Add error callback (RHBZ#602599).

Read the note in the man page before using this feature.

4 files changed, 58 insertions, 5 deletions

diff --git a/src/generator.ml b/src/generator.ml
index 0ffd3c70..cf28978d 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -6337,6 +6337,7 @@ and generate_linker_script () =
     "guestfs_get_error_handler";
     "guestfs_get_out_of_memory_handler";
     "guestfs_last_error";
+    "guestfs_set_close_callback";
     "guestfs_set_error_handler";
     "guestfs_set_launch_done_callback";
     "guestfs_set_log_message_callback";
@@ -6885,6 +6886,13 @@ is_available (const char *group)
   return r == 0;
 }
 
+static void
+incr (guestfs_h *g, void *iv)
+{
+  int *i = (int *) iv;
+  (*i)++;
+}
+
 ";
 
   (* Generate a list of commands which are not tested anywhere. *)
@@ -7066,11 +7074,22 @@ int main (int argc, char *argv[])
   ) test_names;
   pr "\n";
 
-  pr "  guestfs_close (g);\n";
-  pr "  unlink (\"test1.img\");\n";
-  pr "  unlink (\"test2.img\");\n";
-  pr "  unlink (\"test3.img\");\n";
-  pr "\n";
+  pr "  /* Check close callback is called. */
+  int close_sentinel = 1;
+  guestfs_set_close_callback (g, incr, &close_sentinel);
+
+  guestfs_close (g);
+
+  if (close_sentinel != 2) {
+    fprintf (stderr, \"close callback was not called\\n\");
+    exit (EXIT_FAILURE);
+  }
+
+  unlink (\"test1.img\");
+  unlink (\"test2.img\");
+  unlink (\"test3.img\");
+
+";
 
   pr "  if (n_failed > 0) {\n";
   pr "    printf (\"***** %%lu / %%d tests FAILED *****\\n\", n_failed, nr_tests);\n";
diff --git a/src/guestfs.c b/src/guestfs.c
index 0e4cb73b..1439361d 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -183,6 +183,8 @@ struct guestfs_h
   void *                     subprocess_quit_cb_data;
   guestfs_launch_done_cb     launch_done_cb;
   void *                     launch_done_cb_data;
+  guestfs_close_cb           close_cb;
+  void *                     close_cb_data;
 
   int msg_next_serial;
 };
@@ -294,6 +296,10 @@ guestfs_close (guestfs_h *g)
   if (g->verbose)
     fprintf (stderr, "closing guestfs handle %p (state %d)\n", g, g->state);
 
+  /* Run user close callback before anything else. */
+  if (g->close_cb)
+    g->close_cb (g, g->close_cb_data);
+
   /* Try to sync if autosync flag is set. */
   if (g->autosync && g->state == READY) {
     guestfs_umount_all (g);
@@ -1927,6 +1933,14 @@ guestfs_set_launch_done_callback (guestfs_h *g,
   g->launch_done_cb_data = opaque;
 }
 
+void
+guestfs_set_close_callback (guestfs_h *g,
+                            guestfs_close_cb cb, void *opaque)
+{
+  g->close_cb = cb;
+  g->close_cb_data = opaque;
+}
+
 /*----------------------------------------------------------------------*/
 
 /* This is the code used to send and receive RPC messages and (for
diff --git a/src/guestfs.h b/src/guestfs.h
index b43cd8bc..3cff4849 100644
--- a/src/guestfs.h
+++ b/src/guestfs.h
@@ -56,10 +56,12 @@ extern guestfs_abort_cb guestfs_get_out_of_memory_handler (guestfs_h *g);
 typedef void (*guestfs_log_message_cb) (guestfs_h *g, void *data, char *buf, int len);
 typedef void (*guestfs_subprocess_quit_cb) (guestfs_h *g, void *data);
 typedef void (*guestfs_launch_done_cb) (guestfs_h *g, void *data);
+typedef void (*guestfs_close_cb) (guestfs_h *g, void *data);
 
 extern void guestfs_set_log_message_callback (guestfs_h *g, guestfs_log_message_cb cb, void *opaque);
 extern void guestfs_set_subprocess_quit_callback (guestfs_h *g, guestfs_subprocess_quit_cb cb, void *opaque);
 extern void guestfs_set_launch_done_callback (guestfs_h *g, guestfs_launch_done_cb cb, void *opaque);
+extern void guestfs_set_close_callback (guestfs_h *g, guestfs_close_cb cb, void *opaque);
 
 /*--- Structures and actions ---*/
 #include <stdint.h>
diff --git a/src/guestfs.pod b/src/guestfs.pod
index 0f60c8e5..2fa3aceb 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -1042,6 +1042,24 @@ The callback function C<cb> will be called when the child process
 becomes ready first time after it has been launched.  (This
 corresponds to a transition from LAUNCHING to the READY state).
 
+=head2 guestfs_set_close_callback
+
+ typedef void (*guestfs_close_cb) (guestfs_h *g, void *opaque);
+ void guestfs_set_close_callback (guestfs_h *g,
+                                  guestfs_close_cb cb,
+                                  void *opaque);
+
+The callback function C<cb> will be called while the handle
+is being closed (synchronously from L</guestfs_close>).
+
+Note that libguestfs installs an L<atexit(3)> handler to try to
+clean up handles that are open when the program exits.  This
+means that this callback might be called indirectly from
+L<exit(3)>, which can cause unexpected problems in higher-level
+languages (eg. if your HLL interpreter has already been cleaned
+up by the time this is called, and if your callback then jumps
+into some HLL function).
+
 =head1 BLOCK DEVICE NAMING
 
 In the kernel there is now quite a profusion of schemata for naming