Fixes random crashes caused by bad wrapper instance cache.

ecr/interface.ecr

@@ -32,12 +32,12 @@ module <%= namespace_name %>
   class <%= abstract_interface_name(object, false) %> < GObject::Object
     include <%= type_name %>
 
-    GICrystal.declare_new_method(<%= abstract_interface_name(object) %>, g_object_get_qdata, g_object_set_qdata)
+    GICrystal.declare_new_method(<%= abstract_interface_name(object) %>, g_object_get_qdata)
 
     # Forbid users to create instances of this.
     private def initialize
     end
 
-    <% render "ecr/g_type_method.ecr" %>
+    <% render "ecr/interface_g_type_method.ecr" %>
   end
 end

ecr/interface_g_type_method.ecr

@@ -0,0 +1,12 @@
+<% if object.type_init -%>
+  @@g_type : UInt64?
+
+  # Returns the type id (GType) registered in GLib type system.
+  def self.g_type : UInt64
+    @@g_type ||= <%= to_lib_namespace(namespace) %>.<%= object.type_init %>.tap do |g_type|
+      # Set the Crystal constructor on type qdata
+      ctor = -><%= abstract_interface_name(object) %>.new(Void*, GICrystal::Transfer)
+      LibGObject.g_type_set_qdata(g_type, GICrystal::INSTANCE_FACTORY, ctor.pointer)
+    end
+  end
+<% end %>

ecr/object.ecr

@@ -77,10 +77,12 @@ module <%= namespace_name %>
       end
     <% end %>
 
-    <% render "ecr/g_type_method.ecr" %>
+    <% render "ecr/object_g_type_method.ecr" %>
     <% render_properties %>
     <% render_methods %>
     <% render_signals %>
     <% render_vfuncs %>
+
+    def_equals_and_hash @pointer
   end
 end

ecr/object_g_type_method.ecr

@@ -0,0 +1,12 @@
+<% if object.type_init -%>
+  @@g_type : UInt64?
+
+  # Returns the type id (GType) registered in GLib type system.
+  def self.g_type : UInt64
+    @@g_type ||= <%= to_lib_namespace(namespace) %>.<%= object.type_init %>.tap do |g_type|
+      # Set the Crystal constructor on type qdata
+      ctor = -><%= namespace_name %>::<%= type_name %>.new(Void*, GICrystal::Transfer)
+      LibGObject.g_type_set_qdata(g_type, GICrystal::INSTANCE_FACTORY, ctor.pointer)
+    end
+  end
+<% end %>

spec/basic_spec.cr

@@ -113,14 +113,27 @@ describe "GObject Binding" do
   end
 
   describe "casts" do
+    it "don't use wrapper cache" do
+      ptr = LibGObject.g_object_new(Test::SubjectChild.g_type, "string", "hey", "int32", 42, Pointer(Void).null)
+      obj = GObject::Object.new(ptr, :full)
+      subject = Test::SubjectChild.cast(obj)
+      # If these pointers are equal, they are the same Crystal object, with luck it may not crash, but
+      # it can crash because the crystal type id is for GObject::Object instead of Test::SubjectChild.
+      #
+      # Note that if the type is an user type, these pointers must be the same!
+      obj.as(Void*).should_not eq(subject.as(Void*))
+    end
+
     it "can downcast objects" do
       child = Test::SubjectChild.new(string: "hey")
       gobj = child.me_as_gobject
-      gobj.ref_count.should eq(1)
+      gobj.ref_count.should eq(2) # we can't reuse the crystal wrapper of non-user objects
       gobj.class.should eq(Test::SubjectChild)
       cast = Test::Subject.cast(gobj)
-      cast.ref_count.should eq(1)
+      cast.ref_count.should eq(3)
       cast.string.should eq("hey")
+      child.should eq(gobj)
+      cast.should eq(gobj)
     end
 
     it "thrown an exception on bad casts" do

spec/inheritance_spec.cr

@@ -66,7 +66,8 @@ describe "Classes inheriting GObject::Object" do
     casted_obj.object_id.should eq(obj.object_id)
   end
 
-  it "create a crystal instance if the object was born on C world" do
+  # Crystal types created in C world are not supported yet
+  pending "creates crystal object for Crystal type born in C world" do
     raw_gobj = LibGObject.g_object_newv(UserObject.g_type, 0, nil)
     wrapper = GObject::Object.new(raw_gobj, :full)
     obj = UserObject.cast(wrapper)
@@ -78,7 +79,7 @@ describe "Classes inheriting GObject::Object" do
     obj.ref_count.should eq(1)
   end
 
