[not-matthias]

The simulation setup runs venv_compat.sh to symlink libpython into a uv venv's lib directory. It warned Failed to symlink libpython in cases where nothing was wrong, and gave no reason at the default log level.

False positives:

• python3 is a uv shim in ~/.local/bin and ~/.local/lib does not exist, so ln fails.
• A non-venv python where ldd cannot find libpython, so the script links a file onto itself.

Real failure the warning should explain:

• A cached .venv whose uv Python moved (e.g. a patch upgrade) has a dangling link. [ -e ] misses it and ln -s fails with "File exists". Valgrind then crashes.

Changes:

• The script skips pythons that are not in a venv (no pyvenv.cfg), runs mkdir -p on the lib directory, and uses ln -sfn so stale links are replaced.
• The warning stays at warn level. It now includes the script error and says flamegraphs may contain artifacts.
• Tests run the script with a fake uv and ldd for the missing lib dir, the dangling link, and the non-venv case. All three fail on the old script.

Fixes COD-3977

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge.

Summary

The PR avoids false libpython warnings and repairs dangling links in Python virtual environments.

• Valgrind setup keeps Python's shared library link usable in virtual environments.
• Valgrind setup explains when a missing Python link may affect flamegraphs.

_{Reviews (2) · Last reviewed commit: "fix(valgrind): stop the libpython symlin..." · Reviewed by Greptile}

[lvaroqui]

LGTM

[codspeed]

Merging this PR will not alter performance

2 warnings, 1 note

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

Learn more about Macro Runners

See affected benchmarks

⚠️ 8 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

ℹ️ 6 benchmarks have no flamegraph

The flamegraph wasn't generated: the symbols of the profiling trace could not be resolved, because no information about the language frames was collected.

See affected benchmarks

✅ 41 untouched benchmarks
⏩ 6 skipped benchmarks¹

---

_{Comparing cod-3977-runner-failed-to-symlink-libpython-warning-fires-falsely-in (d9612e3) with main (db7de03)}

Footnotes

1. 6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