NAME

nbd_set_debug_callback - set the debug callback

SYNOPSIS

 #include <libnbd.h>
 typedef struct {
   int (*callback) (void *user_data, const char *context,
                    const char *msg);
   void *user_data;
   void (*free) (void *user_data);
 } nbd_debug_callback;
 int nbd_set_debug_callback (struct nbd_handle *h,
                             nbd_debug_callback debug_callback);

DESCRIPTION

Set the debug callback. This function is called when the library emits debug messages, when debugging is enabled on a handle. The callback parameters are "user_data" passed to this function, the name of the libnbd function emitting the debug message ("context"), and the message itself ("msg"). If no debug callback is set on a handle then messages are printed on "stderr".

The callback should not call "nbd_*" APIs on the same handle since it can be called while holding the handle lock and will cause a deadlock.

RETURN VALUE

If the call is successful the function returns 0.

ERRORS

On error "-1" is returned.

Refer to "ERROR HANDLING" in libnbd(3) for how to get further details of the error.

The following parameters must not be NULL: "h". For more information see "Non-NULL parameters" in libnbd(3).

VERSION

This function first appeared in libnbd 1.0.

If you need to test if this function is available at compile time check if the following macro is defined:

 #define LIBNBD_HAVE_NBD_SET_DEBUG_CALLBACK 1

SEE ALSO

nbd_create(3), libnbd(3).

AUTHORS

Eric Blake

Richard W.M. Jones

COPYRIGHT

Copyright (C) 2019-2021 Red Hat Inc.

LICENSE

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA