In PLy_function_build_args(), the code loops repeatedly, constructing

one argument at a time and then inserting the argument into a Python
list via PyList_SetItem(). This "steals" the reference to the argument:
that is, the reference to the new list member is now held by the Python
list itself. This works fine, except if an elog occurs. This causes the
function's PG_CATCH() block to be invoked, which decrements the
reference counts on both the current argument and the list of arguments.
If the elog happens to occur during the second or subsequent iteration
of the loop, the reference count on the current argument will be
decremented twice.

The fix is simple: set the local pointer to the current argument to NULL
immediately after adding it to the argument list. This ensures that the
Py_XDECREF() in the PG_CATCH() block doesn't double-decrement.

diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index c5192b63d4c4c17a9d9a851df5f67a40bdbca8ce..bffaa1e710c85276d04ad977a3026bdc995f409d 100644 (file)
--- a/src/pl/plpython/plpython.c
+++ b/src/pl/plpython/plpython.c
@@ -903,6 +903,7 @@ PLy_function_build_args(FunctionCallInfo fcinfo, PLyProcedure * proc)
                         * FIXME -- error check this
                         */
                        PyList_SetItem(args, i, arg);
+                       arg = NULL;
                }
        }
        PG_CATCH();