Stackless issue #253: disable Cython hack starting with Python 3.8.0b1

Disable the support for Cython versions below 0.29.
Starting with Stackless version 3.8.0b1 extension modules compiled with
regular C-Python and Cython versions below 0.29 no longer work with
Stackless Python.

Author: Anselm Kruis

Include/internal/stackless_impl.h

@@ -30,6 +30,18 @@ extern "C" {
  * This would usually be done in place with the assembly macros.
  */
 
+#ifndef SLP_END_OF_OLD_CYTHON_HACK_VERSION
+/*
+ * If PY_VERSION_HEX < SLP_END_OF_OLD_CYTHON_VERSION_HEX support for
+ * Cython versions prior to 0.29 (2018-10-14) is enabled.
+ *
+ * It is a hack for binary compatibility with Cython extension modules, which
+ * were created with an older Cython compiled with regular C-Python.
+ * See Stackless issue #168
+ */
+#define SLP_END_OF_OLD_CYTHON_HACK_VERSION (0x030800b1)
+#endif
+
 /*
  * Macros used to extract bit-field values from an integer in a portable
  * way.

Objects/frameobject.c

@@ -447,7 +447,7 @@ frame_dealloc(PyFrameObject *f)
 
     Py_TRASHCAN_SAFE_BEGIN(f)
 
-#if defined(STACKLESS) && PY_VERSION_HEX < 0x03080000
+#if defined(STACKLESS) && PY_VERSION_HEX < SLP_END_OF_OLD_CYTHON_HACK_VERSION
     /* Clear the magic for the old Cython frame hack.
      * See below in PyFrame_New() for a detailed explanation.
      */
@@ -777,7 +777,7 @@ PyFrame_New(PyThreadState *tstate, PyCodeObject *code,
     PyFrameObject *f = _PyFrame_New_NoTrack(tstate, code, globals, locals);
     if (f) {
         _PyObject_GC_TRACK(f);
-#if defined(STACKLESS) && PY_VERSION_HEX < 0x03080000
+#if defined(STACKLESS) && PY_VERSION_HEX < SLP_END_OF_OLD_CYTHON_HACK_VERSION
         if (code->co_argcount > 0) {
             /*
              * A hack for binary compatibility with Cython extension modules, which

Python/ceval.c

@@ -3955,7 +3955,7 @@ _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
          */
         f->f_execute = PyEval_EvalFrameEx_slp;
 
-#if PY_VERSION_HEX < 0x03080000
+#if PY_VERSION_HEX < SLP_END_OF_OLD_CYTHON_HACK_VERSION
         /* Older versions of Cython used to create frames using C-Python layout
          * of PyFrameObject. As a consequence f_code is overwritten by the first
          * item of f_localsplus[]. To be able to fix it, we have a copy of

Stackless/changelog.txt

@@ -9,6 +9,12 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://github.com/stackless-dev/stackless/issues/253
+  Disable the support for Cython versions below 0.29.
+  Starting with Stackless version 3.8.0b1 extension modules compiled with
+  regular C-Python and Cython versions below 0.29 no longer work with
+  Stackless Python.
+
 - https://github.com/stackless-dev/stackless/issues/231
   Update Stackless related bitbucket.org URLs to github.com
 

Stackless/module/stacklessmodule.c

@@ -1826,6 +1826,9 @@ PyInit__stackless(void)
     INSERT("channel",   &PyChannel_Type);
     INSERT("atomic",    &PyAtomic_Type);
     INSERT("pickle_with_tracing_state", Py_False);
+#if PY_VERSION_HEX < SLP_END_OF_OLD_CYTHON_HACK_VERSION
+    INSERT("_with_old_cython_hack", Py_True);
+#endif
 
     tmp = get_test_nostacklesscallobj();
     if (!tmp)

Stackless/unittests/test_capi.py

@@ -34,7 +34,6 @@
 import glob
 import pickle
 import _teststackless
-
 from support import test_main  # @UnusedImport
 from support import (StacklessTestCase, withThreads, require_one_thread,
                      testcase_leaks_references)
@@ -49,6 +48,12 @@
 else:
     _thread = None
 
+try:
+    from stackless._stackless import _with_old_cython_hack
+except ImportError:
+    _with_old_cython_hack = False
+
+
 
 class Test_PyEval_EvalFrameEx(StacklessTestCase):
     @staticmethod
@@ -169,6 +174,7 @@ def f():
         self.assertIn(str(exc), msg)
         #print(msg)
 
+    @unittest.skipUnless(_with_old_cython_hack, "feature not enabled at compile time")
     def test_oldcython_frame(self):
         # A test for Stackless issue #168
         self.assertEqual(self.call_PyEval_EvalFrameEx(47110816, oldcython=True), 47110816)
@@ -182,7 +188,8 @@ def f2(code):
             return code
 
         self.assertIs(_teststackless.test_PyEval_EvalFrameEx(f.__code__, f.__globals__, (f.__code__,), oldcython=False), f.__code__)
-        self.assertIs(_teststackless.test_PyEval_EvalFrameEx(f.__code__, f.__globals__, (f2.__code__,), oldcython=True), f2.__code__)
+        if _with_old_cython_hack:
+            self.assertIs(_teststackless.test_PyEval_EvalFrameEx(f.__code__, f.__globals__, (f2.__code__,), oldcython=True), f2.__code__)
 
     @testcase_leaks_references("f->f_code get overwritten without Py_DECREF")
     def test_oldcython_frame_code_is_1st_arg_bad(self):