Re: [Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Kevin Wolf <kwolf@redhat.com>]

Am 18.03.2014 um 11:09 hat Markus Armbruster geschrieben:
> Kevin Wolf <kwolf@redhat.com> writes:
> 
> > It takes an errp argument. That's enough for error handling.
> >
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  block.c | 21 ++++++++++-----------
> >  1 file changed, 10 insertions(+), 11 deletions(-)
> >
> > diff --git a/block.c b/block.c
> > index acb70fd..b4f3f77 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -783,18 +783,18 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
> >      return open_flags;
> >  }
> >  
> > -static int bdrv_assign_node_name(BlockDriverState *bs,
> > -                                 const char *node_name,
> > -                                 Error **errp)
> > +static void bdrv_assign_node_name(BlockDriverState *bs,
> > +                                  const char *node_name,
> > +                                  Error **errp)
> >  {
> >      if (!node_name) {
> > -        return 0;
> > +        return;
> >      }
> >  
> >      /* empty string node name is invalid */
> >      if (node_name[0] == '\0') {
> >          error_setg(errp, "Empty node name");
> > -        return -EINVAL;
> > +        return;
> >      }
> >  
> >      /* takes care of avoiding namespaces collisions */
> > @@ -807,14 +807,12 @@ static int bdrv_assign_node_name(BlockDriverState *bs,
> >      /* takes care of avoiding duplicates node names */
> >      if (bdrv_find_node(node_name)) {
> >          error_setg(errp, "Duplicate node name");
> > -        return -EINVAL;
> > +        return;
> >      }
> >  
> >      /* copy node name into the bs and insert it into the graph list */
> >      pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
> >      QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
> > -
> > -    return 0;
> >  }
> >  
> >  /*
> > @@ -849,9 +847,10 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
> >      trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
> >  
> >      node_name = qdict_get_try_str(options, "node-name");
> > -    ret = bdrv_assign_node_name(bs, node_name, errp);
> > -    if (ret < 0) {
> > -        return ret;
> > +    bdrv_assign_node_name(bs, node_name, &local_err);
> > +    if (error_is_set(&local_err)) {
> > +        error_propagate(errp, local_err);
> > +        return -EINVAL;
> >      }
> >      qdict_del(options, "node-name");
> 
> Please use 'if (local_err)' instead of 'if (error_is_set(&local_err))'.
> See commit 84d18f0.

I can do that; this patch predates your change and I just dug it out
from an old branch. Note that there are still many places that use
error_is_set() where it's not necessary, including documentation that
should show how to do things right, e.g. docs/writing-qmp-commands.txt.

(By the way, would the actual problem with Coverity in commit 84d18f0
not be fixed more easily and for all instances by making error_is_set()
a static inline function in the header?)

What was the proper use case for error_is_set() again? Or can we get rid
of it? As long as it's there, you'll keep getting new offenders.

Kevin