Many constants cannot be used in "fixed array length in a declaration" because they are negative numbers, which is not only legal but the only choice for MPI_UNDEFINED, so you cannot use that criteria for anything. We say "All named constants, with the exceptions noted below for Fortran, can be used in initialization expressions or assignments," which means the following is valid: #include <mpi.h> static int x = MPI_ANY_SOURCE; int main(void) { return 0; } C static global initialization of integers requires compile-time constants (example below). While we may have implied that all constants could be link-time constants, this is only possible for non-integer constants, i.e. handles and buffer address constants. % cat init.c extern int w; static int* p = &w; static int q = w; % gcc -c init.c init.c:3:16: error: initializer element is not a compile-time constant static int q = w; ^ 1 error generated. Jeff On Tue, May 2, 2023 at 9:51 PM Rolf Rabenseifner via mpi-forum < [email protected]> wrote:

Dear implementor of an MPI library,

Based on the discussion today in the MPI forum meeting, I have the following urgent question to you:

Did you implement all MPI constants that are described in Annex A.1.1 as of type "const int (or unnamed enum)" as "C integer constant expression" (according to the specification of the C language)?

If yes, then all is okay and the proposed change of the MPI standard in https://github.com/mpi-forum/mpi-standard/pull/821/files will not require any change of your MPI implementation.

If not, then please can you tell which MPI constant(s) MPI_XXX

- have you implemented in a way that

- it still can be used in an initialization expression, i.e., in a application statement like int x=MPI_XXX; - but it cannot be used as a case-label in a switch statement like switch(MPI_XXX) { case MPI_XXX: printf("XXX\n"); default: ; } - and cannot be used as a fixed array length in a declaration like float x[MPI_XXX];

- and how implemented you such an MPI constant that this problem arises?

We'll discuss this again tomorrow May 3, 2023 at the beginning of the MPI forum meeting.

See you hopefully at the meeting, and hopefully reporting that you have no problem with the proposal,

kind regards Rolf

----- Original Message -----

...

From: "Rolf Rabenseifner" <[email protected]> To: "Main MPI Forum mailing list" <[email protected]> Cc: "Puri Bangalore" <[email protected]>, "Claudia Blaas-Schenner" <

[email protected]>, "Jeff

...

Hammond" <[email protected]> Sent: Tuesday, May 2, 2023 2:04:01 PM Subject: Re: Informal meeting announcement for the May 2023 meeting of the MPI Forum

...

Der forum memebers, dear Wesley,

please can we add in the agenda after

Informal Errata Reading 705 Fortran has only compile-time constants Rolf

an additional slot

Errata Discussion 657 All C const int (or unnamed enum) as compile-time constants Rolf, Jeff H.

Bestr regards Rolf

----- Original Message -----

...

From: "Rolf Rabenseifner" <[email protected]> To: "Main MPI Forum mailing list" <[email protected]> Cc: "Puri Bangalore" <[email protected]>, "Claudia Blaas-Schenner" <[email protected]> Sent: Saturday, April 29, 2023 7:38:00 AM Subject: Informal meeting announcement for the May 2023 meeting of the MPI Forum

...

Dear forum members,

I would like to make the following announcements for the next MPI Forum Meeting (May 2-5, 2023):

- informal reading and discussion #705 Errata: Fortran has only compile-time constants Rolf Issue https://github.com/mpi-forum/mpi-issues/issues/705 PR https://github.com/mpi-forum/mpi-standard/pull/819 PDF

https://github.com/mpi-forum/mpi-standard/files/11358444/mpi41-report_Issue7...

...

This errata should be completely discussed in next (May 2-5, 2023)

meeting.

...

It is then planned to have an final errata reading plus errata vote at next meeting (July 10-13, 2023).

It is a bug since MPI-2.2 because a problem in C was directly mapped to Fortran. This mapping was wrong. In Fortran, there is no distinction between link-time and compile-time constants.

Best regards Rolf Rabenseifner

-- Dr. Rolf Rabenseifner . . . . . . . . . .. . . [email protected] . High Performance Computing Center (HLRS) . . . ++49(0)711/685-65530 . University of Stuttgart . . . . . . www.hlrs.de/people/rabenseifner . Nobelstr. 19, 70569 Stuttgart, Germany

-- Dr. Rolf Rabenseifner . . . . . . . . . .. . . [email protected] . High Performance Computing Center (HLRS) . . . ++49(0)711/685-65530 . University of Stuttgart . . . . . . www.hlrs.de/people/rabenseifner . Nobelstr. 19, 70569 Stuttgart, Germany _______________________________________________ mpi-forum mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpi-forum

-- Jeff Hammond [email protected] http://jeffhammond.github.io/