get_hash_info might potentially swallow errors in sysmodule.c

[sobolevn]

Bug report

cpython/Python/sysmodule.c

Lines 1494 to 1526 in 54bde5d

	static PyObject *
	get_hash_info(PyThreadState *tstate)
	{
	PyObject *hash_info;
	int field = 0;
	PyHash_FuncDef *hashfunc;
	hash_info = PyStructSequence_New(&Hash_InfoType);
	if (hash_info == NULL)
	return NULL;
	hashfunc = PyHash_GetFuncDef();
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(8*sizeof(Py_hash_t)));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromSsize_t(_PyHASH_MODULUS));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(_PyHASH_INF));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(0)); // This is no longer used
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(_PyHASH_IMAG));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyUnicode_FromString(hashfunc->name));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(hashfunc->hash_bits));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(hashfunc->seed_bits));
	PyStructSequence_SET_ITEM(hash_info, field++,
	PyLong_FromLong(Py_HASH_CUTOFF));
	if (_PyErr_Occurred(tstate)) {
	Py_CLEAR(hash_info);
	return NULL;
	}
	return hash_info;

This code only checks for errors in the very last line:

cpython/Python/sysmodule.c

Lines 1522 to 1526 in 54bde5d

	if (_PyErr_Occurred(tstate)) {
	Py_CLEAR(hash_info);
	return NULL;
	}
	return hash_info;

I think that this pattern should not be used. Because it can potentially swallow previous errors on only show the very last one.

I propose to refactor this code to show the first error instead.

Linked PRs

• gh-115320: Refactor get_hash_info in sysmodule.c not to swallow errors #115321
• [3.12] gh-115320: Refactor get_hash_info in sysmodule.c not to swallow errors (GH-115321) #116323
• [3.11] gh-115320: Refactor get_hash_info in sysmodule.c not to swallow errors (GH-115321) #116324