MPI_Buffer_detach_c - Removes an existing buffer (for use in MPI_Bsend etc)

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of  the
       function  and Fortran routines in the last argument.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI job.  The error handler may be  changed
       with    MPI_Comm_set_errhandler   (for   communicators),   MPI_File_set_errhandler   (for   files),   and
       MPI_Win_set_errhandler (for RMA windows).  The MPI-1 routine MPI_Errhandler_set may be used but  its  use
       is  deprecated.   The  predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be
       returned.  Note that MPI does not guarantee that an MPI program can continue past an error; however,  MPI
       implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.

       MPI_ERR_ARG
              -  Invalid  argument.   Some  argument  is invalid and is not identified by a specific error class
              (e.g., MPI_ERR_RANK ).
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

       MPI_Buffer_detach_c -  Removes an existing buffer (for use in MPI_Bsend etc)

       The  reason  that MPI_Buffer_detach returns the address and size of the buffer being detached is to allow
       nested libraries to replace and restore the buffer.  For example, consider

       int size, mysize, idummy;
       void *ptr, *myptr, *dummy;
       MPI_Buffer_detach(&ptr, &size);
       MPI_Buffer_attach(myptr, mysize);
       .
       .
       .
       .
       .
       .
       library code ...
       .
       .
       .
       MPI_Buffer_detach(&dummy, &idummy);
       MPI_Buffer_attach(ptr, size);

       This is much like the action of the Unix signal routine and has the same strengths  (it  is  simple)  and
       weaknesses (it only works for nested usages).

       Note  that  for  this  approach  to work, MPI_Buffer_detach must return MPI_SUCCESS even when there is no
       buffer to detach.  In that case, it returns a size of zero.  The MPI 1.1 standard  for  MPI_BUFFER_DETACH
       contains the text

       The statements made in this section describe the behavior of MPI for
       buffered-mode sends. When no buffer is currently associated, MPI behaves
       as if a zero-sized buffer is associated with the process.

       This  could  be  read  as  applying  only  to  the various Bsend routines.  This implementation takes the
       position that this applies to MPI_BUFFER_DETACH as well.

       Even  though  the  bufferptr argument is declared as void* , it is really the address of a void pointer.
       See the rationale in the standard for more details.

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

       The  Fortran  binding  for  this  routine  is  different.   Because Fortran does not have pointers, it is
       impossible to provide a way to use the output of this routine to exchange buffers.  In  this  case,  only
       the size field is set.

buffer_addr
              - initial buffer address (choice) (choice)
       size   - buffer size, in bytes (integer) (integer)

       MPI_Buffer_attach

                                                    1/21/2022                             MPI_Buffer_detach_c(3)

       #ifdef ENABLE_QMPI
       #ifndef MPICH_MPI_FROM_PMPI
       int QMPI_Buffer_detach_c(QMPI_Context context, int tool_id, void *buffer_addr,
       MPI_Count *size) MPICH_API_PUBLIC

       The user is responsible for ensuring that multiple threads do not try to update the same MPI object  from
       different threads.  This routine should not be used from within a signal handler.

       The  MPI  standard defined a thread-safe interface but this does not mean that all routines may be called
       without any thread locks.  For example, two threads must not attempt to change the contents of  the  same
       MPI_Info  object  concurrently.   The  user is responsible in this case for using some mechanism, such as
       thread locks, to ensure that only one thread at a time makes use of this routine.  Because the buffer for
       buffered sends (e.g., MPI_Bsend ) is shared by all threads in a process,  the  user  is  responsible  for
       ensuring that only one thread at a time calls this routine or MPI_Buffer_attach .