Using getproctitle() changes the result of getthreadtitle()?

[wimglenn]

I found something that seems undesirable - when using getproctitle() the result returned by getthreadtitle() seems to mutate.

Minimal reproducer:

$ cat issueexample.py
from setproctitle import getthreadtitle, getproctitle
print("0.", getthreadtitle(), getproctitle())
print("1.", getthreadtitle(), getproctitle())

Demo:

$ python3 issueexample.py
0. python3 python3 issueexample.py
1. python3 issueex python3 issueexample.py

The change also affects the /proc/{pid}/task/{pid}/comm file.

Shouldn't using getters not modify the results in any way?

I'm on Linux (RHEL8) using setproctitle 1.3.3. I also could reproduce this in a debian container (docker.io/library/python:3.12)

Not sure if related, but with debug logging on I also see a message about "setup was called more than once!":

$ SPT_DEBUG=1 python issueexample.py
[SPT]: module init
[SPT]: reading argc/argv from Python main
[SPT]: found 2 arguments
[SPT]: walking from environ to look for the arguments
[SPT]: found environ at 0x7fffffffb5d4
[SPT]: found argv[1] at 0x7fffffffb5c4: issueexample.py
[SPT]: argv[0] should be at 0x7fffffffb5bd
[SPT]: found argv[0]: python
[SPT]: environ has been copied
0. python python issueexample.py
[SPT]: setup was called more than once!
1. python issueexa python issueexample.py