diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 0ffb3253e8..6300178ccd 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -4399,7 +4399,7 @@ struct virNetworkObjListData {
     bool error;
 };
 
-static void
+static int
 virNetworkObjListPopulate(void *payload,
                           const void *name ATTRIBUTE_UNUSED,
                           void *opaque)
@@ -4409,7 +4409,7 @@ virNetworkObjListPopulate(void *payload,
     virNetworkPtr net = NULL;
 
     if (data->error)
-        return;
+        return 0;
 
     virObjectLock(obj);
 
@@ -4434,6 +4434,7 @@ virNetworkObjListPopulate(void *payload,
 
  cleanup:
     virObjectUnlock(obj);
+    return 0;
 }
 
 int
@@ -4478,7 +4479,7 @@ struct virNetworkObjListForEachHelperData {
     int ret;
 };
 
-static void
+static int
 virNetworkObjListForEachHelper(void *payload,
                                const void *name ATTRIBUTE_UNUSED,
                                void *opaque)
@@ -4487,6 +4488,7 @@ virNetworkObjListForEachHelper(void *payload,
 
     if (data->callback(payload, data->opaque) < 0)
         data->ret = -1;
+    return 0;
 }
 
 /**
@@ -4524,7 +4526,7 @@ struct virNetworkObjListGetHelperData {
     bool error;
 };
 
-static void
+static int
 virNetworkObjListGetHelper(void *payload,
                            const void *name ATTRIBUTE_UNUSED,
                            void *opaque)
@@ -4533,11 +4535,11 @@ virNetworkObjListGetHelper(void *payload,
     virNetworkObjPtr obj = payload;
 
     if (data->error)
-        return;
+        return 0;
 
     if (data->nnames >= 0 &&
         data->got == data->nnames)
-        return;
+        return 0;
 
     virObjectLock(obj);
 
@@ -4557,6 +4559,7 @@ virNetworkObjListGetHelper(void *payload,
 
  cleanup:
     virObjectUnlock(obj);
+    return 0;
 }
 
 int
diff --git a/src/conf/nwfilter_params.c b/src/conf/nwfilter_params.c
index b6c6e78ee6..496ffdabf8 100644
--- a/src/conf/nwfilter_params.c
+++ b/src/conf/nwfilter_params.c
@@ -709,19 +709,19 @@ struct addToTableStruct {
 };
 
 
-static void
+static int
 addToTable(void *payload, const void *name, void *data)
 {
     struct addToTableStruct *atts = (struct addToTableStruct *)data;
     virNWFilterVarValuePtr val;
 
     if (atts->errOccurred)
-        return;
+        return 0;
 
     val = virNWFilterVarValueCopy((virNWFilterVarValuePtr)payload);
     if (!val) {
         atts->errOccurred = 1;
-        return;
+        return 0;
     }
 
     if (virNWFilterHashTablePut(atts->target, (const char *)name, val) < 0) {
@@ -731,6 +731,8 @@ addToTable(void *payload, const void *name, void *data)
         atts->errOccurred = 1;
         virNWFilterVarValueFree(val);
     }
+
+    return 0;
 }
 
 
diff --git a/src/conf/snapshot_conf.c b/src/conf/snapshot_conf.c
index 58646bd982..c7794e9b19 100644
--- a/src/conf/snapshot_conf.c
+++ b/src/conf/snapshot_conf.c
@@ -844,48 +844,49 @@ struct virDomainSnapshotNameData {
     bool error;
 };
 
