[vala] Fix memory leak when defining async functions targeting glib < 2.20.

[Luca Bruno <lucabru src gnome org>]

commit e60d03f2f93bb33652768957c8304c4e3e0f4d85
Author: Luca Bruno <lucabru src gnome org>
Date:   Tue Jun 4 22:46:23 2013 +0200

    Fix memory leak when defining async functions targeting glib < 2.20.
    
    Fixes bug 684182

 codegen/valagasyncmodule.vala |   22 +++++++++++++++++++++-
 1 files changed, 21 insertions(+), 1 deletions(-)
---
diff --git a/codegen/valagasyncmodule.vala b/codegen/valagasyncmodule.vala
index 3317c7f..068392e 100644
--- a/codegen/valagasyncmodule.vala
+++ b/codegen/valagasyncmodule.vala
@@ -23,11 +23,20 @@
 using GLib;
 
 public class Vala.GAsyncModule : GtkModule {
+       bool needs_dummy_object (Method m) {
+               var t = m.parent_symbol as TypeSymbol;
+               return t == null || !t.is_subtype_of (gobject_type) || m is CreationMethod || m.binding != 
MemberBinding.INSTANCE
+                       && !context.require_glib_version (2, 20);
+       }
+
        CCodeStruct generate_data_struct (Method m) {
                string dataname = Symbol.lower_case_to_camel_case (get_ccode_name (m)) + "Data";
                var data = new CCodeStruct ("_" + dataname);
 
                data.add_field ("int", "_state_");
+               if (needs_dummy_object (m)) {
+                       data.add_field ("GObject*", "_dummy_object_");
+               }
                data.add_field ("GObject*", "_source_object_");
                data.add_field ("GAsyncResult*", "_res_");
                data.add_field ("GSimpleAsyncResult*", "_async_result");
@@ -137,6 +146,14 @@ public class Vala.GAsyncModule : GtkModule {
                        }
                }
 
+               if (needs_dummy_object (m)) {
+                       // free dummy object being created in g_simple_async_result_new
+                       var dummy_object = new CCodeMemberAccess.pointer (new CCodeIdentifier ("_data_"), 
"_dummy_object_");
+                       var free_dummy_object = new CCodeFunctionCall (new CCodeIdentifier 
("g_object_unref"));
+                       free_dummy_object.add_argument (dummy_object);
+
+                       ccode.add_expression (free_dummy_object);
+               }
 
                var freecall = new CCodeFunctionCall (new CCodeIdentifier ("g_slice_free"));
                freecall.add_argument (new CCodeIdentifier (dataname));
@@ -213,12 +230,15 @@ public class Vala.GAsyncModule : GtkModule {
                        if (context.require_glib_version (2, 20)) {
                                create_result.add_argument (new CCodeConstant ("NULL"));
                        } else {
+                               // needs dummy object
                                var object_creation = new CCodeFunctionCall (new CCodeIdentifier 
("g_object_newv"));
                                object_creation.add_argument (new CCodeConstant ("G_TYPE_OBJECT"));
                                object_creation.add_argument (new CCodeConstant ("0"));
                                object_creation.add_argument (new CCodeConstant ("NULL"));
 
-                               create_result.add_argument (object_creation);
+                               ccode.add_assignment (new CCodeMemberAccess.pointer (data_var, 
"_dummy_object_"), object_creation);
+
+                               create_result.add_argument (new CCodeMemberAccess.pointer (data_var, 
"_dummy_object_"));
                        }
                }