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From: Rich Felker <dalias@libc.org>
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Subject: Re: Re: asctime(0) Segmentation fault
Date: Sat, 19 Apr 2014 23:15:00 -0400
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On Sat, Apr 19, 2014 at 10:51:34PM -0400, John Mudd wrote:
> That was incomplete.
> 
> >From Python-2.7.6/Lib/test/test_time.py:
> 
>     def test_asctime(self):
>         time.asctime(time.gmtime(self.t))
>         self.assertRaises(TypeError, time.asctime, 0)
>         self.assertRaises(TypeError, time.asctime, ())
>         # XXX: Posix compiant asctime should refuse to convert
>         # year > 9999, but Linux implementation does not.

This is false. POSIX explicitly says the behavior is undefined:

    However, the behavior is undefined if timeptr->tm_wday or
    timeptr->tm_mon are not within the normal ranges as defined in
    <time.h>, or if timeptr->tm_year exceeds {INT_MAX}-1990, or if the
    above algorithm would attempt to generate more than 26 bytes of
    output (including the terminating null).

(http://pubs.opengroup.org/onlinepubs/9699919799/functions/asctime.html)

This agrees with ISO C.

Thus the test Python is performing is invalid.

However I'm unclear on how it involves a null pointer being passed to
asctime. Are you sure this is actually the offending test?

Rich