strptime doesn't fill in tm_wday and tm_yday.

Peter Rosin peda@lysator.liu.se
Thu May 12 09:01:00 GMT 2011


Den 2011-05-11 19:34 skrev Corinna Vinschen:
> On May 11 16:52, Peter Rosin wrote:
>> Hello!
>>
>> The following STC hints at a problem in strptime:
...
>> Opengroup has this to say about only filling in some fields:
>>
>> 	"It is unspecified whether multiple calls to strptime()
>> 	using the same tm structure will update the current
>> 	contents of the structure or overwrite all contents of
>> 	the structure. Conforming applications should make a
>> 	single call to strptime() with a format and all data
>> 	needed to completely specify the date and time being
>> 	converted."
>>
>> but I don't think it applies since indeed I do completely specify
>> the date in my strptime call.
> 
> The Cygwin implementation of strptime is taken from NetBSD and enhanced
> only in terms of support for the E and O modifiers.  The NetBSD and
> OpenBSD versions also support a non-POSIX format specifier %u (day of
> week, monday = 1).  Other than that, the Cygwin strptime behaves exactly
> as the BSD implementation.  tm_wday is only set if you specify %a, %A or
> %w.  tm_yday is only set if you specify %j.
> 
> Despite the example in the strptime man page of POSIX.1-2008, POSIX does
> not specify that strptime has to fill out tm fields which are not also
> specified in the format string.  You should better memset the tm
> structure to 0 before calling strptime.

Since you pulled out your "POSIX does not require it" card, I'm grasping
for my "Cygwin should behave like Linux" card. :-)

Seriously, of course I need to handle quirks in strptime if I want the
users of my application to be happy, but that does not mean that strptime
can't be a little bit more helpful on Cygwin.  Maybe someone with a
copyright assignment can find some inspiration in the patch [1] I sent
for the newlib strptime?

Cheers,
Peter

[1] http://sourceware.org/ml/newlib/2011/msg00177.html

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