qapi: Simplify excess input reporting in input visitors

When reporting that an unvisited member remains at the end of an
input visit for a struct, we were using g_hash_table_find()
coupled with a callback function that always returns true, to
locate an arbitrary member of the hash table.  But if all we
need is an arbitrary entry, we can get that from a single-use
iterator, without needing a tautological callback function.

Technically, our cast of &(GQueue *) to (void **) is not strict
C (while void * must be able to hold all other pointers, nothing
says a void ** has to be the same width or representation as a
GQueue **).  The kosher way to write it would be the verbose:

    void *tmp;
    GQueue *any;
    if (g_hash_table_iter_next(&iter, NULL, &tmp)) {
        any = tmp;

But our code base (not to mention glib itself) already has other
cases of assuming that ALL pointers have the same width and
representation, where a compiler would have to go out of its way
to mis-compile our borderline behavior.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1455778109-6278-2-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 3 insertions, 9 deletions

diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
index d54f75b..ae5b955 100644
--- a/qapi/opts-visitor.c
+++ b/qapi/opts-visitor.c
@@ -157,17 +157,11 @@ opts_start_struct(Visitor *v, const char *name, void **obj,
 }
 
 
-static gboolean
-ghr_true(gpointer ign_key, gpointer ign_value, gpointer ign_user_data)
-{
-    return TRUE;
-}
-
-
 static void
 opts_end_struct(Visitor *v, Error **errp)
 {
     OptsVisitor *ov = to_ov(v);
+    GHashTableIter iter;
     GQueue *any;
 
     if (--ov->depth > 0) {
@@ -175,8 +169,8 @@ opts_end_struct(Visitor *v, Error **errp)
     }
 
     /* we should have processed all (distinct) QemuOpt instances */
-    any = g_hash_table_find(ov->unprocessed_opts, &ghr_true, NULL);
-    if (any) {
+    g_hash_table_iter_init(&iter, ov->unprocessed_opts);
+    if (g_hash_table_iter_next(&iter, NULL, (void **)&any)) {
         const QemuOpt *first;
 
         first = g_queue_peek_head(any);