dbus_error handling was being abused quite wrongly.  This might even
fix a couple of potential memory leaks...  Paul Sladen <ubuntu@paul.sladen.org>


diff -ur hal-0.5.9.1/hald/linux/addons/addon-acpi.c hal-0.5.9.1.sladen/hald/linux/addons/addon-acpi.c
--- hal-0.5.9.1/hald/linux/addons/addon-acpi.c	2007-10-04 18:55:13.000000000 +0300
+++ hal-0.5.9.1.sladen/hald/linux/addons/addon-acpi.c	2007-10-04 20:03:07.000000000 +0300
@@ -185,6 +185,8 @@
 	DBusError error;
 	char event[256];
 
+	dbus_error_init (&error);
+
 	while (fgets (event, sizeof event, eventfp))
 	{
 		HAL_DEBUG (("event is '%s'", event));
@@ -200,12 +202,16 @@
 				HAL_DEBUG (("button event"));
 
 				/* TODO: only rescan if button got state */
-				dbus_error_init (&error);
 				if (libhal_device_rescan (ctx, udi, &error)) {
-					dbus_error_init (&error);
+					if (dbus_error_is_set (&error)) {
+						dbus_error_free (&error);
+					}
 					type = libhal_device_get_property_string(ctx, udi, 
 										 "button.type",
 										 &error);
+					if (dbus_error_is_set (&error)) {
+						dbus_error_free (&error);
+					}
 					if (type != NULL) {
 						libhal_device_emit_condition (ctx, udi, "ButtonPressed",
 									      type, &error);
@@ -216,31 +222,28 @@
 				}
 			} else if (strncmp (acpi_path, "ac_adapter", sizeof ("ac_adapter") - 1) == 0) {
 				HAL_DEBUG (("ac_adapter event"));
-				dbus_error_init (&error);
 				libhal_device_rescan (ctx, udi, &error);
 			} else if (strncmp (acpi_path, "battery", sizeof ("battery") - 1) == 0) {
 				HAL_DEBUG (("battery event"));
-				dbus_error_init (&error);
 				libhal_device_rescan (ctx, udi, &error);
 #ifdef BUILD_ACPI_IBM
 			} else if (strncmp (acpi_path, "ibm/hotkey", sizeof ("ibm/hotkey") -1) == 0) {
 				/* handle ibm ACPI hotkey events*/
 				handle_ibm_acpi_events(ctx, acpi_num1, acpi_num2);	
 #endif
-			} 
+		} 
 
 		} else {
 			HAL_DEBUG (("cannot parse event"));
 		}
 
 		if (dbus_error_is_set (&error)) {
-	        	/* Free the error (which include a dbus_error_init()) 
-			   This should prevent errors if a call above fails */
+			/* NB: dbus_error_free (&error)	 performs   dbus_error_init (error); */
 			dbus_error_free (&error);
 		}
 	}
 
-	dbus_error_free (&error);
+	/* dbus-errors.c: "An error only needs to be freed if it's been set, not if it's merely been initialized." */
 	fclose (eventfp);
 }