Provided by: libnbd-dev_1.2.2-1ubuntu2_amd64 bug


       nbd_set_debug_callback - set the debug callback


        #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);


       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.


       If the call is successful the function returns 0.


       On error "-1" is returned.

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


       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:



       nbd_create(3), libnbd(3).


       Eric Blake

       Richard W.M. Jones


       Copyright (C) 2019 Red Hat Inc.


       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