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bpo-28994: PyErr_NormalizeException() no longer recursive. #2035

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Merged
serhiy-storchaka merged 4 commits into from
Nov 5, 2017
Merged

bpo-28994: PyErr_NormalizeException() no longer recursive. #2035

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4dcbd8f
bpo-28994: PyErr_NormalizeException() no longer recursive.
serhiy-storchaka Jun 9, 2017
31d42cf
Merge branch 'master' into PyErr_NormalizeException-nonrecursive
serhiy-storchaka Oct 26, 2017
0386148
Merge branch 'master' into PyErr_NormalizeException-nonrecursive
serhiy-storchaka Nov 4, 2017
9a6bcbd
Clean up the code and take a chance MemoryError raised by normalizing…
serhiy-storchaka Nov 4, 2017
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34 changes: 20 additions & 14 deletions Python/errors.c
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Original file line number Diff line number Diff line change
Expand Up @@ -226,17 +226,18 @@ PyErr_ExceptionMatches(PyObject *exc)
void
PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
{
PyObject *type = *exc;
PyObject *value = *val;
PyObject *inclass = NULL;
PyObject *initial_tb = NULL;
PyThreadState *tstate = NULL;
int recursion_depth = 0;
PyObject *type, *value, *initial_tb;
PyThreadState *tstate;

restart:
type = *exc;
if (type == NULL) {
/* There was no exception, so nothing to do. */
return;
}

value = *val;
/* If PyErr_SetNone() was used, the value will have been actually
set to NULL.
*/
Expand All @@ -245,14 +246,18 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
Py_INCREF(value);
}

if (PyExceptionInstance_Check(value))
inclass = PyExceptionInstance_Class(value);

/* Normalize the exception so that if the type is a class, the
value will be an instance.
*/
if (PyExceptionClass_Check(type)) {
PyObject *inclass;
int is_subclass;

if (PyExceptionInstance_Check(value))
inclass = PyExceptionInstance_Class(value);
else
inclass = NULL;

if (inclass) {
is_subclass = PyObject_IsSubclass(inclass, type);
if (is_subclass < 0)
Expand All @@ -266,7 +271,7 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
value as an argument to instantiation of the type
class.
*/
if (!inclass || !is_subclass) {
if (!is_subclass) {
PyObject *fixed_value;

fixed_value = _PyErr_CreateException(type, value);
Expand All @@ -289,6 +294,7 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
*exc = type;
*val = value;
return;

finally:
Py_DECREF(type);
Py_DECREF(value);
Expand All @@ -298,6 +304,7 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
*/
initial_tb = *tb;
PyErr_Fetch(exc, val, tb);
assert(*exc != NULL);
if (initial_tb != NULL) {
if (*tb == NULL)
*tb = initial_tb;
Expand All @@ -306,18 +313,17 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
}
/* normalize recursively */

@pitrou pitrou Jun 13, 2017

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Update this comment perhaps?

tstate = PyThreadState_GET();
if (++tstate->recursion_depth > Py_GetRecursionLimit()) {
--tstate->recursion_depth;
if (++recursion_depth > Py_GetRecursionLimit() - tstate->recursion_depth) {

@pitrou pitrou Jun 13, 2017

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Since the function isn't recursive anymore, is there any reason you're still bothering with recursion_depth?

@serhiy-storchaka serhiy-storchaka Jun 14, 2017

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A guard against infinite loop.

/* throw away the old exception and use the recursion error instead */
Py_INCREF(PyExc_RecursionError);
Py_SETREF(*exc, PyExc_RecursionError);
Py_INCREF(PyExc_RecursionErrorInst);
Py_SETREF(*val, PyExc_RecursionErrorInst);
Py_XSETREF(*val, PyExc_RecursionErrorInst);
/* just keeping the old traceback */
return;
}
PyErr_NormalizeException(exc, val, tb);
--tstate->recursion_depth;
/* eliminate tail recursion */
goto restart;
}


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