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| From | Ian Collins <ian-news@hotmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: What is "complexifying" C? |
| Date | 2015-03-23 17:01 +1300 |
| Message-ID | <cn9hgdF9hh7U1@mid.individual.net> (permalink) |
| References | (15 earlier) <2a74b8f4-d5b5-417b-9277-cc668478bfce@googlegroups.com> <cn7ga8FdhbaU4@mid.individual.net> <946d02bc-ea08-44ac-9b3b-7e5092b7a05f@googlegroups.com> <cn8fo3FdhbaU5@mid.individual.net> <6d47d194-da07-45fb-9e12-b6d85483037b@googlegroups.com> |
Malcolm McLean wrote:
> On Sunday, March 22, 2015 at 6:25:16 PM UTC, Ian Collins wrote:
>> Malcolm McLean wrote:
>>> On Sunday, March 22, 2015 at 9:28:50 AM UTC, Ian Collins wrote:
>>>> Malcolm McLean wrote:
>>>>
>>>> Maybe id does, but closing a file when it goes out of scope certainly
>>>> does not.
>>>>
>>> The C++ code
>>>
>>> class MyStream
>>> {
>>> FILE *fp;
>>> ~MyStream()
>>> {
>>> fclose(fp);
>>> }
>>> }
>>>
>>> isn't joke code. But it's obviously written by someone unaware of the
>>> fact that fclose() can return an error condition.
>>
>> How many C programmers check the return form fclose?
>>
>> I just checked a large open source code base (the Illumos kernel) and
>> the there are ~3000 calls to fclose, ~1900 of those are of the form
>> "(void) fclose(fp)"
>>
> I seldom check fclose().
> Normally you can get away with it, or, for scratch programs, putting
> up an error message isn't going to help.
>
> It's the general principle. Operations like closing files, which aren't
> pure frees of memory, shouldn't be in destructors, at least in C++.
That goes against one of the cornerstones of modern C++: RAII. See
http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization
> If at some point you need to move from unchecked fclose() to checked
> fclose(), and all the FILE *s are wrapped up in C++ classes written
> with the fclose() in the destructor, then you've got a major headache.
Actually you don't. You hare in a far better position than you would be
with the closes scattered throughout the code. You only have to change
the code in one place.
I use a reference counting object to manage file descriptors in my C++
code. I can call the object's close() member if I want to close a file
descriptor early, but I rarely do. If I want to add debug to file
closes I just add it to the objects destructor.
Many of the system libraries I use have void close_XXX() functions, so
there is no risk (real or perceived) in encapsulating this in an object
destructor. I know what ever my code does (return early, throw an
exception) I won't leak handles.
--
Ian Collins
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What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-16 22:55 +0100
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-16 22:55 +0000
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-16 16:41 -0700
Re: What is "complexifying" C? Richard Heathfield <rjh@cpax.org.uk> - 2015-03-17 00:05 +0000
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-17 01:12 +0000
Re: What is "complexifying" C? Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 13:58 -0700
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 07:16 +0100
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-17 13:50 +0000
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 14:59 +0100
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 15:22 +0100
Re: What is "complexifying" C? David Brown <david.brown@hesbynett.no> - 2015-03-17 16:16 +0100
Re: What is "complexifying" C? Kaz Kylheku <kaz@kylheku.com> - 2015-03-17 14:39 +0000
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-17 15:23 +0000
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-18 15:40 -0700
Re: What is "complexifying" C? Kaz Kylheku <kaz@kylheku.com> - 2015-03-18 22:49 +0000
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-19 13:55 +0000
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-19 15:37 +0000
Re: What is "complexifying" C? jacob navia <jacob@jacob.remcomp.fr> - 2015-03-19 23:06 +0100
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-19 22:38 +0000
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-20 19:43 +1300
Re: What is "complexifying" C? jacob navia <jacob@jacob.remcomp.fr> - 2015-03-20 07:49 +0100
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-20 02:29 -0500
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-20 21:37 +1300
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-20 03:40 -0500
Re: What is "complexifying" C? David Brown <david.brown@hesbynett.no> - 2015-03-20 10:18 +0100
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-21 00:19 -0500
