adapt METH_FASTCALL handling to signature change of _PyCFunctionFast() in Py3.7

Cython/Utility/ModuleSetupCode.c

@@ -196,17 +196,22 @@
   #define Py_TPFLAGS_HAVE_FINALIZE 0
 #endif
 
-#ifndef METH_FASTCALL
-  // new in CPython 3.6
+#if PY_VERSION_HEX < 0x030700A0 || !defined(METH_FASTCALL)
+  // new in CPython 3.6, but changed in 3.7
+  #ifndef METH_FASTCALL
      #define METH_FASTCALL 0x80
-  typedef PyObject *(*__Pyx_PyCFunctionFast) (PyObject *self, PyObject **args,
+  #endif
+  typedef PyObject *(*__Pyx_PyCFunctionFast) (PyObject *self, PyObject **args, Py_ssize_t nargs);
+  // new in CPython 3.7, used to be old signature of _PyCFunctionFast() in 3.6
+  typedef PyObject *(*__Pyx_PyCFunctionFastWithKeywords) (PyObject *self, PyObject **args,
                                                           Py_ssize_t nargs, PyObject *kwnames);
 #else
   #define __Pyx_PyCFunctionFast _PyCFunctionFast
+  #define __Pyx_PyCFunctionFastWithKeywords _PyCFunctionFastWithKeywords
 #endif
 #if CYTHON_FAST_PYCCALL
 #define __Pyx_PyFastCFunction_Check(func) \
-    ((PyCFunction_Check(func) && (METH_FASTCALL == (PyCFunction_GET_FLAGS(func) & ~(METH_CLASS | METH_STATIC | METH_COEXIST)))))
+    ((PyCFunction_Check(func) && (METH_FASTCALL == (PyCFunction_GET_FLAGS(func) & ~(METH_CLASS | METH_STATIC | METH_COEXIST | METH_KEYWORDS)))))
 #else
 #define __Pyx_PyFastCFunction_Check(func) 0
 #endif

Cython/Utility/ObjectHandling.c

@@ -1146,8 +1146,13 @@ static PyObject* __Pyx__CallUnboundCMethod0(__Pyx_CachedCFunction* cfunc, PyObje
         (likely((cfunc)->flag == METH_NOARGS) ?  (*((cfunc)->func))(self, NULL) : \
          (likely((cfunc)->flag == (METH_VARARGS | METH_KEYWORDS)) ?  ((*(PyCFunctionWithKeywords)(cfunc)->func)(self, $empty_tuple, NULL)) : \
              ((cfunc)->flag == METH_VARARGS ?  (*((cfunc)->func))(self, $empty_tuple) : \
-              (PY_VERSION_HEX >= 0x030600B1 && (cfunc)->flag == METH_FASTCALL ?  (*(__Pyx_PyCFunctionFast)(cfunc)->func)(self, &PyTuple_GET_ITEM($empty_tuple, 0), 0, NULL) : \
-                __Pyx__CallUnboundCMethod0(cfunc, self))))) : \
+              (PY_VERSION_HEX >= 0x030600B1 && (cfunc)->flag == METH_FASTCALL ? \
+                (PY_VERSION_HEX >= 0x030700A0 ? \
+                    (*(__Pyx_PyCFunctionFast)(cfunc)->func)(self, &PyTuple_GET_ITEM($empty_tuple, 0), 0) : \
+                    (*(__Pyx_PyCFunctionFastWithKeywords)(cfunc)->func)(self, &PyTuple_GET_ITEM($empty_tuple, 0), 0, NULL)) : \
+              (PY_VERSION_HEX >= 0x030700A0 && (cfunc)->flag == (METH_FASTCALL | METH_KEYWORDS) ? \
+                    (*(__Pyx_PyCFunctionFastWithKeywords)(cfunc)->func)(self, &PyTuple_GET_ITEM($empty_tuple, 0), 0, NULL) : \
+                    __Pyx__CallUnboundCMethod0(cfunc, self)))))) : \
         __Pyx__CallUnboundCMethod0(cfunc, self))
 #else
 #define __Pyx_CallUnboundCMethod0(cfunc, self)  __Pyx__CallUnboundCMethod0(cfunc, self)
@@ -1642,9 +1647,10 @@ static CYTHON_INLINE PyObject * __Pyx_PyCFunction_FastCall(PyObject *func_obj, P
     PyCFunctionObject *func = (PyCFunctionObject*)func_obj;
     PyCFunction meth = PyCFunction_GET_FUNCTION(func);
     PyObject *self = PyCFunction_GET_SELF(func);
+    int flags = PyCFunction_GET_FLAGS(func);
 
     assert(PyCFunction_Check(func));
-    assert(METH_FASTCALL == (PyCFunction_GET_FLAGS(func) & ~(METH_CLASS | METH_STATIC | METH_COEXIST)));
+    assert(METH_FASTCALL == (flags & ~(METH_CLASS | METH_STATIC | METH_COEXIST | METH_KEYWORDS)));
     assert(nargs >= 0);
     assert(nargs == 0 || args != NULL);
 
@@ -1653,7 +1659,11 @@ static CYTHON_INLINE PyObject * __Pyx_PyCFunction_FastCall(PyObject *func_obj, P
        caller loses its exception */
     assert(!PyErr_Occurred());
 
-    return (*((__Pyx_PyCFunctionFast)meth)) (self, args, nargs, NULL);
+    if ((PY_VERSION_HEX < 0x030700A0) || unlikely(flags & METH_KEYWORDS)) {
+        return (*((__Pyx_PyCFunctionFastWithKeywords)meth)) (self, args, nargs, NULL);
+    } else {
+        return (*((__Pyx_PyCFunctionFast)meth)) (self, args, nargs);
+    }
 }
 #endif  /* CYTHON_FAST_PYCCALL */