Re: Cygwin strptime() is missing "%s" which strftime() has

[Corinna Vinschen <vinschen at redhat dot com>]

On Jul 24 17:36, Craig Howland wrote:
> On 07/24/2017 04:41 PM, Brian Inglis wrote:
> > On Mon, 24 Jul 2017 02:32:14 -0700, Corinna Vinschen wrote:> On Jul 23 22:07,
> > Brian Inglis wrote:
> > > > On 2017-07-23 20:09, Lavrentiev, Anton (NIH/NLM/NCBI) [C] wrote:
> > > > > > But that's just scanning a decimal integer to time_t.
> > > > > It's not a question of whether I can or can't convert a string into an
> > > > > integer, rather it's a question about portability of code that uses %s for
> > > > > both functions and expects it to work unchanged in the Cygwin environment.
> > > > > Also, strptime() was designed to be a reversal to strftime() (from the
> > > > > man-pages: the  strptime() function is the converse function to
> > > > > strftime(3)) so both are supposed to "understand" the same basic set of
> > > > > formats.  Because of Cygwin's strptime() missing "%s", the following also
> > > > > does not work even from command line:
> > > > > 
> > > > > $ date +"%s" | strptime "%s"
> > > > Attached diff for proposed strptime %s and %F support.
> > > > Let me know if you would prefer a different approach before I submit a git
> > > > format-patch.
> > > Approach looks good, so please send the patch to the newlib mailing list
> > > with a nice log message.
> > Thinking just "add strptime %F %s support"; involved because I use date and
> > dateutils a lot in shell scripts; also hope this will also allow %F %s support
> > in dateutils strptime, which the OP just added to his cygwin posts.
> > 
> > > In fact, just send patches like these immediately in the right format to
> > > the right list.  Chances are good that the patch is taken without further
> > > ado and you skip the part where you have to send the patch twice :)
> > Darn, originated on cygwin list, forwarded to cygwin-patches, forgot this should
> > have gone to newlib list.
> > 
> > > In this case I have a nit, but this should be discussed on the right
> > > mailing list so all affected parties can chime in.  Hint: strtoimax is
> > > not available on all platforms yet (patches still in limbo)...
> > Figured there would need to be some tweaks for newlib platforms, compilers, and
> > style, so made some changes, attached another diff for discussion, before
> > submitting a patch.
> > Let me know if you want conditionals or declarations changed, hoisted to
> > function start, case braces removed, other issues?
> > 
> Neither %F nor %s are defined for strptime() in POSIX, so they should not be
> expected to be portable.  (See
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/strptime.html) For
> that matter, %s is not defined for strftime(), either in POSIX or C99, even
> though it is in Newlib.  If either of these are added, they should have
> gates (or at the very least, comments) to show they are extensions.  (They
> appear to be GLIBC extensions, based on comments in the man page from a
> GLIBC-based system.)

Right, in theory.  Just a bit late in the game I guess.  We already
support %u, %V, %Z unconditionally.  I checked the FreeBSD code and
they don't even bother to add comments ¯\_(ツ)_/¯


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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