[Bug c++/13115] New: wrong class hierarchy

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

using g++ version 3.2.2 and 3.3, for the following testcase:
struct A { };
struct B : public virtual A {
    virtual double f();
};
struct C : public A { };
struct D : public A {
    virtual double f();
};
struct E: public B, virtual public C { };
struct F: virtual public D, public virtual C {
    int fi;
};
struct G : public E, public F, public virtual C { };
double B::f(){return 0.0;}
double D::f(){return 0.0;}
int main(void) {
    G g;
    return 0;
}

using g++ -fdump-class-hierarchy t.C command, we got the following class layout 
for class G:


Class G
   size=20 align=4
G (0x4009ad40) 0
    vptridx=0 vptr=((&G::_ZTV1G) + 20)
  E (0x4009ad80) 0 nearly-empty
      primary-for G (0x4009ad40)
      subvttidx=4
    B (0x4009ae40) 0 nearly-empty
        primary-for E (0x4009ad80)
        subvttidx=8
      A (0x4009ae80) 0 empty virtual canonical
          vbaseoffset=-12
    C (0x4009adc0) 16 empty virtual canonical
        vbaseoffset=-16
      A (0x4009ae00) 16 empty
  F (0x4009aec0) 4
      subvttidx=12 vptridx=20 vptr=((&G::_ZTV1G) + 44)
    D (0x4009af80) 4 nearly-empty virtual canonical
        primary-for F (0x4009aec0)
        vptridx=24 vbaseoffset=-20
      A (0x4009afc0) 4 empty
    C (0x4009af00) 16 empty virtual non-canonical
      A (0x4009af40) 16 empty
  C (0x400a4000) 16 empty virtual non-canonical
      vbaseoffset=-16
    A (0x400a4040) 16 empty

This is wrong, because F and D are at offset 4, then at offset 8 should be F's 
data member fi, then there is 4 bytes unused space, and then C is put at offset 
16. 

With g++ -fabi-version=2 -fdump-class-hierarchy t.C command, we got a different 
class layout for G:

Class G
   size=16 align=4
G (0x4817c0) 0
    vptridx=0 vptr=((&G::_ZTV1G) + 20)
  E (0x481800) 0 nearly-empty
      primary-for G (0x4817c0)
      subvttidx=4
    B (0x4818c0) 0 nearly-empty
        primary-for E (0x481800)
        subvttidx=8
      A (0x481900) 0 empty virtual canonical
          vbaseoffset=-12
    C (0x481840) 12 empty virtual canonical
        vbaseoffset=-16
      A (0x481880) 16 empty
  F (0x481940) 4
      subvttidx=12 vptridx=20 vptr=((&G::_ZTV1G) + 44)
    D (0x481a00) 4 nearly-empty virtual canonical
        primary-for F (0x481940)
        vptridx=24 vbaseoffset=-20
      A (0x481a40) 4 empty
    C (0x481980) 12 empty virtual non-canonical
      A (0x4819c0) 12 empty
  C (0x481a80) 12 empty virtual non-canonical
      vbaseoffset=-16
    A (0x481ac0) 12 empty

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.

-- 
           Summary: wrong class hierarchy
           Product: gcc
           Version: 3.2.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yanliu at ca dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: linuxppc


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