From: raskolnikov@gnu.org   
      
   >   
   > Indeed, think about this code:   
   >   
   >     X* p = new Y[2];   
   >     x[1].foo = 1;   
   >   
   > That is UB too, because x[1] which is *(x+1) relies on its knowledge of   
   > sizeof(X) to know how much to advance the memory address 'p' -- i.e. if   
   > sizeof(X) < sizeof(Y), it would most probably overwrite data of the   
   > first element instead of what you intended to do. Thus, it is impossible   
   > to treat arrays polymorphically, because you always need the size of the   
   > concrete type of its element to access the array. Just think of 'delete   
   > []' of one of those other operations that rely on the concrete type,   
   > because of how 'delete []' might be implemented.   
   >   
      
   To avoid further misunderstandings, I mean 'x' when I say 'p' and the   
   first line on the code above should read 'X* x = ...'.   
      
   Sorry for the confusion.   
      
   JP   
      
      
   --   
         [ See http://www.gotw.ca/resources/clcm.htm for info about ]   
         [ comp.lang.c++.moderated.    First time posters: Do this! ]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)