From: Jeff Squyres <jsquyres@XXXXXXXXX>
Date: November 28, 2007 10:28:52 AM CST
To: mpi-21@XXXXXXXXXXXXX
Subject: Re: [mpi-21] MPI::BOTTOM
Reply-To: mpi-21@XXXXXXXXXXXXX

On Nov 27, 2007, at 5:40 PM, Dave Goodell wrote:

> "const TYPE * FOO" indicates that the data pointed to by FOO is  
> read-only.  So "*FOO = BAR;" would be an illegal statement.
>
> "TYPE * const FOO" indicates that the memory holding the value of  
> FOO is read-only.  So "FOO = &BAR;" would be an illegal statement.
>
> The latter seems to be what is desired for MPI::BOTTOM: an address  
> that cannot be changed but a the data that it references can.


Good point.  I think you're right -- I ran a few tests to convince  
myself that changing the type of MPI::BOTTOM to (void * const) won't  
break anything in terms of the other existing bindings.

However, in terms of what MPI::BOTTOM *should* be, shouldn't it be  
*both* consts?  We don't want the value to change, nor do we want the  
pointed-to- contents where it points to change:

     extern const void * const BOTTOM;

Technically, though, with your suggestion, you couldn't change the  
pointed-to contents without casting anyway (because you can't assign  
to *(void*)).  So this might be a good enough solution.

-- 
Jeff Squyres
Cisco Systems