[Bug c++/13114] New: wrong class hierarchy

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

The testcase failed on both g++ 3.3 and 3.2.2 versions on linuxppc machine. 
Here is the testcase:
struct W { };
struct X : public W { };
struct Y : public W { };
struct Z : virtual public X, public Y { };
struct ZZ : public Z {
    int i;
    int func() { return 0;};
};

int main(void) {
    ZZ zz;
    return 0;
}


using g++ -fdump_class_hierarchy t.C with/without option -fabi-version=2 ( what 
this option means? I could not find this "2" meaning in option description.)
we got two different class hierarchy. But both are incorrect. Here is the class 
layout of ZZ without -fabi-version=2 option ( the default should be -fabi-
version=0):
Class ZZ
   size=8 align=4
ZZ (0x40983b00) 0
    vptridx=0 vptr=((&ZZ::_ZTV2ZZ) + 12)
  Z (0x40983b40) 0 nearly-empty
      primary-for ZZ (0x40983b00)
      subvttidx=4
    X (0x40983c00) 4 empty virtual canonical
        vbaseoffset=-12
      W (0x40983c40) 4 empty
    Y (0x40983b80) 0 empty
      W (0x40983bc0) 0 empty

This class hierarchy is wrong, because the base class X shares the same offset 
with ZZ's data member int i. 

Using g++ -fabi-version=2 -fdump-class-hierarchy t.C, I got a different class 
layout for ZZ:

Class ZZ
   size=12 align=4
ZZ (0x40983b00) 0
    vptridx=0 vptr=((&ZZ::_ZTV2ZZ) + 12)
  Z (0x40983b40) 0 nearly-empty
      primary-for ZZ (0x40983b00)
      subvttidx=4
    X (0x40983c00) 8 empty virtual canonical
        vbaseoffset=-12
      W (0x40983c40) 12 empty
    Y (0x40983b80) 0 empty
      W (0x40983bc0) 0 empty

This time the offset of X's W is at offset 12, which is also wrong according to 
C++ ABI, it should be put at the same offset with X.

-- 
           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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13114