[mutter] launcher: refactor handling errors in meta_launcher_new

[Ray Strode <halfline src gnome org>]

commit 1845bfe1b6235ed80e2737078843ffc5feb7c7b8
Author: Marek Chalupa <mchqwerty gmail com>
Date:   Thu Sep 3 16:03:41 2015 +0200

    launcher: refactor handling errors in meta_launcher_new
    
    Fill in missing error checks and use g_error, since any
    error in this phase would lead to crash later anyway.
    This way we'll at least know what went wrong.
    
    Although it was not the patch's original intention, it fixes
    https://bugzilla.gnome.org/show_bug.cgi?id=754520
    
    https://bugzilla.gnome.org/show_bug.cgi?id=753434

 src/backends/native/meta-launcher.c |   65 +++++++++++++++++++---------------
 1 files changed, 36 insertions(+), 29 deletions(-)
---
diff --git a/src/backends/native/meta-launcher.c b/src/backends/native/meta-launcher.c
index 988aef8..616c092 100644
--- a/src/backends/native/meta-launcher.c
+++ b/src/backends/native/meta-launcher.c
@@ -53,26 +53,50 @@ struct _MetaLauncher
   gboolean session_active;
 };
 
+static void
+report_error_and_die (const char *prefix,
+                      GError *error)
+{
+  /* if a function returns due to g_return_val_if_fail,
+   * then the error may not be set */
+  if (error)
+    g_error ("%s: %s", prefix, error->message);
+  else
+    g_error (prefix);
+
+  /* the error is not freed, but it is ok as g_error aborts the process */
+}
+
 static Login1Session *
 get_session_proxy (GCancellable *cancellable)
 {
   Login1Session *session_proxy;
+  GError *error = NULL;
+
   session_proxy = login1_session_proxy_new_for_bus_sync (G_BUS_TYPE_SYSTEM,
                                                          G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
                                                          "org.freedesktop.login1",
                                                          "/org/freedesktop/login1/session/self",
-                                                         cancellable, NULL);
+                                                         cancellable, &error);
+  if (!session_proxy)
+    report_error_and_die ("Failed getting session proxy", error);
+
   return session_proxy;
 }
 
 static Login1Seat *
 get_seat_proxy (GCancellable *cancellable)
 {
-  return login1_seat_proxy_new_for_bus_sync (G_BUS_TYPE_SYSTEM,
-                                             G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
-                                             "org.freedesktop.login1",
-                                             "/org/freedesktop/login1/seat/self",
-                                             cancellable, NULL);
+  GError *error = NULL;
+  Login1Seat *seat = login1_seat_proxy_new_for_bus_sync (G_BUS_TYPE_SYSTEM,
+                                                         G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
+                                                         "org.freedesktop.login1",
+                                                         "/org/freedesktop/login1/seat/self",
+                                                         cancellable, &error);
+  if (!seat)
+    report_error_and_die ("Could not get seat proxy", error);
+
+  return seat;
 }
 
 static void
@@ -252,7 +276,7 @@ on_active_changed (Login1Session *session,
   sync_active (self);
 }
 
-static gboolean
+static void
 get_kms_fd (Login1Session *session_proxy,
             int *fd_out)
 {
@@ -262,21 +286,12 @@ get_kms_fd (Login1Session *session_proxy,
 
   /* XXX -- use udev to find the DRM master device */
   if (!get_device_info_from_path ("/dev/dri/card0", &major, &minor))
-    {
-      g_warning ("Could not stat /dev/dri/card0: %m");
-      return FALSE;
-    }
+    g_error ("Could not stat /dev/dri/card0: %m");
 
   if (!take_device (session_proxy, major, minor, &fd, NULL, &error))
-    {
-      g_warning ("Could not open DRM device: %s\n", error->message);
-      g_error_free (error);
-      return FALSE;
-    }
+    report_error_and_die ("Could not open DRM device", error);
 
   *fd_out = fd;
-
-  return TRUE;
 }
 
 MetaLauncher *
@@ -289,17 +304,12 @@ meta_launcher_new (void)
 
   session_proxy = get_session_proxy (NULL);
   if (!login1_session_call_take_control_sync (session_proxy, FALSE, NULL, &error))
-    {
-      g_warning ("Could not take control: %s", error->message);
-      g_error_free (error);
-      goto out;
-    }
+    report_error_and_die ("Could not take control", error);
 
-  if (!get_kms_fd (session_proxy, &kms_fd))
-    goto out;
+  get_kms_fd (session_proxy, &kms_fd);
 
   self = g_slice_new0 (MetaLauncher);
-  self->session_proxy = g_object_ref (session_proxy);
+  self->session_proxy = session_proxy;
   self->seat_proxy = get_seat_proxy (NULL);
 
   self->session_active = TRUE;
@@ -311,9 +321,6 @@ meta_launcher_new (void)
 
   g_signal_connect (self->session_proxy, "notify::active", G_CALLBACK (on_active_changed), self);
 
-out:
-  g_object_unref (session_proxy);
-
   return self;
 }