Issue #11286: Fixed unpickling of empty 2.x strings.

Lib/test/pickletester.py

@@ -1094,6 +1094,10 @@ class AbstractPickleTests(unittest.TestCase):
             self.assertEqual(len(loaded), len(data))
             self.assertEqual(loaded, data)
 
+    def test_empty_bytestring(self):
+        # issue 11286
+        empty = self.loads(b'\x80\x03U\x00q\x00.', encoding='koi8-r')
+        self.assertEqual(empty, '')
 
 # Test classes for reduce_ex
 

Lib/test/test_pickle.py

@@ -31,9 +31,9 @@ class PyPicklerTests(AbstractPickleTests):
         f.seek(0)
         return bytes(f.read())
 
-    def loads(self, buf):
+    def loads(self, buf, **kwds):
         f = io.BytesIO(buf)
-        u = self.unpickler(f)
+        u = self.unpickler(f, **kwds)
         return u.load()
 
 
@@ -45,8 +45,8 @@ class InMemoryPickleTests(AbstractPickleTests):
     def dumps(self, arg, proto=None):
         return pickle.dumps(arg, proto)
 
-    def loads(self, buf):
-        return pickle.loads(buf)
+    def loads(self, buf, **kwds):
+        return pickle.loads(buf, **kwds)
 
 
 class PyPersPicklerTests(AbstractPersistentPicklerTests):
@@ -64,12 +64,12 @@ class PyPersPicklerTests(AbstractPersistentPicklerTests):
         f.seek(0)
         return f.read()
 
-    def loads(self, buf):
+    def loads(self, buf, **kwds):
         class PersUnpickler(self.unpickler):
             def persistent_load(subself, obj):
                 return self.persistent_load(obj)
         f = io.BytesIO(buf)
-        u = PersUnpickler(f)
+        u = PersUnpickler(f, **kwds)
         return u.load()
 
 

Lib/test/test_pickletools.py

@@ -9,8 +9,8 @@ class OptimizedPickleTests(AbstractPickleTests, AbstractPickleModuleTests):
     def dumps(self, arg, proto=None):
         return pickletools.optimize(pickle.dumps(arg, proto))
 
-    def loads(self, buf):
-        return pickle.loads(buf)
+    def loads(self, buf, **kwds):
+        return pickle.loads(buf, **kwds)
 
     # Test relies on precise output of dumps()
     test_pickle_to_2x = None

Modules/_pickle.c

@@ -977,11 +977,6 @@ _Unpickler_Read(UnpicklerObject *self, char **s, Py_ssize_t n)
 {
     Py_ssize_t num_read;
 
-    if (n == 0) {
-        *s = NULL;
-        return 0;
-    }
-
     if (self->next_read_idx + n <= self->input_len) {
         *s = self->input_buffer + self->next_read_idx;
         self->next_read_idx += n;