Fix GIL handling on function exit for re-assigned Python arguments.

Cython/Compiler/Nodes.py

@@ -2146,6 +2146,7 @@ class FuncDefNode(StatNode, BlockNode):
             if entry.type.is_pyobject:
                 if entry.is_arg and not entry.cf_is_reassigned:
                     continue
+            if entry.type.needs_refcounting:
                 assure_gil('success')
             # FIXME ideally use entry.xdecref_cleanup but this currently isn't reliable
             code.put_var_xdecref(entry, have_gil=gil_owned['success'])
@@ -2162,6 +2163,8 @@ class FuncDefNode(StatNode, BlockNode):
                     continue
                 if not acquire_gil and not entry.cf_is_reassigned:
                     continue
+                if entry.type.needs_refcounting:
+                    assure_gil('success')
 
             # FIXME use entry.xdecref_cleanup - del arg seems to be the problem
             code.put_var_xdecref(entry, have_gil=gil_owned['success'])

tests/run/with_gil.pyx

@@ -478,6 +478,20 @@ cdef void _void_with_python_objects() nogil:
         obj2 = [456]
 
 
+def void_with_py_arg_reassigned(x):
+    """
+    >>> void_with_py_arg_reassigned(123)
+    """
+    with nogil:
+        _void_with_py_arg_reassigned(x)
+
+
+cdef void _void_with_py_arg_reassigned(x) nogil:
+    c = 123
+    with gil:
+        x = [456]
+
+
 cdef void test_timing_callback() with gil:
   pass