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List:       kde-devel
Subject:    Re: C++ question (virtual inheritance)
From:       Sarang Lakare <sarang () users ! sourceforge ! net>
Date:       2003-02-20 21:15:20
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Stefan's testcase is exactly like the E():D(this) that is shown below and they 
say that "this" is undefined. Here is what Stefan had:

    struct B {
        B(A *) {}
    };
    
    struct C : virtual public A, public B {
        C() : B(this) {}
    };

So upcast from C* to A* might use the path C* -> B* -> A* but B* is not 
defined hence it will seg fault.

Sarang


On Thursday 20 February 2003 03:46 pm, Christian Loose wrote:
>           struct A { };
>           struct B : virtual A { };
>           struct C : B { };
>           struct D : virtual A { D(A*); };
>           struct X { X(A*); };
>           struct E : C, D, X {
>                   E() : D(this),  // undefined: upcast from E* to A*
>                                   // might use path E* -> D* -> A*
>                                   // but D is not constructed
>                   // D((C*)this), // defined:
>                                   // E* -> C* defined because E() has
> started // and C* -> A* defined because
>                                   // C fully constructed
>                   X(this)         // defined: upon construction of X,
>                                   // C/B/D/A sublattice is fully
> constructed { }
>           };

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sarang Lakare
mailto:sarang@users#sourceforge.net
web:http://www.cs.sunysb.edu/~lsarang/linux
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