[pypy-dev] Hash compatibility between PyPy and CPython

[Manuel Jacob]

Hi,

Do we in general try to stay compatible with the hashes of CPython?

I'm currently debugging a failure in lib-python's test_hash on linux32 
in the py3.5 branch [1].  The test fails because currently on PyPy3.5, 
hash(int(-2**31)) == -2147483648 while hash(float(-2**31)) == -2.  On 
CPython 3.6.5, both are -2.

It seems like our float hashes are 100% compatible with CPython, but our 
int hashes are different in some cases (like the one above).  In any 
case, i think that the invariant hash(i) == hash(float(i)) should hold 
for any int i that can be represented exactly by a float.  Now the 
question is: should we change our int hash to be compatible with 
CPython?

-Manuel

[1] 
http://buildbot.pypy.org/summary/longrepr?testname=unmodified&builder=pypy-c-jit-linux-x86-32&build=4661&mod=lib-python.3.test.test_hash