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tachyon fails to attach with _ctypes imported #144563
Description
Activity
I think this is MacOS-specific -- reproduced it there.
I couldn't reproduce it on Linux:
Details
❯ uv run -p 3.15 --with polars python t.py 78672 ^Z [1]+ Stopped uv run -p 3.15 --with polars python t.py ✦ ❯ uv run -p 3.15 python -m profiling.sampling attach -d 1 78672 Captured 1 001 samples in 1,00 seconds Sample rate: 1 000,99 samples/sec Error rate: 0,00 Profile Stats: nsamples sample% tottime (s) cumul% cumtime (s) filename:lineno(function) 1001/1001 100.0 1.001 100.0 1.001 t.py:6(<module>) Legend: nsamples: Direct/Cumulative samples (direct executing / on call stack) sample%: Percentage of total samples this function was directly executing tottime: Estimated total time spent directly in this function cumul%: Percentage of total samples when this function was on the call stack cumtime: Estimated cumulative time (including time in called functions) filename:lineno(function): Function location and name Summary of Interesting Functions: Functions with Highest Direct/Cumulative Ratio (Hot Spots): 1.000 direct/cumulative ratio, 100.0% direct samples: t.py:(<module>) Functions with Highest Call Frequency (Indirect Calls): Functions with Highest Call Magnification (Cumulative/Direct):if I change it to
import polars as pl, attach fails with:
Failed to read debug offsets structure from remote processCouldn't reproduce on MacOS.
Couldn't reproduce on MacOS.
Sorry then does this means that you cannot reproduce anywhere?
Bug report
Bug description:
test.py:
import os import polars print(os.getpid()) while True: pass
running it gives
uv run -p 3.15 --with polars test.py:
9586attach fails (
sudo runmode seems to work)
sudo uv run -p 3.15 python -m profiling.sampling attach 9586:Password: Can't determine the Python version of the remote processif I change it to
import polars as pl, attach fails with:
Failed to read debug offsets structure from remote processCPython versions tested on:
3.15
Operating systems tested on:
macOS
@mstarodub does it work if you don't import polars?
Also can you try with the current main without uv in the mix?
Couldn't reproduce on MacOS.
Sorry then does this means that you cannot reproduce anywhere?
No. I couldn't reproduce only the quoted part (if I change it to
import polars as pl).Importing
polarsdoes something to the runtime that Tachyon can no longer attach to it, and this happens only on MacOS, in this specific uv setup.
Beforeimport polarsis executed, Tachyon can attach. After it is executed, Tachyon no longer recognizes the Python version.Also can you try with the current main without uv in the mix?
I'll try to find a uv-free repro, but until then uv is currently necessary with how it manages environments.
This won't reproduce for
uv run -p ./python.exebut will reproduce foruv run -p 3.15. Something about different environments, but I couldn't figure out what yet.Also can you try with the current main without uv in the mix?
This won't reproduce without uv in the mix, and even with uv but on main.
I'd still investigate to understand what exactly doesimport polarsdo that Tachyon can no longer attach, unless you recognize this as a fixed regression? Maybe I'll try to bisect if I can't find any sensible idea on what happens here.Smaller repro:
# t.py import os import _remote_debugging print(_remote_debugging.RemoteUnwinder(os.getpid())) import polars print(_remote_debugging.RemoteUnwinder(os.getpid()))
❯ uv run -p 3.15 --with polars t.py <_remote_debugging.RemoteUnwinder object at 0x7cdc00000> Traceback (most recent call last): File "/Users/.../Python/cpython/t.py", line 9, in <module> print(_remote_debugging.RemoteUnwinder(os.getpid())) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^ RuntimeError: Can't determine the Python version of the remote process ❯ uv run -p ./python.exe --with polars t.py <_remote_debugging.RemoteUnwinder object at 0xaeb490020> <_remote_debugging.RemoteUnwinder object at 0xaeb490020>Also can you try with the current main without uv in the mix?
This won't reproduce without uv in the mix, and even with uv but on main.
I'd still investigate to understand what exactly doesimport polarsdo that Tachyon can no longer attach, unless you recognize this as a fixed regression? Maybe I'll try to bisect if I can't find any sensible idea on what happens here.I do not recognise the problem from the top of my head but we have fixed a bunch of stuff around the area where we recognise the offsets and the memory map.
uv python also statically compiles everything so perhaps there is dome weird side effect to that
@johnslavik can you try to repro by using the same commit uv is using for the 3.15 version?
Reacted by Bartosz Sławecki8 remaining items
Just to make sure I'm understanding correctly, this only reproduces with 3.15 from uv (i.e.,
python-build-standalone)? We statically linklibpython, but it's complicated astral-sh/python-build-standalone#592Whatever you do in macOS makes ctypes dlopen the dylib and create multiple mappings without initialising it. Not sure exactly if this is something specific on how you build or is just something that can happen in a regular build but for some reason we don't catch it.
Just to make sure I'm understanding correctly, this only reproduces with 3.15 from uv (i.e.,
python-build-standalone)?3.14 too IIRC. Need to verify and perhaps adjust labels, will do that in a second.
EDIT: Confirmed 3.14.On macOS,
python-build-standalonedynamically links libpython which likely explains the behavior. Only on Linux is statically linking done.- added a commit that references this issue
on Feb 10, 2026 - added a commit that references this issue
on Feb 10, 2026
Bug report
Bug description:
test.py:
running it gives
uv run -p 3.15 --with polars test.py:9586
attach fails (
sudo runmode seems to work)sudo uv run -p 3.15 python -m profiling.sampling attach 9586:if I change it to
import polars as pl, attach fails with:Failed to read debug offsets structure from remote processCPython versions tested on:
3.15
Operating systems tested on:
macOS
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