[Backport r51248 | neal.norwitz]

Fix segfault when doing string formatting on subclasses of long if
__oct__, __hex__ don't return a string.

Klocwork 308

3 files changed, 15 insertions, 2 deletions

diff --git a/Lib/test/test_format.py b/Lib/test/test_format.py
index 29594475c2..a9b31707a2 100644
--- a/Lib/test/test_format.py
+++ b/Lib/test/test_format.py
@@ -230,6 +230,14 @@ test_exc(u'no format', '1', TypeError,
 test_exc(u'no format', u'1', TypeError,
          "not all arguments converted during string formatting")
 
+class Foobar(long):
+    def __oct__(self):
+        # Returning a non-string should not blow up.
+        return self + 1
+
+test_exc('%o', Foobar(), TypeError,
+         "expected string or Unicode object, long found")
+
 if sys.maxint == 2**31-1:
     # crashes 2.2.1 and earlier:
     try:
diff --git a/Misc/NEWS b/Misc/NEWS
index 7b7ce1c482..d68e31ff35 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -30,7 +30,9 @@ Core and builtins
 - Fix memory leak of coding spec in Parser/tokenizer.c.
 
 - Fix memory leak in file_init.
- 
+
+- Fix segfault when doing string formatting on subclasses of long.
+
 - Overflow checking code in integer division ran afoul of new gcc
   optimizations.  Changed to be more standard-conforming.
 
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index e7ce15f0c5..9abd6dcf52 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -3665,12 +3665,15 @@ _PyString_FormatLong(PyObject *val, int flags, int prec, int type,
 	if (!result)
 		return NULL;
 
+	buf = PyString_AsString(result);
+	if (!buf)
+		return NULL;
+
 	/* To modify the string in-place, there can only be one reference. */
 	if (result->ob_refcnt != 1) {
 		PyErr_BadInternalCall();
 		return NULL;
 	}
-	buf = PyString_AsString(result);
 	len = PyString_Size(result);
 	if (buf[len-1] == 'L') {
 		--len;