[issue26703] Socket state corrupts when original assignment goes out of scope

[JoshN]

New submission from JoshN:

Creating a socket in one thread and sharing it with another will cause the 
socket to corrupt as soon as the thread it was created in exits.

Example code:
import socket, threading, time, os

def start():
a = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
a.bind(("", 8080))
a.set_inheritable(True)

thread = threading.Thread(target=abc, args=(a.fileno(),))
thread.start()

time.sleep(2)
print("Main thread exiting, socket is still valid: " + str(a) + "\n")

def abc(b):
sock = socket.socket(fileno=b)
for _ in range(3):
print("Passed as an argument:" + str(sock) + "\n=")

time.sleep(1.1)

start()

Note that, as soon as the main thread exits, the socket isn't closed, nor is 
the fd=-1, etc. Doing anything with this corrupted object throws WinError 10038 
('operation performed on something that is not a socket').

I should note that the main thread exiting doesn't seem to be the cause, it is 
the original object containing the socket going out of scope that causes the 
socket to become corrupted.

-JoshN

--
components: IO
messages: 262951
nosy: JoshN
priority: normal
severity: normal
status: open
title: Socket state corrupts when original assignment goes out of scope
type: crash
versions: Python 3.5

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[issue26703] Socket state corrupts when original socket object goes out of scope in a different thread

[JoshN]

Changes by JoshN :


--
title: Socket state corrupts when original assignment goes out of scope -> 
Socket state corrupts when original socket object goes out of scope in a 
different thread

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[issue26703] Socket state corrupts when original socket object goes out of scope in a different thread

[JoshN]

JoshN added the comment:

I do understand that the docs are a bit strange on the issue. For example, 
actually testing the line you referenced ("...fileno will return the same 
socket and not a duplicate.") by creating 2 sockets and testing sameness with 
the 'is' operator returns false.

I tried to trim the example code as much as possible - I did test disabling the 
garbage collector, playing with inheritance, etc, but trimmed them out as they 
didn't have any effect on my system.


I think my main issue was, when this occurs, the socket 'breaks' as you 
mentioned instead of closing. Was almost sure it was a bug. Using detach works 
for this UDP example, but I wasn't sure if detaching the socket actually closes 
it (e.g. in a stream oriented connection).

So this is considered normal behavior then?

--

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[issue26703] Socket state corrupts when original socket object goes out of scope in a different thread

[JoshN]

JoshN added the comment:

Josh/Martin/Antoine: Thank you for the tips - I was not aware of the underlying 
mechanics, especially the separate abstraction layers.

I did RTFM up and down before posting this, to be sure. My apologies for the 
inconvenience.

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