From 87e97ae4ad8942bc0cc09174d8964c3e02b6b03b Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Mon, 27 Jun 2022 16:56:37 +0100
Subject: [PATCH 01/11] Add test for creating frame object when making a
 generator.

---
 Lib/test/test_generators.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 87a7dd69d106c4..2e5bff9cc787fe 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -170,6 +170,21 @@ def f():
             g.send(0)
         self.assertEqual(next(g), 1)
 
+    def test_handle_frame_object_in_creation(self):
+
+        def cb(*args):
+            try:
+                sys._getframe(1)
+            except ValueError:
+                pass
+
+        gc.set_threshold(1, 0, 0)
+        gc.callbacks.append(cb)
+
+        def gen():
+            yield 1
+
+        gen()
 
 class ExceptionTest(unittest.TestCase):
     # Tests for the issue #23353: check that the currently handled exception

From 583d16470101800ceac6fc73bb46f37dc853404b Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Mon, 27 Jun 2022 19:39:36 +0100
Subject: [PATCH 02/11] Don't expose incomplete frames as frame objects.

---
 Include/internal/pycore_frame.h |  7 +++++++
 Python/frame.c                  |  8 ++++++--
 Python/sysmodule.c              | 14 +++++++++++---
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/Include/internal/pycore_frame.h b/Include/internal/pycore_frame.h
index eed26fbb06218a..fc29063cbf24e2 100644
--- a/Include/internal/pycore_frame.h
+++ b/Include/internal/pycore_frame.h
@@ -210,6 +210,13 @@ PyGenObject *_PyFrame_GetGenerator(_PyInterpreterFrame *frame)
     return (PyGenObject *)(((char *)frame) - offset_in_gen);
 }
 
+
+static inline bool
+_PyFrame_IsIncomplete(_PyInterpreterFrame *frame)
+{
+    return frame->prev_instr < _PyCode_CODE(frame->f_code) + frame->f_code->_co_firsttraceable;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Python/frame.c b/Python/frame.c
index 206ecab44c1b87..7c6705e208f3d3 100644
--- a/Python/frame.c
+++ b/Python/frame.c
@@ -68,9 +68,13 @@ take_ownership(PyFrameObject *f, _PyInterpreterFrame *frame)
     f->f_frame = frame;
     frame->owner = FRAME_OWNED_BY_FRAME_OBJECT;
     assert(f->f_back == NULL);
-    if (frame->previous != NULL) {
+    _PyInterpreterFrame *prev = frame->previous;
+    while (prev && _PyFrame_IsIncomplete(prev)) {
+        prev = prev->previous;
+    }
+    if (prev) {
         /* Link PyFrameObjects.f_back and remove link through _PyInterpreterFrame.previous */
-        PyFrameObject *back = _PyFrame_GetFrameObject(frame->previous);
+        PyFrameObject *back = _PyFrame_GetFrameObject(prev);
         if (back == NULL) {
             /* Memory error here. */
             assert(PyErr_ExceptionMatches(PyExc_MemoryError));
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 444042f82d9473..93120071b400fd 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1776,9 +1776,17 @@ sys__getframe_impl(PyObject *module, int depth)
         return NULL;
     }
 
-    while (depth > 0 && frame != NULL) {
-        frame = frame->previous;
-        --depth;
+    if (frame != NULL) {
+        while (depth > 0) {
+            frame = frame->previous;
+            if (frame == NULL) {
+                break;
+            }
+            if (_PyFrame_IsIncomplete(frame)) {
+                continue;
+            }
+            --depth;
+        }
     }
     if (frame == NULL) {
         _PyErr_SetString(tstate, PyExc_ValueError,

From 5043a8bd8bf501cf867fa1ad165058e4b23f0774 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 10:08:17 +0100
Subject: [PATCH 03/11] Add news

---
 .../2022-06-28-10-08-06.gh-issue-94262.m-HWUZ.rst              | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-06-28-10-08-06.gh-issue-94262.m-HWUZ.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-06-28-10-08-06.gh-issue-94262.m-HWUZ.rst b/Misc/NEWS.d/next/Core and Builtins/2022-06-28-10-08-06.gh-issue-94262.m-HWUZ.rst
new file mode 100644
index 00000000000000..7ba39bbcfe21da
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-06-28-10-08-06.gh-issue-94262.m-HWUZ.rst	
@@ -0,0 +1,3 @@
+Don't create frame objects for incomplete frames. Prevents the creation of
+generators and closures from being observable to Python and C extensions,
+restoring the behavior of 3.10 and earlier.

From e81c1f35f32b8fe0c0a1a3b254241c5bb9d71371 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 12:57:38 +0100
Subject: [PATCH 04/11] Cleanup after test.

