[Python-Dev] Py_ssize_t

[Raymond Hettinger]

After thinking more about Py_ssize_t, I'm surprised that we're not hearing about 
64 bit users having a couple of major problems.

If I'm understanding what was done for dictionaries, the hash table can grow 
larger than the range of hash values.  Accordingly, I would expect large 
dictionaries to have an unacceptably large number of collisions.  OTOH, we 
haven't heard a single complaint, so perhaps my understanding is off.

The other area where I expected to hear wailing and gnashing of teeth is users 
compiling with third-party extensions that haven't been updated to a Py_ssize_t 
API and still use longs.  I would have expected some instability due to the size 
mismatches in function signatures -- the difference would only show-up with 
giant sized data structures -- the bigger they are, the harder they fall.  OTOH, 
there have not been any compliants either -- I would have expected someone to 
submit a patch to pyport.h that allowed a #define to force Py_ssize_t back to a 
long so that the poster could make a reliable build that included non-updated 
third-party extensions.

In the absence of a bug report, it's hard to know whether there is a real 
problem.  Have all major third-party extensions adopted Py_ssize_t or is some 
divine force helping unconverted extensions work with converted Python code? 
Maybe the datasets just haven't gotten big enough yet.


Raymond