`traverse_module_state` can return `int`, do not use `(void)` for it

[sobolevn]

Bug report

traverse_module_state can in theory return non-zero code:

cpython/Modules/_interpchannelsmodule.c

Lines 283 to 302 in 0d9d489

	static int
	traverse_module_state(module_state *state, visitproc visit, void *arg)
	{
	/* external types */
	Py_VISIT(state->send_channel_type);
	Py_VISIT(state->recv_channel_type);
	/* heap types */
	Py_VISIT(state->ChannelInfoType);
	Py_VISIT(state->ChannelIDType);
	/* exceptions */
	Py_VISIT(state->ChannelError);
	Py_VISIT(state->ChannelNotFoundError);
	Py_VISIT(state->ChannelClosedError);
	Py_VISIT(state->ChannelEmptyError);
	Py_VISIT(state->ChannelNotEmptyError);
	return 0;
	}

because PY_VISIT can return it:

cpython/Include/objimpl.h

Lines 193 to 200 in 0d9d489

	#define Py_VISIT(op) \
	do { \
	if (op) { \
	int vret = visit(_PyObject_CAST(op), arg); \
	if (vret) \
	return vret; \
	} \
	} while (0)

So, using it like this:

cpython/Modules/_interpchannelsmodule.c

Lines 3627 to 3629 in 0d9d489

	// Now we clear the module state.
	(void)clear_module_state(state);
	return 0;

Is also not really correct. I will send a PR with the fix.

Linked PRs

• gh-135839: Fix traverse_module_state usage in _interpchannelsmodule #135840

[brianschubert]

FWIW, I peaked at the git blame, and I didn't find any discussions in the past PRs about wanting to ignore the return value