[pooma-dev] domain architecture diagram

[Julian C. Cummings]

I meant to send a note about this a few days,
but anyway, the Intel VTune compiler "passes"
the empty base class test.  The SGI MIPSpro
compiler on Nirvana does not.  It gives a size
of "2" for the derived class rather than "1".

Julian C.


> -----Original Message-----
> From: Mark Mitchell [mailto:mark at codesourcery.com]
> Sent: Sunday, July 01, 2001 11:18 PM
> To: cummings at linkline.com; Pooma-Dev
> Subject: RE: [pooma-dev] domain architecture diagram
> 
> 
>  I don't know if
> > this issue of the empty base class is important anymore
> > with current C++ compilers.
> 
> This was the only part of this discussion I was smart enough to
> understand, so I decided to reply to it. :-)
> 
> In G++ 3.0, there is no empty base class penalty.  The same will
> be true for any IA64 C++ ABI compliant compiler.  Modern versions
> of the EDG front end (used in KCC, the Intel compiler, the SGI
> compiler, the DEC/Compaq compiler, and elsewhere) are capable of
> avoiding the penalty.  However, I do now know if the vendors were
> willing to turn on this feature, since it will break compatibility
> with previous versions of their compilers.  And, I do not know
> whether VC++ is capable of avoiding the penalty.
> 
> Irrelevant compilers for computers named after fruit are mentioned
> only because I know that the mere presence of this sentence will
> get people's adrenalin pumping in New Mexico. :-)  Seriously, I
> know nothing of whether Metrowerks can do this or not.
> 
> It would be great if someone could try out:
> 
>  struct S { };
>  struct T : public S { char c; };
> 
>  int main () { return sizeof (T); }
> 
> with KCC.  If things are good, the program will return 1; if bad,
> some greater value.
> 
> -- 
> Mark Mitchell                mark at codesourcery.com
> CodeSourcery, LLC            http://www.codesourcery.com
>