virtual inheritance problem

[Wolfgang Bangerth]

Ryszard Kabatek <rysio@rumcajs.chemie.uni-halle.de> 
Wed, 10 Mar 1999 10:42:23 +0100 (CET) writes:

>Egcs-1.1.1 produces wrong code:
>
>starting test
>A::foo  0xbffff8d8 1
>B::foo  0xbffff8d0 1073783640        <-- should be 1
>C::foo  0xbffff8d0 1073783640        <-- should be 1
>D::foo  0xbffff8c4 1073783640        <-- should be 1
>E::foo  0xbffff8c0 1
>object constructed
>E::foo  0xbffff8c0 1
>test finished


You are calling virtual functions from the constructor, i.e. at a time
where derived classes may not have been able to
1/ set their virtual function's addresses in the virtual function table
   (this is why you get to see the output of the functions [ABCD]::foo,
    which later will not be called anymore since E::foo is there); and
2/ set their member variables' values, since base classes are always
   constructed first.

The program is therefore bound to produce rather random output.

Regards
  Wolfgang


-------------------------------------------------------------------------
Wolfgang Bangerth            email:       wolf@gaia.iwr.uni-heidelberg.de
                             www: http://gaia.iwr.uni-heidelberg.de/~wolf