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| From | James Kuyper <jameskuyper@verizon.net> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: is there anything unstandard in the c part here |
| Date | 2011-07-28 23:40 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <j0ta2k$mb8$1@dont-email.me> (permalink) |
| References | (6 earlier) <771efdaf-2685-40a5-9496-b00282102893@p20g2000yqp.googlegroups.com> <slrnj32idm.bt4.angel+news@pearlgates.net> <0.782bdffc5969106a905f.20110728151147BST.87ei1apk9o.fsf@bsb.me.uk> <j0t5h1$d5$1@dont-email.me> <0.0e061992fb5956cafd3e.20110729041715BST.87oc0dojwk.fsf@bsb.me.uk> |
On 07/28/2011 11:17 PM, Ben Bacarisse wrote:
> James Kuyper <jameskuyper@verizon.net> writes:
>
>> On 07/28/2011 10:11 AM, Ben Bacarisse wrote:
>>> Angel <angel+news@spamcop.net> writes:
>> ...
>>>> Of course, had you written
>>>>
>>>> pa = malloc(50 * sizeof *pa);
>>>>
>>>> you would have avoided the issue altogether, as this is always right no
>>>> matter what the type of pa might be.
>>>
>>> Not if the error that gets introduced is in the type of pa.
>>
>> Could you give us an example of such an error? That code fragment seems.
>> to me, to necessarily and inherently correctly allocate exactly room for
>> 50 elements of whatever type pa points at (assuming that later code
>> deals properly with the possibility that pa==NULL). The only error it
>> could contain is the 50, and inserting the cast won't do anything to
>> deal with the possibility of that kind of error.
>
> Example below. Yes, it's contrived. I think all examples will be
> contrived because I think the case is very weak (I'm not making the
> case, just illustrating it).
>
...
>>> I am having difficulty imagining a real-world situation where such a
>>> problem won't be detected in other places (which is why I think it's a
>>> weak argument) but there are programs which use the preferred idiom that
>>> can be made silently incorrect by a typo which would provoke a
>>> diagnostic using the cast malloc idiom.
>>
>> Please demonstrate how this can happen.
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
>
> struct p2d { double coords[2]; };
> struct p3d { double coords[3]; };
>
> void unit(double *d, size_t n)
> {
> d[0] = 1;
> for (size_t i = 1; i < n; i++) d[i] = 0;
> }
>
> int main(void)
> {
> struct p2d *point = malloc(sizeof *point);
> unit(point->coords, 3);
> /* ... */
> free(point);
> return 0;
> }
>
> The bug here is the typo on the declaration of point.
Yes, and explicitly converting the value returned by malloc would
probably not trigger a diagnostic, because the cast is fairly likely to
contain the same typo:
struct p2d *point = (struct p2d*)malloc(sizeof *point);
If it didn't have such a typo in the first place, I would expect the
resulting diagnostic to cause it to be "corrected" to match the declaration.
--
James Kuyper
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is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-25 17:45 -0600
Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-25 23:53 +0000
Re: is there anything unstandard in the c part here gwowen <gwowen@gmail.com> - 2011-07-26 01:50 -0700
Re: is there anything unstandard in the c part here tom st denis <tom@iahu.ca> - 2011-07-26 06:17 -0700
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 11:08 -0400
Re: is there anything unstandard in the c part here tom st denis <tom@iahu.ca> - 2011-07-26 10:51 -0700
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:08 -0700
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:41 -0400
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 10:58 +0000
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 13:58 +0100
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:24 -0400
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 11:07 +0000
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:02 -0400
Re: is there anything unstandard in the c part here Roberto Waltman <usenet@rwaltman.com> - 2011-07-28 17:16 -0400
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-26 09:39 -0400
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-07-27 07:24 +0100
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 07:11 -0400
Re: is there anything unstandard in the c part here Noob <root@127.0.0.1> - 2011-07-27 15:20 +0200
Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-27 14:25 +0000
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 08:10 -0700
Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-27 17:42 +0000
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 12:02 -0700
Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:04 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 22:35 -0400
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-27 13:34 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 02:13 +0100
Re: is there anything unstandard in the c part here Ike Naar <ike@sverige.freeshell.org> - 2011-07-28 07:33 +0000
Re: is there anything unstandard in the c part here Willem <willem@toad.stack.nl> - 2011-07-28 07:58 +0000
Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 04:25 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 12:26 +0100
Re: is there anything unstandard in the c part here gwowen <gwowen@gmail.com> - 2011-07-28 04:24 -0700
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 11:36 +0000
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 15:11 +0100
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-28 14:50 +0000
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 17:28 +0100
Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-28 10:38 -0600
Re: is there anything unstandard in the c part here Michael Press <rubrum@pacbell.net> - 2011-08-02 17:20 -0700
Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-08-02 23:26 -0600
Re: is there anything unstandard in the c part here Michael Press <rubrum@pacbell.net> - 2011-08-03 16:09 -0700
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:22 -0400
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 22:22 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 04:17 +0100
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 23:40 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 13:52 +0100
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-07-31 09:19 +0100
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-31 09:49 -0400
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-02 06:56 +0100
