[Mpi-22] Borderline ticket #107: Types of predefined constants in Appendix A

[Rolf Rabenseifner]

Hi Erez,

I thought that the first colored sentence
   "Constants with the type const int may also be implemented as
    literal integer constants substituted by the preprocessor."
allows to implement
>        #define MPI_ERR_BUFFER 0

Your second topic:
I'm not a C const specialist. I filled only in what I got as
input from the Forum.
If something is really wrong, we should use the errata method
as soon as possible.

Best regards
Rolf

On Mon, 3 Aug 2009 17:36:42 +0000
  Erez Haba <erezh_at_[hidden]> wrote:
> This might be nitpicking but wouldn't that force implementation to 
>typecast their definition of error codes? For example,
> 
>        #define MPI_ERR_BUFFER 0
> 
> Is not a correct definition with the proposed change, because it is 
>not typed. Thus, it needs to change to
> 
> #define MPI_ERR_BUFFER (int)0   // you don't really need to define 
>it as (const int)0
> 
> as a result the following statement
> 
>        short x = MPI_ERR_BUFFER;
> 
> which compiled correctly before, would break with this change.
> 
> 
> Second comment.
> 
> Adding the 'const' modifier to all types is very confusing imho. I 
>understand that it meant to make it clear that the values are 
>constants and should not change, but still is very confusing.
> 
>For example,
> 
>        C Type: void * const
>        MPI_BOTTOM
> 
> This means that the value of MPI_BOTTOM is constant and not the 
>memory it points to. however at first look you might think that it's 
>the later. (if it was, it would break any application that uses it 
>because the API's do not take a pointer to const void)
> 
> In any case implementers should define MPI_BOTTOM as
> 
>        #define MPI_BOTTOM (void*)0
> 
> Rather than
> 
>        #define MPI_BOTTOM (void* const)0
> 
> As the value is constant and you don't need to add the const 
>modifier.
> 
> 
> Note that the 'constness' of these values is already stated in the 
>title of the section '19.1.1 Defined Constants'
> 
> 
> Except for my comments above, the text formatting looks good to me. 
>(I abstained at the meeting)
> 
> Just my 2c,
> .Erez
> 
> 
> P.S.it looks odd that the int and void* types have const modifiers 
>while mpi types do not; like MPI_Datatype. I think that this needs to 
>be consistent.
> 
> -----Original Message-----
>From: mpi-22-bounces_at_[hidden] 
>[mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Rolf 
>Rabenseifner
> Sent: Monday, August 03, 2009 8:50 AM
> To: MPI Forum
> Subject: [Mpi-22] Borderline ticket #107: Types of predefined 
>constants in Appendix A
> 
> Dear all,
> 
> ticket 107 was the only passed ticket with more no + abstain + miss
> votes
> than yes votes.
> 
> MPI-2.1 had only C++ type information in this Appendix.
> With this ticket, C and Fortran type information is added
> to achieve consistency between all language bindings.
> 
> I've implemented it and
> https://svn.mpi-forum.org/trac/mpi-forum-web/attachment/ticket/107/appLang-ticket107-more-readable.pdf
> gives you an impression of the final (uncolored) document.
> (The new advices in Section 6.7.2 are not yet implemented).
> 
> I hope you can now live with the result.
> 
> If you would voted now with yes (based on the pdf),
> but you haven't voted yes at the meeting,
> then a short reply would be fine.
> 
> The same of course if you now disagree with your yes at the meeting.
> 
> Best regards
> Rolf
> 
> Dr. Rolf Rabenseifner . . . . . . . . . .. email 
>rabenseifner_at_[hidden]
> High Performance Computing Center (HLRS) . phone 
>++49(0)711/685-65530
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 
>685-65832
> Head of Dpmt Parallel Computing . . . 
>www.hlrs.de/people/rabenseifner
> Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)
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> 
> 
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Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner_at_[hidden]
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)