Resolve the RuntimeWarning from Cython about PyFrameObject changing size.

By simply not typing it at the Cython level at all. No need since we're directing through functions now.

src/gevent/_compat.h

@@ -65,15 +65,27 @@ static PyObject* PyFrame_GetCode(PyFrameObject* frame)
    straightforward. Still, it is critical that the cython declaration of
    this function use ``object`` as its return type.)
  */
-static PyObject* Gevent_PyFrame_GetBack(PyFrameObject* frame)
+static PyObject* Gevent_PyFrame_GetBack(PyObject* frame)
 {
-    PyObject* back = (PyObject*)PyFrame_GetBack(frame);
+    PyObject* back = (PyObject*)PyFrame_GetBack((PyFrameObject*)frame);
     if (back) {
         return back;
     }
     Py_RETURN_NONE;
 }
 
+/* These are just for typing purposes to appease the compiler. */
+
+static int Gevent_PyFrame_GetLineNumber(PyObject* o)
+{
+    return PyFrame_GetLineNumber((PyFrameObject*)o);
+}
+
+static PyObject* Gevent_PyFrame_GetCode(PyObject* o)
+{
+    return (PyObject*)PyFrame_GetCode((PyFrameObject*)o);
+}
+
 #ifdef __cplusplus
 }
 #ifdef __clang__

src/gevent/_gevent_cgreenlet.pxd

@@ -53,17 +53,30 @@ cdef inline void greenlet_init():
         _greenlet_imported = True
 
 ctypedef object CodeType
+ctypedef object FrameType
 
 cdef extern from "_compat.h":
-    int PyFrame_GetLineNumber(FrameType frame)
-    CodeType PyFrame_GetCode(FrameType frame)
+    int Gevent_PyFrame_GetLineNumber(FrameType frame)
+    CodeType Gevent_PyFrame_GetCode(FrameType frame)
     object Gevent_PyFrame_GetBack(FrameType frame)
-    ctypedef class types.FrameType [object PyFrameObject]:
-        pass
+    # We don't do this:
+    #
+    # ctypedef class types.FrameType [object PyFrameObject]:
+    #     pass
+    #
+    # to avoid "RuntimeWarning: types.FrameType size changed, may
+    # indicate binary incompatibility. Expected 56 from C header, got
+    # 120 from PyObject" on Python 3.11. That makes the functions that
+    # really require that kind of object not safe and capable of crashing the
+    # interpreter.
+    #
+    # However, as of cython 3.0a11, that results in a failure to compile if
+    # we have a local variable typed as FrameType, so we can't do that.
+    #
+    # Also, it removes a layer of type checking and makes it possible to crash
+    # the interpreter if you call these functions with something that's not a PyFrameObject.
+    # Don't do that.
 
-@cython.nonecheck(False)
-cdef inline object get_f_back(FrameType frame):
-    return Gevent_PyFrame_GetBack(frame)
 
 cdef void _init()
 
@@ -89,7 +102,7 @@ cdef class _Frame:
 
 
 @cython.final
-@cython.locals(frame=FrameType,
+@cython.locals(# frame=FrameType, # See above about why we cannot do this
                newest_Frame=_Frame,
                newer_Frame=_Frame,
                older_Frame=_Frame)

src/gevent/greenlet.py

@@ -56,9 +56,9 @@ locals()['get_my_hub'] = lambda s: s.parent
 locals()['get_generic_parent'] = lambda s: s.parent
 
 # Frame access
-locals()['PyFrame_GetCode'] = lambda frame: frame.f_code
-locals()['PyFrame_GetLineNumber'] = lambda frame: frame.f_lineno
-locals()['get_f_back'] = lambda frame: frame.f_back
+locals()['Gevent_PyFrame_GetCode'] = lambda frame: frame.f_code
+locals()['Gevent_PyFrame_GetLineNumber'] = lambda frame: frame.f_lineno
+locals()['Gevent_PyFrame_GetBack'] = lambda frame: frame.f_back
 
 
 if _PYPY:
@@ -159,15 +159,15 @@ def _extract_stack(limit):
         # Arguments are always passed to the constructor as Python objects,
         # meaning we wind up boxing the f_lineno just to unbox it if we pass it.
         # It's faster to simply assign once the object is created.
-        older_Frame.f_code = PyFrame_GetCode(frame)  # pylint:disable=undefined-variable
-        older_Frame.f_lineno = PyFrame_GetLineNumber(frame) # pylint:disable=undefined-variable
+        older_Frame.f_code = Gevent_PyFrame_GetCode(frame)  # pylint:disable=undefined-variable
+        older_Frame.f_lineno = Gevent_PyFrame_GetLineNumber(frame) # pylint:disable=undefined-variable
         if newer_Frame is not None:
             newer_Frame.f_back = older_Frame
         newer_Frame = older_Frame
         if newest_Frame is None:
             newest_Frame = newer_Frame
 
-        frame = get_f_back(frame) # pylint:disable=undefined-variable
+        frame = Gevent_PyFrame_GetBack(frame) # pylint:disable=undefined-variable
 
     return newest_Frame