nbd_set_debug_callback - set the debug callback

       Eric Blake

       Richard W.M. Jones

       Copyright Red Hat

       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.

       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).

       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

libnbd-1.22.2                                      2025-06-16                          nbd_set_debug_callback(3)

       nbd_set_debug_callback - set the debug callback

       If the call is successful the function returns 0.

nbd_create(3), libnbd(3).

        #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
            );

       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