MPI_SESSION_CREATE_ERRHANDLER(3)		     Open MPI			  MPI_SESSION_CREATE_ERRHANDLER(3)

MPI_Session_create_errhandler — Creates an error handler that can be attached to sessions

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Session_create_errhandler(MPI_Session_errhandler_function *function,
	      MPI_Errhandler *errhandler)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'

	  MPI_SESSION_CREATE_ERRHANDLER(FUNCTION, ERRHANDLER, IERROR)
	      EXTERNAL	  FUNCTION
	      INTEGER ERRHANDLER, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_Session_create_errhandler(session_errhandler_fn, errhandler, ierror)
	      PROCEDURE(MPI_Session_errhandler_function) :: session_errhandler_fn
	      TYPE(MPI_Errhandler), INTENT(OUT) :: errhandler
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER
       • function : User-defined error handling procedure (function).

OUTPUT PARAMETERS
       • errhandler : MPI error handler (handle).

       • ierror : Fortran only: Error status (integer).

DESCRIPTION
       MPI_Session_create_errhandler  creates  an error handler that can be attached to sessions. This function is
       identical to MPI_Errhandler_create <#mpi-errhandler-create>, the use of which is deprecated. In C, the user
       routine should be a function of type MPI_Session_errhandler_function, which is defined as

	  typedef void MPI_Session_errhandler_function(MPI_Session *, int *, ...);

       The first argument is the session in use. The second is the error code to be returned by	 the  MPI  routine
       that  raised  the  error.  This	typedef	 replaces MPI_Handler_function, the use of which is deprecated. In
       Fortran, the user routine should be of this form:

	  SUBROUTINE SESSION_ERRHANDLER_FUNCTION(SESSION, ERROR_CODE, ...)
	     INTEGER SESSION, ERROR_CODE

ERRORS
       Almost all MPI routines return an error value; C routines as the return result of the function and  Fortran
       routines in the last argument.

       Before  the error value is returned, the current MPI error handler associated with the communication object
       (e.g., communicator, window, file) is called.  If no communication object is associated with the MPI  call,
       then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When
       MPI_COMM_SELF is not initialized (i.e.,	before	MPI_Init  <#mpi-init>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#mpi-finalize>,  or  when	using the Sessions Model exclusively) the error raises the
       initial error handler. The initial error handler can  be	 changed  by  calling  MPI_Comm_set_errhandler	<#
       mpi-comm-set-errhandler>	 on  MPI_COMM_SELF  when  using the World model, or the mpi_initial_errhandler CLI
       argument	 to  mpiexec  or  info	key   to   MPI_Comm_spawn   <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.   If  no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error  handler  is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT  An  error handler that can be invoked on a communicator, window, file, or session. When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the  group
	 of processes in the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 then	MPI_Session_set_errhandler   <#mpi-session-set-errhandler>  or	at
	 MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026			  MPI_SESSION_CREATE_ERRHANDLER(3)
