Thomas <thger...@hhu.de> added the comment:
I have simplified the test case a bit more:
import multiprocessing.pool, zipfile
# Create a ZipFile with two files and same content
with zipfile.ZipFile("test.zip", "w", zipfile.ZIP_STORED) as z:
z.writestr("file1", b"0"*10000)
z.writestr("file2", b"0"*10000)
# Read file1 with two threads at once
with zipfile.ZipFile("test.zip", "r") as z:
pool = multiprocessing.pool.ThreadPool(2)
while True:
pool.map(z.read, ["file1", "file1"])
Two files are sufficient to cause the error. It does not matter which files are
read or which content they have.
I also narrowed down the point of failure a bit. After
self._file.seek(self._pos)
in _SharedFile.read (
https://github.com/python/cpython/blob/c79667ff7921444911e8a5dfa5fba89294915590/Lib/zipfile.py#L742
), the following assertion should hold:
assert(self._file.tell() == self._pos)
The issue occurs when seeking to position 35 (size of header + length of name).
Most of the time, self._file.tell() will then be 35 as expected, but sometimes
it is 8227 instead, i.e. 35 + 8192.
I am not sure how this can happen since the file object should be locked.
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue42369>
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