Re: [PATCH] pretty: Provide a strict ISO8601 date format

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 29, 2014, 18:41 UTC
Message-ID: <xmqq1trz6sv0.fsf@gitster.dls.corp.google.com>
In-Reply-To: <20140829174439.GA10274@odin.ulthar.us>

Scott Schmit <i.grok@comcast.net> writes:

Show 26 quoted lines

> On Thu, Aug 28, 2014 at 03:53:13PM -0700, Junio C Hamano wrote:
>> Beat Bolli writes:
>> > +	else if (mode == DATE_ISO8601_STRICT)
>> > +		strbuf_addf(&timebuf, "%04d-%02d-%02dT%02d:%02d:%02d%+03d:%02d",
>> > +				tm->tm_year + 1900,
>> > +				tm->tm_mon + 1,
>> > +				tm->tm_mday,
>> > +				tm->tm_hour, tm->tm_min, tm->tm_sec,
>> > +				tz / 100, abs(tz % 100));
>> 
>> Wouldn't this misidentify a zone that is 30 minutes off of GMT,
>> i.e. tz == -30?  tz/100 would not be negative and "%+03d:" would
>> happily show "+00:", no?
>
> No.  strbuf_addf uses strbuf_vaddf which uses vsnprintf(3).  From man
> vsnprintf(3):
>>   The flag characters
>>       The character % is followed by zero or more of the following
>>       flags:
>>
>>       +      A sign (+ or -) should always be placed before a number
>>              produced by a signed conversion.  By default a sign is
>>              used only for negative numbers.  A + overrides a space if
>>              both are used.
>
> Perhaps you misread "%+03d:" as "+%02d:"?

I do not think 03 vs 02 makes any difference wrt what I was wondering.

You feed tz/100 to "%+03d:" (the "sign and hour" part of the timezone). What if tz is -30, i.e. less than an hour but still a negative offset? tz/100 would be zero and tz % 100 would be -30.

    tz = -30;
    printf("%+03d:%02d", tz / 100, abs(tz % 100));

would show what?