`sys.audit(0)` aborts due to an assertion in debug build

[devdanzin]

Crash report

What happened?

There is an assert in sysmodule.c that makes the interpreter abort when calling sys.audit with a non-string value in debug builds:

cpython/Python/sysmodule.c

Line 522 in f6cc7c8

assert(PyUnicode_Check(args[0]));

Python 3.14.0a1+ (heads/main:c5b99f5c2c, Oct 26 2024, 12:35:53) [GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.audit(9)
python: ./Python/sysmodule.c:522: sys_audit: Assertion `PyUnicode_Check(args[0])' failed.
Aborted (core dumped)

This assert seems completely unnecessary, as the code that runs the hooks (which only triggers if there is some hook registered) will raise an exception if the first argument to sys.audit isn't a string:

Python 3.14.0a1+ (heads/remove_sysaudit_assert:ba8ac4d398, Oct 26 2024, 19:45:11) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.addaudithook(lambda *args: None)
>>> sys.audit(9)
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    sys.audit(9)
    ~~~~~~~~~^^^
TypeError: expected str for argument 'event', not int

I'll submit a trivial PR removing this assert.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux, Windows

Output from running 'python -VV' on the command line:

Python 3.14.0a1+ (heads/main:c5b99f5c2c, Oct 26 2024, 12:35:53) [GCC 13.2.0]

Linked PRs

• gh-126018: Avoid aborting due to unnecessary assert in sys.audit #126020
• [3.13] gh-126018: Avoid aborting due to unnecessary assert in sys.audit (GH-126020) #126042

[picnixz]

Ok, 3.12 is actually not affected:

cpython/Python/sysmodule.c

Lines 499 to 514 in 67b2701

	if (!should_audit(tstate->interp)) {
	Py_RETURN_NONE;
	}
	PyObject *auditEvent = args[0];
	if (!auditEvent) {
	_PyErr_SetString(tstate, PyExc_TypeError,
	"expected str for argument 'event'");
	return NULL;
	}
	if (!PyUnicode_Check(auditEvent)) {
	_PyErr_Format(tstate, PyExc_TypeError,
	"expected str for argument 'event', not %.200s",
	Py_TYPE(auditEvent)->tp_name);
	return NULL;
	}

[devdanzin]

Ok, 3.12 is actually not affected:

Hmm. The assert was deliberately added in #108965. @vstinner, what do you think about the proposal to remove the eager assert for non-string argument to sys.audit?

[picnixz]

Closing since completed and backported. Thanks!