---
 Lib/test/test_generators.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 2e5bff9cc787fe..068a92d9550a14 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -178,13 +178,18 @@ def cb(*args):
             except ValueError:
                 pass
 
-        gc.set_threshold(1, 0, 0)
-        gc.callbacks.append(cb)
-
         def gen():
             yield 1
 
-        gen()
+        thresholds = gc.get_threshold()
+        gc.callbacks.append(cb)
+        gc.set_threshold(1, 0, 0)
+
+        try:
+            gen()
+        finally:
+            gc.set_threshold(*thresholds)
+            gc.callbacks.pop()
 
 class ExceptionTest(unittest.TestCase):
     # Tests for the issue #23353: check that the currently handled exception

From 6d071657e154f627126b30b64696cd0692c15467 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 13:02:06 +0100
Subject: [PATCH 05/11] Explain _PyFrame_IsIncomplete()

---
 Include/internal/pycore_frame.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Include/internal/pycore_frame.h b/Include/internal/pycore_frame.h
index fc29063cbf24e2..2accf903f369bb 100644
--- a/Include/internal/pycore_frame.h
+++ b/Include/internal/pycore_frame.h
@@ -210,7 +210,10 @@ PyGenObject *_PyFrame_GetGenerator(_PyInterpreterFrame *frame)
     return (PyGenObject *)(((char *)frame) - offset_in_gen);
 }
 
-
+/* Determine whether a frame is incomplete.
+ * A frame is incomplete until the first RESUME instruction
+ * as it may be part way through creating cell objects or a
+ * generator or coroutine. */
 static inline bool
 _PyFrame_IsIncomplete(_PyInterpreterFrame *frame)
 {

From ce0d4b5b8d2255ab3e1ae2aaa2ec39e672f84d2a Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 15:21:39 +0100
Subject: [PATCH 06/11] Try harder to break things

---
 Lib/test/test_generators.py | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 068a92d9550a14..d9b2f86882fa15 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -172,11 +172,11 @@ def f():
 
     def test_handle_frame_object_in_creation(self):
 
+        #Attempt to expose partially constructed frames
+        #See https://github.com/python/cpython/issues/94262
+
         def cb(*args):
-            try:
-                sys._getframe(1)
-            except ValueError:
-                pass
+            inspect.stack()
 
         def gen():
             yield 1
@@ -184,13 +184,29 @@ def gen():
         thresholds = gc.get_threshold()
         gc.callbacks.append(cb)
         gc.set_threshold(1, 0, 0)
-
         try:
             gen()
         finally:
             gc.set_threshold(*thresholds)
             gc.callbacks.pop()
 
+        class Sneaky:
+            def __del__(self):
+                raise KeyboardInterrupt
+
+        sneaky = Sneaky()
+        sneaky._s = Sneaky()
+        sneaky._s._s = sneaky
+        del sneaky
+
+        gc.set_threshold(1, 0, 0)
+        try:
+            gen()
+        finally:
+            gc.set_threshold(*thresholds)
+
+
+
 class ExceptionTest(unittest.TestCase):
     # Tests for the issue #23353: check that the currently handled exception
     # is correctly saved/restored in PyEval_EvalFrameEx().

From f56451bc4aea748369d7ba28bff9a28b6e8e4e66 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 15:22:13 +0100
Subject: [PATCH 07/11] Avoid creating frame objects for incomplete frames vai
 f_back.

---
 Objects/frameobject.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 9ff0443e4558f4..44cc06205a6237 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -1169,8 +1169,14 @@ PyFrame_GetBack(PyFrameObject *frame)
 {
     assert(frame != NULL);
     PyFrameObject *back = frame->f_back;
-    if (back == NULL && frame->f_frame->previous != NULL) {
-        back = _PyFrame_GetFrameObject(frame->f_frame->previous);
+    if (back == NULL) {
+        _PyInterpreterFrame *prev = frame->f_frame->previous;
+        while (prev && _PyFrame_IsIncomplete(prev)) {
+            prev = prev->previous;
+        }
+        if (prev) {
+            back = _PyFrame_GetFrameObject(prev);
+        }
     }
     Py_XINCREF(back);
     return back;

From b69e8034d9ee549f5b7816b38056400b64dc6e92 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 16:09:41 +0100
Subject: [PATCH 08/11] Fix test

---
 Lib/test/test_generators.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index d9b2f86882fa15..92f71397486c81 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -182,6 +182,7 @@ def gen():
             yield 1
 
         thresholds = gc.get_threshold()
+
         gc.callbacks.append(cb)
         gc.set_threshold(1, 0, 0)
         try:
@@ -197,11 +198,14 @@ def __del__(self):
         sneaky = Sneaky()
         sneaky._s = Sneaky()
         sneaky._s._s = sneaky
-        del sneaky
 
         gc.set_threshold(1, 0, 0)
         try:
-            gen()
+            del sneaky
+            try:
+                gen()
+            except KeyboardInterrupt:
+                pass
         finally:
             gc.set_threshold(*thresholds)
 

From c648d46ec789782cade7541c5182fc476ce1fe52 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 16:10:09 +0100
Subject: [PATCH 09/11] Assert frame is valid when creating frame object.

