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musllinux wheel fails to load on Alpine: “initial-exec TLS resolves to dynamic definition” when importing cachebox #41

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#42
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musllinux wheel fails to load on Alpine: “initial-exec TLS resolves to dynamic definition” when importing cachebox#41
#42

Description

@mpihelgas
mpihelgas
opened on Dec 30, 2025

Problem description

Importing cachebox v5.2.0 inside an Alpine (musl) container raises an error:

ImportError: Error relocating /venv/lib/python3.12/site-packages/cachebox/_core.cpython-312-x86_64-linux-musl.so: (null): initial-exec TLS resolves to dynamic definition in /venv/lib/python3.12/site-packages/cachebox/_core.cpython-312-x86_64-linux-musl.so

Some initial workarounds I already tested

  • Same application loads fine on Debian-based container base image.
  • Reverting to an earlier version (e.g., v5.1.0) of cachebox avoids the error on Alpine.

Environment

  • Base image: python:3.12-alpine (musl libc)
  • Python: 3.12
  • cachebox: 5.2.0 (wheel from PyPI)
  • Package with the cachebox dependency: openfeature-provider-flagd v0.2.6

Details

From the cachebox v.5.2.0 release changelog we can see:

Starting now, cachebox uses mimalloc as the default allocator for some targets ( thanks to @chirizxc, #37)

Mimalloc’s TLS model (initial-exec) is known to break with musl when the library is dlopened; upstream recommends rebuilding with -DMI_LOCAL_DYNAMIC_TLS=ON or switching to the local-dynamic model.

Summary

The published cachebox v5.2.0 wheel seems to fail consistently on the Alpine-based image.
Would it be possible to disable the mimalloc feature for musllinux wheels or adjust the mimalloc build flags so the extension can load on musl?

References

Activity

  1. chirizxc commented on Dec 30, 2025

    @chirizxc
    chirizxc
    on Dec 30, 2025
    Contributor

    seems need to add local_dynamic_tls

    [dependencies.mimalloc]
version = "0.1.48"
features = ["v3", "override", "local_dynamic_tls"]
optional = true

  2. awolverp commented on Dec 31, 2025

    @awolverp
    awolverp
    on Dec 31, 2025
    Owner

    Thank you for reporting ❤️ It will be fixed now

  3. awolverp
    closed this as completedin #42on Dec 31, 2025

  4. chirizxc commented on Dec 31, 2025

    @chirizxc
    chirizxc
    on Dec 31, 2025
    Contributor

    @awolverp Should we add tests for this?

    FROM docker.io/library/python:3.13-alpine

WORKDIR /app

ENV UV_LINK_MODE=copy \
    UV_COMPILE_BYTECODE=1 \
    UV_PYTHON_DOWNLOADS=0

COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/

RUN uv pip install cachebox==5.2.0 --system

RUN cat <<'EOF' > /app/example.py
import cachebox

print(f"{cachebox.__version__}")

cache = cachebox.FIFOCache(maxsize=128)
cache["key"] = "value"
assert cache["key"] == "value"
EOF

RUN addgroup -S user && adduser -S -G user user
RUN chown -R user:user /app
USER user

CMD ["python", "example.py"]

    https://github.com/lava-sh/toml-rs/blob/main/.github%2Fworkflows%2Fci.yml#L158-L186

  5. chirizxc commented on Dec 31, 2025

    @chirizxc
    chirizxc
    on Dec 31, 2025
    Contributor
    Image

    5.2.0

  6. chirizxc commented on Dec 31, 2025

    @chirizxc
    chirizxc
    on Dec 31, 2025
    Contributor
    Image

    5.2.1

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