events: Add a warning event and direct all warning messages through it.

This also causes warnings to be printed even in non-verbose mode,
which is useful.

examples/debug-logging.c

@@ -17,7 +17,10 @@ static void message_callback (guestfs_h *g, void *opaque, uint64_t event, int ev
  * debug messages.
  */
 static const uint64_t event_bitmask =
-  GUESTFS_EVENT_LIBRARY | GUESTFS_EVENT_APPLIANCE | GUESTFS_EVENT_TRACE;
+  GUESTFS_EVENT_LIBRARY |
+  GUESTFS_EVENT_WARNING |
+  GUESTFS_EVENT_APPLIANCE |
+  GUESTFS_EVENT_TRACE;
 
 int
 main (int argc, char *argv[])

generator/events.ml

@@ -39,6 +39,8 @@ let events = [
   "enter";                              (* enter a function *)
 
   "libvirt_auth";                       (* libvirt authentication request *)
+
+  "warning";                            (* warnings from the library *)
 ]
 
 let events = mapi (fun i name -> name, 1 lsl i) events

java/t/GuestFS420LogMessages.java

@@ -62,7 +62,7 @@ public class GuestFS420LogMessages
             LogEvent le = new LogEvent ();
             g.set_event_callback (le,
                                   GuestFS.EVENT_APPLIANCE|GuestFS.EVENT_LIBRARY|
-                                  GuestFS.EVENT_TRACE);
+                                  GuestFS.EVENT_WARNING|GuestFS.EVENT_TRACE);
 
             // Now make sure we see some messages.
             g.set_trace (true);

ocaml/t/guestfs_420_log_messages.ml

@@ -32,7 +32,7 @@ let log g ev eh buf array =
 let () =
   let g = new Guestfs.guestfs () in
   let events = [ Guestfs.EVENT_APPLIANCE; Guestfs.EVENT_LIBRARY;
-                 Guestfs.EVENT_TRACE ] in
+                 Guestfs.EVENT_WARNING; Guestfs.EVENT_TRACE ] in
   ignore (g#set_event_callback log events);
 
   g#set_trace true;

perl/t/410-close-event.t

@@ -48,7 +48,7 @@ sub close_callback {
 
 # Register an event callback for all log messages.
 my $events = $Sys::Guestfs::EVENT_APPLIANCE | $Sys::Guestfs::EVENT_LIBRARY |
-    $Sys::Guestfs::EVENT_TRACE;
+    $Sys::Guestfs::EVENT_WARNING | $Sys::Guestfs::EVENT_TRACE;
 my $eh;
 $eh = $g->set_event_callback (\&log_callback, $events);
 ok ($eh >= 0);

perl/t/420-log-messages.t

@@ -48,7 +48,7 @@ sub close_callback {
 
 # Register an event callback for all log messages.
 my $events = $Sys::Guestfs::EVENT_APPLIANCE | $Sys::Guestfs::EVENT_LIBRARY |
-    $Sys::Guestfs::EVENT_TRACE;
+    $Sys::Guestfs::EVENT_WARNING | $Sys::Guestfs::EVENT_TRACE;
 my $eh;
 $eh = $g->set_event_callback (\&log_callback, $events);
 ok ($eh >= 0);

python/t/420-log-messages.py

@@ -34,7 +34,8 @@ def log_callback (ev,eh,buf,array):
            (guestfs.event_to_string (ev), eh, buf, array))
 
 # Register an event callback for all log messages.
-events = guestfs.EVENT_APPLIANCE | guestfs.EVENT_LIBRARY | guestfs.EVENT_TRACE
+events = guestfs.EVENT_APPLIANCE | guestfs.EVENT_LIBRARY \
+         | guestfs.EVENT_WARNING | guestfs.EVENT_TRACE
 g.set_event_callback (log_callback, events)
 
 # Now make sure we see some messages.

ruby/t/tc_420_log_messages.rb

@@ -36,7 +36,7 @@ class TestLoad < Test::Unit::TestCase
 
     # Grab log, trace and daemon messages into our custom callback.
     event_bitmask = Guestfs::EVENT_APPLIANCE | Guestfs::EVENT_LIBRARY |
-      Guestfs::EVENT_TRACE
+      Guestfs::EVENT_WARNING | Guestfs::EVENT_TRACE
     g.set_event_callback(log, event_bitmask)
 
     # Make sure we see some messages.

src/errors.c

@@ -57,7 +57,7 @@ void
 guestfs___warning (guestfs_h *g, const char *fs, ...)
 {
   va_list args;
-  CLEANUP_FREE char *msg = NULL, *msg2 = NULL;
+  CLEANUP_FREE char *msg = NULL;
   int len;
 
   va_start (args, fs);
@@ -66,11 +66,7 @@ guestfs___warning (guestfs_h *g, const char *fs, ...)
 