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-20 03:15 -0700
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-22 13:51 +1300
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-22 15:21 +1300
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-22 00:57 -0700
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-22 22:28 +1300
Re: What is "complexifying" C? fir <profesor.fir@gmail.com> - 2015-03-22 02:59 -0700
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-22 11:16 -0700
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 07:25 +1300
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-22 12:06 -0700
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 17:01 +1300
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-23 03:09 -0700
Re: What is "complexifying" C? fir <profesor.fir@gmail.com> - 2015-03-23 01:42 -0700
Re: What is "complexifying" C? Melzzzzz <mel@zzzzz.com> - 2015-03-22 19:32 +0100
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-22 17:34 -0500
Re: What is "complexifying" C? Richard Damon <Richard@Damon-Family.org> - 2015-03-22 20:07 -0400
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-23 00:00 -0500
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 18:04 +1300
Re: What is "complexifying" C? Richard Damon <Richard@Damon-Family.org> - 2015-03-23 23:22 -0400
Re: What is "complexifying" C? Richard Damon <Richard@Damon-Family.org> - 2015-03-22 14:54 -0400
Re: What is "complexifying" C? Melzzzzz <mel@zzzzz.com> - 2015-03-23 00:35 +0100
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 17:06 +1300
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 17:25 +1300
Re: What is "complexifying" C? Martin Shobe <martin.shobe@yahoo.com> - 2015-03-22 23:33 -0500
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-23 18:01 +1300
Re: What is "complexifying" C? James Kuyper <jameskuyper@verizon.net> - 2015-03-23 09:41 -0400
Re: What is "complexifying" C? James Kuyper <jameskuyper@verizon.net> - 2015-03-23 10:23 -0400
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-24 07:10 +1300
Re: What is "complexifying" C? James Kuyper <jameskuyper@verizon.net> - 2015-03-23 14:57 -0400
Re: What is "complexifying" C? David Brown <david.brown@hesbynett.no> - 2015-03-24 09:36 +0100
Re: What is "complexifying" C? Richard Heathfield <rjh@cpax.org.uk> - 2015-03-24 08:42 +0000
Re: What is "complexifying" C? David Brown <david.brown@hesbynett.no> - 2015-03-24 11:23 +0100
Re: What is "complexifying" C? Richard Heathfield <rjh@cpax.org.uk> - 2015-03-24 10:52 +0000
Re: What is "complexifying" C? raltbos@xs4all.nl (Richard Bos) - 2015-03-29 16:58 +0000
Re: What is "complexifying" C? Melzzzzz <mel@zzzzz.com> - 2015-03-22 02:38 +0100
Re: What is "complexifying" C? Richard Damon <Richard@Damon-Family.org> - 2015-03-22 09:11 -0400
Re: What is "complexifying" C? Les Cargill <lcargill99@comcast.com> - 2015-03-20 06:30 -0500
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-20 10:31 +0000
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-20 13:49 +0000
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-20 09:23 -0700
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-21 08:28 +1300
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-20 01:04 -0700
Re: What is "complexifying" C? Keith Thompson <kst-u@mib.org> - 2015-03-17 08:05 -0700
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 16:08 +0100
Re: What is "complexifying" C? Keith Thompson <kst-u@mib.org> - 2015-03-17 11:09 -0700
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 21:37 +0100
Re: What is "complexifying" C? Robert Wessel <robertwessel2@yahoo.com> - 2015-03-18 00:40 -0500
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-17 15:34 +0000
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-17 15:06 +0000
Re: What is "complexifying" C? Melzzzzz <mel@zzzzz.com> - 2015-03-17 00:05 +0100
Re: What is "complexifying" C? Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-16 23:20 +0000
Re: What is "complexifying" C? Ian Collins <ian-news@hotmail.com> - 2015-03-17 16:42 +1300
Re: What is "complexifying" C? Mark Storkamp <mstorkamp@yahoo.com> - 2015-03-17 08:59 -0500
Re: What is "complexifying" C? jacob navia <jacob@spamsink.net> - 2015-03-17 15:18 +0100
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-17 14:41 +0000
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-18 15:47 -0700
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-19 00:26 +0000
Re: What is "complexifying" C? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-19 03:23 -0700
Re: What is "complexifying" C? Bartc <bc@freeuk.com> - 2015-03-19 11:19 +0000
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