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Re: How to access the virtual table?


On Friday 12 September 2014 12:14 PM, Jan Hubicka wrote:
I am trying to access the virtual table.
My pass is hooked after pass_ipa_pta.

Consider Class A which contains virtual function.
An object created as :
     A a;
is translated in GIMPLE as
     struct A a;

 From variable "a" we can get its type which is "struct A".
I tried to see how the dump_vtable function access the table.

To access the virtual table for class A, Below is the code which I tried.

     tree t = TREE_TYPE (a);
     tree binfo = TYPE_BINFO (t);
     tree vtab = BINFO_VTABLE (binfo);

     FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (DECL_INITIAL
(vtab)), ix, value)

Using the above iterator, entries of the virtual table should be accessible.
However, I am not able to do so.
You can check dump_tree (vtab) to see if you are seeing an VAR_DECL.  BINFO_VTABLE
is usually POINTER_PLUS_EXPR, so you want to access DECL_INITIAL
of TREE_OPERAND (vtab) in that case.

If you want to access an virtual method with given token (position in vtable),
you can just use gimple_get_virt_method_for_binfo (or borrow code from there
for things you need).
Thanks a lot. This helped.


Honza
Kindly inform me the way to access the virtual table.
Also how to fetch the functions from that virtual table?

Regards,
Swati


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