-static void virDomainSnapshotObjListCopyNames(void *payload,
-                                              const void *name ATTRIBUTE_UNUSED,
-                                              void *opaque)
+static int virDomainSnapshotObjListCopyNames(void *payload,
+                                             const void *name ATTRIBUTE_UNUSED,
+                                             void *opaque)
 {
     virDomainSnapshotObjPtr obj = payload;
     struct virDomainSnapshotNameData *data = opaque;
 
     if (data->error)
-        return;
+        return 0;
     /* Caller already sanitized flags.  Filtering on DESCENDANTS was
      * done by choice of iteration in the caller.  */
     if ((data->flags & VIR_DOMAIN_SNAPSHOT_LIST_LEAVES) && obj->nchildren)
-        return;
+        return 0;
     if ((data->flags & VIR_DOMAIN_SNAPSHOT_LIST_NO_LEAVES) && !obj->nchildren)
-        return;
+        return 0;
 
     if (data->flags & VIR_DOMAIN_SNAPSHOT_FILTERS_STATUS) {
         if (!(data->flags & VIR_DOMAIN_SNAPSHOT_LIST_INACTIVE) &&
             obj->def->state == VIR_DOMAIN_SHUTOFF)
-            return;
+            return 0;
         if (!(data->flags & VIR_DOMAIN_SNAPSHOT_LIST_DISK_ONLY) &&
             obj->def->state == VIR_DOMAIN_DISK_SNAPSHOT)
-            return;
+            return 0;
         if (!(data->flags & VIR_DOMAIN_SNAPSHOT_LIST_ACTIVE) &&
             obj->def->state != VIR_DOMAIN_SHUTOFF &&
             obj->def->state != VIR_DOMAIN_DISK_SNAPSHOT)
-            return;
+            return 0;
     }
 
     if ((data->flags & VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL) &&
         virDomainSnapshotIsExternal(obj))
-        return;
+        return 0;
     if ((data->flags & VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL) &&
         !virDomainSnapshotIsExternal(obj))
-        return;
+        return 0;
 
     if (data->names && data->count < data->maxnames &&
         VIR_STRDUP(data->names[data->count], obj->def->name) < 0) {
         data->error = true;
-        return;
+        return 0;
     }
     data->count++;
+    return 0;
 }
 
 int
@@ -1012,7 +1013,7 @@ struct snapshot_act_on_descendant {
     void *data;
 };
 
-static void
+static int
 virDomainSnapshotActOnDescendant(void *payload,
                                  const void *name,
                                  void *data)
@@ -1024,6 +1025,7 @@ virDomainSnapshotActOnDescendant(void *payload,
                                                            curr->iter,
                                                            curr->data);
     (curr->iter)(payload, name, curr->data);
+    return 0;
 }
 
 /* Run iter(data) on all descendants of snapshot, while ignoring all
@@ -1055,7 +1057,7 @@ struct snapshot_set_relation {
     virDomainSnapshotObjListPtr snapshots;
     int err;
 };
-static void
+static int
 virDomainSnapshotSetRelations(void *payload,
                               const void *name ATTRIBUTE_UNUSED,
                               void *data)
@@ -1085,6 +1087,7 @@ virDomainSnapshotSetRelations(void *payload,
     obj->parent->nchildren++;
     obj->sibling = obj->parent->first_child;
     obj->parent->first_child = obj;
+    return 0;
 }
 
 /* Populate parent link and child count of all snapshots, with all
diff --git a/src/conf/virchrdev.c b/src/conf/virchrdev.c
index 701b326fb2..bca9c37d42 100644
--- a/src/conf/virchrdev.c
+++ b/src/conf/virchrdev.c
@@ -292,13 +292,14 @@ virChrdevsPtr virChrdevAlloc(void)
 /**
  * Helper to clear stream callbacks when freeing the hash
  */
-static void virChrdevFreeClearCallbacks(void *payload,
-                                         const void *name ATTRIBUTE_UNUSED,
-                                         void *data ATTRIBUTE_UNUSED)
+static int virChrdevFreeClearCallbacks(void *payload,
+                                       const void *name ATTRIBUTE_UNUSED,
+                                       void *data ATTRIBUTE_UNUSED)
 {
     virStreamPtr st = payload;
 
     virFDStreamSetInternalCloseCb(st, NULL, NULL, NULL);
+    return 0;
 }
 
 /**
diff --git a/src/conf/virdomainobjlist.c b/src/conf/virdomainobjlist.c
index 61fe468fde..05c532a3ba 100644
--- a/src/conf/virdomainobjlist.c
+++ b/src/conf/virdomainobjlist.c
@@ -607,7 +607,7 @@ struct virDomainObjListData {
 };
 
