tests/qtest: Add a function that gets a list with available machine types

For the upcoming patches, we will need a way to gets a list with all
available machine types. Refactor the qtest_cb_for_every_machine()
to split the related code out into a separate new function, and
gather the aliases of the various machine types, too.

Message-Id: <20211201104347.51922-4-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/qtest/libqtest.c

@@ -1321,16 +1321,29 @@ static bool qtest_is_old_versioned_machine(const char *mname)
     return res;
 }
 
-void qtest_cb_for_every_machine(void (*cb)(const char *machine),
-                                bool skip_old_versioned)
+struct MachInfo {
+    char *name;
+    char *alias;
+};
+
+/*
+ * Returns an array with pointers to the available machine names.
+ * The terminating entry has the name set to NULL.
+ */
+static struct MachInfo *qtest_get_machines(void)
 {
+    static struct MachInfo *machines;
     QDict *response, *minfo;
     QList *list;
     const QListEntry *p;
     QObject *qobj;
     QString *qstr;
-    const char *mname;
     QTestState *qts;
+    int idx;
+
+    if (machines) {
+        return machines;
+    }
 
     qts = qtest_init("-machine none");
     response = qtest_qmp(qts, "{ 'execute': 'query-machines' }");
@@ -1338,25 +1351,54 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
     list = qdict_get_qlist(response, "return");
     g_assert(list);
 
-    for (p = qlist_first(list); p; p = qlist_next(p)) {
+    machines = g_new(struct MachInfo, qlist_size(list) + 1);
+
+    for (p = qlist_first(list), idx = 0; p; p = qlist_next(p), idx++) {
         minfo = qobject_to(QDict, qlist_entry_obj(p));
         g_assert(minfo);
+
         qobj = qdict_get(minfo, "name");
         g_assert(qobj);
         qstr = qobject_to(QString, qobj);
         g_assert(qstr);
-        mname = qstring_get_str(qstr);
-        /* Ignore machines that cannot be used for qtests */
-        if (!strncmp("xenfv", mname, 5) || g_str_equal("xenpv", mname)) {
-            continue;
-        }
-        if (!skip_old_versioned || !qtest_is_old_versioned_machine(mname)) {
-            cb(mname);
+        machines[idx].name = g_strdup(qstring_get_str(qstr));
+
+        qobj = qdict_get(minfo, "alias");
+        if (qobj) {                               /* The alias is optional */
+            qstr = qobject_to(QString, qobj);
+            g_assert(qstr);
+            machines[idx].alias = g_strdup(qstring_get_str(qstr));
+        } else {
+            machines[idx].alias = NULL;
         }
     }
 
     qtest_quit(qts);
     qobject_unref(response);
+
+    memset(&machines[idx], 0, sizeof(struct MachInfo)); /* Terminating entry */
+    return machines;
+}
+
+void qtest_cb_for_every_machine(void (*cb)(const char *machine),
+                                bool skip_old_versioned)
+{
+    struct MachInfo *machines;
+    int i;
+
+    machines = qtest_get_machines();
+
+    for (i = 0; machines[i].name != NULL; i++) {
+        /* Ignore machines that cannot be used for qtests */
+        if (!strncmp("xenfv", machines[i].name, 5) ||
+            g_str_equal("xenpv", machines[i].name)) {
+            continue;
+        }
+        if (!skip_old_versioned ||
+            !qtest_is_old_versioned_machine(machines[i].name)) {
+            cb(machines[i].name);
+        }
+    }
 }
 
 /*