Remove special handling of Pyston v1 (GH-4211)

Looking at the Cython code I spotted a few areas where it contains special paths for Pyston v1.
Pyston v1 only supports python2 and is dead but we did release a new Pyston v2 which is a fork of CPython 3.8.
As we don't currently set `PYSTON_VERSION` in v2 the current code can't trigger and can be removed.

I hoped we would not need any special casing for v2 because it should be fully compatible with CPython but
https://github.com/cython/cython/issues/4200 may temporarily need one but I think the current
code is overkill and if necessary I can add (part of) it back later on.

Cython/Utility/Coroutine.c

@@ -719,7 +719,7 @@ PyObject *__Pyx_Coroutine_SendEx(__pyx_CoroutineObject *self, PyObject *value, i
 
     exc_state = &self->gi_exc_state;
     if (exc_state->exc_type) {
-        #if CYTHON_COMPILING_IN_PYPY || CYTHON_COMPILING_IN_PYSTON
+        #if CYTHON_COMPILING_IN_PYPY
         // FIXME: what to do in PyPy?
         #else
         // Generators always return to their most recent caller, not
@@ -775,7 +775,7 @@ static CYTHON_INLINE void __Pyx_Coroutine_ResetFrameBackpointer(__Pyx_ExcInfoStr
     PyObject *exc_tb = exc_state->exc_traceback;
 
     if (likely(exc_tb)) {
-#if CYTHON_COMPILING_IN_PYPY || CYTHON_COMPILING_IN_PYSTON
+#if CYTHON_COMPILING_IN_PYPY
     // FIXME: what to do in PyPy?
 #else
         PyTracebackObject *tb = (PyTracebackObject *) exc_tb;
@@ -2122,7 +2122,7 @@ static void __Pyx__ReturnWithStopIteration(PyObject* value); /*proto*/
 
 static void __Pyx__ReturnWithStopIteration(PyObject* value) {
     PyObject *exc, *args;
-#if CYTHON_COMPILING_IN_CPYTHON || CYTHON_COMPILING_IN_PYSTON
+#if CYTHON_COMPILING_IN_CPYTHON
     __Pyx_PyThreadState_declare
     if ((PY_VERSION_HEX >= 0x03030000 && PY_VERSION_HEX < 0x030500B1)
             || unlikely(PyTuple_Check(value) || PyExceptionInstance_Check(value))) {

Cython/Utility/CythonFunction.c

@@ -1612,8 +1612,8 @@ static PyObject* __Pyx_Method_ClassMethod(PyObject *method) {
         return PyClassMethod_New(method);
     }
 #else
-#if CYTHON_COMPILING_IN_PYSTON || CYTHON_COMPILING_IN_PYPY
-    // special C-API function only in Pyston and PyPy >= 5.9
+#if CYTHON_COMPILING_IN_PYPY
+    // special C-API function only in PyPy >= 5.9
     if (PyMethodDescr_Check(method))
 #else
     #if PY_MAJOR_VERSION == 2

Cython/Utility/ModuleSetupCode.c

@@ -55,7 +55,6 @@
 
 #ifdef PYPY_VERSION
   #define CYTHON_COMPILING_IN_PYPY 1
-  #define CYTHON_COMPILING_IN_PYSTON 0
   #define CYTHON_COMPILING_IN_CPYTHON 0
   #define CYTHON_COMPILING_IN_LIMITED_API 0
 
@@ -107,64 +106,9 @@
   #undef CYTHON_USE_EXC_INFO_STACK
   #define CYTHON_USE_EXC_INFO_STACK 0
 