 
-static void
+static int
 virDomainObjListCount(void *payload,
                       const void *name ATTRIBUTE_UNUSED,
                       void *opaque)
@@ -627,6 +627,7 @@ virDomainObjListCount(void *payload,
     }
  cleanup:
     virObjectUnlock(obj);
+    return 0;
 }
 
 
@@ -653,7 +654,7 @@ struct virDomainIDData {
 };
 
 
-static void
+static int
 virDomainObjListCopyActiveIDs(void *payload,
                               const void *name ATTRIBUTE_UNUSED,
                               void *opaque)
@@ -668,6 +669,7 @@ virDomainObjListCopyActiveIDs(void *payload,
         data->ids[data->numids++] = obj->def->id;
  cleanup:
     virObjectUnlock(obj);
+    return 0;
 }
 
 
@@ -697,7 +699,7 @@ struct virDomainNameData {
 };
 
 
-static void
+static int
 virDomainObjListCopyInactiveNames(void *payload,
                                   const void *name ATTRIBUTE_UNUSED,
                                   void *opaque)
@@ -706,7 +708,7 @@ virDomainObjListCopyInactiveNames(void *payload,
     struct virDomainNameData *data = opaque;
 
     if (data->oom)
-        return;
+        return 0;
 
     virObjectLock(obj);
     if (data->filter &&
@@ -720,6 +722,7 @@ virDomainObjListCopyInactiveNames(void *payload,
     }
  cleanup:
     virObjectUnlock(obj);
+    return 0;
 }
 
 
@@ -753,7 +756,7 @@ struct virDomainListIterData {
 };
 
 
-static void
+static int
 virDomainObjListHelper(void *payload,
                        const void *name ATTRIBUTE_UNUSED,
                        void *opaque)
@@ -762,6 +765,7 @@ virDomainObjListHelper(void *payload,
 
     if (data->callback(payload, data->opaque) < 0)
         data->ret = -1;
+    return 0;
 }
 
 
@@ -850,7 +854,7 @@ struct virDomainListData {
 };
 
 
-static void
+static int
 virDomainObjListCollectIterator(void *payload,
                                 const void *name ATTRIBUTE_UNUSED,
                                 void *opaque)
@@ -858,6 +862,7 @@ virDomainObjListCollectIterator(void *payload,
     struct virDomainListData *data = opaque;
 
     data->vms[data->nvms++] = virObjectRef(payload);
+    return 0;
 }
 
 
diff --git a/src/locking/lock_daemon.c b/src/locking/lock_daemon.c
index a5a40fef5a..23f52b5f8e 100644
--- a/src/locking/lock_daemon.c
+++ b/src/locking/lock_daemon.c
@@ -649,7 +649,7 @@ struct virLockDaemonClientReleaseData {
     bool gotError;
 };
 
-static void
+static int
 virLockDaemonClientReleaseLockspace(void *payload,
                                     const void *name ATTRIBUTE_UNUSED,
                                     void *opaque)
@@ -664,6 +664,7 @@ virLockDaemonClientReleaseLockspace(void *payload,
         data->hadSomeLeases = true;
     else if (rc < 0)
         data->gotError = true;
+    return 0;
 }
 
 
diff --git a/src/nwfilter/nwfilter_dhcpsnoop.c b/src/nwfilter/nwfilter_dhcpsnoop.c
index 7dbf467fe8..c671cd8818 100644
--- a/src/nwfilter/nwfilter_dhcpsnoop.c
+++ b/src/nwfilter/nwfilter_dhcpsnoop.c
@@ -1864,7 +1864,7 @@ virNWFilterSnoopPruneIter(const void *payload,
  * Iterator to write all leases of a single request to a file.
  * Call this function with the SnoopLock held.
  */
-static void
+static int
 virNWFilterSnoopSaveIter(void *payload,
                          const void *name ATTRIBUTE_UNUSED,
                          void *data)
@@ -1880,6 +1880,7 @@ virNWFilterSnoopSaveIter(void *payload,
         ignore_value(virNWFilterSnoopLeaseFileWrite(tfd, req->ifkey, ipl));
 