   if (len < 0) return;
 
-  len = asprintf (&msg2, _("warning: %s"), msg);
-
-  if (len < 0) return;
-
-  guestfs___call_callbacks_message (g, GUESTFS_EVENT_LIBRARY, msg2, len);
+  guestfs___call_callbacks_message (g, GUESTFS_EVENT_WARNING, msg, len);
 }
 
 /* Debug messages. */

src/events.c

@@ -130,19 +130,26 @@ guestfs___call_callbacks_message (guestfs_h *g, uint64_t event,
 
   if ((event == GUESTFS_EVENT_APPLIANCE ||
        event == GUESTFS_EVENT_LIBRARY ||
+       event == GUESTFS_EVENT_WARNING ||
        event == GUESTFS_EVENT_TRACE) &&
-      (g->verbose || event == GUESTFS_EVENT_TRACE)) {
+      (g->verbose ||
+       event == GUESTFS_EVENT_WARNING ||
+       event == GUESTFS_EVENT_TRACE)) {
     bool from_appliance = event == GUESTFS_EVENT_APPLIANCE;
     size_t i, i0;
 
     /* APPLIANCE =>  <buf>
      * LIBRARY =>    libguestfs: <buf>\n
+     * WARNING =>    libguestfs: warning: <buf>\n
      * TRACE =>      libguestfs: trace: <buf>\n  (RHBZ#673479)
      */
 
     if (event != GUESTFS_EVENT_APPLIANCE)
       fputs ("libguestfs: ", stderr);
 
+    if (event == GUESTFS_EVENT_WARNING)
+      fputs ("warning: ", stderr);
+
     if (event == GUESTFS_EVENT_TRACE)
       fputs ("trace: ", stderr);
 

src/guestfs.pod

@@ -2791,6 +2791,16 @@ verbose flag is set in which case they are sent to stderr.  You can
 override the printing of verbose messages to stderr by setting up a
 callback.
 
+=item GUESTFS_EVENT_WARNING
+(payload type: message buffer)
+
+The callback function is called whenever a warning message is
+generated by the library part of libguestfs.
+
+If no callback is registered: the messages are printed to stderr.  You
+can override the printing of warning messages to stderr by setting up
+a callback.
+
 =item GUESTFS_EVENT_TRACE
 (payload type: message buffer)
 
@@ -2843,8 +2853,8 @@ in the C<event_bitmask>.
 
 For example, to register for all log message events, you could call
 this function with the bitmask
-C<GUESTFS_EVENT_APPLIANCE|GUESTFS_EVENT_LIBRARY>.  To register a
-single callback for all possible classes of events, use
+C<GUESTFS_EVENT_APPLIANCE|GUESTFS_EVENT_LIBRARY|GUESTFS_EVENT_WARNING>.
+To register a single callback for all possible classes of events, use
 C<GUESTFS_EVENT_ALL>.
 
 C<flags> should always be passed as 0.
@@ -2933,9 +2943,9 @@ capture debug and other messages.  In libguestfs E<le> 1.8 these were
 sent unconditionally to C<stderr>.
 
 Events associated with log messages are: C<GUESTFS_EVENT_LIBRARY>,
-C<GUESTFS_EVENT_APPLIANCE> and C<GUESTFS_EVENT_TRACE>.  (Note that
-error messages are not events; you must capture error messages
-separately).
+C<GUESTFS_EVENT_APPLIANCE>, C<GUESTFS_EVENT_WARNING> and
+C<GUESTFS_EVENT_TRACE>.  (Note that error messages are not events; you
+must capture error messages separately).
 
 Programs have to set up a callback to capture the classes of events of
 interest:
@@ -2943,8 +2953,8 @@ interest:
  int eh =
    guestfs_set_event_callback
      (g, message_callback,
-      GUESTFS_EVENT_LIBRARY|GUESTFS_EVENT_APPLIANCE|
-      GUESTFS_EVENT_TRACE,
+      GUESTFS_EVENT_LIBRARY | GUESTFS_EVENT_APPLIANCE |
+      GUESTFS_EVENT_WARNING | GUESTFS_EVENT_TRACE,
       0, NULL) == -1)
  if (eh == -1) {
    // handle error in the usual way

tests/c-api/test-debug-to-file.c

@@ -67,7 +67,8 @@ main (int argc, char *argv[])
 
   if (guestfs_set_event_callback
       (g, debug_to_file,
-       GUESTFS_EVENT_LIBRARY|GUESTFS_EVENT_APPLIANCE|GUESTFS_EVENT_TRACE,
+       GUESTFS_EVENT_LIBRARY | GUESTFS_EVENT_APPLIANCE |
+       GUESTFS_EVENT_WARNING | GUESTFS_EVENT_TRACE,
        0, debugfp) == -1)
     exit (EXIT_FAILURE);