Asterisk glob expansion (*) unexpected behaviour in bash on WSL's 9P mounts

[daubmannus]

Windows Version

Microsoft Windows [Version 10.0.19045.5011]

WSL Version

2.3.24.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.15.153.1-2

Distro Version

Ubuntu 22.04.5

Other Software

No response

Repro Steps

The behavior described in the report is observed only on WSL's 9P mounts of Windows disks.

sudo mkdir -p /mnt/c/test
cd /mnt/c/test
touch 1 2

run the script

#!/bin/bash

# save true file number
true_f_num=$(for fn in *; do echo; done | wc -l)

while :; do
    # count of iterations to outer loop pipe
    echo
    
    # save current file list in file
    echo -n '' >.list
    
    for fn in *; do
        echo "$fn" >>.list
    
    # line below causes unexpected behaviour
    # on 9P mounts (like /mnt/c/...)
    # (WSL2, ubuntu 22.04)
    done | cat > .tmp; rm .tmp
    
    # check 
    [ $(cat .list | wc -l ) -ne $true_f_num ] && break

done | wc -l

output: some random number

cat .list

output:

1
2
2

• by default, pathname expansion omits files whose names start with . unless the . is explicitly matched by the pattern. Therefore, in the above code, .tmp is not expected to appear in the expansion of *, regardless of the relative timing of its creation.

• in the example command, pathname expansion is expected to be performed, once, before any iterations of the loop body are performed.

• it is not expected for pathname expansion to yield duplicate pathnames, because that is not consistent with the Bash or POSIX specifications.

The appearance of duplicate lines in .list indicates that at least one of the previous two expectations is violated. This would be a bug.

see the discussion here:
https://stackoverflow.com/a/79146114/10244657

Expected Behavior

Script runs forever.
File .list is populated with an exact list of files on each iteration of the loop.

Actual Behavior

On WSL's 9P mounts of Windows' disks script stops after some random number of iterations, outputs this number.
File .list contains the name of one of the files in the current directory twice.

Diagnostic Logs

WslLogs-2024-11-01_06-25-00.zip

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[github-actions]

Diagnostic information

Issue was edited and new log file was found: https://github.com/user-attachments/files/17595981/WslLogs-2024-11-01_06-25-00.zip
Detected appx version: 2.3.24.0

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This issue has been automatically closed since it has not had any author activity for the past 7 days. If you're still experiencing this issue please re-file it as a new issue.

Thank you!