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User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0; NetCaptor 
6.5.0PB8)

Description of problem:
G++3 gives wrong layout of class E object in the testcase below.

1. The testcase
---------------
struct A {
    int a;
};

struct B : public virtual A {};

struct C {
  long double c;
};

struct D : public virtual C {
    int d;
};

struct E : public B, public D {
    int e;
};


2. The issue
------------
Expected layout of class E on ia64 is the following:
    Offset Size	Contents
    [0000] 8	B's virtual table pointer (B is the primary base for E)
    [0008] 8	D's virtual table pointer
    [0010] 4	D::d
    [0014] 4	Padding to round up D size to multiple of pointer align (8)
    [0018] 4	E::e
    [001c] 4	A::a
    [0020] 16	C::c

But G++3 compiler gives another object layout for E:
    Offset Size	Contents
    [0000] 8	B's virtual table pointer (B is the primary base for E)
    [0008] 8	Padding 
    [0010] 8	D's virtual table pointer
    [0018] 4	D::d
    [001c] 4	E::e
    [0020] 4	A::a
    [0024] 12	Padding
    [0030] 16	C::c

The layout is different and is wrong.

3. Details and analisis
-----------------------
We see difference in three points here, all related to padding bytes added.

I. Padding after B's virtual table pointer
This is the major inconsistency. Let's see...

The C++ ABI says [Chapter 2: Data Layout/2.4 Non-POD Class Types/II. Allocation 
of Members Other Than Virtual Bases]:
"if D is not an empty base class (including all data members), start at offset 
dsize(C), incremented if necessary for alignment to nvalign(type(D)) for base 
classes or to align(type(D)) for data members. "

In our case, nvalign(D) == 8, align(D) == 16. 
So, it looks like g++3 did increment address to keep 16-bytes alignment of 
class D. But this is valid for data members only and not for base classes. Such 
behaviour is wrong. Since D is the base class, it should be aligned to nvalign
(D)==8 bytes within class E and there should not be any padding.

In other words, g++3 erroneously uses align(D) instead of nvalign(D).

II. No padding after D::d
Class D is laying out using common rules. It means that D should be finalized 
either - rounded up to a non-zero multiple of align(D). 
g++3 does not perform this step for base classes. See Bugzilla Bug #64535 for 
details.


III. Extra padding after A::a
There is nothing wrong - C::c should be 16-byte aligned.
Difference is just a side-effect of inconsistency listed above.


Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
It's not so easy to dump object as showed above. So we are using run-time test 
which checks offset of class D within the object E. It used to be sizeof(void 
*), i.e. D is comming right after class B, when B contains only the virtual 
table pointer.

1. Build attached fail.cpp test using simple command line
     g++3 fail.cpp
2. Run it
     ./a.out
3. Look for 'passed' word in the output


Actual Results:  failed
D's offset is 16
expected 8


Expected Results:  passed

Additional info: