Re: [Qemu-devel] [PATCH v2 1/6] pci: Clean up error checking in pci_add_capability()

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 06, 2017 at 06:14:02PM +0200, Markus Armbruster wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
> 
> > On Fri, Jun 02, 2017 at 03:54:37PM +0800, Mao Zhongyi wrote:
> >> On success, pci_add_capability2() returns a positive value. On
> >> failure, it sets an error and return a negative value.
> >> 
> >> pci_add_capability() laboriously checks this behavior. No other
> >> caller does. Drop the checks from pci_add_capability().
> >> 
> >> Cc: mst@redhat.com
> >> Cc: marcel@redhat.com
> >> Cc: armbru@redhat.com
> >> Signed-off-by: Mao Zhongyi <maozy.fnst@cn.fujitsu.com>
> >> Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
> >> ---
> >>  hw/pci/pci.c | 6 +-----
> >>  1 file changed, 1 insertion(+), 5 deletions(-)
> >> 
> >> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> >> index 98ccc27..53566b8 100644
> >> --- a/hw/pci/pci.c
> >> +++ b/hw/pci/pci.c
> >> @@ -2270,12 +2270,8 @@ int pci_add_capability(PCIDevice *pdev, uint8_t cap_id,
> >>      Error *local_err = NULL;
> >>  
> >>      ret = pci_add_capability2(pdev, cap_id, offset, size, &local_err);
> >> -    if (local_err) {
> >> -        assert(ret < 0);
> >> +    if (ret < 0) {
> >>          error_report_err(local_err);
> >> -    } else {
> >> -        /* success implies a positive offset in config space */
> >> -        assert(ret > 0);
> >>      }
> >>      return ret;
> >>  }
> >
> >
> > I don't see why this is a good idea. You drop a bunch of
> > asserts, so naturally code is slightly tighter. We could gain
> > the same by building with NDEBUG but we don't, we rather
> > have more safety.
> 
> It's a good idea because it's what we do basically everywhere when a
> function sets an error and returns a distinct error value.

We typically just do

        if (local_err) {
            error_report_err(local_err);
		...
	}