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Subject: Re: [OMPI devel] [RFC] mca_base_open() NULL
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-08 08:15:56

On May 8, 2008, at 8:06 AM, Josh Hursey wrote:

>> --> If not intended to be used by users (i.e., it's an internal
>> mechanism only), is there a reason why we're not using a zero-length
>> string (e.g., mpirun --mca foo "")?
> I think a zero length string might get confusing with the empty
> string. The empty string is taken to mean auto-select from all
> available components, which currently cannot be specified on the
> command line as an -mca option. The 0 length string is close and
> nearly indistinguishable in an (A)MCA file from a NULL string.

Ah, right. Should we introduce another keyword, "all"? This would
then be symmetric to "none" and could be the default value. An empty
string would then be an error.

Per the larger issue, I wonder if we should simply disallow NULL
default string parameter values. This might simplify a lot of things...

Jeff Squyres
Cisco Systems