---
 Include/internal/pycore_frame.h | 27 +++++++++++++++++----------
 Objects/codeobject.c            | 11 +++++------
 2 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/Include/internal/pycore_frame.h b/Include/internal/pycore_frame.h
index 2accf903f369bb..994c205c3d1644 100644
--- a/Include/internal/pycore_frame.h
+++ b/Include/internal/pycore_frame.h
@@ -134,6 +134,21 @@ _PyFrame_SetStackPointer(_PyInterpreterFrame *frame, PyObject **stack_pointer)
     frame->stacktop = (int)(stack_pointer - frame->localsplus);
 }
 
+/* Determine whether a frame is incomplete.
+ * A frame is incomplete if it is part way through
+ * creating cell objects or a generator or coroutine.
+ *
+ * Frames on the frame stack are incomplete until the
+ * first RESUME instruction.
+ * Frames owned by a generator are always complete.
+ */
+static inline bool
+_PyFrame_IsIncomplete(_PyInterpreterFrame *frame)
+{
+    return frame->owner != FRAME_OWNED_BY_GENERATOR &&
+    frame->prev_instr < _PyCode_CODE(frame->f_code) + frame->f_code->_co_firsttraceable;
+}
+
 /* For use by _PyFrame_GetFrameObject
   Do not call directly. */
 PyFrameObject *
@@ -145,6 +160,8 @@ _PyFrame_MakeAndSetFrameObject(_PyInterpreterFrame *frame);
 static inline PyFrameObject *
 _PyFrame_GetFrameObject(_PyInterpreterFrame *frame)
 {
+
+    assert(!_PyFrame_IsIncomplete(frame));
     PyFrameObject *res =  frame->frame_obj;
     if (res != NULL) {
         return res;
@@ -210,16 +227,6 @@ PyGenObject *_PyFrame_GetGenerator(_PyInterpreterFrame *frame)
     return (PyGenObject *)(((char *)frame) - offset_in_gen);
 }
 
-/* Determine whether a frame is incomplete.
- * A frame is incomplete until the first RESUME instruction
- * as it may be part way through creating cell objects or a
- * generator or coroutine. */
-static inline bool
-_PyFrame_IsIncomplete(_PyInterpreterFrame *frame)
-{
-    return frame->prev_instr < _PyCode_CODE(frame->f_code) + frame->f_code->_co_firsttraceable;
-}
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index c38c51b45321c1..956b2c7fb9c36f 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -638,11 +638,10 @@ PyCode_New(int argcount, int kwonlyargcount,
                                      exceptiontable);
 }
 
-static const char assert0[4] = {
-    LOAD_ASSERTION_ERROR,
-    0,
-    RAISE_VARARGS,
-    1
+static const char assert0[6] = {
+    RESUME, 0,
+    LOAD_ASSERTION_ERROR, 0,
+    RAISE_VARARGS, 1
 };
 
 PyCodeObject *
@@ -666,7 +665,7 @@ PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno)
     if (filename_ob == NULL) {
         goto failed;
     }
-    code_ob = PyBytes_FromStringAndSize(assert0, 4);
+    code_ob = PyBytes_FromStringAndSize(assert0, 6);
     if (code_ob == NULL) {
         goto failed;
     }

From cf0b32c0216357a893e22d0fe93f744c55c49ec7 Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Tue, 28 Jun 2022 16:15:06 +0100
Subject: [PATCH 10/11] Prevent test polluting environment

---
 Lib/test/test_generators.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 92f71397486c81..12ae43e17a54e4 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -193,7 +193,10 @@ def gen():
 
         class Sneaky:
             def __del__(self):
-                raise KeyboardInterrupt
+                try:
+                    raise KeyboardInterrupt
+                except:
+                    pass
 
         sneaky = Sneaky()
         sneaky._s = Sneaky()
@@ -202,10 +205,7 @@ def __del__(self):
         gc.set_threshold(1, 0, 0)
         try:
             del sneaky
-            try:
-                gen()
-            except KeyboardInterrupt:
-                pass
+            gen()
         finally:
             gc.set_threshold(*thresholds)
 

From 939769cab192429916417b8176b8eea069efecee Mon Sep 17 00:00:00 2001
From: Mark Shannon <mark@hotpy.org>
Date: Wed, 29 Jun 2022 11:19:53 +0100
Subject: [PATCH 11/11] Create all frames on stack from finalizer.

---
 Lib/test/test_generators.py | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 12ae43e17a54e4..e5aa7da1e0df13 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -193,10 +193,7 @@ def gen():
 
         class Sneaky:
             def __del__(self):
-                try:
-                    raise KeyboardInterrupt
-                except:
-                    pass
+                inspect.stack()
 
         sneaky = Sneaky()
         sneaky._s = Sneaky()