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[Python] pa.output_stream() aborts the process on a read-only buffer #50831
Description
Describe the bug, including details regarding any error messages, version, and platform.
I've been fuzzing Python C extension modules for a small research project, and this one came up. It reproduces with the binary wheel from a plain pip install pyarrow.
Versions
pyarrow 25.0.0, CPython 3.12.3, Ubuntu 24.04 x86_64.
Reproducer
import pyarrow as pa
pa.output_stream(pa.py_buffer(b'x'))The process aborts (SIGABRT, exit 134) after printing:
/arrow/cpp/src/arrow/io/memory.cc:165: Check failed: buffer->is_mutable() Must pass mutable buffer
[1] 3911118 IOT instruction (core dumped) python
memoryview(b'') and an empty py_buffer do the same:
pa.output_stream(memoryview(b'')) # SIGABRT
pa.output_stream(pa.py_buffer(b'')) # SIGABRTWhat does work
A mutable buffer, a path, and BufferOutputStream are all fine:
>>> b = pa.allocate_buffer(16)
>>> b.is_mutable
True
>>> type(pa.output_stream(b))
<class 'pyarrow.lib.FixedSizeBufferWriter'>
>>> type(pa.output_stream('/tmp/o.bin'))
<class 'pyarrow.lib.OSFile'>And pa.py_buffer is documented to produce a read-only buffer:
>>> pa.py_buffer(b'x').is_mutable
FalseWhy I think it is worth reporting
output_stream's own docstring lists buffer among the accepted source types:
source : str, Path, buffer, file-like object
The source to open for writing.
so passing a buffer is the documented usage, and a read-only one terminates the interpreter rather than raising.
This looks to me like a bug, but I'm not certain it is one, so I'm filing an issue.
Component(s)
Python
Activity
[-]`pa.output_stream()` aborts the process on a read-only buffer[/-][+][Python] `pa.output_stream()` aborts the process on a read-only buffer[/+]nil68657 commentedon Aug 8, 2026
take
Reranko05 commentedon Aug 9, 2026
@nil68657 Since #50833 addresses this issue, would you be okay with assigning this issue to @erichanwang? If so, could you also help review the PR?
apacheGH-50831: [Python] Guard FixedSizeBufferWriter against read-onl…
nil68657 commentedon Aug 10, 2026
Sure, I can be a reviewer
Reranko05 commentedon Aug 10, 2026
@erichanwang could you comment "take" here so that I can assign you the issue.
nil68657 commentedon Oct 6, 2026
Any updates on this? I can take this back up.