ci: Drop libFuzzer from msan fuzz task #33666

1. 
   maflcko commented at 9:41 am on October 21, 2025: member

   libFuzzer is mostly unmaintained (https://llvm.org/docs/LibFuzzer.html#status), and it isn’t really needed by the CI tasks. While it provides some additional stats like rss or the max input byte size, they are not essential. Dropping libFuzzer here would also drop the “60 seconds sanity check” for empty folders, but I think this is an acceptable price to pay to silence false-positives that were hit for years.

   Also, there seems to be a history of intermittent false-positive msan warnings (https://github.com/bitcoin/bitcoin/pull/33600#issuecomment-3391921802).

   It is unclear what exactly is causing the false-positives, so just disable libFuzzer in this task for now, to work around them.

2. ci: Drop libFuzzer from msan fuzz task fa70e23de7
3. DrahtBot added the label Tests on Oct 21, 2025
4. 
   DrahtBot commented at 9:41 am on October 21, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33666.

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   ACK	kevkevinpal, dergoegge

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5. 
   kevkevinpal commented at 2:53 pm on October 21, 2025: contributor

   ACK fa70e23

   I’ve seen false positives before from the msan fuzz task before it makes sense to disable it for now till we find the root cause of the false positives.

   ---

   In this doc it mentions that the maintainers moved on to another project “centipede”. Is there any motivation to try and support this in Bitcoin Core?

   libFuzzer is mostly unmaintained (https://llvm.org/docs/LibFuzzer.html#status)

6. 
   maflcko commented at 3:00 pm on October 21, 2025: member

   centipede

   Yes, it would be nice to support it, but at least I couldn’t get it running. At least inside oss-fuzz, see also https://github.com/google/oss-fuzz/issues/10434

7. 
   fanquake commented at 7:18 am on October 23, 2025: member

   @dergoegge @marcofleon any opinion here?
8. 
   dergoegge commented at 7:24 am on October 23, 2025: member

   I guess the only thing we’re loosing here is that if there is a harness with no corpus we won’t be doing our short “sanity” 60 second fuzz from scratch.

   I know that it is possible to get libFuzzer running with MSan because I’m doing that in my own infra but that is an entirely different setup (e.g. the llvm version is different).

   Perhaps in the future we can re-enable libFuzzer but for now I see no reason not to drop it, given that there are repeated annoying false-positives. Concept ACK.

9. 
   maflcko commented at 7:44 am on October 23, 2025: member

   Thx, added the sanity drop to the description.
10. dergoegge approved
11. 
    dergoegge commented at 7:55 am on October 23, 2025: member

    ACK fa70e23de75baaf8c1ef6836ffe8ca73562c8937
12. fanquake merged this on Oct 24, 2025
13. fanquake closed this on Oct 24, 2025

    ---

14. maflcko deleted the branch on Oct 24, 2025
15. TheCharlatan referenced this in commit f50d90fcbb on Oct 29, 2025
16. fanquake added the label Fuzzing on Oct 30, 2025

Contributors
maflcko DrahtBot kevkevinpal fanquake dergoegge

Labels
Tests Fuzzing