关于gobject中使用private data的原理的讨论

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13∶13
wsgalaxy    hi,I am learning gtk, and I am confused about the private data of gobject
If class C extends B, and B extends A, could b have the private data struct defined by G_ADD_PRIVATE ?
It seems that the private data struct is append after the instance struct, and if the instance is extended by other class, the private data struct is overwrited
13∶29
exalm[m]    wsgalaxy: class C struct will have class B struct embedded (which will have class A struct in it, etc), including a pointer to its private data struct somewhere inside (useless, since you cannot do anything with it)
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15∶00
wsgalaxy    exalm[m]: Do you mean that the private data pointer is stored outside the inheritance tree of instance struct?
exalm[m]    wsgalaxy: inheritance tree? It‘s just a field in a struct, the inheritance here is including parent struct as is (since it‘s not pointer). And only a pointer to private struct is stored, so that one isn‘t directly included
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wsgalaxy    https://paste.gnome.org/puhzhhytx
As describe below, where  would the private data pointer be stored?
I mean ‘above‘... my poor english..
Company    wsgalaxy: there‘s the get_instance_private() function
baedert[w]    wsgalaxy: You can always read the code if the documentation doesn‘t explain something and you want to know internals: https://gitlab.gnome.org/GNOME/glib/blob/master/gobject/gtype.c#L1846
Company    it‘s a neat magic trick that glib pulls about hiding the private data
wsgalaxy: usually an object would be in memory like this (without private data):
[ Object | Widget | Button ]
 ↖ pointer used
with private data, glib handles objects like this:
[ ButtonPrivate | WidgetPrivate | ObjectPrivate | Object | Widget | Button ]
                                                 ↖ pointer used
(yay, hexchat screws that up completely)
all of these structs have a known size, so going from the actual used pointer to the relevant priv pointer is just a subtraction
which is what get_instance_private() does
wsgalaxy    oh, I know , so the private data is store before the object struct but not after......this make me clear, thanks for your wonderful explanation!!!??
Company    ??

关于gobject中使用private data的原理的讨论

标签：read   原理   ext   hand   use   i know   nal   HERE   class   

原文地址：https://www.cnblogs.com/wsgalaxy/p/10059005.html