[issue21614] Case sensitivity problem in multiprocessing.

[Zachary Ware]

Zachary Ware  added the comment:

With no activity here in over 5 years and no confirmation on any version but 
2.7, I'm closing the issue.  If it can be confirmed on 3.8, the issue can be 
reopened.

--
nosy: +zach.ware
resolution:  -> out of date
stage:  -> resolved
status: open -> closed

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[issue21614] Case sensitivity problem in multiprocessing.

[Brett Cannon]

Change by Brett Cannon :


--
nosy:  -brett.cannon

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[issue21614] Case sensitivity problem in multiprocessing.

[Nick Coghlan]

Changes by Nick Coghlan :


--
type: crash -> behavior

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[issue21614] Case sensitivity problem in multiprocessing.

[Nick Coghlan]

Nick Coghlan added the comment:

(Adding Richard as the multiprocessing maintainer, and Christian as the creator 
of the backport to 2.4/2.5)

Note that on a case-insensitive filesystem, the fopen() call is likely 
succeeding, and it's the subsequent case_ok() check that's failing. The 
assumption of case sensitivity is embedded fairly deeply in the import system, 
as otherwise it makes it pretty easy to accidentally import the same module 
multiple times under different names.

However, if importing the same module multiple times under different names 
isn't a concern, then setting PYTHONCASEOK should allow multiprocessing to 
import the module using the incorrect capitalisation.

More significant changes to the way the standard library's multiprocessing 
module starts subprocesses on Windows won't be implemented for Python 2.7 - 
actually fixing the subprocess spawning to work as intended in all cases (as 
was done in Python 3.4) relies on the import system changes defined in PEP 451. 

In theory, I expect a multiprocessing2 backport could be written that depends 
on importib2 (to enable Python 3.4+ import semantics in Python 2.7), but I'm 
not aware of anyone currently working on such a project.

James's comment sounds like a potentially different problem (e.g. there are 
some hardcoded platform dependent limits on absolute path lengths for module 
filenames - 255 in the case of Windows)

--
nosy: +christian.heimes, sbt

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[issue21614] Case sensitivity problem in multiprocessing.

[James Burke]

James Burke added the comment:

I'm also getting this error.

It appears to me to be caused by the length of the module name rather than case.
mp_bug.py will run fine for me, but if I change it to mp_bug_longname.py then I 
will get this error.

import multiprocessing
import time

class MP_Bug(multiprocessing.Process):
def __init__(self):
multiprocessing.Process.__init__(self)
def run(test):
for x in range(1, 10):
print x
time.sleep(1)

if __name__ == '__main__':
p = MP_Bug()
p.start()

--
nosy: +James.Burke

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[issue21614] Case sensitivity problem in multiprocessing.

[Ben Yelsey]

Ben Yelsey added the comment:

Hi, could you please list more exact steps to reproduce, e.g. directory/file 
layout and import statements?

--
nosy: +inlinestyle

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[issue21614] Case sensitivity problem in multiprocessing.

[Antoine Pitrou]

Antoine Pitrou added the comment:

Can you try with Python 3.x? The import machinery is different there.

--
nosy: +ncoghlan, pitrou

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[issue21614] Case sensitivity problem in multiprocessing.

[Nathan McCorkle]

Nathan McCorkle added the comment:

I've just got done experiencing this bug. It would be much more helpful if the 
error message was a bit more helpful (I had no idea where to start looking with 
the "ImportError: No module named [moduleStartingMultiprocess]" exception 
message)

--
nosy: +nmz787

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[issue21614] Case sensitivity problem in multiprocessing.

[R. David Murray]

Changes by R. David Murray :


--
nosy: +brett.cannon, eric.snow

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[issue21614] Case sensitivity problem in multiprocessing.

[Colin Davidson]

New submission from Colin Davidson:

On windows 7, if a Python app is run (under python 2.7.6) and the invoking 
filename is capitalized differently from the source file itself, a subsequent 
attempt to use the multiprocessing module to "fork" a process will fail in the 
"forking" module. This happens because the fopen at line 1559 in import.c (in 
the "imp" module find_module method) uses the invoking capitalization, rather 
than the file capitalization and fails to open the file.

The traceback gives lines 380 then 489 in forking.py, but as noted, the problem 
is in import.c (or in the Python startup, which could convert the 
capitalization...).

--
components: Interpreter Core, Windows
messages: 219423
nosy: ColinPDavidson
priority: normal
severity: normal
status: open
title: Case sensitivity problem in multiprocessing.
type: crash
versions: Python 2.7

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