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Respect $SOURCE_DATE_EPOCH in generate_bram_types_sim.py #4683

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@keszybz keszybz commented Oct 24, 2024

What are the reasons/motivation for this change?

I'm working on build reproducibility of Fedora packages, and this patch fixes an issue observed in test rebuilds.

Explain how this is achieved.

The variable is set in build environments to allow the build to be reproducible (identical result in independent builds), see https://reproducible-builds.org/docs/source-date-epoch/. The code snippet is based on the sample from that page too.

If applicable, please suggest to reviewers how they can test the change.

Generate the output without $SOURCE_DATE_EPOCH set, which should result in a file with a current timestamp, and then again with SOURCE_DATE_EPOCH set, which should result in the specified timestamp.

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keszybz commented Oct 24, 2024

Downstream pull request: https://src.fedoraproject.org/rpms/yosys/pull-request/5

with open(filename, "w") as f:
f.write("// **AUTOGENERATED FILE** **DO NOT EDIT**\n")
f.write(f"// Generated by {sys.argv[0]} at {datetime.now(timezone.utc)}\n")
f.write(f"// Generated by {sys.argv[0]} at {build_date}\n")
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Do we even need the build date here? The file modification time indicates it already...

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I don't think it's particularly useful, but meh, I don't care either way, as long as the file doesn't change between rebuilds ;)

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I think you can go ahead and remove the generation time outright. It's an outlier among the other "Generated by" string formatting in the codebase

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Updated.

I'm working on build reproducibility of Fedora packages, and this patch fixes
an issue observed in test rebuilds: the timestamp was set to the actual time
of the build, making builds nonreproducible.

Other "Generated by" strings do not include a timestamp, so drop it here too.
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3 participants