     virNWFilterSnoopReqUnlock(req);
+    return 0;
 }
 
 /*
diff --git a/src/nwfilter/nwfilter_gentech_driver.c b/src/nwfilter/nwfilter_gentech_driver.c
index 5a4cff142e..761a01b1c2 100644
--- a/src/nwfilter/nwfilter_gentech_driver.c
+++ b/src/nwfilter/nwfilter_gentech_driver.c
@@ -219,19 +219,20 @@ struct printString
 };
 
 
-static void
+static int
 printString(void *payload ATTRIBUTE_UNUSED, const void *name, void *data)
 {
     struct printString *ps = data;
 
     if ((STREQ((char *)name, NWFILTER_STD_VAR_IP) && !ps->reportIP) ||
         (STREQ((char *)name, NWFILTER_STD_VAR_MAC) && !ps->reportMAC))
-        return;
+        return 0;
 
     if (virBufferUse(&ps->buf) && ps->separator)
         virBufferAdd(&ps->buf, ps->separator, -1);
 
     virBufferAdd(&ps->buf, name, -1);
+    return 0;
 }
 
 /**
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 7223b9e296..c6ff0da6d9 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2836,9 +2836,9 @@ qemuDomainSnapshotDiscard(virQEMUDriverPtr driver,
 }
 
 /* Hash iterator callback to discard multiple snapshots.  */
-void qemuDomainSnapshotDiscardAll(void *payload,
-                                  const void *name ATTRIBUTE_UNUSED,
-                                  void *data)
+int qemuDomainSnapshotDiscardAll(void *payload,
+                                 const void *name ATTRIBUTE_UNUSED,
+                                 void *data)
 {
     virDomainSnapshotObjPtr snap = payload;
     virQEMUSnapRemovePtr curr = data;
@@ -2850,6 +2850,7 @@ void qemuDomainSnapshotDiscardAll(void *payload,
                                     curr->metadata_only);
     if (err && !curr->err)
         curr->err = err;
+    return 0;
 }
 
 int
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index f0b47e78a6..e4b1e8bb92 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -401,9 +401,9 @@ struct _virQEMUSnapRemove {
     bool current;
 };
 
-void qemuDomainSnapshotDiscardAll(void *payload,
-                                  const void *name,
-                                  void *data);
+int qemuDomainSnapshotDiscardAll(void *payload,
+                                 const void *name,
+                                 void *data);
 
 int qemuDomainSnapshotDiscardAllMetadata(virQEMUDriverPtr driver,
                                          virDomainObjPtr vm);
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 77f4baa430..a7ab6deda6 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2240,7 +2240,7 @@ qemuDomainReset(virDomainPtr dom, unsigned int flags)
 
 
 /* Count how many snapshots in a set are external snapshots or checkpoints.  */
-static void
+static int
 qemuDomainSnapshotCountExternal(void *payload,
                                 const void *name ATTRIBUTE_UNUSED,
                                 void *data)
@@ -2250,6 +2250,7 @@ qemuDomainSnapshotCountExternal(void *payload,
 
     if (virDomainSnapshotIsExternal(snap))
         (*count)++;
+    return 0;
 }
 
 static int
@@ -10770,7 +10771,7 @@ qemuDomainBlockResize(virDomainPtr dom,
 }
 
 
-static void
+static int
 qemuDomainBlockStatsGatherTotals(void *payload,
                                  const void *name ATTRIBUTE_UNUSED,
                                  void *opaque)
@@ -10791,6 +10792,7 @@ qemuDomainBlockStatsGatherTotals(void *payload,
     QEMU_BLOCK_STAT_TOTAL(rd_total_times);
     QEMU_BLOCK_STAT_TOTAL(flush_total_times);
 #undef QEMU_BLOCK_STAT_TOTAL
+    return 0;
 }
 
