block/gluster: Use g_autofree for string in qemu_gluster_parse_json()

In the loop in qemu_gluster_parse_json() we do:

    char *str = NULL;
    for(...) {
        str = g_strdup_printf(...);
        ...
        if (various errors) {
            goto out;
        }
        ...
        g_free(str);
        str = NULL;
    }
    return 0;
out:
    various cleanups;
    g_free(str);
    ...
    return -errno;

Coverity correctly complains that the assignment "str = NULL" at the
end of the loop is unnecessary, because we will either go back to the
top of the loop and overwrite it, or else we will exit the loop and
then exit the function without ever reading str again. The assignment
is there as defensive coding to ensure that str is only non-NULL if
it's a live allocation, so this is intentional.

We can make Coverity happier and simplify the code here by using
g_autofree, since we never need 'str' outside the loop.

Resolves: Coverity CID 1527385
Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-ID: <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>

block/gluster.c

@@ -514,7 +514,6 @@ static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
     SocketAddressList **tail;
     QDict *backing_options = NULL;
     Error *local_err = NULL;
-    char *str = NULL;
     const char *ptr;
     int i, type, num_servers;
 
@@ -547,7 +546,8 @@ static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
     tail = &gconf->server;
 
     for (i = 0; i < num_servers; i++) {
-        str = g_strdup_printf(GLUSTER_OPT_SERVER_PATTERN"%d.", i);
+        g_autofree char *str = g_strdup_printf(GLUSTER_OPT_SERVER_PATTERN"%d.",
+                                               i);
         qdict_extract_subqdict(options, &backing_options, str);
 
         /* create opts info from runtime_type_opts list */
@@ -658,8 +658,6 @@ static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
 
         qobject_unref(backing_options);
         backing_options = NULL;
-        g_free(str);
-        str = NULL;
     }
 
     return 0;
@@ -668,7 +666,6 @@ static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
     error_propagate(errp, local_err);
     qapi_free_SocketAddress(gsconf);
     qemu_opts_del(opts);
-    g_free(str);
     qobject_unref(backing_options);
     errno = EINVAL;
     return -errno;