Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
| From | James Kuyper <jameskuyper@verizon.net> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: A Note on Readability |
| Date | 2015-07-13 12:38 -0400 |
| Organization | Self |
| Message-ID | <55A3E9A3.7030602@verizon.net> (permalink) |
| References | (16 earlier) <3db40dfc-407c-4229-9c61-aac75246cb7e@googlegroups.com> <kfny4imv32v.fsf@x-alumni2.alumni.caltech.edu> <dd0b8b64-04ae-4804-8c95-bfdcb34a26ad@googlegroups.com> <lny4ilmdyy.fsf@kst-u.example.com> <51b626e2-ffe7-45ad-949a-398cf5ab45cd@googlegroups.com> |
On 07/13/2015 11:48 AM, David Kleinecke wrote:
> On Sunday, July 12, 2015 at 11:24:15 AM UTC-7, Keith Thompson wrote:
>> David Kleinecke <dkleinecke@gmail.com> writes:
...
>>> Remember I am disucssing the C90 standard and there is no section
>>> 4.6 in the C90 standard. I have no problems with the quoted 4.6 but
>>> I don't think it answers my original complaint.
>>
>> [...]
>>
>> It's actually 4p6 (section 4, paragraph 6), not 4.6.
>>
>> In the C11 standard, section 4 paragraph 6 says, in part:
>>
>> A conforming implementation may have extensions (including
>> additional library functions), provided they do not alter the
>> behavior of any strictly conforming program.
>>
>> In the C90 standard, section 4 paragraph 2 says, in part:
>>
>> A conforming implementation may have extensions (including
>> additional library functions), provided they do not alter the
>> behavior of any strictly conforming program.
>
> But it does say what an extension is - apart from an enlarged library.
>
> I said I thought that that meant, in complier terms, that any point
> where the parse fails could be given meaning (implementation-defined,
> of course). But there doesn't seem to be agreement that that is what
> the standard intended.
It's also not what the standard says. If the parse fails, you have a
syntax error, and the program is not strictly conforming, so a
conforming extension is allowed to to alter the behavior of such a
program. However, having a parse failure is not the only way that an
extension can change the behavior - anything that prevents a program
from being strictly conforming could also be the basis for a conforming
extension. Other possibilities:
1. constraint violation
2. code with undefined behavior
3. code with unspecified behavior
4. code with implementation-defined behavior
5. code which exceeds any of the minimum implementation limits.
The third case is somewhat restrictive: the only kind of extension you
can provide that way is one that involves making a specific choice among
the possibilities allowed by the standard. The fourth one is even more
restricted - you must document the choice, and your compiler must
implement that choice. The other three cases all give you pretty much
unlimited freedom to do whatever you want.
> To illustrate what I meant consider the keyword "if". It must be
> followed by "(". If I added the option that it could be followed by,
> say, '[' and gave the construct some meaning that would be an
> acceptable extension.
>
> But my attempt to describe extensions is restrictive. Could I perhaps
> define more keywords? For example
> until (...) {...}
> with meaning "while not".
'until' is a name reserved to the users for all purposes. Therefore, a
conforming implementation of C can't treat it as a keyword if it occurs
in a strictly conforming program. However, if you use a construct with
undefined behavior to turn on recognition of 'until' as a keyword, that
would be allowed. You could also make recognition of 'until' as a
keyword be controlled by a #pragma.
> I think any of things would be an acceptable extension because any
> correct strictly conforming program would not be impacted.
Recognizing something as a keyword prevents it from being recognized as
an identifier during translation phase 7. Any strictly conforming
program that used 'until' as the name of an object, a function, a label,
a struct/union/enumeration tag or member name would parse as a syntax
error if your compiler recognizes it as a keyword instead.
> Are C99, C11, etc. extensions of C90?
They are C90 extensions, but they are not conforming extensions of C90.
Both of them changed the behavior of programs that have strictly
conforming behavior under C90.
