Re: [libvirt] [PATCH 3/3] libvirt-domain: virConnectListDomains: Return 0 on zero-size buffer

On Mon, Nov 18, 2019 at 01:18:19PM +0100, Erik Skultety wrote: > It doesn't make sense to pass a target buffer into an API, declaring its > size as 0 and expect some meaningful result. Since this used to work > pre-Glib era, we shouldn't end with an error, but we can return 0 > for the number of domains immediately, instead of calling into the > daemon, which is exactly what the daemon would have returned anyway. Passing in size as 0 is going to be normal practice, given the calling convention of this API design. > > Signed-off-by: Erik Skultety <eskultet(a)redhat.com&gt; > --- > src/libvirt-domain.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c > index 02622cb2ca..0def40fdf7 100644 > --- a/src/libvirt-domain.c > +++ b/src/libvirt-domain.c > @@ -62,6 +62,9 @@ virConnectListDomains(virConnectPtr conn, int *ids, int maxids) > virCheckNonNullArgGoto(ids, error); > virCheckNonNegativeArgGoto(maxids, error); > > + if (maxids == 0) > + return 0; This is too late really, as we alrady checked 'ids'.

IMHO, we should only mandate a non-NULL 'ids' parameter when maxids > 0 a few lines earlier All the other legacy APIs share the same validation flaw so will also need fixing.