[sound-juicer] Fix -Wsuggest-attribute warnings

[Phillip Wood <pwood src gnome org>]

commit 0992050834f97d96f8d246244474e3a274544893
Author: Phillip Wood <phillip wood dunelm org uk>
Date:   Fri Feb 3 11:32:00 2017 +0000

    Fix -Wsuggest-attribute warnings
    
    Add a couple of function attributes suggested by the compiler.

 src/sound-juicer.h |    2 +-
 tests/mb-test.c    |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/sound-juicer.h b/src/sound-juicer.h
index 66083cf..2e87343 100644
--- a/src/sound-juicer.h
+++ b/src/sound-juicer.h
@@ -136,7 +136,7 @@ extern GtkCellRenderer *toggle_renderer, *title_renderer, *artist_renderer, *com
 /**
  * Debug
  */
-void sj_debug (SjDebugDomain domain, const gchar* format, ...);
+G_GNUC_PRINTF(2,3) void sj_debug (SjDebugDomain domain, const gchar* format, ...);
 
 /**
  * GSettings key names
diff --git a/tests/mb-test.c b/tests/mb-test.c
index 0fd0c7c..5566659 100644
--- a/tests/mb-test.c
+++ b/tests/mb-test.c
@@ -41,7 +41,7 @@ release_type_to_id (const char *type)
        return NULL;
 }
 
-static void
+G_GNUC_NORETURN static void
 metadata_cb (GObject *object, GAsyncResult *result, gpointer user_data)
 {
   SjMetadataGetter* metadata = SJ_METADATA_GETTER (object);