[Bug c++/13115] [ABI] wrong class hierarchy

["yanliu at ca dot ibm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From yanliu at ca dot ibm dot com  2003-11-25 03:25 -------
(In reply to comment #3)
> Not a bug. your analysis is wrong.
> >This time, C is put at offset 12, but G's E's C's A object is put at offset 
16, 
> >and  G's F's C's A is put at offset 12, so is G's C's A is also at offset12. 
> >This is wrong, since these A should be the same A object.
> No, those are distinct A objects. A is inherited both virtually and non-
virtually
> within the heirarchy


Thanks for the quick reply. But I don't agree with you. In this testcase, there 
are three different A objects in the class layout of G. One is a virtual base A 
object which is from B's route. Another is D's A object. And a third one is  
C's A object. The third A object can be reached from three different paths. It 
can be reached from G->C->A, from G->E->C->A, or from G->F->C->A. Since C is a 
virtual base of G, these three A objects should refer to the same A object. But 
g++ with option -qabi-version=2, givea different offsets for the same A object. 

The following is our compiler's results:

Class G
   size=16 align=4
G (0x00000000) 0
    vptridx=0 vptr=((&G::_ZTV1G) + 20)
  E (0x00000000) 0 nearly-empty
      primary-for G (0x00000000)
      subvttidx=4
    B (0x00000000) 0 nearly-empty
        primary-for E (0x00000000)
        subvttidx=8
      A (0x00000000) 0 empty virtual canonical
          vbaseoffset=-12
    C (0x00000000) 12 empty virtual canonical
        vbaseoffset=-16
      A (0x00000000) 12 empty
  F (0x00000000) 4
      subvttidx=12 vptridx=20 vptr=((&G::_ZTV1G) + 44)
    D (0x00000000) 4 nearly-empty virtual canonical
        primary-for F (0x00000000)
        vptridx=24 vbaseoffset=-20
      A (0x00000000) 4 empty
    C (0x00000000) 12 empty virtual canonical
        vbaseoffset=-16
      A (0x00000000) 12 empty
  C (0x00000000) 12 empty virtual canonical
      vbaseoffset=-16
    A (0x00000000) 12 empty



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13115