SF bug 555042: zip() may trigger MemoryError.
NOT a bugfix candidate: this is a fix to an optimization introduced
in 2.3.
diff --git a/Lib/test/test_b2.py b/Lib/test/test_b2.py
index 72810cb..459fd6b 100644
--- a/Lib/test/test_b2.py
+++ b/Lib/test/test_b2.py
@@ -344,7 +344,17 @@
if not exc:
raise TestFailed, 'zip(a, b) - missing expected TypeError'
+# Make sure zip doesn't try to allocate a billion elements for the
+# result list when one of its arguments doesn't say how long it is.
+# A MemoryError is the most likely failure mode.
+class SequenceWithoutALength:
+ def __getitem__(self, i):
+ if i == 5:
+ raise IndexError
+ else:
+ return i
+vereq(zip(SequenceWithoutALength(), xrange(2**30)),
+ list(enumerate(range(5))))
# Epilogue -- unlink the temp file
-
unlink(TESTFN)
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index fb6810e..d0411e2 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1717,13 +1717,18 @@
/* args must be a tuple */
assert(PyTuple_Check(args));
- /* Guess at result length: the shortest of the input lengths. */
+ /* Guess at result length: the shortest of the input lengths.
+ If some argument refuses to say, we refuse to guess too, lest
+ an argument like xrange(sys.maxint) lead us astray.*/
len = -1; /* unknown */
for (i = 0; i < itemsize; ++i) {
PyObject *item = PyTuple_GET_ITEM(args, i);
int thislen = PySequence_Length(item);
- if (thislen < 0)
+ if (thislen < 0) {
PyErr_Clear();
+ len = -1;
+ break;
+ }
else if (len < 0 || thislen < len)
len = thislen;
}