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Make rust build deterministic #1213

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Summary

We disable LTO and use codegen-units = 1 for deterministic build results of the rust code.
See https://reproducible-builds.org/ for why this is good.

rust-lang/rust#128675 states that the default codegen-units = 16 should be deterministic, but here it clearly is not.

Test Plan

@facebook-github-bot facebook-github-bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Sep 25, 2024
@zsol
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zsol commented Sep 25, 2024

Hey @bmwiedemann thanks for the PR!

here it clearly is not

Could you help me understand why not? How can I reproduce this nondeterminism?

@bmwiedemann
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I just did two clean builds as similar as possible. Same CPU, same username, same path, same timezone, locale, umask, date... and it still differed in the /usr/lib64/python3.12/site-packages/libcst/native.cpython-312-x86_64-linux-gnu.so

https://rb.zq1.de/compare.factory-20240904/diffs/python-libcst-compare.out shows a (partially filtered) diff.

@bmwiedemann
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hmm. For some reason the variations are gone now with rust-1.81.0

@bmwiedemann
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There are still variations - they just don't appear every time.

@bmwiedemann bmwiedemann reopened this Oct 14, 2024
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3 participants