-  it "create a crystal instance if the object with float ref was born on C world" do
+  pending "creates crystal object for Crystal type with float ref born in C world" do
     raw_gobj = LibGObject.g_object_newv(UserFloatRefObject.g_type, 0, nil)
     wrapper = GObject::Object.new(raw_gobj, :full)
     obj = UserFloatRefObject.cast(wrapper)

spec/libtest/test_subject.c

@@ -519,7 +519,7 @@ GList* test_subject_return_list_of_iface_transfer_full(TestSubject* self) {
   GList* list = NULL;
   g_object_ref(self);
   list = g_list_append(list, self);
-  list = g_list_append(list, test_subject_new_from_string("Subject from C"));
+  list = g_list_append(list, test_subject_new_from_string("Born in C"));
   return list;
 }
 

spec/list_spec.cr

@@ -2,27 +2,27 @@ require "./spec_helper"
 
 describe "GList" do
   it "works with interfaces" do
-    subject = Test::Subject.new(string: "Subject from Crystal")
+    subject = Test::Subject.new(string: "Born in Crystal")
 
     list = subject.return_list_of_iface_transfer_full
     list.size.should eq(2)
 
     subject_from_c = list[0]
     subject_from_c.object_id.should eq(subject.object_id)
-    Test::Subject.cast(subject_from_c).string.should eq("Subject from Crystal")
-    Test::Subject.cast(list[1]).string.should eq("Subject from C")
+    Test::Subject.cast(subject_from_c).string.should eq("Born in Crystal")
+    Test::Subject.cast(list[1]).string.should eq("Born in C")
   end
 
   it "works with GObjects" do
-    subject = Test::Subject.new(string: "Subject from Crystal")
+    subject = Test::Subject.new(string: "Born in Crystal")
 
     list = subject.return_list_of_gobject_transfer_full
     list.size.should eq(2)
 
     subject_from_c = list[0]
     subject_from_c.object_id.should eq(subject.object_id)
-    Test::Subject.cast(subject_from_c).string.should eq("Subject from Crystal")
-    Test::Subject.cast(list[1]).string.should eq("Subject from C")
+    Test::Subject.cast(subject_from_c).string.should eq("Born in Crystal")
+    Test::Subject.cast(list[1]).string.should eq("Born in C")
   end
 
   it "works on transfer full" do

spec/s_list_spec.cr

@@ -7,9 +7,8 @@ describe "GSList" do
     list = subject.return_slist_of_iface_transfer_full
     list.size.should eq(2)
 
-    subject_from_c = list[0]
-    subject_from_c.object_id.should eq(subject.object_id)
-    Test::Subject.cast(subject_from_c).string.should eq("Subject from Crystal")
+    list[0].object_id.should eq(subject.object_id)
+    Test::Subject.cast(list[0]).string.should eq("Subject from Crystal")
     Test::Subject.cast(list[1]).string.should eq("Subject from C")
   end
 
@@ -19,9 +18,11 @@ describe "GSList" do
     list = subject.return_slist_of_gobject_transfer_full
     list.size.should eq(2)
 
-    subject_from_c = list[0]
-    subject_from_c.object_id.should eq(subject.object_id)
-    Test::Subject.cast(subject_from_c).string.should eq("Subject from Crystal")
+    list[0].object_id.should eq(subject.object_id)
+    list[0].as(Test::Subject).string.should eq("Subject from Crystal")
+    Test::Subject.cast(list[0]).string.should eq("Subject from Crystal")
+
+    list[1].as(Test::Subject).string.should eq("Subject from C")
     Test::Subject.cast(list[1]).string.should eq("Subject from C")
   end
 

spec/vfunc_spec.cr

@@ -86,7 +86,7 @@ describe "GObject vfuncs" do
     obj.float64.should eq(3.3)
     obj.string.should eq("string")
     subject = Test::Subject.cast(obj.obj)
-    subject.ref_count.should eq(1)
+    subject.ref_count.should eq(2) # now 2 wrappers for the same C obj
     subject.string.should eq("hey")
   end
 
@@ -98,7 +98,7 @@ describe "GObject vfuncs" do
     obj.float64.should eq(3.3)
     obj.string.should eq("string")
     subject = Test::Subject.cast(obj.obj)
-    subject.ref_count.should eq(1)
+    subject.ref_count.should eq(2) # now 2 wrappers for the same C obj
     subject.string.should eq("hey")
   end
 

src/bindings/g_object/lib_g_object.cr

@@ -5,6 +5,9 @@ lib LibGObject
   # So we can re-use the Crystal objects saving some memory allocations.
   fun g_object_set_qdata(object : Void*, quark : UInt32, data : Void*)
 
