Build failure: llvm-21.1.7 (test failure: xunit-output.py; aarch64-darwin)

Nixpkgs version

• Stable (25.11)

Steps to reproduce

I ran into this running the following command on a MacBook Pro:

nix-build --log-format bar-with-logs --no-substitute --no-out-link '<nixpkgs>' -A fish. (Using --no-substitue to hopefully work around #507531).

Can Hydra reproduce this build failure?

No, Hydra cannot reproduce this build failure.

Link to Hydra build job

https://hydra.nixos.org/job/nixpkgs/nixpkgs-25.11-darwin/llvm.aarch64-darwin

Relevant log output

$ nix-build --log-format bar-with-logs --no-substitute --no-out-link '<nixpkgs>' -A
[SNIP: Full log too long for GitHub]
llvm> PASS: lit :: test-output-resultdb.py (59901 of 59915)
llvm> PASS: lit :: usage.py (59902 of 59915)
llvm> PASS: lit :: time-tests.py (59903 of 59915)
llvm> PASS: lit :: xunit-output-report-failures-only.py (59904 of 59915)
llvm> FAIL: lit :: xunit-output.py (59905 of 59915)
llvm> ******************** TEST 'lit :: xunit-output.py' FAILED ********************
llvm> Exit Code: 137
llvm> Command Output (stdout):
llvm> --
llvm> # RUN: at line 4
llvm> rm -rf /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml
llvm> # executed command: rm -rf /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml
llvm> # RUN: at line 5
llvm> not env -u FILECHECK_OPTS "/nix/store/ilwzyqwswbcv0gir1pscaga63cjirwkr-python3-3.13.12-env/bin/python3.13" /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/utils/lit/lit.py -j1 --order=lexical --xunit-xml-output /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml Inputs/xunit-output
llvm> # executed command: not env -u FILECHECK_OPTS /nix/store/ilwzyqwswbcv0gir1pscaga63cjirwkr-python3-3.13.12-env/bin/python3.13 /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/utils/lit/lit.py -j1 --order=lexical --xunit-xml-output /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml Inputs/xunit-output
llvm> # .---command stdout------------
llvm> # | -- Testing: 5 tests, 1 workers --
llvm> # | FAIL: test-data :: bad&name.ini (1 of 5)
llvm> # | ********** TEST 'test-data :: bad&name.ini' RESULTS **********
llvm> # | value0: 1
llvm> # | value1: 2.3456
llvm> # | **********
llvm> # | EXCLUDED: test-data :: excluded.ini (2 of 5)
llvm> # | UNSUPPORTED: test-data :: missing_feature.ini (3 of 5)
llvm> # | PASS: test-data :: pass.ini (4 of 5)
llvm> # | UNSUPPORTED: test-data :: unsupported.ini (5 of 5)
llvm> # | ********************
llvm> # | Failed Tests (1):
llvm> # |   test-data :: bad&name.ini
llvm> # |
llvm> # |
llvm> # | Testing Time: 0.33s
llvm> # |
llvm> # | Total Discovered Tests: 5
llvm> # |   Excluded   : 1 (20.00%)
llvm> # |   Unsupported: 2 (40.00%)
llvm> # |   Passed     : 1 (20.00%)
llvm> # |   Failed     : 1 (20.00%)
llvm> # `-----------------------------
llvm> # RUN: at line 7
llvm> sh -c 'if command -v xmllint 2>/dev/null; then xmllint --noout /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml; fi'
llvm> # executed command: sh -c 'if command -v xmllint 2>/dev/null; then xmllint --noout /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit/tests/Output/xunit-output.py.tmp.xunit.xml; fi'
llvm> # .---command stdout------------
llvm> # | /nix/store/pdh8rmwz180559s2qbabjfdjss2li058-libxml2-2.15.1-bin/bin/xmllint
llvm> # `-----------------------------
llvm> # error: command failed with exit status: 137
llvm> --
llvm> ********************
llvm> PASS: lit :: unique-output-file.py (59906 of 59915)
llvm> PASS: lit :: use-llvm-tool.py (59907 of 59915)
llvm> PASS: lit :: shtest-recursive-substitution.py (59908 of 59915)
llvm> PASS: lit :: allow-retries.py (59909 of 59915)
llvm> PASS: lit :: xfail-cl.py (59910 of 59915)
llvm> PASS: Polly :: ScheduleOptimizer/pattern-matching-based-opts_5.ll (59911 of 59915)
llvm> PASS: lit :: shtest-timeout.py (59912 of 59915)
llvm> PASS: lit :: selecting.py (59913 of 59915)
llvm> PASS: lit :: shtest-shell.py (59914 of 59915)
llvm> PASS: lit :: shtest-define.py (59915 of 59915)
llvm> ********************
llvm> Failed Tests (1):
llvm>   lit :: xunit-output.py
llvm> Testing Time: 1383.10s
llvm> Total Discovered Tests: 68742
llvm>   Skipped          :    33 (0.05%)
llvm>   Unsupported      :  2591 (3.77%)
llvm>   Passed           : 65923 (95.90%)
llvm>   Expectedly Failed:   194 (0.28%)
llvm>   Failed           :     1 (0.00%)
llvm> FAILED: [code=1] CMakeFiles/check-all /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/CMakeFiles/check-all
llvm> cd /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build && /nix/store/ilwzyqwswbcv0gir1pscaga63cjirwkr-python3-3.13.12-env/bin/python3.13 /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/./bin/llvm-lit --verbose -j16 --param polly_site_config=/nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test/lit.site.cfg --param polly_unit_site_config=/nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test/Unit/lit.site.cfg /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/mlgo-utils /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/test
llvm> ninja: build stopped: subcommand failed.
error: builder for '/nix/store/fdym92qpd192ci1q9k3mc176fr8ay4qj-llvm-21.1.7.drv' failed with exit code 1;
       last 25 log lines:
       > PASS: lit :: use-llvm-tool.py (59907 of 59915)
       > PASS: lit :: shtest-recursive-substitution.py (59908 of 59915)
       > PASS: lit :: allow-retries.py (59909 of 59915)
       > PASS: lit :: xfail-cl.py (59910 of 59915)
       > PASS: Polly :: ScheduleOptimizer/pattern-matching-based-opts_5.ll (59911 of 59915)
       > PASS: lit :: shtest-timeout.py (59912 of 59915)
       > PASS: lit :: selecting.py (59913 of 59915)
       > PASS: lit :: shtest-shell.py (59914 of 59915)
       > PASS: lit :: shtest-define.py (59915 of 59915)
       > ********************
       > Failed Tests (1):
       >   lit :: xunit-output.py
       >
       >
       > Testing Time: 1383.10s
       >
       > Total Discovered Tests: 68742
       >   Skipped          :    33 (0.05%)
       >   Unsupported      :  2591 (3.77%)
       >   Passed           : 65923 (95.90%)
       >   Expectedly Failed:   194 (0.28%)
       >   Failed           :     1 (0.00%)
       > FAILED: [code=1] CMakeFiles/check-all /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/CMakeFiles/check-all
       > cd /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build && /nix/store/ilwzyqwswbcv0gir1pscaga63cjirwkr-python3-3.13.12-env/bin/python3.13 /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/./bin/llvm-lit --verbose -j16 --param polly_site_config=/nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test/lit.site.cfg --param polly_unit_site_config=/nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test/Unit/lit.site.cfg /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/mlgo-utils /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/tools/polly/test /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/utils/lit /nix/var/nix/b/35dbzf5dxqs6dyq73qdld403ff/llvm-src-21.1.7/llvm/build/test
       > ninja: build stopped: subcommand failed.
       For full logs, run:
          nix-store -l /nix/store/fdym92qpd192ci1q9k3mc176fr8ay4qj-llvm-21.1.7.drv