-#elif defined(PYSTON_VERSION)
-  #define CYTHON_COMPILING_IN_PYPY 0
-  #define CYTHON_COMPILING_IN_PYSTON 1
-  #define CYTHON_COMPILING_IN_CPYTHON 0
-  #define CYTHON_COMPILING_IN_LIMITED_API 0
-
-  #ifndef CYTHON_USE_TYPE_SLOTS
-    #define CYTHON_USE_TYPE_SLOTS 1
-  #endif
-  #undef CYTHON_USE_TYPE_SPECS
-  #define CYTHON_USE_TYPE_SPECS 0
-  #undef CYTHON_USE_PYTYPE_LOOKUP
-  #define CYTHON_USE_PYTYPE_LOOKUP 0
-  #undef CYTHON_USE_ASYNC_SLOTS
-  #define CYTHON_USE_ASYNC_SLOTS 0
-  #undef CYTHON_USE_PYLIST_INTERNALS
-  #define CYTHON_USE_PYLIST_INTERNALS 0
-  #ifndef CYTHON_USE_UNICODE_INTERNALS
-    #define CYTHON_USE_UNICODE_INTERNALS 1
-  #endif
-  #undef CYTHON_USE_UNICODE_WRITER
-  #define CYTHON_USE_UNICODE_WRITER 0
-  #undef CYTHON_USE_PYLONG_INTERNALS
-  #define CYTHON_USE_PYLONG_INTERNALS 0
-  #ifndef CYTHON_AVOID_BORROWED_REFS
-    #define CYTHON_AVOID_BORROWED_REFS 0
-  #endif
-  #ifndef CYTHON_ASSUME_SAFE_MACROS
-    #define CYTHON_ASSUME_SAFE_MACROS 1
-  #endif
-  #ifndef CYTHON_UNPACK_METHODS
-    #define CYTHON_UNPACK_METHODS 1
-  #endif
-  #undef CYTHON_FAST_THREAD_STATE
-  #define CYTHON_FAST_THREAD_STATE 0
-  #undef CYTHON_FAST_GIL
-  #define CYTHON_FAST_GIL 0
-  #undef CYTHON_METH_FASTCALL
-  #define CYTHON_METH_FASTCALL 0
-  #undef CYTHON_FAST_PYCALL
-  #define CYTHON_FAST_PYCALL 0
-  #undef CYTHON_PEP487_INIT_SUBCLASS
-  #define CYTHON_PEP487_INIT_SUBCLASS 0
-  #undef CYTHON_PEP489_MULTI_PHASE_INIT
-  #define CYTHON_PEP489_MULTI_PHASE_INIT 0
-  #undef CYTHON_USE_MODULE_STATE
-  #define CYTHON_USE_MODULE_STATE 0
-  #undef CYTHON_USE_TP_FINALIZE
-  #define CYTHON_USE_TP_FINALIZE 0
-  #undef CYTHON_USE_DICT_VERSIONS
-  #define CYTHON_USE_DICT_VERSIONS 0
-  #undef CYTHON_USE_EXC_INFO_STACK
-  #define CYTHON_USE_EXC_INFO_STACK 0
-
 #elif defined(CYTHON_LIMITED_API)
   // EXPERIMENTAL !!
   #define CYTHON_COMPILING_IN_PYPY 0
-  #define CYTHON_COMPILING_IN_PYSTON 0
   #define CYTHON_COMPILING_IN_CPYTHON 0
   #define CYTHON_COMPILING_IN_LIMITED_API 1
 
@@ -217,7 +161,6 @@
 
 #else
   #define CYTHON_COMPILING_IN_PYPY 0
-  #define CYTHON_COMPILING_IN_PYSTON 0
   #define CYTHON_COMPILING_IN_CPYTHON 1
   #define CYTHON_COMPILING_IN_LIMITED_API 0
 
@@ -625,11 +568,7 @@ class __Pyx_FakeReference {
   #define PyMem_RawFree(p)             PyMem_Free(p)
 #endif
 
-#if CYTHON_COMPILING_IN_PYSTON
-  // special C-API functions only in Pyston
-  #define __Pyx_PyCode_HasFreeVars(co)  PyCode_HasFreeVars(co)
-  #define __Pyx_PyFrame_SetLineNumber(frame, lineno) PyFrame_SetLineNumber(frame, lineno)
-#elif CYTHON_COMPILING_IN_LIMITED_API
+#if CYTHON_COMPILING_IN_LIMITED_API
   #define __Pyx_PyCode_HasFreeVars(co)  (PyCode_GetNumFree(co) > 0)
   #define __Pyx_PyFrame_SetLineNumber(frame, lineno)
 #else

Cython/Utility/Profile.c

@@ -6,7 +6,7 @@
 // but maybe some other profilers don't.
 
 #ifndef CYTHON_PROFILE
-#if CYTHON_COMPILING_IN_LIMITED_API || CYTHON_COMPILING_IN_PYPY || CYTHON_COMPILING_IN_PYSTON
+#if CYTHON_COMPILING_IN_LIMITED_API || CYTHON_COMPILING_IN_PYPY
   #define CYTHON_PROFILE 0
 #else
   #define CYTHON_PROFILE 1

tests/compile/buildenv.pyx

@@ -36,7 +36,6 @@ cdef extern from *:
     cdef int CYTHON_COMPILING_IN_CPYTHON
     cdef int CYTHON_COMPILING_IN_LIMITED_API
     cdef int CYTHON_COMPILING_IN_PYPY
-    cdef int CYTHON_COMPILING_IN_PYSTON
     cdef int CYTHON_USE_PYLONG_INTERNALS
     cdef int CYTHON_USE_PYLIST_INTERNALS
     cdef int CYTHON_USE_UNICODE_INTERNALS
@@ -80,7 +79,6 @@ PY_VERSION_HEX  0x{PY_VERSION_HEX:X}
 CYTHON_COMPILING_IN_CPYTHON  {CYTHON_COMPILING_IN_CPYTHON}
 CYTHON_COMPILING_IN_LIMITED_API  {CYTHON_COMPILING_IN_LIMITED_API}
 CYTHON_COMPILING_IN_PYPY  {CYTHON_COMPILING_IN_PYPY}
-CYTHON_COMPILING_IN_PYSTON  {CYTHON_COMPILING_IN_PYSTON}
 
 CYTHON_USE_PYLONG_INTERNALS  {CYTHON_USE_PYLONG_INTERNALS}
 CYTHON_USE_PYLIST_INTERNALS  {CYTHON_USE_PYLIST_INTERNALS}