Many places have missing `PyErr_NoMemory()` call after failing memory allocation

[sobolevn]

Crash report

1. remove_unused_consts in Python/flowgraph.c

When PyMem_Malloc(nconsts * sizeof(Py_ssize_t)); fails, we need to set an exception.

cpython/Python/flowgraph.c

Lines 3267 to 3283 in 29a920e

	static int
	remove_unused_consts(basicblock *entryblock, PyObject *consts)
	{
	assert(PyList_CheckExact(consts));
	Py_ssize_t nconsts = PyList_GET_SIZE(consts);
	if (nconsts == 0) {
	return SUCCESS; /* nothing to do */
	}
	Py_ssize_t *index_map = NULL;
	Py_ssize_t *reverse_index_map = NULL;
	int err = ERROR;
	index_map = PyMem_Malloc(nconsts * sizeof(Py_ssize_t));
	if (index_map == NULL) {
	goto end;
	}

Linked PRs

• gh-151126: Fix missing PyErr_NoMemory() in remove_unused_consts #151127
• [3.15] gh-151126: Fix missing PyErr_NoMemory() in remove_unused_consts (GH-151127) #151134
• [3.14] gh-151126: Fix missing PyErr_NoMemory() in remove_unused_consts (GH-151127) #151135
• [3.13] gh-151126: Fix missing PyErr_NoMemory() in remove_unused_consts (GH-151127) #151136
• gh-151126: Add PyErr_NoMemory() in strong_cache_node_new #151137

[sobolevn]

Well, actually a lot of places have the same problem. I will turn this issue into a meta one and will 1 PR per module, so it would be easier to review / backport.

[serhiy-storchaka]

This is probably a new code. Such errors were fixed in old code years ago.