Message 236993 - Python tracker

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Author	belopolsky
Recipients	BreamoreBoy, belopolsky, flox, python-dev
Date	2015-03-01.22:30:58
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<[email protected]>
In-reply-to

Content
We still have the following in Lib/test/test_time.py: # Issue #13312: it may return wrong value for year < TIME_MINYEAR + 1900 # Skip the value test, but check that no error is raised self.yearstr(TIME_MINYEAR) I reviewed the current time.asctime() code and it does look like it invokes undefined behavior for extremely large negative years. The problem is that in C struct tm, year is stored as year - 1900 and for year < -2147481748 (= -2**31 + 1900) we trigger an overflow of a signed integer. Can someone confirm that on AMD64 FreeBSD subtracting 1900 from -2147483648 and then adding it back does not give -2147483648?

We still have the following in Lib/test/test_time.py:

        # Issue #13312: it may return wrong value for year < TIME_MINYEAR + 1900
        # Skip the value test, but check that no error is raised
        self.yearstr(TIME_MINYEAR)


I reviewed the current time.asctime() code and it does look like it invokes undefined behavior for extremely large negative years.

The problem is that in C struct tm, year is stored as year - 1900 and for year < -2147481748 (= -2**31 + 1900) we trigger an overflow of a signed integer.

Can someone confirm that on AMD64 FreeBSD subtracting 1900 from -2147483648 and then adding it back does not give -2147483648?

History
Date	User	Action	Args
2015-03-01 22:30:58	belopolsky	set	recipients: + belopolsky, flox, BreamoreBoy, python-dev
2015-03-01 22:30:58	belopolsky	set	messageid: <[email protected]>
2015-03-01 22:30:58	belopolsky	link	issue13312 messages
2015-03-01 22:30:58	belopolsky	create