gh-150213: Fix OOM error handling in _interpchannels

Lib/test/test__interpchannels.py

@@ -1838,5 +1838,68 @@ def test_force_close(self):
             fix.clean_up()
 
 
+class InterpChannelsOOMTest(TestBase):
+    def test_create_no_memory(self):
+        _testcapi = import_helper.import_module('_testcapi')
+
+        raised_memoryerror = False
+        for start in range(1, 20):
+            with self.subTest(start=start):
+                cid = None
+                _testcapi.set_nomemory(start, start + 1)
+                try:
+                    try:
+                        cid = _channels.create(REPLACE)
+                    except MemoryError:
+                        raised_memoryerror = True
+                    except SystemError as exc:
+                        self.fail(
+                            f"missing MemoryError at start={start}: {exc}")
+                finally:
+                    _testcapi.remove_mem_hooks()
+                if cid is not None:
+                    _channels.destroy(cid)
+
+        self.assertTrue(
+            raised_memoryerror,
+            "_testcapi.set_nomemory did not trigger a MemoryError from "
+            "_channels.create() within start=1..20; widen range")
+
+    def test_close_nonempty_no_memory(self):
+        _testcapi = import_helper.import_module('_testcapi')
+
+        raised_memoryerror = False
+        for start in range(1, 30):
+            with self.subTest(start=start):
+                cid = _channels.create(REPLACE)
+                try:
+                    _channels.send(cid, b'spam', blocking=False)
+
+                    _testcapi.set_nomemory(start, start + 1)
+                    try:
+                        _channels.close(cid, send=True)
+                    except MemoryError:
+                        raised_memoryerror = True
+                    except SystemError as exc:
+                        self.fail(
+                            f"missing MemoryError at start={start}: {exc}")
+                    finally:
+                        _testcapi.remove_mem_hooks()
+                finally:
+                    try:
+                        _channels.close(cid, force=True)
+                    except Exception:
+                        pass
+                    try:
+                        _channels.destroy(cid)
+                    except Exception:
+                        pass
+
+        self.assertTrue(
+            raised_memoryerror,
+            "_testcapi.set_nomemory did not trigger a MemoryError from "
+            "_channel_set_closing within start=1..30; widen range")
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2026-05-22-10-13-00.gh-issue-150213.Vw3u8K.rst

@@ -0,0 +1,3 @@
+Fix missing :exc:`MemoryError` in several out-of-memory error paths in
+:mod:`!_interpchannels`. Previously these paths could raise
+:exc:`SystemError` or trigger an assertion failure in debug builds.

Modules/_interpchannelsmodule.c

@@ -922,6 +922,7 @@ _channelends_new(void)
 {
     _channelends *ends = GLOBAL_MALLOC(_channelends);
     if (ends== NULL) {
+        PyErr_NoMemory();
         return NULL;
     }
     ends->numsendopen = 0;
@@ -1115,6 +1116,7 @@ _channel_new(PyThread_type_lock mutex, struct _channeldefaults defaults)
     assert(check_unbound(defaults.unboundop));
     _channel_state *chan = GLOBAL_MALLOC(_channel_state);
     if (chan == NULL) {
+        PyErr_NoMemory();
         return NULL;
     }
     chan->mutex = mutex;
@@ -1313,6 +1315,7 @@ _channelref_new(int64_t cid, _channel_state *chan)
 {
     _channelref *ref = GLOBAL_MALLOC(_channelref);
     if (ref == NULL) {
+        PyErr_NoMemory();
         return NULL;
     }
     ref->cid = cid;
@@ -1698,6 +1701,7 @@ _channel_set_closing(_channelref *ref, PyThread_type_lock mutex) {
     }
     chan->closing = GLOBAL_MALLOC(struct _channel_closing);
     if (chan->closing == NULL) {
+        PyErr_NoMemory();
         goto done;
     }
     chan->closing->ref = ref;
@@ -2948,7 +2952,7 @@ channelsmod_create(PyObject *self, PyObject *args, PyObject *kwds)
     if (handle_channel_error(err, self, cid)) {
         assert(cidobj == NULL);
         err = channel_destroy(&_globals.channels, cid);
-        if (handle_channel_error(err, self, cid)) {
+        if (err != 0 && handle_channel_error(err, self, cid)) {
             // XXX issue a warning?
         }
         return NULL;