gh-118926: Spill deferred references to stack in cases generator (#122748)

This automatically spills the results from `_PyStackRef_FromPyObjectNew`
to the in-memory stack so that the deferred references are visible to
the GC before we make any possibly escaping call.

Co-authored-by: Ken Jin <kenjin@python.org>

1 files changed, 23 insertions, 17 deletions

diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h
index 5890fcea8e6..31f95eb4686 100644
--- a/Python/generated_cases.c.h
+++ b/Python/generated_cases.c.h
@@ -867,8 +867,10 @@
                     PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
                     PyObject *self = ((PyMethodObject *)callable_o)->im_self;
                     maybe_self = PyStackRef_FromPyObjectNew(self);
+                    stack_pointer[-1 - oparg] = maybe_self;
                     PyObject *method = ((PyMethodObject *)callable_o)->im_func;
                     func = PyStackRef_FromPyObjectNew(method);
+                    stack_pointer[-2 - oparg] = func;
                     /* Make sure that callable and all args are in memory */
                     args[-2] = func;
                     args[-1] = maybe_self;
@@ -1063,12 +1065,12 @@
                 PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
                 STAT_INC(CALL, hit);
                 self = PyStackRef_FromPyObjectNew(((PyMethodObject *)callable_o)->im_self);
+                stack_pointer[-1 - oparg] = self;
                 func = PyStackRef_FromPyObjectNew(((PyMethodObject *)callable_o)->im_func);
+                stack_pointer[-2 - oparg] = func;
                 PyStackRef_CLOSE(callable);
             }
             // flush
-            stack_pointer[-2 - oparg] = func;
-            stack_pointer[-1 - oparg] = self;
             // _CHECK_FUNCTION_VERSION
             callable = stack_pointer[-2 - oparg];
             {
@@ -1172,13 +1174,13 @@
                 assert(PyStackRef_IsNull(null));
                 assert(Py_TYPE(callable_o) == &PyMethod_Type);
                 self = PyStackRef_FromPyObjectNew(((PyMethodObject *)callable_o)->im_self);
+                stack_pointer[-1 - oparg] = self;
                 method = PyStackRef_FromPyObjectNew(((PyMethodObject *)callable_o)->im_func);
+                stack_pointer[-2 - oparg] = method;
                 assert(PyStackRef_FunctionCheck(method));
                 PyStackRef_CLOSE(callable);
             }
             // flush
-            stack_pointer[-2 - oparg] = method;
-            stack_pointer[-1 - oparg] = self;
             // _PY_FRAME_GENERAL
             args = &stack_pointer[-oparg];
             self_or_null = stack_pointer[-1 - oparg];
@@ -2534,6 +2536,7 @@
             int matches = PyErr_GivenExceptionMatches(exc_value, PyExc_StopIteration);
             if (matches) {
                 value = PyStackRef_FromPyObjectNew(((PyStopIterationObject *)exc_value)->value);
+                stack_pointer[-2] = value;
                 PyStackRef_CLOSE(sub_iter_st);
                 PyStackRef_CLOSE(last_sent_val_st);
                 PyStackRef_CLOSE(exc_value_st);
@@ -2545,7 +2548,6 @@
                 goto exception_unwind;
             }
             stack_pointer[-3] = none;
-            stack_pointer[-2] = value;
             stack_pointer += -1;
             assert(WITHIN_STACK_BOUNDS());
             DISPATCH();
@@ -3330,8 +3332,8 @@
                 assert(seq);
                 assert(it->it_index < PyList_GET_SIZE(seq));
                 next = PyStackRef_FromPyObjectNew(PyList_GET_ITEM(seq, it->it_index++));
+                stack_pointer[0] = next;
             }
-            stack_pointer[0] = next;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
             DISPATCH();
@@ -3423,8 +3425,8 @@
                 assert(seq);
                 assert(it->it_index < PyTuple_GET_SIZE(seq));
                 next = PyStackRef_FromPyObjectNew(PyTuple_GET_ITEM(seq, it->it_index++));
+                stack_pointer[0] = next;
             }
-            stack_pointer[0] = next;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
             DISPATCH();
@@ -3634,8 +3636,10 @@
                     PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
                     PyObject *self = ((PyMethodObject *)callable_o)->im_self;
                     maybe_self = PyStackRef_FromPyObjectNew(self);
+                    stack_pointer[-1 - oparg] = maybe_self;
                     PyObject *method = ((PyMethodObject *)callable_o)->im_func;
                     func = PyStackRef_FromPyObjectNew(method);
+                    stack_pointer[-2 - oparg] = func;
                     /* Make sure that callable and all args are in memory */
                     args[-2] = func;
                     args[-1] = maybe_self;
@@ -4071,6 +4075,7 @@
             // _LOAD_CONST
             {
                 value = PyStackRef_FromPyObjectNew(GETITEM(FRAME_CO_CONSTS, oparg));
+                stack_pointer[0] = value;
             }
             // _RETURN_VALUE_EVENT
             val = value;
@@ -4453,10 +4458,10 @@
                 STAT_INC(LOAD_ATTR, hit);
                 assert(descr != NULL);
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
                 null = PyStackRef_NULL;
                 PyStackRef_CLOSE(owner);
             }
-            stack_pointer[-1] = attr;
             if (oparg & 1) stack_pointer[0] = null;
             stack_pointer += (oparg & 1);
             assert(WITHIN_STACK_BOUNDS());
@@ -4577,9 +4582,9 @@
                 assert(descr != NULL);
                 assert(_PyType_HasFeature(Py_TYPE(descr), Py_TPFLAGS_METHOD_DESCRIPTOR));
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
                 self = owner;
             }
-            stack_pointer[-1] = attr;
             stack_pointer[0] = self;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
@@ -4613,9 +4618,9 @@
                 assert(descr != NULL);
                 assert(_PyType_HasFeature(Py_TYPE(descr), Py_TPFLAGS_METHOD_DESCRIPTOR));
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
                 self = owner;
             }
-            stack_pointer[-1] = attr;
             stack_pointer[0] = self;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
@@ -4661,9 +4666,9 @@
                 assert(descr != NULL);
                 assert(_PyType_HasFeature(Py_TYPE(descr), Py_TPFLAGS_METHOD_DESCRIPTOR));
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
                 self = owner;
             }
-            stack_pointer[-1] = attr;
             stack_pointer[0] = self;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
@@ -4739,8 +4744,8 @@
                 assert(descr != NULL);
                 PyStackRef_CLOSE(owner);
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
             }
-            stack_pointer[-1] = attr;
             DISPATCH();
         }
 
