build: Bump clang minimum supported version to 19 #36036

1. 
   maflcko commented at 1:47 PM on August 20, 2026: member

   Most supported operating systems ship with clang-19 (or later), so bump the minimum to that and allow new code to drop workarounds for previous clang bugs.

   (For this bump, only C++20 CTAD will become available.)

   This patch will only be released in version 33.x, next year (2027).

   For reference:

   • https://packages.debian.org/bookworm/clang-22
   • https://packages.ubuntu.com/noble/clang-20
   • CentOS-like 8/9/10 ship clang-21 via Stream
   • Free/Open/Net*BSD ship clang-19
   • OpenSuse Tumbleweed ships with https://software.opensuse.org/package/clang (clang22); leap:latest with clang-19
   • macOS 14: depends/release cross-builds are unaffected and use clang-19
   • macOS 14: Native builds use llvm-19-ish via XCode CLT 26.3 since #36287
   • Windows: VS ships Clang 22

   On operating systems where the minimum Clang version is not shipped by default, the user would have to use GCC, or install Clang in a different way. For example:

   • https://packages.debian.org/bookworm/g++ (g++-12)
   • https://packages.ubuntu.com/jammy/g++-12
   • https://apt.llvm.org/, brew, nix, guix, or compile clang from source, ...
2. DrahtBot added the label Build system on Aug 20, 2026
3. 
   DrahtBot commented at 1:47 PM on August 20, 2026: contributor

   <!--e57a25ab6845829454e8d69fc972939a-->

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

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   External sites

   • Code coverage & benchmarks: https://corecheck.dev/bitcoin/bitcoin/pulls/36036
   • Ralph review <img src=https://review.fish.foo/assets/bitcoin/bitcoin/36036.png alt="Ralph review status"> https://git.fish.foo/bitcoin/bitcoin/pulls/36036#author-ralph

   <!--021abf342d371248e50ceaed478a90ca-->

   Reviews

   See the guideline and AI policy for information on the review process.

   Type	Reviewers
   ACK	fanquake, hebasto
   Concept ACK	l0rinc, winterrdog

   If your review is incorrectly listed, please copy-paste <code>&lt;!--meta-tag:bot-skip--&gt;</code> into the comment that the bot should ignore.

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #36042 _{<img src="https://drahtbot.space/ack_count/bitcoin/bitcoin/36042.svg">} (build: Bump g++ minimum supported version to 13 by maflcko)
   • #36033 _{<img src="https://drahtbot.space/ack_count/bitcoin/bitcoin/36033.svg">} ([wip,nomerge,rfc] build: Require C++23 compiler by maflcko)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

   <!--5faf32d7da4f0f540f40219e4f7537a3-->

4. maflcko marked this as a draft on Aug 20, 2026
5. maflcko added this to the milestone 33.0 on Aug 20, 2026
6. maflcko force-pushed on Aug 20, 2026
7. DrahtBot added the label CI failed on Aug 20, 2026
8. maflcko force-pushed on Aug 20, 2026
9. maflcko removed the label CI failed on Aug 20, 2026
10. DrahtBot added the label CI failed on Aug 20, 2026
11. maflcko removed the label CI failed on Aug 20, 2026
12. DrahtBot added the label CI failed on Aug 20, 2026
13. maflcko removed the label CI failed on Aug 20, 2026
14. DrahtBot added the label CI failed on Aug 20, 2026
15. DrahtBot removed the label CI failed on Sep 17, 2026
16. DrahtBot added the label Needs rebase on Oct 8, 2026
17. maflcko force-pushed on Oct 8, 2026
18. DrahtBot removed the label Needs rebase on Oct 8, 2026
19. DrahtBot added the label CI failed on Oct 9, 2026
20. maflcko removed this from the milestone 33.0 on Oct 12, 2026
21. 
    hebasto commented at 11:25 AM on October 20, 2026: member

    Concept ACK.

22. 
    l0rinc commented at 11:47 AM on October 20, 2026: contributor

    Concept ACK, please check if Ralph's objections are valid. Will review properly after it's out of draft - unless you want a detailed review now.

