Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.c > #108212
| From | Ken Brody <kenbrody@spamcop.net> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: How to fix warning: [-Wdate-time] |
| Date | 2017-04-17 12:06 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <od2p00$v2c$1@dont-email.me> (permalink) |
| References | (1 earlier) <ocntai$1a6$1@news.xmission.com> <b31df4fa-3791-4093-8d89-5d502e38503d@googlegroups.com> <8e289215-369a-43c5-aa46-9428ad81a224@googlegroups.com> <lnpogdtjmy.fsf@kst-u.example.com> <195fbe3a-b69c-45e4-ac6e-a45a1913a834@googlegroups.com> |
On 4/16/2017 2:44 PM, supercat@casperkitty.com wrote:
> On Saturday, April 15, 2017 at 5:02:05 PM UTC-5, Keith Thompson wrote:
>> The problem would be that the expansions of __DATE__ and __TIME__ would
>> be whatever was passed on the compiler command line and not, as the
>> standard specifies and a reader will assume, the date and time of
>> translation.
>
> The Standard does not require any particular degree of precision, nor does
> it specify the means via which an implementation would determine the time.
> There is no requirement that platforms which host C compilers need to have
> any kind of real-time clock functionality. If a compiler included a
> command-line option to say "Don't trust the system clock--the time is
> actually 1989-06-05 04:32:10, I don't think the Standard would require that
> the compiler not believe the command line.
NB: I am in no way a "language lawyer".
Looking at N1256 (yes, I know it's not the latest, but it's the latest I
have on this computer), section 6.10.8 says this about __DATE__:
"If the date of translation is not available, an implementation-defined
valid date shall be supplied."
A similar statement is made about __TIME__.
Without a detailed explanation of what "is not available" means, you could
easily say that "using compiler flag X will cause the compiler to behave as
if the date and time are not available" is still conforming.
> Further, in the event that a project happens to be built in multiple steps
> that occur days apart, I don't think the Standard specifies which moment in
> the build process should be identified by __DATE__ and __TIME__. I would
> think a conforming implementation could defer the evaluation of those
> strings to build time (the compiler would have to supply place-holder text
> and specify everyplace where that text appears within objects' initial
> values, but designing that feature into a compiler and linker would not be
> difficult).
Also, what happens if the computer/compiler isn't that fast, and the file
takes more than a second to preprocess? Can __TIME__ at the top of the file
be different than at the bottom of the file?
Finally, can the time be available at the top of the file, but not at the
bottom? (Consider, for example, a hardware clock that for some reason fails
during the compile. Or maybe your internet connection to nist.gov goes down.)
I would expect that any non-DS9K compiler would simply get the date/time at
the start of the compile, and keep using that throughout the compile. But
that doesn't mean the Standard requires it.
[...]
--
Kenneth Brody
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
How to fix warning: [-Wdate-time] MehdiAmini <atorrses@gmail.com> - 2017-04-13 14:44 +0430
Re: How to fix warning: [-Wdate-time] Barry Schwarz <schwarzb@dqel.com> - 2017-04-13 05:28 -0700
Re: How to fix warning: [-Wdate-time] MehdiAmini <atorrses@gmail.com> - 2017-04-14 12:55 +0430
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-14 08:50 -0700
Re: How to fix warning: [-Wdate-time] Ken Brody <kenbrody@spamcop.net> - 2017-04-14 13:42 -0400
Re: How to fix warning: [-Wdate-time] James Kuyper <jameskuyper@verizon.net> - 2017-04-14 14:26 -0400
Re: How to fix warning: [-Wdate-time] David Brown <david.brown@hesbynett.no> - 2017-04-17 16:26 +0200
Re: How to fix warning: [-Wdate-time] "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-17 10:52 -0400
Re: How to fix warning: [-Wdate-time] David Brown <david.brown@hesbynett.no> - 2017-04-17 20:00 +0200
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-17 08:08 -0700
Re: How to fix warning: [-Wdate-time] David Brown <david.brown@hesbynett.no> - 2017-04-17 20:04 +0200
Re: How to fix warning: [-Wdate-time] Mehdi Amini <atorrses@gmail.com> - 2017-04-15 07:50 +0430
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-15 15:05 -0700
Re: How to fix warning: [-Wdate-time] Ken Brody <kenbrody@spamcop.net> - 2017-04-17 11:42 -0400
Re: How to fix warning: [-Wdate-time] supercat@casperkitty.com - 2017-04-17 08:55 -0700
Re: How to fix warning: [-Wdate-time] "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-17 11:57 -0400
Re: How to fix warning: [-Wdate-time] gazelle@shell.xmission.com (Kenny McCormack) - 2017-04-13 13:09 +0000
Re: How to fix warning: [-Wdate-time] jadill33@gmail.com - 2017-04-13 06:27 -0700
Re: How to fix warning: [-Wdate-time] supercat@casperkitty.com - 2017-04-15 08:56 -0700
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-15 15:01 -0700
Re: How to fix warning: [-Wdate-time] supercat@casperkitty.com - 2017-04-16 11:44 -0700
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-16 13:45 -0700
Re: How to fix warning: [-Wdate-time] Ken Brody <kenbrody@spamcop.net> - 2017-04-17 12:14 -0400
Re: How to fix warning: [-Wdate-time] Ken Brody <kenbrody@spamcop.net> - 2017-04-17 12:06 -0400
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-17 09:25 -0700
Re: How to fix warning: [-Wdate-time] "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-17 12:45 -0400
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-17 12:02 -0700
Re: How to fix warning: [-Wdate-time] "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-17 15:23 -0400
Re: How to fix warning: [-Wdate-time] Lowell Gilbert <lgusenet@be-well.ilk.org> - 2017-04-18 13:27 -0400
Re: How to fix warning: [-Wdate-time] Ken Brody <kenbrody@spamcop.net> - 2017-04-18 14:23 -0400
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-18 12:10 -0700
Re: How to fix warning: [-Wdate-time] raltbos@xs4all.nl (Richard Bos) - 2017-04-22 21:20 +0000
Re: How to fix warning: [-Wdate-time] James Kuyper <jameskuyper@verizon.net> - 2017-04-22 22:45 -0400
Re: How to fix warning: [-Wdate-time] Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-17 11:30 -0700
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-17 12:30 -0700
Re: How to fix warning: [-Wdate-time] raltbos@xs4all.nl (Richard Bos) - 2017-04-22 21:24 +0000
Re: How to fix warning: [-Wdate-time] Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-27 13:33 -0700
Re: How to fix warning: [-Wdate-time] Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-27 13:26 -0700
Re: How to fix warning: [-Wdate-time] gordonb.5zr1e@burditt.org (Gordon Burditt) - 2017-04-14 13:35 -0500
Re: How to fix warning: [-Wdate-time] supercat@casperkitty.com - 2017-04-14 12:17 -0700
Re: How to fix warning: [-Wdate-time] gordonb.k4gmo@burditt.org (Gordon Burditt) - 2017-04-16 00:04 -0500
Re: How to fix warning: [-Wdate-time] Noob <root@127.0.0.1> - 2017-04-16 11:04 +0200
Re: How to fix warning: [-Wdate-time] supercat@casperkitty.com - 2017-04-16 11:52 -0700
Re: How to fix warning: [-Wdate-time] raltbos@xs4all.nl (Richard Bos) - 2017-04-22 21:28 +0000
Re: How to fix warning: [-Wdate-time] Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-04-18 21:34 -0600
Re: How to fix warning: [-Wdate-time] Keith Thompson <kst-u@mib.org> - 2017-04-17 08:09 -0700
csiph-web