fix hashing

[bdaf8532-ded6-4d4c-9bb3-51fd76040dc1]

BPO	400503
Nosy	@gvanrossum, @tim-one, @freddrake
Files	None: None

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields: ```python assignee = 'https://github.com/freddrake' closed_at = created_at = labels = [] title = 'fix hashing' updated_at = user = 'https://bugs.python.org/tmick' ``` bugs.python.org fields: ```python activity = actor = 'fdrake' assignee = 'fdrake' closed = True closed_date = None closer = None components = ['None'] creation = creator = 'tmick' dependencies = [] files = ['2435'] hgrepos = [] issue_num = 400503 keywords = ['patch'] message_count = 8.0 messages = ['32676', '32677', '32678', '32679', '32680', '32681', '32682', '32683'] nosy_count = 4.0 nosy_names = ['gvanrossum', 'tim.peters', 'fdrake', 'tmick'] pr_nums = [] priority = 'normal' resolution = None stage = None status = 'closed' superseder = None type = None url = 'https://bugs.python.org/issue400503' versions = [] ```

[bdaf8532-ded6-4d4c-9bb3-51fd76040dc1]

[freddrake]

Applied verbatim; patch to PC/winreg.c applied to PC/_winreg.c due to name change.

[gvanrossum]

just testing the SF patch manager

[gvanrossum]

Tim, please review! Then assign to Trent if it's OK to commit.

[tim-one]

Changed to Accepted, assigned back to Trent for commit.

Looks good, Trent! My only gripe is about the hash function for complex numbers (because it's symmetric), but that problem existed before and you haven't made it any worse. Ship it (I'll improve the complex hash later).

[tim-one]

Changed to Accepted, assigned back to Trent for commit.

Looks good, Trent! My only gripe is about the hash function for complex numbers (because it's symmetric), but that problem existed before and you haven't made it any worse. Ship it (I'll improve the complex hash later).

[bdaf8532-ded6-4d4c-9bb3-51fd76040dc1]

This patch addresses two main issues: (1) There exist some non-fatal errors in some of the hash algorithms. For exmaple, in float_hash and complex_hash a certain part of the value is not included in the hash calculation. See Tim's, Guido's, and my discussion of this on python-dev in May under the title "fix float_hash and complex_hash for 64-bit *nix"

(2) The hash algorithms that use pointers (e.g. func_hash, code_hash) are universally not correct on Win64 (they assume that sizeof(long) == sizeof(void*))

As well, this patch significantly cleans up the hash code. It adds the two function _Py_HashDouble and _PyHash_VoidPtr that the various hashing routine are changed to use.

These help maintain the hash function invariant: (a==b) => (hash(a)==hash(b))) I have added Lib/test/test_hash.py and Lib/test/output/test_hash to test this for some cases.

[bdaf8532-ded6-4d4c-9bb3-51fd76040dc1]

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