 
@@ -15548,7 +15550,7 @@ struct _virQEMUSnapReparent {
 };
 
 
-static void
+static int
 qemuDomainSnapshotReparentChildren(void *payload,
                                    const void *name ATTRIBUTE_UNUSED,
                                    void *data)
@@ -15557,7 +15559,7 @@ qemuDomainSnapshotReparentChildren(void *payload,
     virQEMUSnapReparentPtr rep = data;
 
     if (rep->err < 0)
-        return;
+        return 0;
 
     VIR_FREE(snap->def->parent);
     snap->parent = rep->parent;
@@ -15565,7 +15567,7 @@ qemuDomainSnapshotReparentChildren(void *payload,
     if (rep->parent->def &&
         VIR_STRDUP(snap->def->parent, rep->parent->def->name) < 0) {
         rep->err = -1;
-        return;
+        return 0;
     }
 
     if (!snap->sibling)
@@ -15573,6 +15575,7 @@ qemuDomainSnapshotReparentChildren(void *payload,
 
     rep->err = qemuDomainSnapshotWriteMetadata(rep->vm, snap, rep->caps,
                                                rep->cfg->snapshotDir);
+    return 0;
 }
 
 
diff --git a/src/test/test_driver.c b/src/test/test_driver.c
index 727382ef1c..21c66dbb66 100644
--- a/src/test/test_driver.c
+++ b/src/test/test_driver.c
@@ -6295,10 +6295,10 @@ struct _testSnapRemoveData {
     bool current;
 };
 
-static void
+static int
 testDomainSnapshotDiscardAll(void *payload,
-                          const void *name ATTRIBUTE_UNUSED,
-                          void *data)
+                             const void *name ATTRIBUTE_UNUSED,
+                             void *data)
 {
     virDomainSnapshotObjPtr snap = payload;
     testSnapRemoveDataPtr curr = data;
@@ -6306,6 +6306,7 @@ testDomainSnapshotDiscardAll(void *payload,
     if (snap->def->current)
         curr->current = true;
     virDomainSnapshotObjListRemove(curr->vm->snapshots, snap);
+    return 0;
 }
 
 typedef struct _testSnapReparentData testSnapReparentData;
@@ -6317,7 +6318,7 @@ struct _testSnapReparentData {
     virDomainSnapshotObjPtr last;
 };
 
-static void
+static int
 testDomainSnapshotReparentChildren(void *payload,
                                    const void *name ATTRIBUTE_UNUSED,
                                    void *data)
@@ -6326,7 +6327,7 @@ testDomainSnapshotReparentChildren(void *payload,
     testSnapReparentDataPtr rep = data;
 
     if (rep->err < 0)
-        return;
+        return 0;
 
     VIR_FREE(snap->def->parent);
     snap->parent = rep->parent;
@@ -6334,11 +6335,12 @@ testDomainSnapshotReparentChildren(void *payload,
     if (rep->parent->def &&
         VIR_STRDUP(snap->def->parent, rep->parent->def->name) < 0) {
         rep->err = -1;
-        return;
+        return 0;
     }
 
     if (!snap->sibling)
         rep->last = snap;
+    return 0;
 }
 
 static int
diff --git a/src/uml/uml_driver.c b/src/uml/uml_driver.c
index b0dba5c82d..d656704eb8 100644
--- a/src/uml/uml_driver.c
+++ b/src/uml/uml_driver.c
@@ -724,9 +724,9 @@ struct umlProcessAutoDestroyData {
     virConnectPtr conn;
 };
 
