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

重現報告中的兩個 Linux 命令，並檢查 CPython 如何根據 argv[0] 和 PATH 判定 sys.executable。將修改過 argv[0] 的情況作為回歸情境；完成的標準是 sys.executable 指向正在執行的 Python 可執行檔，而不是空路徑或無關的路徑。該 issue 引用了相關的 PR gh-145486。