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-02 06:53 -0400
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-28 07:36 -0400
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-28 13:16 -0400
Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-26 14:58 +0000
Re: is there anything unstandard in the c part here Paul N <gw7rib@aol.com> - 2011-07-26 14:56 -0700
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:13 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 07:28 -0400
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 04:44 -0700
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-07-27 08:24 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-27 22:41 -0400
Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:19 -0700
Re: is there anything unstandard in the c part here Tim Rentsch <txr@alumni.caltech.edu> - 2011-07-28 16:06 -0700
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 01:54 -0600
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 11:01 -0400
Re: is there anything unstandard in the c part here Chad <cdalten@gmail.com> - 2011-07-26 09:49 -0700
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-07-26 13:18 -0400
Re: is there anything unstandard in the c part here John Gordon <gordon@panix.com> - 2011-07-26 17:44 +0000
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 17:45 +0000
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
Re: is there anything unstandard in the c part here Bill Waddington <william.waddington@beezmo.com> - 2011-07-26 11:55 -0700
Re: is there anything unstandard in the c part here lawrence.jones@siemens.com - 2011-07-26 18:11 -0400
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-27 20:58 -0600
Re: is there anything unstandard in the c part here arnuld <sunrise@invalid.address> - 2011-08-02 05:24 +0000
Re: is there anything unstandard in the c part here Ian Collins <ian-news@hotmail.com> - 2011-08-02 18:10 +1200
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-02 00:03 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-02 06:59 -0400
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-08-02 16:06 +0000
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-27 00:06 -0700
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-02 06:58 +0100
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-02 00:01 -0700
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-05 06:22 +0100
Re: is there anything unstandard in the c part here Keith Thompson <kst-u@mib.org> - 2011-08-04 23:54 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-05 07:37 -0400
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:05 +0100
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-13 08:26 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 14:09 +0100
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-08-02 12:58 -0400
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-08-10 01:31 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-10 08:28 -0400
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:14 +0100
Re: is there anything unstandard in the c part here "io_x" <a@b.c.invalid> - 2011-08-13 10:08 +0200
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-08-13 08:35 -0400
Re: is there anything unstandard in the c part here "J. J. Farrell" <jjf@bcs.org.uk> - 2011-08-14 04:00 +0100
Re: is there anything unstandard in the c part here Kenneth Brody <kenbrody@spamcop.net> - 2011-08-15 14:43 -0400
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-08-10 01:34 -0700
Re: is there anything unstandard in the c part here Gareth Owen <gwowen@gmail.com> - 2011-08-13 08:16 +0100
Re: is there anything unstandard in the c part here Barry Schwarz <schwarzb@dqel.com> - 2011-07-25 17:52 -0700
Re: is there anything unstandard in the c part here "J. J. Farrell" <jjf@bcs.org.uk> - 2011-07-26 02:10 +0100
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 06:17 +0000
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 00:03 -0700
Re: is there anything unstandard in the c part here "Kleuskes & Moos" <kleuske@xs4all.nl> - 2011-07-26 00:08 -0700
Re: is there anything unstandard in the c part here Ian Collins <ian-news@hotmail.com> - 2011-07-26 19:43 +1200
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 07:56 +0000
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 04:50 -0700
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 12:03 +0000
Re: is there anything unstandard in the c part here Seebs <usenet-nospam@seebs.net> - 2011-07-26 18:42 +0000
Re: is there anything unstandard in the c part here Nobody <nobody@nowhere.com> - 2011-07-27 19:10 +0100
Re: is there anything unstandard in the c part here Angel <angel+news@spamcop.net> - 2011-07-26 11:53 +0000
Re: is there anything unstandard in the c part here Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-07-26 00:07 -0700
Re: is there anything unstandard in the c part here James Kuyper <jameskuyper@verizon.net> - 2011-07-26 06:29 -0400
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-27 21:32 -0600
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-28 12:19 +0100
Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 20:25 -0400
Re: is there anything unstandard in the c part here Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-28 18:38 -0600
Re: is there anything unstandard in the c part here pete <pfiland@mindspring.com> - 2011-07-28 21:05 -0400
Re: is there anything unstandard in the c part here "Morris Keesan" <mkeesan@post.harvard.edu> - 2011-07-29 14:16 -0400
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-29 20:27 +0100
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 01:10 -0600
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-07-30 00:56 -0600
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-30 12:23 +0100
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 00:01 -0600
Re: is there anything unstandard in the c part here Ike Naar <ike@sverige.freeshell.org> - 2011-08-01 07:50 +0000
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 07:43 -0600
Re: is there anything unstandard in the c part here Ike Naar <ike@sdf.lonestar.org> - 2011-08-01 15:20 +0000
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-01 14:27 +0100
Re: is there anything unstandard in the c part here Uno <Uno@example.invalid> - 2011-08-01 08:02 -0600
Re: is there anything unstandard in the c part here Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-01 15:42 +0100
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