Re: [Xen-devel] [PATCH] tools: libxl: directly initialise saved_* in _libxl_types.c

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Jan 08, 2015 at 10:57:47AM +0000, Ian Campbell wrote:
> 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@xxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

> ---
>  tools/libxl/gentypes.py |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/tools/libxl/gentypes.py b/tools/libxl/gentypes.py
> index 3e73821..d9e14fd 100644
> --- 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" % \
> -- 
> 1.7.10.4

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