[Python-bugs-list] [ python-Bugs-689659 ] 64-bit int and long hash keys incompatible

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Bugs item #689659, was opened at 2003-02-19 18:17
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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=689659&group_id=5470

Category: Python Interpreter Core
Group: Platform-specific
Status: Open
Resolution: None
>Priority: 6
Submitted By: Mark Dickinson (marketdickinson)
>Assigned to: Tim Peters (tim_one)
Summary: 64-bit int and long hash keys incompatible

Initial Comment:
For 64-bit platforms, it seems that ints and longs with the 
same value don't necessarily give the same hash key.  
An example is below; the phenomenon seems to occur 
for a range of numbers between 2**32 and 2**64. 
 
I assume this is unintentional?  It looks suspiciously as 
though the function long_hash in Objects/longobject.c 
has 32-bitness hard-coded. Lines 1288-1289 of that file 
in the Python 2.2.2 source read: 
 
      /* Force a 32-bit circular shift */ 
      x = ((x << SHIFT) & ~MASK) | ((x >> (32-SHIFT)) & 
MASK); 
 
And here's the Python example: 
 
Python 2.2.2 (#22, Dec 23 2002, 12:02:55) 
[GCC 3.0.3] on sunos5 
Type "help", "copyright", "credits" or "license" for more 
information. 
>>> x = 4503599627370496L 
>>> y = 4503599627370496 
>>> h = {x: 'anything', y: 'something else'} 
>>> h[x] 
'anything' 
>>> h[y] 
'something else' 
>>> x == y 
1 
 
All the best, 
 
Mark 
 

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>Comment By: Tim Peters (tim_one)
Date: 2003-02-19 18:29

Message:
Logged In: YES 
user_id=31435

Good catch!  Agreed on all counts, and boosted priority 
because Python is trying to blur the distinction between 
ints and longs, so that this is likely to bite harder in the 
future.  Assigned to me, but a patch would be appreciated 
(don't know when I can make time for this, and I don't have 
a 64-bit box for testing).

It should be enough to replace "32" with "8*sizeof(long)".

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