Re: winsup/cygwin/libc/strptime.cc(__strptime) strptime %F issue

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Aug 23 13:25, Brian Inglis wrote:
> On 2017-08-23 12:51, Brian Inglis wrote:
> > On 2017-07-23 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"
> > Testing revealed a separate issue with %F format which I will follow up on in
> > a different thread.
> Actually same thread, different subject.
> 
> Cygwin strptime(3) (also strptime(1)) fails with default width, without an
> explicit width, because of the test in the following code:
> 
> case 'F':	/* The date as "%Y-%m-%d". */
> 	{
> 	  LEGAL_ALT(0);
> 	  ymd |= SET_YMD;
> 	  char *tmp = __strptime ((const char *) bp, "%Y-%m-%d",
> 				  tm, era_info, alt_digits,
> 				  locale);
> 	  if (tmp && (uint) (tmp - (char *) bp) > width)
> 	    return NULL;
> 	  bp = (const unsigned char *) tmp;
> 	  continue;
> 	}
> 
> as default width is zero so test fails and returns NULL.
> 
> Simple patch for this as with the other cases supporting width is to change the
> test to:
> 
> 	  if (tmp && width && (uint) (tmp - (char *) bp) > width)
> 
> but this does not properly support [+0] flags or width in the format as
> specified by glibc (latest POSIX punts on %F) for compatibility with strftime(),
> affecting only the %Y format, supplying %[+0]<w-6>F, to support signed and zero
> filled fixed and variable length year fields in %F format.

Ok, I admit I didn't understand this fully.  What is '<w-6>'?
Can you give a real world example?

> So do you want compatible support or just the quick fix?

Quick and then right?  Fixing this in two steps is just as well.


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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