[libvirt] [PATCH]: fix ruby-libvirt bindings when virConnectNum* returns 0

[Chris Lalancette <clalance redhat com>]

Attached is a simple patch to fix a problem I ran into when using the
ruby-libvirt bindings with libvirt 0.4.3.  Basically, if you call any of the
virConnectList* functions with a "max" of 0, it returns "Invalid Arg".  To get
around this, modify the ruby-libvirt bindings to return an empty list if we get
num == 0 when calling the corresponding virConnectNumOf* function.  This should
solve: https://bugzilla.redhat.com/show_bug.cgi?id=451666

Signed-off-by: Chris Lalancette <clalance redhat com>

diff -r b02171cfad7d ext/libvirt/_libvirt.c
--- a/ext/libvirt/_libvirt.c	Wed Apr 16 09:47:27 2008 -0700
+++ b/ext/libvirt/_libvirt.c	Tue Jun 17 11:06:26 2008 +0200
@@ -256,7 +256,11 @@ static VALUE vol_new(virStorageVolPtr n,
                                                                         \
         num = virConnectNumOf##objs(conn);                              \
         _E(num < 0, create_error(e_RetrieveError, "virConnectNumOf" # objs, "", conn));   \
-                                                                        \
+        if (num == 0) {                                                 \
+            /* if num is 0, don't call virConnectList* function */      \
+            result = rb_ary_new2(num);                                  \
+            return result;                                              \
+        }                                                               \
         names = ALLOC_N(char *, num);                                   \
         r = virConnectList##objs(conn, names, num);                     \
         if (r < 0) {                                                    \