Fix build with Python 3.11

The PyFrameObject structure members have been removed from the public C API.

python/google/protobuf/pyext/descriptor.cc

@@ -58,6 +58,43 @@
               : 0)                                               \
        : PyBytes_AsStringAndSize(ob, (charpp), (sizep)))
 
+#if PY_VERSION_HEX < 0x030900B1 && !defined(PYPY_VERSION)
+static inline PyCodeObject* PyFrame_GetCode(PyFrameObject *frame)
+{
+    Py_INCREF(frame->f_code);
+    return frame->f_code;
+}
+
+static inline PyFrameObject* PyFrame_GetBack(PyFrameObject *frame)
+{
+    Py_XINCREF(frame->f_back);
+    return frame->f_back;
+}
+#endif
+
+#if PY_VERSION_HEX < 0x030B00A7 && !defined(PYPY_VERSION)
+static inline PyObject* PyFrame_GetLocals(PyFrameObject *frame)
+{
+#if PY_VERSION_HEX >= 0x030400B1
+    if (PyFrame_FastToLocalsWithError(frame) < 0) {
+        return NULL;
+    }
+#else
+    PyFrame_FastToLocals(frame);
+#endif
+    Py_INCREF(frame->f_locals);
+    return frame->f_locals;
+}
+#endif
+
+#if PY_VERSION_HEX < 0x030B00A7 && !defined(PYPY_VERSION)
+static inline PyObject* PyFrame_GetGlobals(PyFrameObject *frame)
+{
+    Py_INCREF(frame->f_globals);
+    return frame->f_globals;
+}
+#endif
+
 namespace google {
 namespace protobuf {
 namespace python {
@@ -96,48 +133,66 @@ bool _CalledFromGeneratedFile(int stacklevel) {
   // This check is not critical and is somewhat difficult to implement correctly
   // in PyPy.
   PyFrameObject* frame = PyEval_GetFrame();
+  PyCodeObject* frame_code = nullptr;
+  PyObject* frame_globals = nullptr;
+  PyObject* frame_locals = nullptr;
+  bool result = false;
+
   if (frame == nullptr) {
-    return false;
+    goto exit;
   }
+  Py_INCREF(frame);
   while (stacklevel-- > 0) {
-    frame = frame->f_back;
+    PyFrameObject* next_frame = PyFrame_GetBack(frame);
+    Py_DECREF(frame);
+    frame = next_frame;
     if (frame == nullptr) {
-      return false;
+      goto exit;
     }
   }
 
-  if (frame->f_code->co_filename == nullptr) {
-    return false;
+  frame_code = PyFrame_GetCode(frame);
+  if (frame_code->co_filename == nullptr) {
+    goto exit;
   }
   char* filename;
   Py_ssize_t filename_size;
-  if (PyString_AsStringAndSize(frame->f_code->co_filename,
+  if (PyString_AsStringAndSize(frame_code->co_filename,
                                &filename, &filename_size) < 0) {
     // filename is not a string.
     PyErr_Clear();
-    return false;
+    goto exit;
   }
   if ((filename_size < 3) ||
       (strcmp(&filename[filename_size - 3], ".py") != 0)) {
     // Cython's stack does not have .py file name and is not at global module
     // scope.
-    return true;
+    result = true;
+    goto exit;
   }
   if (filename_size < 7) {
     // filename is too short.
-    return false;
+    goto exit;
   }
   if (strcmp(&filename[filename_size - 7], "_pb2.py") != 0) {
     // Filename is not ending with _pb2.
-    return false;
+    goto exit;
   }
 
-  if (frame->f_globals != frame->f_locals) {
+  frame_globals = PyFrame_GetGlobals(frame);
+  frame_locals = PyFrame_GetLocals(frame);
+  if (frame_globals != frame_locals) {
     // Not at global module scope
-    return false;
+    goto exit;
   }
 #endif
-  return true;
+  result = true;
+exit:
+  Py_XDECREF(frame_globals);
+  Py_XDECREF(frame_locals);
+  Py_XDECREF(frame_code);
+  Py_XDECREF(frame);
+  return result;
 }
 
 // If the calling code is not a _pb2.py file, raise AttributeError.