tools: libxl: directly initialise saved_* in _libxl_types.c

Coverity complains:
> /tools/libxl/_libxl_types.c: 9194 in libxl__device_channel_parse_json()
> 9188             }
> 9189             x = libxl__json_map_get("connection.socket", o, JSON_MAP);
> 9190             if (x) {
> 9191                 libxl_device_channel_init_connection(p, LIBXL_CHANNEL_CONNECTION_SOCKET);
> 9192                 {
> 9193                     const libxl__json_object *saved_path = NULL;
> >>>     CID 1261758:  Unused value  (UNUSED_VALUE)
> >>>     Value from "x" is assigned to "saved_path" here, but that
> >>>     stored value is not used before it is overwritten.
> 9194                     saved_path = x;
> 9195                     x = libxl__json_map_get("path", x, JSON_STRING | JSON_NULL);
> 9196                     if (x) {
> 9197                         rc = libxl__string_parse_json(gc, x, &p->u.socket.path);
> 9198                         if (rc)
> 9199                             goto out;

Which we can avoid by initialising saved_%s as we define it. Resulting
in numerous instances of the generated code changing like this:
         if (x) {
             libxl_channelinfo_init_connection(p, LIBXL_CHANNEL_CONNECTION_PTY);
             {
-                const libxl__json_object *saved_path = NULL;
-                saved_path = x;
+                const libxl__json_object *saved_path = x;
                 x = libxl__json_map_get("path", x, JSON_STRING | JSON_NULL);
                 if (x) {
                     rc = libxl__string_parse_json(gc, x, &p->u.pty.path);

CID: 1261758, 1261759 (and I would have expected others, but not
seeing them for some reason).

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/gentypes.py b/tools/libxl/gentypes.py
index 3e738215beced2142373bf8df0cfb8ed776d228b..d9e14fde672ed0b3dc2f1df8c8ef4d50cfc8edb8 100644 (file)
--- a/tools/libxl/gentypes.py
+++ b/tools/libxl/gentypes.py
@@ -432,8 +432,7 @@ def libxl_C_type_parse_json(ty, w, v, indent = "    ", parent = None, discrimina
         for f in [f for f in ty.fields if not f.const and not f.type.private]:
             saved_var_name = "saved_%s" % f.name
             s += "{\n"
-            s += "    const libxl__json_object *%s = NULL;\n" % saved_var_name
-            s += "    %s = x;\n" % saved_var_name
+            s += "    const libxl__json_object *%s = x;\n" % saved_var_name
             if isinstance(f.type, idl.KeyedUnion):
                 for x in f.type.fields:
                     s += "    x = libxl__json_map_get(\"%s\", %s, JSON_MAP);\n" % \