Message 236993 - Python tracker

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In-reply-to
Author	belopolsky
Recipients	BreamoreBoy, belopolsky, flox, python-dev
Date	2015年03月01日.22:30:58
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1425249058.26.0.276403152484.issue13312@psf.upfronthosting.co.za>

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?

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?

History
Date	User	Action	Args
2015年03月01日 22:30:58	belopolsky	set	recipients: + belopolsky, flox, BreamoreBoy, python-dev
2015年03月01日 22:30:58	belopolsky	set	messageid: <1425249058.26.0.276403152484.issue13312@psf.upfronthosting.co.za>
2015年03月01日 22:30:58	belopolsky	link	issue13312 messages
2015年03月01日 22:30:58	belopolsky	create

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