Re: GObject: Freeing memory of instance members?

2007-05-05 Thread Yeti 
On Thu, May 03, 2007 at 08:03:15PM -0300, Alexandre Moreira wrote:
 
 Hey Yeti, since you're on the subject of object destruction, could you
 explain me the difference between the finalize and dispose methods ? I
 use finalize for everything but I believe I should be using dispose
 somewhere, it wouldn't exist if it were useless...I guess :)

See

  http://developer.gnome.org/doc/API/2.0/gobject/gobject-memory.html

Yeti

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Re: GObject: Freeing memory of instance members?

2007-05-05 Thread Yeti 
On Thu, May 03, 2007 at 08:16:23PM -0300, Alexandre Moreira wrote:
 
 At your class_init you should peek (g_type_class_peek_parent, using
 your class pointer as parameter) a pointer to your parent class and
 keep it in a global storage, accessible to your finalize.

Actually, what you should do is to use a macro from the
G_DEFINE_TYPE() family that does these things automaticaly
(the parent class variable is named my_type_parent_class).

 Then, in your finalize method you call the finalize method on this
 pointer you just got from peek_parent, something like:
 
 G_OBJECT_CLASS(parent_class)-finalize(pointer_to_the_object_being_finalized);

This still holds, except for the name.

Yeti

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Re: GObject: Freeing memory of instance members?

2007-05-05 Thread Øystein Johansen 
David Nečas (Yeti) wrote:
 Actually, what you should do is to use a macro from the
 G_DEFINE_TYPE() family that does these things automaticaly
 (the parent class variable is named my_type_parent_class).

Wow! A really powerful macro. I actually had to run a 'gcc -E' to
convince myself. Here's what it does:

Declare the functions:
my_type_init
my_type_class_init

Generate the functions:
my_type_class_intern_init (which sets the parent_class)
my_type_get_type

declare the variable:
my_type_parent_class

Why hasn't anyone told me of this macro before? Do you also have a macro
that cleans my house og does the laundry?

Thanks,
-Øystein



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Re: GObject: Freeing memory of instance members?

2007-05-05 Thread Øystein Johansen 
Øystein Johansen wrote:
 Wow! A really powerful macro. I actually had to run a 'gcc -E' to
 convince myself. Here's what it does:
 
 Declare the functions:
 my_type_init
 my_type_class_init

Hello?! Wait a minute The macro (G_DEFINE_TYPE) prototypes the
instance init function to:

static void my_thing_init( MyThing *self);

(line 358 in my gtype.h)

however API reference for GInstanceInitFunc() saysthe arguments should be:
(GTypeInstance *instance, gpointer g_class);

http://developer.gnome.org/doc/API/2.0/gobject/gobject-Type-Information.html#GInstanceInitFunc

I also get a error when compiling.
error: conflicting types for 'my_thing_init'
error: previous declaration of 'my_thing_init' was here
...
..
.
.

-Øystein

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Re: GObject: Freeing memory of instance members?

2007-05-05 Thread Yeti 
On Sat, May 05, 2007 at 05:45:06PM +0200, ??ystein Johansen wrote:
 
 Hello?! Wait a minute The macro (G_DEFINE_TYPE) prototypes the
 instance init function to:
 
 static void my_thing_init( MyThing *self);
 
 (line 358 in my gtype.h)
 
 however API reference for GInstanceInitFunc() saysthe arguments should be:
 (GTypeInstance *instance, gpointer g_class);

Yes, but almost no-one actually uses the second argument.
And since unused trailing arguments can be safely ignored in
C, commonly they are not even declared.

If you really need the second argument (for instance when
a parent class performs some common initialization based on
subclass-specified information and therefore it needs to
know the actual type being initialized) you cannot use these
macros.

Yeti

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GObject: Freeing memory of instance members?

2007-05-03 Thread Øystein Johansen 
Hi,

I've just started to use GObject, and I think I understand most of it by
now. There's still some questions remaining. Here's one:

I have an instance struct that has a pointer to a some data that's
dynamically allocated in a method. How can I free this memory when the
object is finalzed? Is this done automatically in g_object_unref() (when
refcounter is zero) ?

-Øystein

PS:
I see a pointer to a func in the info struct called base_finalize and
another called class_finalize, but these seems to be used for cleaning
up when I have base_init and class_init.
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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Yeti 
On Thu, May 03, 2007 at 09:51:05PM +0200, ?ystein Johansen wrote:
 
 I have an instance struct that has a pointer to a some data that's
 dynamically allocated in a method. How can I free this memory when the
 object is finalzed? Is this done automatically in g_object_unref() (when
 refcounter is zero) ?

When the reference count reaches zero and the object is
finalized, its finalize() method is called.  And that's
where you should free any possibly allocated memory.
Remember to chain up parent class finalize() method in your
finalize().

