🚀 go-pugleaf

> ==========Fergus Henderson, 11/21/95==========
 
> If you changed the line
 
>        D1 d1 (7);
 
> to
 
>      D1 &d1 = *(D1 *) malloc(sizeof(D1) + sizeof(D2));
>      new (&d1) D1 (7);
 
> then the storage would be definitely large enough to hold either
> a D1 or a D2 and would be correctly aligned to hold any object,
> so this problem wouldn't arise.

Although it would be overkill as far as allocating
enough storage, how this insures correct alignment
less clear, at least to me.  Is there a constraint on
where in an object image the "this" pointer points?
Or is it that the low address of a memory block
is supposed to be passed when this form of new
is used (my memory is fuzzy on this)?  I had the
impression that the "this" pointer could have an
environment specific (or even variable between classes)
relationship to the object instance.  Certainly some
hardware architectures would favor a centrist "this"
pointer for some sizes of objects (small signed offsets
imbedded in instructions dereferencing "this").

Good Day
Dick
Dick.Menninger@DaytonOH.ATTGIS.COM
---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]