let CPython do the exception instantiation on 'raise' in Py3 to make sure we...

let CPython do the exception instantiation on 'raise' in Py3 to make sure we handle all special cases correctly

Cython/Utility/Exceptions.c

@@ -135,7 +135,6 @@ raise_error:
 #else /* Python 3+ */
 
 static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject *cause) {
-    PyObject* owned_instance = NULL;
     if (tb == Py_None) {
         tb = 0;
     } else if (tb && !PyTraceBack_Check(tb)) {
@@ -143,11 +142,9 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
             "raise: arg 3 must be a traceback or None");
         goto bad;
     }
-    if (value == Py_None)
-        value = 0;
 
     if (PyExceptionInstance_Check(type)) {
-        if (value) {
+        if (value && value != Py_None) {
             PyErr_SetString(PyExc_TypeError,
                 "instance exception may not have a separate value");
             goto bad;
@@ -156,21 +153,7 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
         type = (PyObject*) Py_TYPE(value);
     } else if (PyExceptionClass_Check(type)) {
         // instantiate the type now (we don't know when and how it will be caught)
-        PyObject *args;
-        if (!value)
-            args = PyTuple_New(0);
-        else if (PyTuple_Check(value)) {
-            Py_INCREF(value);
-            args = value;
-        } else
-            args = PyTuple_Pack(1, value);
-        if (!args)
-            goto bad;
-        owned_instance = PyEval_CallObject(type, args);
-        Py_DECREF(args);
-        if (!owned_instance)
-            goto bad;
-        value = owned_instance;
+        PyErr_NormalizeException(&type, &value, &tb);
         if (!PyExceptionInstance_Check(value)) {
             PyErr_Format(PyExc_TypeError,
                          "calling %R should have returned an instance of "
@@ -222,7 +205,6 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
     }
 
 bad:
-    Py_XDECREF(owned_instance);
     return;
 }
 #endif

tests/run/reraise_3args.pyx

+
+import sys
+
+
+class MyError(Exception):
+    def __init__(self, name, var):
+        self.name = name
+        self.var = var
+
+
+def reraise_explicitly():
+    """
+    >>> try: reraise_explicitly()
+    ... except MyError: print("RAISED!")
+    ... else: print("NOT RAISED!")
+    RAISED!
+    """
+    try:
+        raise MyError('Oh no!', 42)
+    except MyError:
+        tmp = sys.exc_info()
+
+    raise tmp[0], tmp[1], tmp[2]