ci: Use APT_LLVM_V in msan task #32999

1. 
   maflcko commented at 7:57 am on July 17, 2025: member

   This skips compilation of clang by using the apt.
2. DrahtBot added the label Tests on Jul 17, 2025
3. 
   DrahtBot commented at 7:58 am on July 17, 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/32999.

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   ACK	willcl-ark, m3dwards

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4. DrahtBot added the label CI failed on Jul 17, 2025
5. in ci/test/01_base_install.sh:62 in bfdda06fa7 outdated

   72-  update-alternatives --install /usr/bin/clang clang /msan/clang_build/bin/clang 100
   73-  update-alternatives --install /usr/bin/llvm-symbolizer llvm-symbolizer /msan/clang_build/bin/llvm-symbolizer 100
   74+  if [ -n "${APT_LLVM_V}" ]; then
   75+    ${CI_RETRY_EXE} git clone --depth=1 https://github.com/llvm/llvm-project -b "llvmorg-20.1.7" /msan/llvm-project
   76+  else
   77+    ${CI_RETRY_EXE} git clone --depth=1 https://github.com/llvm/llvm-project -b "llvmorg-20.1.0" /msan/llvm-project
   

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   fanquake commented at 8:54 am on July 17, 2025:

   .8 while touching?

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   fanquake commented at 9:02 am on July 17, 2025:

   Actually, I’m wondering why these can’t both be 20.1.8? If the checkout needs to match the apt version, then its going to break whenever the apt is updated but this isn’t bumped.

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   maflcko commented at 9:22 am on July 17, 2025:

   There shouldn’t be any breaking changes in minor versions, so anything is probably fine here. However, if msan fuzz wants to use a different major version, it seems better to keep it separate?

   Maybe a follow-up can investigate if msan fuzz can bootstrap compiler-rt (libfuzzer) directly, and remove all of this code here.

   however, my guess is that you still need to compile at least libcxx(abi) in this this if-branch.

6. ci: Use APT_LLVM_V in msan task

   Also, use update-alternatives to avoid having to manually specify
   clang-${APT_LLVM_V} or llvm-symbolizer-${APT_LLVM_V} everywhere.

   fad040a578
7. maflcko force-pushed on Jul 17, 2025
8. maflcko marked this as ready for review on Jul 17, 2025
9. maflcko removed the label CI failed on Jul 17, 2025
10. willcl-ark approved
11. 
    willcl-ark commented at 2:15 pm on July 17, 2025: member

    ACK fad040a5787a8ac0a13aef5c54e5a675de239e92

    Code changes look correct to me.

    In the CI run this installed clang-20.1.7 from apt, before cloning https://github.com/llvm/llvm-project -b llvmorg-20.1.7 and building the llvm runtimes with msan enabled.

    nit: I do notice that bitcoin configure output claims it’s using clang from /bin/clang++ which differs from the update-alternatives dir used: /usr/bin/clang++, but it appears to be the correct version so I guess it’s an apt install symlink?:

    0C++ compiler .......................... Clang 20.1.7, /bin/clang++
    

12. 
    maflcko commented at 2:24 pm on July 17, 2025: member

    bin

    It is a symlink:

    0# podman run --rm   'ubuntu:questing' ls -ld /bin 
    1lrwxrwxrwx 1 root root 7 Apr 24 16:59 /bin -> usr/bin
    

13. 
    m3dwards commented at 5:03 pm on July 18, 2025: contributor

    ACK fad040a5787a8ac0a13aef5c54e5a675de239e92

    This will cut down on the msan job run time a lot when the docker build cache is empty.

14. 
    fanquake commented at 10:45 am on July 21, 2025: member

    Should probably adjust the timeout / comment: https://github.com/bitcoin/bitcoin/blob/5878f35446ae260ccb0ab5051b795b4364f77951/.cirrus.yml#L160 but given it’s being moved in #32989, left a note there.
15. fanquake merged this on Jul 21, 2025
16. fanquake closed this on Jul 21, 2025

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Contributors
maflcko DrahtBot fanquake willcl-ark m3dwards

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