Remove Stackless hack for looking up "PyFrameObject.f_localsplus" from...

Remove Stackless hack for looking up "PyFrameObject.f_localsplus" from Stackless 3.8 on. CPython never needed this.

Closes https://github.com/cython/cython/issues/4329

.github/workflows/ci.yml

@@ -121,6 +121,11 @@ jobs:
             backend: c
             env: { STACKLESS: true, PY: 3 }
             extra_hash: "-stackless"
+          - os: ubuntu-18.04
+            python-version: 3.8
+            backend: c
+            env: { STACKLESS: true, PY: 3 }
+            extra_hash: "-stackless"
           # Pypy
           - os: ubuntu-18.04
             python-version: pypy-2.7

Cython/Utility/ObjectHandling.c

@@ -2442,13 +2442,18 @@ static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args,
 #endif
 
 #if !CYTHON_VECTORCALL
+#if PY_VERSION_HEX >= 0x03080000
+  #include "frameobject.h"
+  #define __Pxy_PyFrame_Initialize_Offsets()
+  #define __Pyx_PyFrame_GetLocalsplus(frame)  ((frame)->f_localsplus)
+#else
   // Initialised by module init code.
   static size_t __pyx_pyframe_localsplus_offset = 0;
 
   #include "frameobject.h"
   // This is the long runtime version of
   //     #define __Pyx_PyFrame_GetLocalsplus(frame)  ((frame)->f_localsplus)
-  // offsetof(PyFrameObject, f_localsplus) differs between regular C-Python and Stackless Python.
+  // offsetof(PyFrameObject, f_localsplus) differs between regular C-Python and Stackless Python < 3.8.
   // Therefore the offset is computed at run time from PyFrame_type.tp_basicsize. That is feasible,
   // because f_localsplus is the last field of PyFrameObject (checked by Py_BUILD_ASSERT_EXPR below).
   #define __Pxy_PyFrame_Initialize_Offsets()  \
@@ -2456,8 +2461,10 @@ static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args,
      (void)(__pyx_pyframe_localsplus_offset = ((size_t)PyFrame_Type.tp_basicsize) - Py_MEMBER_SIZE(PyFrameObject, f_localsplus)))
   #define __Pyx_PyFrame_GetLocalsplus(frame)  \
     (assert(__pyx_pyframe_localsplus_offset), (PyObject **)(((char *)(frame)) + __pyx_pyframe_localsplus_offset))
-#endif // !CYTHON_VECTORCALL
 #endif
+#endif /* !CYTHON_VECTORCALL */
+
+#endif /* CYTHON_FAST_PYCALL */
 
 
 /////////////// PyFunctionFastCall ///////////////