always instantiate exceptions directly when raising them, fix Py3 crash when...

always instantiate exceptions directly when raising them, fix Py3 crash when an exception type does not create an exception instance (works in Py2, although not in PyPy)

Cython/Utility/Exceptions.c

@@ -60,39 +60,40 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
 #if PY_MAJOR_VERSION < 3
 static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb,
                         CYTHON_UNUSED PyObject *cause) {
-    /* cause is unused */
+    /* 'cause' is only used in Py3 */
     Py_XINCREF(type);
-    Py_XINCREF(value);
-    Py_XINCREF(tb);
-    /* First, check the traceback argument, replacing None with NULL. */
-    if (tb == Py_None) {
-        Py_DECREF(tb);
-        tb = 0;
-    }
-    else if (tb != NULL && !PyTraceBack_Check(tb)) {
-        PyErr_SetString(PyExc_TypeError,
-            "raise: arg 3 must be a traceback or None");
-        goto raise_error;
-    }
-    /* Next, replace a missing value with None */
-    if (value == NULL) {
-        value = Py_None;
+    if (!value || value == Py_None)
+        value = NULL;
+    else
         Py_INCREF(value);
+
+    if (!tb || tb == Py_None)
+        tb = NULL;
+    else {
+        Py_INCREF(tb);
+        if (!PyTraceBack_Check(tb)) {
+            PyErr_SetString(PyExc_TypeError,
+                "raise: arg 3 must be a traceback or None");
+            goto raise_error;
+        }
     }
+
     #if PY_VERSION_HEX < 0x02050000
-    if (!PyClass_Check(type))
+    if (PyClass_Check(type))
     #else
-    if (!PyType_Check(type))
+    if (PyType_Check(type))
     #endif
-    {
+        /* instantiate the type now (we don't know when and how it will be caught) */
+        PyErr_NormalizeException(&type, &value, &tb);
+
+    else {
         /* Raising an instance.  The value should be a dummy. */
-        if (value != Py_None) {
+        if (value) {
             PyErr_SetString(PyExc_TypeError,
                 "instance exception may not have a separate value");
             goto raise_error;
         }
         /* Normalize to raise <class>, <instance> */
-        Py_DECREF(value);
         value = type;
         #if PY_VERSION_HEX < 0x02050000
             if (PyInstance_Check(type)) {
@@ -128,6 +129,7 @@ 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)) {
@@ -146,13 +148,38 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
         }
         value = type;
         type = (PyObject*) Py_TYPE(value);
-    } else if (!PyExceptionClass_Check(type)) {
+    } 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;
+        if (!PyExceptionInstance_Check(value)) {
+            PyErr_Format(PyExc_TypeError,
+                         "calling %R should have returned an instance of "
+                         "BaseException, not %R",
+                         type, Py_TYPE(value));
+            goto bad;
+        }
+    } else {
         PyErr_SetString(PyExc_TypeError,
             "raise: exception class must be a subclass of BaseException");
         goto bad;
     }
 
-    if (cause) {
+    if (cause && cause != Py_None) {
         PyObject *fixed_cause;
         if (PyExceptionClass_Check(cause)) {
             fixed_cause = PyObject_CallObject(cause, NULL);
@@ -169,9 +196,6 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
                             "BaseException");
             goto bad;
         }
-        if (!value) {
-            value = PyObject_CallObject(type, NULL);
-        }
         PyException_SetCause(value, fixed_cause);
     }
 
@@ -188,6 +212,7 @@ static void __Pyx_Raise(PyObject *type, PyObject *value, PyObject *tb, PyObject
     }
 
 bad:
+    Py_XDECREF(owned_instance);
     return;
 }
 #endif

tests/run/broken_exception.pyx

+
+import sys
+
+def exception_creates_invalid_instance():
+    """
+    >>> print( exception_creates_invalid_instance() )
+    OK
+    """
+    class MyException(Exception):
+        def __new__(cls, *args):
+            return object()
+
+    if sys.version_info[0] >= 3:
+        expected_error = TypeError
+    else:
+        expected_error = MyException
+
+    try:
+        raise MyException
+    except expected_error:
+        return "OK"