Re: [Libguestfs] [libnbd PATCH] python: Plug some memory leaks on error paths

Inspection of the generated code showed several places where we did not release references on all error paths. In particular, switching things to always jump to an out: label, even when the underlying C function cannot fail, makes it easier to clean up when the user passes wrong types to a function call. One of the easiest triggers without this patch was this one-liner: $ nbdsh -c 'h.block_status(512, 0, 1)' which fails due to '1' not being callable, but leaked malloc'd memory in the process. --- generator/Python.ml | 55 +++++++++++++++++++++++++++++---------------- 1 file changed, 36 insertions(+), 19 deletions(-)

@@ -395,12 +396,13 @@ let print_python_binding name { args; optargs; ret; may_set_error } = pr " %s_buf = nbd_internal_py_get_aio_buffer (%s);\n" n n | Closure { cbname } -> pr " /* Increment refcount since pointer may be saved by libnbd. */\n"; - pr " Py_INCREF (%s_user_data->fn);\n" cbname; pr " if (!PyCallable_Check (%s_user_data->fn)) {\n" cbname; pr " PyErr_SetString (PyExc_TypeError,\n"; pr " \"callback parameter %s is not callable\");\n" cbname; - pr " return NULL;\n"; - pr " }\n" + pr " %s_user_data->fn = NULL;\n" cbname; + pr " goto out;\n"; + pr " }\n"; + pr " Py_INCREF (%s_user_data->fn);\n" cbname