Python 3.9 is now built with -fvisibility=hidden. The Py_GetArgcArgv() function is no longer exported. Previously, it was exported because all symbols were exported by default.

I'm working on a PR to export it again.

Fedora downstream issue, setproctitle is broken on Python 3.9: https://bugzilla.redhat.com/show_bug.cgi?id=1792059

setproctitle upstream report:
https://github.com/dvarrazzo/py-setproctitle/issues/76

See also bpo-15577 "Real argc and argv in embedded interpreter".

See also bpo-5672 "Implement a way to change the python process name", especially this comment:
https://bugs.python.org/issue5672#msg108524

"""
setproctitle is quite stable, my company uses it in production environment very heavily with python 2.x. Probably its users base is not huge, but that's because it's a relatively specialized tool.

Python3 porting is not straightforward because python2 exports the original argv pointer using Py_GetArgcArgv() whereas python3 only exports a decoded version in a wchar_t* array. This may not be a showstopper: probably the original argv can still be found scanning backwards from environ: I want to test it but I haven't had requests for it yet, so it wasn't a top priority.

So, while I'd be pleased to have it included in the stdlib, I'm not really convinced it would be useful to such a large audience. Anyway I'm available for any improvement it would make the tool more useful and to anybody eager to push for its inclusion.
"""

See also bpo-29857: Provide `sys.executable_argv` for host application's command line arguments.

See also bpo-23427 "Python should expose command when invoked with -c"

Thank you for opening this. FYI:

> probably the original argv can still be found scanning backwards from environ

this is how the module works indeed in Python 3.

New changeset e81f6e687d0f04a45f2389d0b43fafd6d8491624 by Victor Stinner in branch 'master':
bpo-40910: Export Py_GetArgcArgv() function (GH-20721)
https://github.com/python/cpython/commit/e81f6e687d0f04a45f2389d0b43fafd6d8491624

Py_GetArgcArgv() is not new at all. It exists since:

commit ac56b03f9a931423714ab3a0e8cfae78f81f9b85
Author: Guido van Rossum <guido@python.org>
Date:   Sun Jul 21 02:33:38 1996 +0000

    New style names for getprogramname and getargcargv


Previously, the function was known as getargcargv() and it existed since:

commit 7b1e974b4bd7c17cd90a6d03bab0aaa079d78d29
Author: Guido van Rossum <guido@python.org>
Date:   Mon Aug 29 10:46:42 1994 +0000

    Makefile.pre.in: add $(OPT) to link command
    audioop.c: fix for MPW
    config.c.in: save original argc/argv for Lance
    rotormodule.c: new coding conventions
    timemodule.c: add casts for Lance

+void
+getargcargv(argc,argv)
+       int *argc;
+       char ***argv;
+{
+       *argc = orig_argc;
+       *argv = orig_argv;
+}
+

New changeset dedaac040fe5b0b88acdec072623bb39ec53687f by Victor Stinner in branch '3.9':
bpo-40910: Export Py_GetArgcArgv() function (GH-20721) (GH-20723)
https://github.com/python/cpython/commit/dedaac040fe5b0b88acdec072623bb39ec53687f

Ok, I fixed Python 3.9: Py_GetArgcArgv() function is exported again.

Let's continue the discussion in bpo-23427.

New changeset e2d47a0568c6da9229580829917fd6aa702133b3 by Victor Stinner in branch 'master':
bpo-40910: PyConfig_Clear() clears _orig_argv (GH-20886)
https://github.com/python/cpython/commit/e2d47a0568c6da9229580829917fd6aa702133b3

New changeset bab0833d49f8d38488ff1469edcec9b47db0dc5c by Miss Islington (bot) in branch '3.9':
bpo-40910: PyConfig_Clear() clears _orig_argv (GH-20886)
https://github.com/python/cpython/commit/bab0833d49f8d38488ff1469edcec9b47db0dc5c