Issue #6083: Fix multiple segmentation faults occured when PyArg_ParseTuple

parses nested mutating sequence.

Lib/test/test_resource.py

@@ -107,6 +107,23 @@ class ResourceTest(unittest.TestCase):
         except (ValueError, AttributeError):
             pass
 
+    # Issue 6083: Reference counting bug
+    def test_setrusage_refcount(self):
+        try:
+            limits = resource.getrlimit(resource.RLIMIT_CPU)
+        except AttributeError:
+            pass
+        else:
+            class BadSequence:
+                def __len__(self):
+                    return 2
+                def __getitem__(self, key):
+                    if key in (0, 1):
+                        return len(tuple(range(1000000)))
+                    raise IndexError
+
+            resource.setrlimit(resource.RLIMIT_CPU, BadSequence())
+
 def test_main(verbose=None):
     support.run_unittest(ResourceTest)