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| author | Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> | 2020-11-21 09:18:41 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-11-21 09:18:41 (GMT) |
| commit | c1bbca5b004b3f74d240ef8a76ff445cc1a27efb (patch) | |
| tree | 902e56c276906522951a81baf8232ddbde0f3e0c /Mac/Unsupported/PythonScript/PythonScript.py | |
| parent | ed0201805c036e4bc26670ec7ccffefb8e219f78 (diff) | |
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bpo-40791: Make compare_digest more constant-time. (GH-20444)
* bpo-40791: Make compare_digest more constant-time.
The existing volatile `left`/`right` pointers guarantee that the reads will all occur, but does not guarantee that they will be _used_. So a compiler can still short-circuit the loop, saving e.g. the overhead of doing the xors and especially the overhead of the data dependency between `result` and the reads. That would change performance depending on where the first unequal byte occurs. This change removes that optimization.
(This is change GH-1 from https://bugs.python.org/issue40791 .)
(cherry picked from commit 31729366e2bc09632e78f3896dbce0ae64914f28)
Co-authored-by: Devin Jeanpierre <jeanpierreda@google.com>
Diffstat (limited to 'Mac/Unsupported/PythonScript/PythonScript.py')
0 files changed, 0 insertions, 0 deletions