migration: simplify exec migration functions

Simplify the exec migration code by using list utility functions.

As a side effect, this also fixes a minor memory leak.  On function return,
"g_auto(GStrv) argv" frees argv and each element, which is wrong, because
the function does not own the individual elements.  To compensate, the code
uses g_steal_pointer which NULLs argv and prevents the destructor from
running, but argv is leaked.

Fixes: cbab4face57b ("migration: convert exec backend ...")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <20240227153321.467343-4-armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

migration/exec.c

@@ -18,6 +18,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/type-helpers.h"
 #include "qemu/error-report.h"
 #include "channel.h"
 #include "exec.h"
@@ -39,51 +40,16 @@ const char *exec_get_cmd_path(void)
 }
 #endif
 
-/* provides the length of strList */
-static int
-str_list_length(strList *list)
-{
-    int len = 0;
-    strList *elem;
-
-    for (elem = list; elem != NULL; elem = elem->next) {
-        len++;
-    }
-
-    return len;
-}
-
-static void
-init_exec_array(strList *command, char **argv, Error **errp)
-{
-    int i = 0;
-    strList *lst;
-
-    for (lst = command; lst; lst = lst->next) {
-        argv[i++] = lst->value;
-    }
-
-    argv[i] = NULL;
-    return;
-}
-
 void exec_start_outgoing_migration(MigrationState *s, strList *command,
                                    Error **errp)
 {
-    QIOChannel *ioc;
-
-    int length = str_list_length(command);
-    g_auto(GStrv) argv = (char **) g_new0(const char *, length + 1);
-
-    init_exec_array(command, argv, errp);
+    QIOChannel *ioc = NULL;
+    g_auto(GStrv) argv = strv_from_str_list(command);
+    const char * const *args = (const char * const *) argv;
     g_autofree char *new_command = g_strjoinv(" ", (char **)argv);
 
     trace_migration_exec_outgoing(new_command);
-    ioc = QIO_CHANNEL(
-        qio_channel_command_new_spawn(
-                            (const char * const *) g_steal_pointer(&argv),
-                            O_RDWR,
-                            errp));
+    ioc = QIO_CHANNEL(qio_channel_command_new_spawn(args, O_RDWR, errp));
     if (!ioc) {
         return;
     }
@@ -105,19 +71,12 @@ static gboolean exec_accept_incoming_migration(QIOChannel *ioc,
 void exec_start_incoming_migration(strList *command, Error **errp)
 {
     QIOChannel *ioc;
-
-    int length = str_list_length(command);
-    g_auto(GStrv) argv = (char **) g_new0(const char *, length + 1);
-
-    init_exec_array(command, argv, errp);
+    g_auto(GStrv) argv = strv_from_str_list(command);
+    const char * const *args = (const char * const *) argv;
     g_autofree char *new_command = g_strjoinv(" ", (char **)argv);
 
     trace_migration_exec_incoming(new_command);
-    ioc = QIO_CHANNEL(
-        qio_channel_command_new_spawn(
-                            (const char * const *) g_steal_pointer(&argv),
-                            O_RDWR,
-                            errp));
+    ioc = QIO_CHANNEL(qio_channel_command_new_spawn(args, O_RDWR, errp));
     if (!ioc) {
         return;
     }