target-alpha: Catch attempt to instantiate abstract type in cpu_init()

This fixes -cpu alpha-cpu asserting.

Cc: qemu-stable@nongnu.org
Signed-off-by: NAndreas Färber <afaerber@suse.de>

target-alpha/cpu.c

@@ -96,14 +96,15 @@ static ObjectClass *alpha_cpu_class_by_name(const char *cpu_model)
     }
 
     oc = object_class_by_name(cpu_model);
-    if (oc != NULL && object_class_dynamic_cast(oc, TYPE_ALPHA_CPU) != NULL) {
+    if (oc != NULL && object_class_dynamic_cast(oc, TYPE_ALPHA_CPU) != NULL &&
+        !object_class_is_abstract(oc)) {
         return oc;
     }
 
     for (i = 0; i < ARRAY_SIZE(alpha_cpu_aliases); i++) {
         if (strcmp(cpu_model, alpha_cpu_aliases[i].alias) == 0) {
             oc = object_class_by_name(alpha_cpu_aliases[i].typename);
-            assert(oc != NULL);
+            assert(oc != NULL && !object_class_is_abstract(oc));
             return oc;
         }
     }
@@ -111,6 +112,9 @@ static ObjectClass *alpha_cpu_class_by_name(const char *cpu_model)
     typename = g_strdup_printf("%s-" TYPE_ALPHA_CPU, cpu_model);
     oc = object_class_by_name(typename);
     g_free(typename);
+    if (oc != NULL && object_class_is_abstract(oc)) {
+        oc = NULL;
+    }
     return oc;
 }