Additional context

This appears not to reproduce on Hydra, which I know makes it trickier, but I have been seeing it consistently for several days, building straight from the latest nixpkgs-25.11-darwin channel without any overlays or anything.

System metadata

• system: "aarch64-darwin"
• host os: Darwin 25.2.0, macOS 26.2
• multi-user?: yes
• sandbox: no
• version: nix-env (Lix, like Nix) 2.95.1 System type: aarch64-darwin Additional system types: x86_64-darwin Features: gc, signed-caches System configuration file: /etc/nix/nix.conf User configuration files: /Users/rkjnsn/.config/nix/nix.conf:/etc/xdg/nix/nix.conf Store directory: /nix/store State directory: /nix/var/nix Data directory: /nix/store/ylbrql19ngr2wypjiviyx21qvbwpd79z-lix-2.95.1/share
• channels(root): "nixpkgs"
• nixpkgs: /Users/rkjnsn/.nix-defexpr/channels/nixpkgs

Notify maintainers

@RossComputerGuy @alyssais @Ericson2314 @emilazy @lovek323 @rrbutani @sternenseemann

---

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Start with the failing xunit-output.py test, its Inputs/xunit-output data, and llvm/utils/lit/lit.py. Reproduce the test on aarch64-darwin and investigate the exit-137 failure around the generated xunit XML and xmllint. Done means the llvm-21.1.7 check-all build passes without this test failure.