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Re: [libvirt] [PATCH] virterror: Don't invoke error callback for ERR_OK



On Tue, Jan 12, 2010 at 03:57:33PM -0500, Cole Robinson wrote:
> On 01/12/2010 03:48 PM, Daniel P. Berrange wrote:
> > On Tue, Jan 12, 2010 at 03:26:28PM -0500, Cole Robinson wrote:
> >> Since virDispatchError is now responsible for invoking the error callback,
> >> give it the same semantics as ReportError, which will skip VIR_ERR_OK
> >> (which is encountered when no error was raised).
> >>
> >> This fixes invoking the error callback after every non-erroring API call.
> >>
> >> Signed-off-by: Cole Robinson <crobinso redhat com>
> >> ---
> >>  src/util/virterror.c |    6 +++++-
> >>  1 files changed, 5 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/src/util/virterror.c b/src/util/virterror.c
> >> index e2128b9..78974ee 100644
> >> --- a/src/util/virterror.c
> >> +++ b/src/util/virterror.c
> >> @@ -603,8 +603,12 @@ virDispatchError(virConnectPtr conn)
> >>      if (!err)
> >>          return;
> >>  
> >> -    /* Set a generic error message if none is already set */
> >> +    /* We never used to raise ERR_OK, so maintain existing behavior */
> >>      if (err->code == VIR_ERR_OK)
> >> +        return;
> >> +
> >> +    /* Set a generic error message if none is already set */
> >> +    if (!err->message)
> >>          virErrorGenericFailure(err);
> >>  
> >>      /* Copy the global error to per-connection error if needed */
> > 
> > We should only ever be invoking virDispatchError() in error paths, so
> > if err->code == VIR_ERR_OK, this means we do need set a generic message
> > because the earlier code indicated an error but forgot to report one.
> > So I don't think this is correct.
> > 
> 
> Ah, I think I wanted to check VIR_ERR_NONE here actually.
> virDispatchError is called regardless of whether an error is actually
> raised, so it may receive a zero'd out/empty virLastErrorObject, which
> is what I'm trying to avoid reporting.

I still don't think you are correct in that. If you run

  # grep --after 1 virDispatchError libvirt.c
        virDispatchError(NULL);
        return (-1);
  --
      virDispatchError(net->conn);
      return -1;
  --
          virDispatchError(NULL);
          return (-1);
  --
      virDispatchError(pool->conn);
      return -1;

Then all cases where virDispatchError() is called should be followed by the
return of an error code, 99% of them are -1 or NULL. There are one or two
where we use '0' for error as a special case. I don't see any places where
virDispatchError() is called in a successful return path. So we should
always be invoking the error callback, and ensuring an error is actually 
set before doing so.

Regards,
Daniel
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