-static void umlProcessAutoDestroyDom(void *payload,
-                                     const void *name,
-                                     void *opaque)
+static int umlProcessAutoDestroyDom(void *payload,
+                                    const void *name,
+                                    void *opaque)
 {
     struct umlProcessAutoDestroyData *data = opaque;
     virConnectPtr conn = payload;
@@ -738,17 +738,17 @@ static void umlProcessAutoDestroyDom(void *payload,
     VIR_DEBUG("conn=%p uuidstr=%s thisconn=%p", conn, uuidstr, data->conn);
 
     if (data->conn != conn)
-        return;
+        return 0;
 
     if (virUUIDParse(uuidstr, uuid) < 0) {
         VIR_WARN("Failed to parse %s", uuidstr);
-        return;
+        return 0;
     }
 
     if (!(dom = virDomainObjListFindByUUID(data->driver->domains,
                                            uuid))) {
         VIR_DEBUG("No domain object to kill");
-        return;
+        return 0;
     }
 
     VIR_DEBUG("Killing domain");
@@ -766,6 +766,7 @@ static void umlProcessAutoDestroyDom(void *payload,
     if (event)
         umlDomainEventQueue(data->driver, event);
     virHashRemoveEntry(data->driver->autodestroy, uuidstr);
+    return 0;
 }
 
 /*
diff --git a/src/util/virclosecallbacks.c b/src/util/virclosecallbacks.c
index 9006d361e5..82d40717a3 100644
--- a/src/util/virclosecallbacks.c
+++ b/src/util/virclosecallbacks.c
@@ -252,7 +252,7 @@ struct virCloseCallbacksData {
     bool oom;
 };
 
-static void
+static int
 virCloseCallbacksGetOne(void *payload,
                         const void *key,
                         void *opaque)
@@ -263,23 +263,24 @@ virCloseCallbacksGetOne(void *payload,
     unsigned char uuid[VIR_UUID_BUFLEN];
 
     if (virUUIDParse(uuidstr, uuid) < 0)
-        return;
+        return 0;
 
     VIR_DEBUG("conn=%p, thisconn=%p, uuid=%s, cb=%p",
               closeDef->conn, data->conn, uuidstr, closeDef->cb);
 
     if (data->conn != closeDef->conn || !closeDef->cb)
-        return;
+        return 0;
 
     if (VIR_EXPAND_N(data->list->entries,
                      data->list->nentries, 1) < 0) {
         data->oom = true;
-        return;
+        return 0;
     }
 
     memcpy(data->list->entries[data->list->nentries - 1].uuid,
            uuid, VIR_UUID_BUFLEN);
     data->list->entries[data->list->nentries - 1].callback = closeDef->cb;
+    return 0;
 }
 
 static virCloseCallbacksListPtr
diff --git a/src/util/virhash.c b/src/util/virhash.c
index fab621ba91..d6f208eacc 100644
--- a/src/util/virhash.c
+++ b/src/util/virhash.c
@@ -738,8 +738,8 @@ struct getKeysIter
     size_t arrayIdx;
 };
 
-static void virHashGetKeysIterator(void *payload,
-                                   const void *key, void *data)
+static int virHashGetKeysIterator(void *payload,
+                                  const void *key, void *data)
 {
     struct getKeysIter *iter = data;
 
@@ -747,6 +747,7 @@ static void virHashGetKeysIterator(void *payload,
     iter->sortArray[iter->arrayIdx].value = payload;
 
     iter->arrayIdx++;
+    return 0;
 }
 
 typedef int (*qsort_comp)(const void *, const void *);
diff --git a/src/util/virhash.h b/src/util/virhash.h
index 50b9a04883..ed6bba3db7 100644
--- a/src/util/virhash.h
+++ b/src/util/virhash.h
@@ -43,8 +43,10 @@ typedef void (*virHashDataFree) (void *payload, const void *name);
  * @data: user supplied data blob
  *
  * Callback to process a hash entry during iteration
+ *
+ * Returns -1 to stop the iteration, e.g. in case of an error
  */
-typedef void (*virHashIterator) (void *payload, const void *name, void *data);
+typedef int (*virHashIterator) (void *payload, const void *name, void *data);
 /**
  * virHashSearcher:
  * @payload: the data in the hash
diff --git a/src/xen/xm_internal.c b/src/xen/xm_internal.c
index a0d6f74fcb..ef1a460a2b 100644
--- a/src/xen/xm_internal.c
+++ b/src/xen/xm_internal.c
@@ -1118,7 +1118,7 @@ struct xenXMListIteratorContext {
     char ** names;
 };
 
