sys.executable is sometimes wrong

Bug report

Bug description:

On Linux, sys.executable is determined using argv[0], and trying to find that in the PATH. This presumes that the Python interpreter has been started by a shell that interprets PATH in the canonical way. There is no guarantee that this happens at all, so sys.executable may point to something completely different, or is even the empty string.

As an example:

bash -c 'exec -a whatever python -c "import sys;print(sys.executable)"'

should output the path of the Python executable, but simply outputs nothing.

Even worse, one can make Python output a wrong executable, as in

bash -c 'exec -a /usr/bin/python python -c "import sys;print(sys.executable)"'

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-145486

Riproduci i due comandi Linux nel report e analizza come CPython determina sys.executable da argv[0] e PATH. Usa i casi con argv[0] alterato come scenari di regressione; il lavoro è completato quando sys.executable identifica l’eseguibile Python in esecuzione invece di un percorso vuoto o non pertinente. L’issue fa riferimento alla PR collegata gh-145486.