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

[mpihelgas]

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

• Musl doesn't support init-exec tls microsoft/mimalloc#644

[chirizxc]

seems need to add local_dynamic_tls

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

[awolverp]

Thank you for reporting ❤️ It will be fixed now

[chirizxc]

@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

[chirizxc]

5.2.0

[chirizxc]

5.2.1