-static void
+static int
 xenXMListIterator(void *payload ATTRIBUTE_UNUSED,
                   const void *name,
                   void *data)
@@ -1127,10 +1127,10 @@ xenXMListIterator(void *payload ATTRIBUTE_UNUSED,
     virDomainDefPtr def = NULL;
 
     if (ctx->oom)
-        return;
+        return 0;
 
     if (ctx->count == ctx->max)
-        return;
+        return 0;
 
     def = xenDaemonLookupByName(ctx->conn, name);
     if (!def) {
@@ -1141,6 +1141,7 @@ xenXMListIterator(void *payload ATTRIBUTE_UNUSED,
     } else {
         virDomainDefFree(def);
     }
+    return 0;
 }
 
 
diff --git a/tests/virhashtest.c b/tests/virhashtest.c
index 41f0e76e29..323c68e20a 100644
--- a/tests/virhashtest.c
+++ b/tests/virhashtest.c
@@ -56,11 +56,12 @@ testHashInit(int size)
     return hash;
 }
 
-static void
+static int
 testHashCheckForEachCount(void *payload ATTRIBUTE_UNUSED,
                           const void *name ATTRIBUTE_UNUSED,
                           void *data ATTRIBUTE_UNUSED)
 {
+    return 0;
 }
 
 static int
@@ -183,7 +184,7 @@ testHashRemove(const void *data ATTRIBUTE_UNUSED)
 const int testHashCountRemoveForEachSome =
     ARRAY_CARDINALITY(uuids) - ARRAY_CARDINALITY(uuids_subset);
 
-static void
+static int
 testHashRemoveForEachSome(void *payload ATTRIBUTE_UNUSED,
                           const void *name,
                           void *data)
@@ -200,12 +201,13 @@ testHashRemoveForEachSome(void *payload ATTRIBUTE_UNUSED,
             break;
         }
     }
+    return 0;
 }
 
 
 const int testHashCountRemoveForEachAll = 0;
 
-static void
+static int
 testHashRemoveForEachAll(void *payload ATTRIBUTE_UNUSED,
                          const void *name,
                          void *data)
@@ -213,12 +215,13 @@ testHashRemoveForEachAll(void *payload ATTRIBUTE_UNUSED,
     virHashTablePtr hash = data;
 
     virHashRemoveEntry(hash, name);
+    return 0;
 }
 
 
 const int testHashCountRemoveForEachForbidden = ARRAY_CARDINALITY(uuids);
 
-static void
+static int
 testHashRemoveForEachForbidden(void *payload ATTRIBUTE_UNUSED,
                                const void *name,
                                void *data)
@@ -238,6 +241,7 @@ testHashRemoveForEachForbidden(void *payload ATTRIBUTE_UNUSED,
             break;
         }
     }
+    return 0;
 }
 
 
@@ -302,15 +306,15 @@ testHashSteal(const void *data ATTRIBUTE_UNUSED)
 }
 
 
-static void
+static int
 testHashIter(void *payload ATTRIBUTE_UNUSED,
              const void *name ATTRIBUTE_UNUSED,
              void *data ATTRIBUTE_UNUSED)
 {
-    return;
+    return 0;
 }
 
-static void
+static int
 testHashForEachIter(void *payload ATTRIBUTE_UNUSED,
                     const void *name ATTRIBUTE_UNUSED,
                     void *data)
@@ -332,6 +336,7 @@ testHashForEachIter(void *payload ATTRIBUTE_UNUSED,
     if (virHashForEach(hash, testHashIter, NULL) >= 0)
         VIR_TEST_VERBOSE("\niterating through hash in ForEach"
                 " should be forbidden");
+    return 0;
 }
 
 static int