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| author | Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> | 2020-11-22 17:33:09 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-11-22 17:33:09 (GMT) |
| commit | db95802bdfac4d13db3e2a391ec7b9e2f8d92dbe (patch) | |
| tree | 44ca395e3010423492b17cd2416eb482241da59a /Python/pythonrun.c | |
| parent | 9ae1742bdf85dc78788ae2d68ab5b02f67f69eb3 (diff) | |
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bpo-40791: Make compare_digest more constant-time. (GH-23438)
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 'Python/pythonrun.c')
0 files changed, 0 insertions, 0 deletions