Clean up some calls to ignore Error objects the right way

Receiving the error in a local variable only to free it is less clear
(and also less efficient) than passing NULL.  Clean up.

Cc: Daniel P. Berrange <berrange@redhat.com>
Cc: Jerome Forissier <jerome@forissier.org>
CC: Greg Kurz <groug@kaod.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200630090351.1247703-4-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

chardev/char-socket.c

@@ -817,22 +817,20 @@ static void tcp_chr_tls_init(Chardev *chr)
 {
     SocketChardev *s = SOCKET_CHARDEV(chr);
     QIOChannelTLS *tioc;
-    Error *err = NULL;
     gchar *name;
 
     if (s->is_listen) {
         tioc = qio_channel_tls_new_server(
             s->ioc, s->tls_creds,
             s->tls_authz,
-            &err);
+            NULL);
     } else {
         tioc = qio_channel_tls_new_client(
             s->ioc, s->tls_creds,
             s->addr->u.inet.host,
-            &err);
+            NULL);
     }
     if (tioc == NULL) {
-        error_free(err);
         tcp_chr_disconnect(chr);
         return;
     }

hw/9pfs/9p.c

@@ -1399,7 +1399,6 @@ static void coroutine_fn v9fs_attach(void *opaque)
     size_t offset = 7;
     V9fsQID qid;
     ssize_t err;
-    Error *local_err = NULL;
 
     v9fs_string_init(&uname);
     v9fs_string_init(&aname);
@@ -1437,9 +1436,8 @@ static void coroutine_fn v9fs_attach(void *opaque)
         error_setg(&s->migration_blocker,
                    "Migration is disabled when VirtFS export path '%s' is mounted in the guest using mount_tag '%s'",
                    s->ctx.fs_root ? s->ctx.fs_root : "NULL", s->tag);
-        err = migrate_add_blocker(s->migration_blocker, &local_err);
-        if (local_err) {
-            error_free(local_err);
+        err = migrate_add_blocker(s->migration_blocker, NULL);
+        if (err < 0) {
             error_free(s->migration_blocker);
             s->migration_blocker = NULL;
             clunk_fid(s, fid);

hw/arm/virt.c

@@ -217,11 +217,9 @@ static bool cpu_type_valid(const char *cpu)
 
 static void create_kaslr_seed(VirtMachineState *vms, const char *node)
 {
-    Error *err = NULL;
     uint64_t seed;
 
-    if (qemu_guest_getrandom(&seed, sizeof(seed), &err)) {
-        error_free(err);
+    if (qemu_guest_getrandom(&seed, sizeof(seed), NULL)) {
         return;
     }
     qemu_fdt_setprop_u64(vms->fdt, node, "kaslr-seed", seed);

hw/ppc/spapr_drc.c

@@ -1163,16 +1163,14 @@ static void rtas_ibm_configure_connector(PowerPCCPU *cpu,
     drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
 
     if (!drc->fdt) {
-        Error *local_err = NULL;
         void *fdt;
         int fdt_size;
 
         fdt = create_device_tree(&fdt_size);
 
         if (drck->dt_populate(drc, spapr, fdt, &drc->fdt_start_offset,
-                              &local_err)) {
+                              NULL)) {
             g_free(fdt);
-            error_free(local_err);
             rc = SPAPR_DR_CC_RESPONSE_ERROR;
             goto out;
         }

ui/vnc.c

@@ -458,9 +458,8 @@ static VncServerInfo2List *qmp_query_server_entry(QIOChannelSocket *ioc,
     Error *err = NULL;
     SocketAddress *addr;
 
-    addr = qio_channel_socket_get_local_address(ioc, &err);
+    addr = qio_channel_socket_get_local_address(ioc, NULL);
     if (!addr) {
-        error_free(err);
         return prev;
     }