.\" -*- nroff -*-
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" $COPYRIGHT$
.TH MPI_Win_create_keyval 3 "May 26, 2022" "4.1.4" "Open MPI"
.SH NAME
\fBMPI_Win_create_keyval\fP \- Creates a keyval for a window.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Win_create_keyval(MPI_Win_copy_attr_function *\fIwin_copy_attr_fn\fP,
	MPI_Win_delete_attr_function *\fIwin_delete_attr_fn\fP,
	int *\fIwin_keyval\fP, void *\fIextra_state\fP)

.fi
.SH Fortran Syntax (see FORTRAN 77 NOTES)
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_WIN_CREATE_KEYVAL(\fIWIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN,
	WIN_KEYVAL, EXTRA_STATE, IERROR\fP)
	EXTERNAL \fIWIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN\fP
	INTEGER \fIWIN_KEYVAL, IERROR\fP
	INTEGER(KIND=MPI_ADDRESS_KIND) \fIEXTRA_STATE\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Win_create_keyval(\fIwin_copy_attr_fn\fP, \fIwin_delete_attr_fn\fP, \fIwin_keyval\fP,
		\fIextra_state\fP, \fIierror\fP)
	PROCEDURE(MPI_Win_copy_attr_function) :: \fIwin_copy_attr_fn\fP
	PROCEDURE(MPI_Win_delete_attr_function) :: \fIwin_delete_attr_fn\fP
	INTEGER, INTENT(OUT) :: \fIwin_keyval\fP
	INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: \fIextra_state\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH C++ Syntax
.nf
#include <mpi.h>
static int MPI::Win::Create_keyval(MPI::Win::Copy_attr_function*
	\fIwin_copy_attr_fn\fP,
	MPI::Win::Delete_attr_function* \fIwin_delete_attr_fn\fP,
	void* \fIextra_state\fP)

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
win_copy_attr_fn
Copy callback function for \fIwin_keyval\fP (function).
.TP 1i
win_delete_attr_fn
Delete callback function for \fIwin_keyval\fP (function).
.TP 1i
extra_state
Extra state for callback functions.

.SH OUTPUT PARAMETERS
.ft R
.TP 1i
win_keyval
Key value for future access (integer).
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
The argument \fIwin_copy_attr_fn\fP may be specified as MPI_WIN_NULL_COPY_FN or MPI_WIN_DUP_FN from either C, C++, or Fortran. MPI_WIN_NULL_COPY_FN is a function that serves only to return \fIflag\fP = 0 and MPI_SUCCESS. MPI_WIN_DUP_FN is a simple-minded copy function that sets \fIflag\fP = 1, returns the value of \fIattribute_val_in\fP in \fIattribute_val_out\fP, and returns MPI_SUCCESS.
.sp
The argument \fIwin_delete_attr_fn\fP may be specified as MPI_WIN_NULL_DELETE_FN from either C, C++, or Fortran. MPI_WIN_NULL_DELETE_FN is a function that serves only to return MPI_SUCCESS.
.sp
The C callback functions are:
.sp
.nf
typedef int MPI_Win_copy_attr_function(MPI_Win \fIoldwin\fP, int \fIwin_keyval\fP,
             void *\fIextra_state\fP, void *\fIattribute_val_in\fP,
             void *\fIattribute_val_out\fP, int *\fIflag\fP);
.fi
.sp
and
.sp
.nf
typedef int MPI_Win_delete_attr_function(MPI_Win \fIwin\fP, int \fIwin_keyval\fP,
             void *\fIattribute_val\fP, void *\fIextra_state\fP);
.fi
.sp
The Fortran callback functions are:
.sp
.nf
SUBROUTINE WIN_COPY_ATTR_FN(\fIOLDWIN, WIN_KEYVAL, EXTRA_STATE,
	ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR\fP)
	INTEGER \fIOLDWIN, WIN_KEYVAL, IERROR\fP
	INTEGER(KIND=MPI_ADDRESS_KIND) \fIEXTRA_STATE, ATTRIBUTE_VAL_IN,
		ATTRIBUTE_VAL_OUT\fP
	LOGICAL \fIFLAG\fP
.fi
.sp
and
.sp
.nf
SUBROUTINE WIN_DELETE_ATTR_FN(\fIWIN, WIN_KEYVAL, ATTRIBUTE_VAL,
	EXTRA_STATE, IERROR\fP)
	INTEGER \fIWIN, WIN_KEYVAL, IERROR\fP
	INTEGER(KIND=MPI_ADDRESS_KIND) \fIATTRIBUTE_VAL, EXTRA_STATE\fP
.fi
.sp
The C++ callbacks are:
.sp
.nf
typedef int MPI::Win::Copy_attr_function(const MPI::Win& \fIoldwin\fP,
	int \fIwin_keyval\fP, void* \fIextra_state\fP, void* \fIattribute_val_in\fP,
	void* \fIattribute_val_out\fP, bool& \fIflag\fP);
.fi
.sp
and
.sp
.nf
typedef int MPI::Win::Delete_attr_function(MPI::Win& \fIwin\fP, int \fIwin_keyval\fP, void* \fIattribute_val\fP, void* \fIextra_state\fP);
.fi

.SH FORTRAN 77 NOTES
.ft R
The MPI standard prescribes portable Fortran syntax for
the \fIEXTRA_STATE\fP argument only for Fortran 90. FORTRAN 77
users may use the non-portable syntax
.sp
.nf
     INTEGER*MPI_ADDRESS_KIND \fIEXTRA_STATE\fP
.fi
.sp
where MPI_ADDRESS_KIND is a constant defined in mpif.h
and gives the length of the declared integer in bytes.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.