+  # This is used only tests
+  fun g_object_new(type : UInt64, first_property_name : Pointer(LibC::Char), ...) : Void*
+
   fun g_signal_new(signal_name : LibC::Char*,
                    itype : UInt64,
                    signal_flags : UInt32,

src/bindings/g_object/object.cr

@@ -444,13 +444,7 @@ module GObject
 
         # Cast a `GObject::Object` to this type, returns nil if cast can't be made.
         def self.cast?(obj : GObject::Object) : self?
-          return if LibGObject.g_type_check_instance_is_a(obj, g_type).zero?
-
-          instance = GICrystal.instance_pointer(obj)
-          # This should never happen with GC resistant objects
-          raise GICrystal::ObjectCollectedError.new if instance.null?
-
-          instance.as(self)
+          new(obj.to_unsafe, :none) unless LibGObject.g_type_check_instance_is_a(obj, g_type).zero?
         end
 
         # A hook to be executed after the underlying gobject has been initialized.
@@ -634,7 +628,7 @@ module GObject
 
     # Cast a `GObject::Object` to `self`, returns nil if the cast can't be made.
     def self.cast?(obj : GObject::Object) : self?
-      new(obj.to_unsafe, GICrystal::Transfer::None) unless LibGObject.g_type_check_instance_is_a(obj, g_type).zero?
+      new(obj.to_unsafe, :none) unless LibGObject.g_type_check_instance_is_a(obj, g_type).zero?
     end
   end
 end

src/generator/object_gen.cr

@@ -80,7 +80,7 @@ module Generator
     def render_qdata_optimized_new_method(io : IO)
       return if !object.inherits?("GObject") && !object.inherits?("GParam")
 
-      io << "GICrystal.declare_new_method(" << type_name << ',' << object.qdata_get_func << ',' << object.qdata_set_func << ")\n"
+      io << "GICrystal.declare_new_method(" << type_name << ',' << object.qdata_get_func << ")\n"
     end
   end
 end

src/gi-crystal.cr

@@ -29,6 +29,8 @@ module GICrystal
 
   # See `declare_new_method`.
   INSTANCE_QDATA_KEY = LibGLib.g_quark_from_static_string("gi-crystal::instance")
+  # See `declare_new_method`.
+  INSTANCE_FACTORY = LibGLib.g_quark_from_static_string("gi-crystal::factory")
 
   # Raised when trying to cast an object that was already collected by GC.
   class ObjectCollectedError < RuntimeError
@@ -117,23 +119,36 @@ module GICrystal
     end
   end
 
-  # This declare the `new` method on a instance of type *type*, *qdata_get_func* and *qdata_set_func* are functions used
-  # to set/get qdata on objects, e.g. `g_object_get_qdata`/`g_object_set_qdata` for GObjects.
+  # This declare the `new` method on a instance of type *type*, *qdata_get_func* (g_object_get_qdata) is used
+  # to fetch a possible already existing Crystal object.
   #
-  # GICrystal stores the Crystal object instance in the GObject, so when it appears from C world we try to re-use the
-  # old Crystal instance if it wasn't garbage collected. The key used for this is `INSTANCE_QDATA_KEY`.
+  # GICrystal stores the User defined Crystal objects instances in the GObject, so when it appears from C
+  # world we can retrieve the Crystal instance back.
   #
   # This is mainly used for `GObject::Object`, since `GObject::ParamSpec` doesn't support casts on GICrystal.
-  macro declare_new_method(type, qdata_get_func, qdata_set_func)
+  macro declare_new_method(type, qdata_get_func)
     # :nodoc:
     def self.new(pointer : Pointer(Void), transfer : GICrystal::Transfer) : self
       # Try to recover the Crystal instance if any
       instance = LibGObject.{{ qdata_get_func }}(pointer, GICrystal::INSTANCE_QDATA_KEY)
       return instance.as({{ type }}) if instance
 
-      # This object never meet Crystal land, so we allocate memory and initialize it.
+      # Try to construct the right wrapper for the matching GObject using the function pointer
+      # to `{{ type }}.new` stored in GType qdata.
+      #
+      # This pointer is stored at type initialization, i.e. the `g_type` class method.
+      instance_g_type = pointer.as(LibGObject::TypeInstance*).value.g_class.value.g_type
+      if instance_g_type != g_type
+        ctor_ptr = LibGObject.g_type_get_qdata(instance_g_type, GICrystal::INSTANCE_FACTORY)
+        if ctor_ptr
+          ctor = Proc(Void*, GICrystal::Transfer, {{ type }}).new(ctor_ptr, Pointer(Void).null)
+          return ctor.call(pointer, transfer)
+        end
+      end
+
+      # This object never meet Crystal land and there's no Crystal wrapper for the exact GType,
+      # so we allocate memory and initialize it for the type we know.
       instance = {{ type }}.allocate
-      LibGObject.{{ qdata_set_func }}(pointer, GICrystal::INSTANCE_QDATA_KEY, Pointer(Void).new(instance.object_id))
       instance.initialize(pointer, transfer)
       GC.add_finalizer(instance)
       instance