[[inferior events] partial cleanup for copy_py_list

[Tom Tromey <tromey@redhat.com>]

This fixes some issues in copy_py_list, but not all.

The patch changes it to check PyList_Append.

I think it should probably use an iterator to go through the list.
Otherwise it is susceptible to a bug where another thread changes the
list while we are iterating over it.

Still, ok to push in this form?

Tom

diff --git a/gdb/python/python.c b/gdb/python/python.c
index 7c686d3..34e5bf8 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -163,10 +163,11 @@ compute_python_string (struct command_line *l)
 }
 
 /* Returns a a copy of the give LIST.
-   Creates a new reference which must be handeld by the caller.  */
+   Creates a new reference which must be handled by the caller.  */
 
 PyObject *
-copy_py_list (PyObject *list){
+copy_py_list (PyObject *list)
+{
   int i;
 
   PyObject *new_list = PyList_New (0);
@@ -174,7 +175,11 @@ copy_py_list (PyObject *list){
     return NULL;
 
   for (i = 0; i < PyList_Size (list); i++)
-    PyList_Append (new_list, PyList_GET_ITEM (list, i));
+    if (PyList_Append (new_list, PyList_GET_ITEM (list, i)) < 0)
+      {
+	Py_DECREF (new_list);
+	return NULL;
+      }
 
   return new_list;
 }