[gnome-builder] source-view-mode: make value copies when emitting actions

[Christian Hergert <chergert src gnome org>]

commit 2f9e2dfe4b3730085f2942675728b0e8fbcf910d
Author: Christian Hergert <chergert redhat com>
Date:   Thu Jul 20 15:25:16 2017 -0700

    source-view-mode: make value copies when emitting actions
    
    I've noticed some weird reference issues when emitting signals
    through the IdeSourceViewMode, so this tries to be safer by
    making full references to the objects during the emission
    procedure.
    
    Additionally, we spill the value array copy to the stack by
    using alloca since there should only ever be a small number of
    values to copy.

 libide/sourceview/ide-source-view-mode.c |   68 +++++++++++++++++++++++------
 1 files changed, 54 insertions(+), 14 deletions(-)
---
diff --git a/libide/sourceview/ide-source-view-mode.c b/libide/sourceview/ide-source-view-mode.c
index 92d9bb3..f66dee8 100644
--- a/libide/sourceview/ide-source-view-mode.c
+++ b/libide/sourceview/ide-source-view-mode.c
@@ -20,6 +20,7 @@
 #define G_LOG_DOMAIN "ide-source-view-mode"
 
 #include <glib/gi18n.h>
+#include <string.h>
 
 #include "ide-debug.h"
 
@@ -167,35 +168,75 @@ proxy_closure_marshal (GClosure     *closure,
                        gpointer      invocation_hint,
                        gpointer      marshal_data)
 {
+  g_autoptr(IdeSourceViewMode) self = NULL;
   GValue *param_copy;
-  IdeSourceViewMode *mode = IDE_SOURCE_VIEW_MODE (g_value_get_object (&param_values[0]));
 
-  param_copy = g_memdup (param_values, sizeof (GValue) * n_param_values);
+  g_assert (closure != NULL);
+  g_assert (param_values != NULL);
 
-  param_copy[0].data[0].v_pointer = mode->view;
-  g_signal_emitv (param_copy,
-                  GPOINTER_TO_INT (closure->data),
-                  0,
-                  return_value);
-  g_free (param_copy);
+  /*
+   * To be absolutely sure about reference counting with GValue and other
+   * ownership mishaps, this proxy makes a full copy of all parameters. It is
+   * certainly slower, but we are only activated from keybindings and the user
+   * can only type so fast...
+   */
+
+  self = g_value_dup_object (&param_values[0]);
+  g_assert (IDE_IS_SOURCE_VIEW_MODE (self));
+
+  if (self->view == NULL)
+    {
+      g_warning ("Cannot proxy signal after destroy has been called");
+      return;
+    }
+
+  /* Just spill to the stack, we only have a small number of params */
+  param_copy = g_alloca (sizeof (GValue) * n_param_values);
+  memset (param_copy, 0, sizeof (GValue) * n_param_values);
+
+  /* Swap the first object into the IdeSourceView */
+  g_value_init (&param_copy[0], G_OBJECT_TYPE (self->view));
+  g_value_set_object (&param_copy[0], self->view);
+
+  /* Copy the rest of the parameters across */
+  for (guint i = 1; i < n_param_values; i++)
+    {
+      g_value_init (&param_copy[i], G_VALUE_TYPE (&param_values[i]));
+      g_value_copy (&param_values[i], &param_copy[i]);
+    }
+
+  /* Emit the signal on the source view */
+  g_signal_emitv (param_copy, GPOINTER_TO_UINT (closure->data), 0, return_value);
+
+  /* Cleanup, dropping our references. */
+  for (guint i = 0; i < n_param_values; i++)
+    g_value_unset (&param_copy[i]);
 }
 
 static void
 proxy_all_action_signals (GType type)
 {
-  GClosure *proxy;
-  guint *signals;
-  guint n_signals, i;
+  g_autofree guint *signals = NULL;
   GSignalQuery query;
+  guint n_signals = 0;
+
+  g_assert (g_type_is_a (type, G_TYPE_OBJECT));
 
   signals = g_signal_list_ids (type, &n_signals);
 
-  for (i = 0; i < n_signals; i++)
+  for (guint i = 0; i < n_signals; i++)
     {
       g_signal_query (signals[i], &query);
 
+      /* We don't support detailed signals */
+      if (query.signal_flags & G_SIGNAL_DETAILED)
+        continue;
+
+      /* Only proxy keybinding action signals */
       if (query.signal_flags & G_SIGNAL_ACTION)
         {
+          GClosure *proxy;
+
           proxy = g_closure_new_simple (sizeof (GClosure), GINT_TO_POINTER (query.signal_id));
           g_closure_set_meta_marshal (proxy, NULL, proxy_closure_marshal);
           g_signal_newv (query.signal_name,
@@ -206,10 +247,9 @@ proxy_all_action_signals (GType type)
                          query.return_type,
                          query.n_params,
                          (GType *)query.param_types);
+          /* Proxy ownership is stolen when sinking the closure */
         }
     }
-
-  g_free (signals);
 }
 
 const gchar *