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

Reproduza os dois comandos Linux do relatório e inspecione como o CPython determina sys.executable a partir de argv[0] e PATH. Use os casos com argv[0] alterado como cenários de regressão; considera-se concluído quando sys.executable identifica o executável Python em execução, em vez de um caminho vazio ou não relacionado. A issue faz referência ao PR vinculado gh-145486.