@@ -4781,8 +4786,8 @@
                 assert(descr != NULL);
                 PyStackRef_CLOSE(owner);
                 attr = PyStackRef_FromPyObjectNew(descr);
+                stack_pointer[-1] = attr;
             }
-            stack_pointer[-1] = attr;
             DISPATCH();
         }
 
@@ -4878,10 +4883,10 @@
                 STAT_INC(LOAD_ATTR, hit);
                 null = PyStackRef_NULL;
                 attr = PyStackRef_FromPyObjectNew(attr_o);
+                stack_pointer[-1] = attr;
                 PyStackRef_CLOSE(owner);
             }
             /* Skip 5 cache entries */
-            stack_pointer[-1] = attr;
             if (oparg & 1) stack_pointer[0] = null;
             stack_pointer += (oparg & 1);
             assert(WITHIN_STACK_BOUNDS());
@@ -5290,7 +5295,7 @@
                                  "no locals found");
                 if (true) goto error;
             }
-            locals = PyStackRef_FromPyObjectNew(l);;
+            locals = PyStackRef_FromPyObjectNew(l);
             stack_pointer[0] = locals;
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
@@ -5958,6 +5963,7 @@
             // _LOAD_CONST
             {
                 value = PyStackRef_FromPyObjectNew(GETITEM(FRAME_CO_CONSTS, oparg));
+                stack_pointer[0] = value;
             }
             // _RETURN_VALUE
             retval = value;
@@ -7018,10 +7024,10 @@
             DEOPT_IF(PyTuple_GET_SIZE(seq_o) != 2, UNPACK_SEQUENCE);
             STAT_INC(UNPACK_SEQUENCE, hit);
             val0 = PyStackRef_FromPyObjectNew(PyTuple_GET_ITEM(seq_o, 0));
+            stack_pointer[0] = val0;
             val1 = PyStackRef_FromPyObjectNew(PyTuple_GET_ITEM(seq_o, 1));
-            PyStackRef_CLOSE(seq);
             stack_pointer[-1] = val1;
-            stack_pointer[0] = val0;
+            PyStackRef_CLOSE(seq);
             stack_pointer += 1;
             assert(WITHIN_STACK_BOUNDS());
             DISPATCH();