[ python-Bugs-874042 ] wrong answers from ctime

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Bugs item #874042, was opened at 2004-01-09 12:57
Message generated for change (Comment added) made by nobody
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Category: Python Library
Group: Python 2.2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: paul rubin (phr)
Assigned to: Nobody/Anonymous (nobody)
Summary: wrong answers from ctime

Initial Comment:
For any time value less than -2**31, ctime returns the
same result, 'Fri Dec 13 12:45:52 1901'.  It should
either compute a correct value (preferable) or raise
ValueError.  It should not return the wrong answer.


>>> from time import *
>>> ctime(-2**31)
'Fri Dec 13 12:45:52 1901'
>>> ctime(-2**34)
'Fri Dec 13 12:45:52 1901'
>>> ctime(-1e30)
'Fri Dec 13 12:45:52 1901'



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Comment By: Nobody/Anonymous (nobody)
Date: 2004-06-05 11:08

Message:
Logged In: NO 

I wish SF would let me upload patches. The below throws a
ValueError when ctime is supplied with a negative value or a
value over sys.maxint.

###
diff -u -r2.140 timemodule.c
--- timemodule.c        2 Mar 2004 04:38:10 -0000       2.140
+++ timemodule.c        5 Jun 2004 17:11:20 -0000
@@ -482,6 +482,10 @@
                        return NULL;
                tt = (time_t)dt;
        }
+       if (tt > INT_MAX || tt < 0) {
+               PyErr_SetString(PyExc_ValueError,
"unconvertible time");
+               return NULL;
+       }
        p = ctime(&tt);
        if (p == NULL) {
                PyErr_SetString(PyExc_ValueError,
"unconvertible time");
###

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Comment By: paul rubin (phr)
Date: 2004-01-09 13:49

Message:
Logged In: YES 
user_id=72053

Python 2.2.2, Red Hat GNU/Linux version 9, not sure what C
runtime, whatever comes with Red Hat 9.

If the value is coming from the C library's ctime function,
then at minimum Python should check that the arg converts to
a valid int32.   It sounds like it's converting large
negative values (like -1e30) to -sys.maxint.  I see that
ctime(sys.maxint+1) is also being converted to a large
negative date.  Since python's ctime (and presumably related
functions) accept long and float arguments, they need to be
range checked.

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Comment By: Tim Peters (tim_one)
Date: 2004-01-09 13:22

Message:
Logged In: YES 
user_id=31435

Please identify the Python version, OS and C runtime you're 
using.  Here on Windows 2.3.3,

>>> import time
>>> time.ctime(-2**31)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ValueError: unconvertible time
>>>

The C standard doesn't define the range of convertible values 
for ctime().  Python raises ValueError if and only if the 
platform ctime() returns a NULL pointer.

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