From 1845bfe1b6235ed80e2737078843ffc5feb7c7b8 Mon Sep 17 00:00:00 2001
From: Marek Chalupa <mchqwerty@gmail.com>
Date: Thu, 3 Sep 2015 16:03:41 +0200
Subject: [PATCH] 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 file changed, 36 insertions(+), 29 deletions(-)

diff --git a/src/backends/native/meta-launcher.c b/src/backends/native/meta-launcher.c
index 988aef888..616c09238 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;
 }