Re: [Vala] Can adding new virtual method break ABI?
If you need to do these things manually, then what's the point in using vala? It's the job of compilers. People who like to do the job of compilers manually should use GObject/C instead. Manually filling a virtual function table and calculate offset of pointers are really of fun. lol Creating some empty functions for padding is even easier and more readable IMO. On Wed, Dec 14, 2011 at 6:15 PM, Mikkel Kamstrup Erlandsen mikkel.kamst...@gmail.com wrote: On 12 December 2011 12:15, Jürg Billeter j...@bitron.ch wrote: On Mon, 2011-12-12 at 12:12 +0100, Luca Bruno wrote: On Mon, Dec 12, 2011 at 12:01 PM, Jürg Billeter j...@bitron.ch wrote: On Sun, 2011-12-11 at 11:34 +0100, Luca Bruno wrote: 2011/12/11 Tal Hadad tal...@hotmail.com This idea is based on the assumption that the size of XClass struct doesn't matter and can be changed(Am I right?). Also, how does the virtual method order is currently done by Vala? Is it alphabetic or by the order of the decelerations? The ordering does not matter, the padding does. Ordering matters as well. Vala uses declaration order. We're talking about virtual methods, aren't we? There's no ABI break if the order of N pointers is exchanged. When a subclass overrides a virtual method, the class_init function uses the offset of the virtual function pointer. If that offset changes, the subclass will need to be recompiled to work again. Indeed. Would it make sense to a [CCode (vfunc_padding = 8)] to class declarations? This could then be decremented when new virtual functions are added (to the end of the class!). Cheers, Mikkel ___ vala-list mailing list vala-list@gnome.org http://mail.gnome.org/mailman/listinfo/vala-list ___ vala-list mailing list vala-list@gnome.org http://mail.gnome.org/mailman/listinfo/vala-list
Re: [Vala] Can adding new virtual method break ABI?
On Wed, Dec 14, 2011 at 11:15 AM, Mikkel Kamstrup Erlandsen mikkel.kamst...@gmail.com wrote: Indeed. Would it make sense to a [CCode (vfunc_padding = 8)] to class declarations? This could then be decremented when new virtual functions are added (to the end of the class!). I'd expect that to be done automatically. -- www.debian.org - The Universal Operating System ___ vala-list mailing list vala-list@gnome.org http://mail.gnome.org/mailman/listinfo/vala-list
Re: [Vala] Can adding new virtual method break ABI?
On Mon, Dec 12, 2011 at 12:01 PM, Jürg Billeter j...@bitron.ch wrote: On Sun, 2011-12-11 at 11:34 +0100, Luca Bruno wrote: 2011/12/11 Tal Hadad tal...@hotmail.com This idea is based on the assumption that the size of XClass struct doesn't matter and can be changed(Am I right?). Also, how does the virtual method order is currently done by Vala? Is it alphabetic or by the order of the decelerations? The ordering does not matter, the padding does. Ordering matters as well. Vala uses declaration order. We're talking about virtual methods, aren't we? There's no ABI break if the order of N pointers is exchanged. -- www.debian.org - The Universal Operating System ___ vala-list mailing list vala-list@gnome.org http://mail.gnome.org/mailman/listinfo/vala-list
Re: [Vala] Can adding new virtual method break ABI?
On Mon, 2011-12-12 at 12:12 +0100, Luca Bruno wrote: On Mon, Dec 12, 2011 at 12:01 PM, Jürg Billeter j...@bitron.ch wrote: On Sun, 2011-12-11 at 11:34 +0100, Luca Bruno wrote: 2011/12/11 Tal Hadad tal...@hotmail.com This idea is based on the assumption that the size of XClass struct doesn't matter and can be changed(Am I right?). Also, how does the virtual method order is currently done by Vala? Is it alphabetic or by the order of the decelerations? The ordering does not matter, the padding does. Ordering matters as well. Vala uses declaration order. We're talking about virtual methods, aren't we? There's no ABI break if the order of N pointers is exchanged. When a subclass overrides a virtual method, the class_init function uses the offset of the virtual function pointer. If that offset changes, the subclass will need to be recompiled to work again. Jürg ___ vala-list mailing list vala-list@gnome.org http://mail.gnome.org/mailman/listinfo/vala-list
[Vala] Can adding new virtual method break ABI?
I've read how GObject define virtual methods, in the XClass struct, and
I'm afraid defining new virtual method can break ABI. Am I right?
Before:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*do_action) (X *self, /* parameters */);
};
After:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*another_action) (X *self, /* parameters */);
void (*do_action) (X *self, /* parameters */);
};
Can this case break ABI?
Tal
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Re: [Vala] Can adding new virtual method break ABI?
2011/12/11 Tal Hadad tal...@hotmail.com
I've read how GObject define virtual methods, in the XClass struct, and
I'm afraid defining new virtual method can break ABI. Am I right?
Before:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*do_action) (X *self, /* parameters */);
};
After:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*another_action) (X *self, /* parameters */);
void (*do_action) (X *self, /* parameters */);
};
Can this case break ABI?
Yes it does. What C programmers often do is adding unused vfuncs as padding
for future extension of the class. From this perspective Vala could
theoretically add some kind of padding to avoid abi breakage.
--
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Re: [Vala] Can adding new virtual method break ABI?
Yes it does. What C programmers often do is adding unused vfuncs as
padding for future extension of the class. From this perspective Vala
could theoretically add some kind of padding to avoid abi breakage.
So what about this idea for fix it:
Create a new attribute property in [CCode], named binary_position, that is used
for virtual methods, but can be used for another things(such as fields, etc.).
It can be used by the developer to avoid this risk, by doing so:
Every time the developer create a new virtual method, he shell pick the
smallest number available for virtual method position, and put it in
binary_position in [CCode].
On every planned ABI(API) break, he can minimize those binary_position(s) for
virtual methods.
This idea is based on the assumption that the size of XClass struct doesn't
matter and can be changed(Am I right?).
Also, how does the virtual method order is currently done by Vala? Is it
alphabetic or by the order of the decelerations?
Thanks
Tal
Date: Sun, 11 Dec 2011 10:48:21 +0100
Subject: Re: [Vala] Can adding new virtual method break ABI?
From: lethalma...@gmail.com
To: tal...@hotmail.com
CC: vala-list@gnome.org
2011/12/11 Tal Hadad tal...@hotmail.com
I've read how GObject define virtual methods, in the XClass struct, and
I'm afraid defining new virtual method can break ABI. Am I right?
Before:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*do_action) (X *self, /* parameters */);
};
After:
struct _XClass
{
GObjectClass parent_class;
/* stuff */
void (*another_action) (X *self, /* parameters */);
void (*do_action) (X *self, /* parameters */);
};
Can this case break ABI?
Yes it does. What C programmers often do is adding unused vfuncs as padding
for future extension of the class. From this perspective Vala could
theoretically add some kind of padding to avoid abi breakage.
--
www.debian.org - The Universal Operating System
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