Interestingly, when I use pip, it builds with clang not gcc. Are you using the same Python interpreter with uv pip? It looks like it's using 3.12 but the pip logs are using 3.9.

Can you reproduce this in CI or a container or something?

pip was using a pyenv installed python 3.9.6, which I think compiles python from source.
uv was using uv installed python (which I think are pre-compiled). my original logs were with python 3.12 but here they are with 3.9.6. it's the same thing.
uv_datrie.log

I have also attached logs for both pip and uv after installing clang and llvm (apt install clang llvm). it seems like pip still chooses to use gcc, but so does uv ?
pip_datrie_with_clang_installed.log
uv_datrie_with_clang_installed.log

I don't have a CI or container setup unfortunately. But my colleague reproduced this issue on his own Ubuntu machine, if that counts for something. pip works for both of us.

Are you still using the uv-managed Python? We build the Python distribution itself with clang so maybe that's the difference? You can pass --python <path> to make sure you're using the same pyenv interpreter to see if that makes a difference.

I don't have a CI or container setup unfortunately. But my colleague reproduced this issue on his own Ubuntu machine, if that counts for something.

We'll need some sort of minimal reproduction to investigate for real.

Thanks for the quick response. See the logs below for an attempt at a minimal reproduction.
There are two python versions here:

• one is installed by 'pyenv install 3.9.6' which compiles from source with gcc (~/.pyenv/versions/3.9.6/bin/python)

• and another with 'uv python install 3.9.6' which as you said is a pre-compiled clang install (~/.local/share/uv/python/cpython-3.9.6-linux-x86_64-gnu/bin/python3 )

As you see in the log:

• 'pip install' installs datrie successfully for the pyenv python with both CC=gcc and CC=clang.
• 'uv pip install' fails with both CC=gcc and CC=clang.
• 'uv pip install --python ~/.pyenv/versions/3.9.6/bin/python' succeeds with both CC=gcc and CC=clang.

In short, the problem appears related to the python installed by uv.

log.txt

Hm. I thought a wrote a reply but it's not here :/

In brief, I think you're running into a quirk of the Python distribution (which is built with clang): https://github.com/indygreg/python-build-standalone/blob/main/docs/quirks.rst#references-to-build-time-paths

I tried to dig into why this specific path (/tools/llvm) is in the distribution but couldn't figure that out. Maybe because I was looking at an aarch64 build though.

Sysconfig contains this for a typical indygreg build (typical that I've looked at / linux):

AR = "/tools/llvm/bin/llvm-ar"

AR is one of the variables that sysconfigpatcher patches. It might be possible to try that tool and see if it helps the build (but no guarantees, it's empirical only.)

If you want to inspect those variables, here's the way to do it:

uv run python -m sysconfig

Thanks! I wonder if we can/should reset some of these at build time.