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Multiple inheritance problem on arm under gcc 3.0.1


Hi folks,
I wonder if anybody has any thoughts on a little problem I have.
Apologies in advance for the length of this post.
I have a struct:

struct Wibble {  int blah[1]; };

and a pair of classes which have members which return a Wibble type:

class A
{
public:
    virtual Wibble F();
};
class B
{
public:
    virtual Wibble F();
};

and a derived class which also returns a Wibble type:

class C : public A, public B
{
public:
    Wibble F();
};

In the class definitions, I simply write the this pointer to an output
port and return a copy of a wibble instance:

Wibble wibble;
Wibble A::F()
{
    cdbg() << "A:" << (int) this << "\n";
    return (wibble);
}
Wibble B::F()
{
    cdbg() << "B:" << (int) this << "\n";
    return (wibble);
}
Wibble C::F()
{
    cdbg() << "C:" << (int) this << "\n";
    return (wibble);
}

And finally, my entry function on an embedded system is:

int C_Entry(void)
{
    C c_obj;
    C* c = &c_obj;
    cdbg() << SerPortStream::hex;
    A * a = c;
    B * b = c;
    cdbg() << "A:" << (int) a << "\n";
    cdbg() << "B:" << (int) b << "\n";
    cdbg() << "C:" << (int) c << "\n";
    a->F();
    b->F();
    c->F();
    cdbg() << "Complete\n";
    return (0);
}

The observed ouput is:
A:3fddc
B:3fde0
C:3fddc
C:3fddc
C:3fde0
C:3fde0
Complete

Which I find disturbing because clearly c's  pointer value is
inconsistent.

Furthermore, if I change my struct definition to remove the array:
 
struct Wibble {  int blah; };

then I get output as expected:

A:3fddc
B:3fde0
C:3fddc
C:3fddc
C:3fddc
C:3fddc
Complete

Anybody had any similar problems ? Are there any work arounds or patches
?

-- 
Andy Parker                       Oxford Semiconductor Ltd
Tel: +44 (0) 1235 824 944         25 Milton Park, Abingdon,
Fax: +44 (0) 1235 821 141         Oxfordshire. OX14 4SH 
andy.parker@oxsemi.com            http://www.oxsemi.com

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