 I see a pointer to a func in the info struct called base_finalize and
 another called class_finalize, but these seems to be used for cleaning
 up when I have base_init and class_init.

Ignore these, they are related to class initialization and
finalization.

Yeti

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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Øystein Johansen 
David Nečas (Yeti) wrote:
 On Thu, May 03, 2007 at 09:51:05PM +0200, ?ystein Johansen wrote:
 I have an instance struct that has a pointer to a some data that's
 dynamically allocated in a method. How can I free this memory when the
 object is finalzed? Is this done automatically in g_object_unref() (when
 refcounter is zero) ?
 
 When the reference count reaches zero and the object is
 finalized, its finalize() method is called.  And that's
 where you should free any possibly allocated memory.

Aha, but how/where to I set the pointer to the finalize() function?

 Remember to chain up parent class finalize() method in your
 finalize().

I will! :-)

-Øystein

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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Yeti 
On Thu, May 03, 2007 at 10:40:17PM +0200, ??ystein Johansen wrote:
 
 Aha, but how/where to I set the pointer to the finalize() function?

In my_class_init() where you override all other methods.
See (almost) any Gtk+ widget for examples.

Yeti

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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Øystein Johansen 
David Nečas (Yeti) wrote:
 On Thu, May 03, 2007 at 10:40:17PM +0200, ??ystein Johansen wrote:
 Aha, but how/where to I set the pointer to the finalize() function?
 
 In my_class_init() where you override all other methods.
 See (almost) any Gtk+ widget for examples.

Aha again! I guess I can free private members in the same method as well?

static void
neural_net_finalize (GObject *object)
{
  NeuralNet *nn;

  g_return_if_fail (IS_NEURAL_NET(object));

  nn = NEURAL_NET(object);

  g_free(nn-priv-weight_h);
  g_free(nn-priv-weight_o);
  g_free(nn-priv-bias_h);
  g_free(nn-priv-bias_o);
  g_free(nn-priv-filename);
  g_free(nn-priv);

  g_message(This is the finalize method and I've freed the instance
members!\n);

}

static void
neural_net_class_init (NeuralNetClass *klass){
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class-finalize = neural_net_finalize;
g_type_class_add_private (klass, sizeof (NeuralNetPrivate));
}

I think this looks ok, doesn't it? No, wait a minite What about the
parent? This class has GObjectClass as parent, how do I call it's finalize?

Thanks,
-Øystein

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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Alexandre Moreira 
On 5/3/07, David Nečas (Yeti) [EMAIL PROTECTED] wrote:
 On Thu, May 03, 2007 at 10:40:17PM +0200, ??ystein Johansen wrote:
 
  Aha, but how/where to I set the pointer to the finalize() function?

 In my_class_init() where you override all other methods.
 See (almost) any Gtk+ widget for examples.

Hey Yeti, since you're on the subject of object destruction, could you
explain me the difference between the finalize and dispose methods ? I
use finalize for everything but I believe I should be using dispose
somewhere, it wouldn't exist if it were useless...I guess :)

Thanks,
Alexandre Moreira.


 Yeti

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Re: GObject: Freeing memory of instance members?

2007-05-03 Thread Alexandre Moreira 
On 5/3/07, Øystein Johansen [EMAIL PROTECTED] wrote:
 David Nečas (Yeti) wrote:
  On Thu, May 03, 2007 at 10:40:17PM +0200, ??ystein Johansen wrote:
  Aha, but how/where to I set the pointer to the finalize() function?
 
  In my_class_init() where you override all other methods.
  See (almost) any Gtk+ widget for examples.

 Aha again! I guess I can free private members in the same method as well?

 static void
 neural_net_finalize (GObject *object)
 {
   NeuralNet *nn;

   g_return_if_fail (IS_NEURAL_NET(object));

   nn = NEURAL_NET(object);

   g_free(nn-priv-weight_h);
   g_free(nn-priv-weight_o);
   g_free(nn-priv-bias_h);
   g_free(nn-priv-bias_o);
   g_free(nn-priv-filename);
   g_free(nn-priv);

   g_message(This is the finalize method and I've freed the instance
 members!\n);

 }

 static void
 neural_net_class_init (NeuralNetClass *klass){
 GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 gobject_class-finalize = neural_net_finalize;
 g_type_class_add_private (klass, sizeof (NeuralNetPrivate));
 }

 I think this looks ok, doesn't it? No, wait a minite What about the
 parent? This class has GObjectClass as parent, how do I call it's finalize?

At your class_init you should peek (g_type_class_peek_parent, using
your class pointer as parameter) a pointer to your parent class and
keep it in a global storage, accessible to your finalize.

Then, in your finalize method you call the finalize method on this
pointer you just got from peek_parent, something like:

G_OBJECT_CLASS(parent_class)-finalize(pointer_to_the_object_being_finalized);

I hope this helps.
Alexandre Moreira.


 Thanks,
 -Øystein

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