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-06 18:54 -0700
A Note on Readability asetofsymbols@gmail.com - 2015-05-06 23:08 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-07 07:34 +0100
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-07 12:22 -0700
Re: A Note on Readability raltbos@xs4all.nl (Richard Bos) - 2015-05-17 10:50 +0000
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-17 09:40 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-17 18:06 +0100
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-18 10:38 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 14:07 -0400
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-19 10:07 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-19 11:23 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-20 08:41 -0700
Re: A Note on Readability asetofsymbols@gmail.com - 2015-05-20 09:03 -0700
Re: A Note on Readability Les Cargill <lcargill99@comcast.com> - 2015-05-20 12:09 -0500
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-21 09:08 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-20 17:15 +0100
Re: A Note on Readability Les Cargill <lcargill99@comcast.com> - 2015-05-20 12:10 -0500
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-21 08:58 -0700
Re: A Note on Readability glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-21 17:33 +0000
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-22 09:47 -0700
Re: A Note on Readability Les Cargill <lcargill99@comcast.com> - 2015-05-20 12:08 -0500
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-20 13:43 -0400
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-20 10:59 -0700
Re: A Note on Readability Les Cargill <lcargill99@comcast.com> - 2015-05-20 18:05 -0500
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-20 17:36 -0700
Re: A Note on Readability Les Cargill <lcargill99@comcast.com> - 2015-05-20 22:12 -0500
Re: A Note on Readability Philip Lantz <prl@canterey.us> - 2015-05-20 20:34 -0700
Re: A Note on Readability glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-21 04:39 +0000
Re: A Note on Readability Philip Lantz <prl@canterey.us> - 2015-05-21 17:41 -0700
Re: A Note on Readability gwowen <gwowen@gmail.com> - 2015-05-21 01:14 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-21 09:26 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-21 10:33 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-22 09:42 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-22 11:53 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-23 10:01 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-23 14:53 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-24 09:18 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-24 13:13 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-25 09:38 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-25 12:40 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-26 10:56 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-26 12:35 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-27 10:08 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-27 11:07 -0700
Re: A Note on Readability Robert Wessel <robertwessel2@yahoo.com> - 2015-05-27 20:17 -0500
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-25 09:56 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-25 13:05 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-26 09:58 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-26 18:16 +0100
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-26 10:55 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-26 12:11 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-26 12:01 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-27 09:58 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-27 18:11 +0100
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-28 12:11 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-28 12:55 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-29 10:08 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-06-01 18:54 +0100
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-10 11:29 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 09:06 -0700
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 13:42 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-12 09:20 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-12 11:24 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 08:48 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-07-13 12:38 -0400
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-13 10:34 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-07-13 14:43 -0400
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-13 12:18 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-07-13 15:27 -0400
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 08:45 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-14 09:05 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 09:41 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-14 10:26 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-15 19:59 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-07-14 12:25 -0400
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-13 13:46 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-07-14 08:33 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-13 11:17 -0700
Re: A Note on Readability Richard Damon <Richard@Damon-Family.org> - 2015-07-13 21:06 -0400
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-07-13 22:38 -0400
Re: A Note on Readability Richard Damon <Richard@Damon-Family.org> - 2015-07-15 08:19 -0400
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-20 09:10 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-07-13 11:00 -0700
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-15 08:11 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-27 10:57 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-24 09:51 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-24 13:36 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-25 10:00 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-25 13:05 -0700
Re: A Note on Readability Philip Lantz <prl@canterey.us> - 2015-05-24 16:43 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-24 09:57 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-24 13:37 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-25 10:14 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-25 13:11 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-26 10:26 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-26 18:38 +0100
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-26 12:24 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-27 10:06 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-27 11:05 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-26 10:38 -0700
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-24 07:01 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-24 09:58 -0700
Re: A Note on Readability Philip Lantz <prl@canterey.us> - 2015-05-25 00:45 -0700
Re: A Note on Readability Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-10 11:09 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-21 09:04 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-21 10:36 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-22 09:56 -0700
Re: A Note on Readability Robert Wessel <robertwessel2@yahoo.com> - 2015-05-22 12:16 -0500
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-22 14:14 -0400
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-23 09:49 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-22 11:55 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-22 11:58 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-20 10:26 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-18 11:08 -0700
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-19 10:09 -0700
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 20:40 +0100
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-17 14:34 -0400
Re: A Note on Readability David Kleinecke <dkleinecke@gmail.com> - 2015-05-18 10:40 -0700
Re: A Note on Readability Keith Thompson <kst-u@mib.org> - 2015-05-18 11:18 -0700
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 14:33 -0400
Re: A Note on Readability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 20:44 +0100
Re: A Note on Readability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 16:07 -0400
csiph-web