SPT_NOENV results in getproctitle missing last char

[elelayan]

OS: Linux xxx 5.10.0-16-amd64 #1 SMP Debian 5.10.127-1 (2022-06-30) x86_64 GNU/Linux
Python: Python 3.7.12 | packaged by conda-forge | (default, Oct 26 2021, 06:08:53) [GCC 9.4.0] on linux

py-setproctitle: 1.3.1 wheel from pypi or master compiled locally with pip install -e ./py-setproctitle --global-option --with-debugging-symbols --global-option --debug

test script:

#!/usr/bin/env python3

import setproctitle


if __name__ == '__main__':
    print("PROCTITLE:", setproctitle.getproctitle())

OUTPUT

$ SPT_NOENV=yes /tmp/hello.py 
PROCTITLE: /tmp/hello.p

EXPECTED OUTPUT (contains the last y)

$ SPT_NOENV=yes /tmp/hello.py 
PROCTITLE: /tmp/hello.py

[elelayan]

I tracked it down to https://github.com/dvarrazzo/py-setproctitle/blob/master/src/spt_status.c#L349

    spt_strlcpy(ps_buffer + ps_buffer_fixed_size, activity,
            ps_buffer_size - ps_buffer_fixed_size);

ps_buffer_fixed_size=0, ps_buffer_size doesn't include the '\0' from the last argv, resulting in spt_strlcpy replacing 'y' with a new '\0'.

A blind fix in https://github.com/dvarrazzo/py-setproctitle/blob/master/src/spt_status.c#L231

            if (!noenv || !*noenv) {
                ....
            }
            else
            {
                end_of_area += 1;
            }

works but I'm not sure if end_of +1 should also be applied in the case when SPT_NOENV is set, getting us an additional character to set the activity...

[mattip]

See also ray-project/ray#40289 where ray tests hit this problem.