (and not IEEE 754 compatible).
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zero up memory "Mark" <mark_cruzNOTFORSPAM@hotmail.com> - 2012-01-23 10:51 -0500
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 16:30 +0000
Re: zero up memory Johann Klammer <klammerj@NOSPAM.a1.net> - 2012-01-23 17:57 +0100
Re: zero up memory Kenneth Brody <kenbrody@spamcop.net> - 2012-01-23 12:07 -0500
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-23 09:08 -0800
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-23 09:22 -0800
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-23 10:13 -0800
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-23 12:00 -0800
Re: zero up memory Kaz Kylheku <kaz@kylheku.com> - 2012-01-23 20:14 +0000
Re: zero up memory "Joel C. Salomon" <joelcsalomon@gmail.com> - 2012-01-23 16:46 -0500
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-23 14:05 -0800
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 23:21 +0000
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-24 09:35 -0800
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-24 20:56 +0000
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-24 14:07 -0800
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-25 17:38 +0000
Re: zero up memory Johann Klammer <klammerj@NOSPAM.a1.net> - 2012-01-24 23:15 +0100
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-24 14:31 -0800
Re: zero up memory Kleuske <kleuske@nowhere.net> - 2012-01-25 15:39 +0000
Re: zero up memory Kleuske <kleuske@nowhere.net> - 2012-01-25 15:49 +0000
Re: zero up memory Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-26 03:09 -0800
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-25 13:05 -0800
Re: zero up memory Sjouke Burry <s@b> - 2012-01-25 23:25 +0000
Re: zero up memory Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-26 03:11 -0800
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-26 11:48 -0800
Re: zero up memory gordonb.p79fg@burditt.org (Gordon Burditt) - 2012-03-12 17:55 -0500
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-03-12 22:10 -0400
Re: zero up memory Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-03-12 23:24 -0400
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-03-12 23:53 -0400
Re: zero up memory gordonb.pu5nu@burditt.org (Gordon Burditt) - 2012-03-13 00:58 -0500
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-03-14 11:17 -0400
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-26 11:19 -0800
Re: zero up memory Kleuske <kleuske@nowhere.net> - 2012-01-27 08:13 +0000
Re: zero up memory Kleuske <kleuske@nowhere.net> - 2012-01-26 14:42 +0000
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-25 12:33 -0800
Re: zero up memory Kleuske <kleuske@nowhere.net> - 2012-01-26 14:12 +0000
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-01-24 17:43 -0500
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-24 16:29 -0800
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-01-24 21:43 -0500
Re: zero up memory Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-01-24 23:58 -0800
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-25 17:52 +0000
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-25 17:48 +0000
Re: zero up memory Robert Wessel <robertwessel2@yahoo.com> - 2012-01-25 12:15 -0600
Re: zero up memory blp@cs.stanford.edu (Ben Pfaff) - 2012-01-25 10:35 -0800
Re: zero up memory Robert Wessel <robertwessel2@yahoo.com> - 2012-01-25 17:15 -0600
Re: zero up memory Robert Wessel <robertwessel2@yahoo.com> - 2012-01-25 17:23 -0600
Re: zero up memory "BartC" <bc@freeuk.com> - 2012-01-25 23:51 +0000
Re: zero up memory Robert Wessel <robertwessel2@yahoo.com> - 2012-01-26 18:35 -0600
Re: zero up memory James Kuyper <jameskuyper@verizon.net> - 2012-01-25 13:17 -0500
Re: zero up memory Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 22:55 +0000
Re: zero up memory jgk@panix.com (Joe keane) - 2012-01-24 20:45 +0000
Re: zero up memory Keith Thompson <kst-u@mib.org> - 2012-01-24 14:13 -0800
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