Re: [PATCH] strptime: Add %F format (glibc extension).

[Natanael Copa <ncopa@alpinelinux.org>]

On Thu, 22 Feb 2018 18:44:41 -0500
Rich Felker <dalias@libc.org> wrote:

> On Thu, Feb 22, 2018 at 10:53:39PM +0100, Przemyslaw Pawelczyk wrote:
> > %F is a shortcut for %Y-%m-%d, the ISO 8601 date format.
> > It's already present in POSIX's strftime(), so it makes sense to support
> > it in a converse function too.
> > ---
> > 
> > I'm not subscribed to ML, so please CC me in case of replying.
> > 
> >  src/time/strptime.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/src/time/strptime.c b/src/time/strptime.c
> > index c54a0d8c4c52..2c0d45574819 100644
> > --- a/src/time/strptime.c
> > +++ b/src/time/strptime.c
> > @@ -59,6 +59,10 @@ char *strptime(const char *restrict s, const char *restrict f, struct tm *restri
> >  			s = strptime(s, "%m/%d/%y", tm);
> >  			if (!s) return 0;
> >  			break;
> > +		case 'F':
> > +			s = strptime(s, "%Y-%m-%d", tm);
> > +			if (!s) return 0;
> > +			break;
> >  		case 'H':
> >  			dest = &tm->tm_hour;
> >  			min = 0;  
> 
> Not having looked at this function in a while, I was doubtful the
> above would work, but in fact it looks like it does (analogous to the
> above case). While lots of this function is underspecified, the
> contract for the return value is well-designed.
> 
> The want_century logic may be incomplete for %D and now %F, though. If
> so that's a separate issue from lack of %F extension and should be
> fixed in a separate patch. I think %F just needs to set want_century
> to 0, but %D might have more work to do.
> 
> Rich

FWIW, '%F' is mentioned here:
http://austingroupbugs.net/view.php?id=879

<tt>F</tt> This specifier is similar to <tt>%Y-%m-%d</tt> where the
characters up to the first <hyphen-minus> separator shall be converted
as for %Y but with unlimited field width, the characters between the
two <hyphen-minus> separators shall be converted as for %m, and the
characters after the last <hyphen-minus> separator shall be converted
as for %d. If a field width is specified, each of the %Y, %m, and %d
conversions shall not convert any characters past the overall %F field
width.

-nc