23. maflcko force-pushed on Oct 20, 2026
24. in .github/workflows/ci.yml:32 in d70ec1737b

      28 | @@ -29,7 +29,7 @@ defaults:
      29 |  jobs:
      30 |    test-each-commit:
      31 |      name: 'test ancestor commits'
      32 | -    runs-on: ${{ github.repository == 'bitcoin/bitcoin' && 'warp-ubuntu-latest-x64-8x' || 'ubuntu-latest' }}
      33 | +    runs-on: ${{ github.repository == 'bitcoin/bitcoin' && 'warp-ubuntu-2604-x64-8x' || 'ubuntu-latest' }}
    

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    maflcko commented at 12:07 PM on October 20, 2026:

    re Ralph: Was hoping they change the image in September, like last time (https://github.blog/changelog/2024-09-25-actions-new-images-and-ubuntu-latest-changes/), but I guess not anymore

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    maflcko commented at 8:34 AM on October 22, 2026:

    fixed in the last commit

25. maflcko marked this as ready for review on Oct 22, 2026
26. maflcko force-pushed on Oct 22, 2026
27. 
    fanquake commented at 9:38 AM on October 22, 2026: member

    Update https://github.com/bitcoin/bitcoin/blob/2034d3078ee1df99cdbfab738b1f2b54c30bd022/src/test/fuzz/vecdeque.cpp#L459 while here?

28. DrahtBot removed the label CI failed on Oct 22, 2026
29. maflcko force-pushed on Oct 22, 2026
30. DrahtBot added the label CI failed on Oct 22, 2026
31. hebasto approved
32. 
    hebasto commented at 10:24 AM on October 22, 2026: member

    ACK fae84b611f0b209387e7ab25348bb5594d052432.

    nit: Maybe squash the 1st and 3rd commits?

33. DrahtBot requested review from l0rinc on Oct 22, 2026
34. maflcko force-pushed on Oct 22, 2026
35. 
    maflcko commented at 10:46 AM on October 22, 2026: member

    nit: Maybe squash the 1st and 3rd commits?

    I think it is fine to keep the removals separate from the bump. Force pushed to fix a Ralph nit

36. 
    hebasto commented at 11:02 AM on October 22, 2026: member

    re-ACK fa70b1cc63a7762a62bc90e0cdd2950706d456fc.

    nit: Maybe squash the 1st and 3rd commits?

    I think it is fine to keep the removals separate from the bump.

    Not sure I follow which "removals" are referred to here.

37. maflcko force-pushed on Oct 22, 2026
38. 
    maflcko commented at 11:27 AM on October 22, 2026: member

    thx, I can't count to 3, squashed now with empty diff

39. DrahtBot removed the label CI failed on Oct 22, 2026
40. hebasto approved
41. 
    hebasto commented at 1:32 PM on October 22, 2026: member

    re-ACK faa98fadbcd2149ce31c0464a7b5e4a600bac5d2.

42. 
    maflcko commented at 11:43 AM on October 27, 2026: member

    cc @winterrdog I see you used Clang 18 in #36160#pullrequestreview-5116887377. Would this change be a problem for you?

43. 
    winterrdog commented at 5:38 PM on October 27, 2026: contributor

    concept ACK

    ---

    re: #36036 (comment)

    Would this change be a problem for you?

    not at all. i can easily switch to clang 20 since i have it installed already

44. maflcko force-pushed on Nov 4, 2026
45. hebasto approved
46. 
    hebasto commented at 11:25 PM on November 4, 2026: member

    re-ACK fac61569443b4bc0e007c5606b8f626405d04758.

    The list of platforms in the PR description could also include Windows, where VS ships Clang 22.

47. build: Bump clang minimum supported version to 19

    Also, in ci: test-each-commit: Bump to Ubuntu 26.04
    for clang-18 -> clang-21

    fa909de36f
48. clang-format: Use Standard: Latest

    It should mostly be irrelevant and generally be fine to format any C++
    code with the latest standard version. So set that here, but it can be
    changed in the future, if there is ever a reason.

    fa6299f87a
49. refactor: Drop unused libc++-16 workarounds

    Also, drop redundant Clang version requirement mentions.

    fa31e25955
50. build: Drop unused clang-17 -Wno-c++23-extensions workaround faffaeb2b6
51. refactor: Remove unused include for clang-cl on Windows

    There is no Windows specific code and clang-cl does not need the include
    here.

    fa8c3c014d
52. maflcko force-pushed on Nov 5, 2026
53. 
    fanquake commented at 4:18 PM on November 5, 2026: member

    utACK fa8c3c014d1eb17c69a7a286b121134a1c310e54

54. DrahtBot requested review from winterrdog on Nov 5, 2026
55. DrahtBot requested review from hebasto on Nov 5, 2026
56. hebasto approved
57. 
    hebasto commented at 9:11 AM on November 6, 2026: member

    re-ACK fa8c3c014d1eb17c69a7a286b121134a1c310e54, rebased and removed -Wno-c++23-extensions since my last review.

58. hebasto merged this on Nov 6, 2026
59. hebasto closed this on Nov 6, 2026

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60. maflcko deleted the branch on Nov 6, 2026

Contributors

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Review Requested
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