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v0.5.1
https://github.com/python/cpython
09 December 2020, 11:06:31 UTC
Revision c1bbca5b004b3f74d240ef8a76ff445cc1a27efb authored by Miss Islington (bot) on 21 November 2020, 09:18:41 UTC, committed by GitHub on 21 November 2020, 09:18:41 UTC 
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>
1 parent ed02018
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Tip revision: c1bbca5b004b3f74d240ef8a76ff445cc1a27efb authored by Miss Islington (bot) on 21 November 2020, 09:18:41 UTC
bpo-40791: Make compare_digest more constant-time. (GH-20444)
Tip revision: c1bbca5
windows-layout-steps.yml 
parameters:
  kind: nuget
  extraOpts: --precompile
  fulltest: false

steps:
- script: .\python.bat PC\layout -vv -s "$(Build.SourcesDirectory)" -b "$(Py_OutDir)\$(arch)" -t "$(Build.BinariesDirectory)\layout-tmp-${{ parameters.kind }}-$(arch)" --copy "$(Build.BinariesDirectory)\layout-${{ parameters.kind }}-$(arch)" ${{ parameters.extraOpts }} --preset-${{ parameters.kind }} --include-tests
  displayName: Create ${{ parameters.kind }} layout

- script: .\python.exe -m test.pythoninfo
  workingDirectory: $(Build.BinariesDirectory)\layout-${{ parameters.kind }}-$(arch)
  displayName: Show layout info (${{ parameters.kind }})

- ${{ if eq(parameters.fulltest, 'true') }}:
  - script: .\python.exe -m test -q -uall -u-cpu -rwW --slowest --timeout=1200 -j0 --junit-xml="$(Build.BinariesDirectory)\test-results-${{ parameters.kind }}.xml" --tempdir "$(Build.BinariesDirectory)\tmp-${{ parameters.kind }}-$(arch)"
    workingDirectory: $(Build.BinariesDirectory)\layout-${{ parameters.kind }}-$(arch)
    displayName: ${{ parameters.kind }} Tests
    env:
      PREFIX: $(Build.BinariesDirectory)\layout-${{ parameters.kind }}-$(arch)

  - task: PublishTestResults@2
    displayName: Publish ${{ parameters.kind }} Test Results
    inputs:
      testResultsFiles: $(Build.BinariesDirectory)\test-results-${{ parameters.kind }}.xml
      mergeTestResults: true
      testRunTitle: ${{ parameters.kind }}-$(testRunTitle)
      platform: $(testRunPlatform)
    condition: succeededOrFailed()
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