Fix SF bug #667147, Segmentation fault printing str subclass
Fix infinite recursion which occurred when printing an object
whose __str__() returned self.
Will backport
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 023fcc8..da4bd03 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1,6 +1,6 @@
# Test enhancements related to descriptors and new-style classes
-from test.test_support import verify, vereq, verbose, TestFailed, TESTFN
+from test.test_support import verify, vereq, verbose, TestFailed, TESTFN, get_original_stdout
from copy import deepcopy
import warnings
@@ -1821,6 +1821,29 @@
unsafecmp(1, 1L)
unsafecmp(1L, 1)
+ class Letter(str):
+ def __new__(cls, letter):
+ if letter == 'EPS':
+ return str.__new__(cls)
+ return str.__new__(cls, letter)
+ def __str__(self):
+ if not self:
+ return 'EPS'
+ return self
+
+ # sys.stdout needs to be the original to trigger the recursion bug
+ import sys
+ test_stdout = sys.stdout
+ sys.stdout = get_original_stdout()
+ try:
+ # nothing should actually be printed, this should raise an exception
+ print Letter('w')
+ except RuntimeError:
+ pass
+ else:
+ raise TestFailed, "expected a RuntimeError for print recursion"
+ sys.stdout = test_stdout
+
def weakrefs():
if verbose: print "Testing weak references..."
import weakref
diff --git a/Misc/NEWS b/Misc/NEWS
index 1fa1c8c..5f415d4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -18,6 +18,9 @@
Passing None is semantically identical to calling sort() with no
arguments.
+- Fixed crash when printing a subclass of str and __str__ returned self.
+ See SF bug #667147.
+
Extension modules
-----------------
diff --git a/Objects/object.c b/Objects/object.c
index 3328643..e3234de 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -158,10 +158,15 @@
PyObject_FREE(op);
}
-int
-PyObject_Print(PyObject *op, FILE *fp, int flags)
+/* Implementation of PyObject_Print with recursion checking */
+static int
+internal_print(PyObject *op, FILE *fp, int flags, int nesting)
{
int ret = 0;
+ if (nesting > 10) {
+ PyErr_SetString(PyExc_RuntimeError, "print recursion");
+ return -1;
+ }
if (PyErr_CheckSignals())
return -1;
#ifdef USE_STACKCHECK
@@ -187,7 +192,8 @@
if (s == NULL)
ret = -1;
else {
- ret = PyObject_Print(s, fp, Py_PRINT_RAW);
+ ret = internal_print(s, fp, Py_PRINT_RAW,
+ nesting+1);
}
Py_XDECREF(s);
}
@@ -204,6 +210,13 @@
return ret;
}
+int
+PyObject_Print(PyObject *op, FILE *fp, int flags)
+{
+ return internal_print(op, fp, flags, 0);
+}
+
+
/* For debugging convenience. See Misc/gdbinit for some useful gdb hooks */
void _PyObject_Dump(PyObject* op)
{