qemu_capabilities: Change virQEMUCapsFillDomainCaps signature

Up till now the virQEMUCapsFillDomainCaps() was type of void as
there was no way for it to fail. This is, however, going to
change in the next commit.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

tests/domaincapstest.c

@@ -28,13 +28,13 @@
 
 #define VIR_FROM_THIS VIR_FROM_NONE
 
-typedef void (*virDomainCapsFill)(virDomainCapsPtr domCaps,
-                                  void *opaque);
+typedef int (*virDomainCapsFill)(virDomainCapsPtr domCaps,
+                                 void *opaque);
 
 #define SET_ALL_BITS(x) \
     memset(&(x.values), 0xff, sizeof(x.values))
 
-static void
+static int
 fillAll(virDomainCapsPtr domCaps,
         void *opaque ATTRIBUTE_UNUSED)
 {
@@ -60,18 +60,20 @@ fillAll(virDomainCapsPtr domCaps,
     SET_ALL_BITS(hostdev->subsysType);
     SET_ALL_BITS(hostdev->capsType);
     SET_ALL_BITS(hostdev->pciBackend);
+    return 0;
 }
 
 
 #ifdef WITH_QEMU
 # include "testutilsqemu.h"
-static void
+static int
 fillQemuCaps(virDomainCapsPtr domCaps,
              void *opaque)
 {
     virQEMUCapsPtr qemuCaps = (virQEMUCapsPtr) opaque;
 
-    virQEMUCapsFillDomainCaps(domCaps, qemuCaps);
+    if (virQEMUCapsFillDomainCaps(domCaps, qemuCaps) < 0)
+        return -1;
 
     /* The function above tries to query host's KVM & VFIO capabilities by
      * calling qemuHostdevHostSupportsPassthroughLegacy() and
@@ -82,6 +84,7 @@ fillQemuCaps(virDomainCapsPtr domCaps,
                              VIR_DOMAIN_HOSTDEV_PCI_BACKEND_DEFAULT,
                              VIR_DOMAIN_HOSTDEV_PCI_BACKEND_KVM,
                              VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO);
+    return 0;
 }
 #endif /* WITH_QEMU */
 
@@ -99,8 +102,10 @@ buildVirDomainCaps(const char *emulatorbin,
     if (!(domCaps = virDomainCapsNew(emulatorbin, machine, arch, type)))
         goto cleanup;
 
-    if (fillFunc)
-        fillFunc(domCaps, opaque);
+    if (fillFunc && fillFunc(domCaps, opaque) < 0) {
+        virObjectUnref(domCaps);
+        domCaps = NULL;
+    }
 
  cleanup:
     return domCaps;