[Mpi3-tools] MPI handles debugging interface

[Ashley Pittman]

On Wed, 2009-06-03 at 08:59 -0400, Jeff Squyres wrote:
> Why use a bunch of individual query functions when we could have a  
> single, much more general form that is more easily extensible?  The  
> query function would essentially be driven by an enum indicating the  
> specific request, and the OUT arguments could be varargs.

> +++ Advantage: this one function can be extended simply by adding new  
> enum values, possibly in an MPI implementation-specific way (e.g.,  
> have some non-standard / value-add functions)

The existing method can also be extended simply by adding new functions,
possibly in a MPI implementation-specific way.

> --- Disadvantage: lose compiler type safety checking when building/ 
> debugging tools that use this interface.

A very valid point, it's far from easy to understand the interface
currently and we need all the help we can get via type checking or any
other means.

> I don't have strong feelings either way.  I think I'm marginally in  
> favor of individual functions just because it gives type safety for  
> tools authors.  But I could be convinced to go the enum/varargs route  
> if people feel strongly.

Personally I'm in favour of extensions being done with sympathy to the
existing interface.  Unless there is a significant reason to move, which
I can't see, changing the communication mechanism is just going to add
confusion and raise the barrier for people implementing either side of
this interface.

Ashley Pittman,