Re: [Vala] Should be warning(maybe error) when method with [ReturnsModifiedPointer] is called from unowned variable

[Jarosław Ciupiński <kotowate gmail com>]

Yes, now I see it. I guess that it might be error specific to
implementation of GLib.SList.

In example that you gave, same behaviour can be seen when removing first
item from other list (given_list). If it is first item, list you were
modifying works fine, but other seems to be broken (it is the same in both
cases, modifying given_list or list).

I won't be able to help you :( (btw, I use Gee for lists/arrays etc).

Jarek

2012/11/6 Tal Hadad <tal_hd hotmail com>

> I'm sorry, the example I gave is bad. Forgot the "unowned" word.
> Example:
>
> unowned GLib.SList list = given_list;
>
> list.remove(data);
>
> Do you see the problem here?
> If "data" is on the FIRST item on the list, it only removes it from
> "list", not from the owned variable "given_list".
>
> I run into bug likes that im my program and just wanted to warn
> Vala devs.
>
> Do you see the problem now?
>
> Tal
>
> Date: Mon, 5 Nov 2012 17:01:14 +0100
> Subject: Re: [Vala] Should be warning(maybe error) when method with
> [ReturnsModifiedPointer] is called from unowned variable
> From: kotowate gmail com
> To: tal_hd hotmail com
> CC: vala-list gnome org
>
> I am confused here. What [ReturnsModifiedPointer] has to do with
> copying/referencing an object?
> With GLib.SList list = given_list; you do not create a copy of an object
> but owned reference/pointer. And if you do anything to that reference, you
> will modify given_list too.
>
> And in most cases not copying object, but referencing it is desired
> behaviour, so I don't see problem here. I would also not desire assuming
> that copy should be created whenever I assign object from unowned reference
> to owned reference.
>
> I think that everything is ok here, unless I am missing something.
> Could you describe the result you expect from the code you provided?
> Jarek
>
> 2012/11/4 Tal Hadad <tal_hd hotmail com>
>
>
>
> There should be warning(maybe error) when method with
>
> [ReturnsModifiedPointer] is called from unowned variable.
>
>
>
> Take a look on GLib.SList. The beginner programer(me too) can be
>
> assign an unowned variable to the list, and remove items, but he
>
> don't know it shell update the owned pointer.
>
>
>
> Example:
>
>
>
> GLib.SList list = given_list;
>
> list.remove(data);
>
>
>
> Naive programers can be fooled(like me) that this code are valid,
>
> since Vala print no errors neither warning.
>
>
>
> I think we all agree it's NOT ok, but do you see this as error or warning?
>
>
>
> Yours
>
> Tal
>
>
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