[glib/gobject-speedups: 4/13] Keep a count of construct params

[Matthias Clasen <matthiasc src gnome org>]

commit 5ca46aa94efa670c904ab9709d46e9ab1b1610f7
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat May 14 22:38:09 2022 -0400

    Keep a count of construct params
    
    This avoids walking the construct params list
    one extra time just to count when constructing
    objects.

 gobject/gobject.c | 43 +++++++++++++++++++++++++++++++++----------
 gobject/gobject.h |  3 ++-
 2 files changed, 35 insertions(+), 11 deletions(-)
---
diff --git a/gobject/gobject.c b/gobject/gobject.c
index f720e1c9c1..de46f7187c 100644
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -478,6 +478,7 @@ g_object_base_class_init (GObjectClass *class)
 
   /* reset instance specific fields and methods that don't get inherited */
   class->construct_properties = pclass ? g_slist_copy (pclass->construct_properties) : NULL;
+  class->n_construct_properties = g_slist_length (class->construct_properties);
   class->get_property = NULL;
   class->set_property = NULL;
 }
@@ -491,6 +492,7 @@ g_object_base_class_finalize (GObjectClass *class)
 
   g_slist_free (class->construct_properties);
   class->construct_properties = NULL;
+  class->n_construct_properties = 0;
   list = g_param_spec_pool_list_owned (pspec_pool, G_OBJECT_CLASS_TYPE (class));
   for (node = list; node; node = node->next)
     {
@@ -627,14 +629,20 @@ validate_and_install_class_property (GObjectClass *class,
   if (install_property_internal (oclass_type, property_id, pspec))
     {
       if (pspec->flags & (G_PARAM_CONSTRUCT | G_PARAM_CONSTRUCT_ONLY))
-        class->construct_properties = g_slist_append (class->construct_properties, pspec);
+        {
+          class->construct_properties = g_slist_append (class->construct_properties, pspec);
+          class->n_construct_properties += 1;
+        }
 
       /* for property overrides of construct properties, we have to get rid
        * of the overridden inherited construct property
        */
       pspec = g_param_spec_pool_lookup (pspec_pool, pspec->name, parent_type, TRUE);
       if (pspec && pspec->flags & (G_PARAM_CONSTRUCT | G_PARAM_CONSTRUCT_ONLY))
-        class->construct_properties = g_slist_remove (class->construct_properties, pspec);
+        {
+          class->construct_properties = g_slist_remove (class->construct_properties, pspec);
+          class->n_construct_properties -= 1;
+        }
 
       return TRUE;
     }
@@ -1872,9 +1880,9 @@ g_object_new_with_custom_constructor (GObjectClass          *class,
   GObjectNotifyQueue *nqueue = NULL;
   gboolean newly_constructed;
   GObjectConstructParam *cparams;
+  gboolean free_cparams = FALSE;
   GObject *object;
   GValue *cvalues;
-  gint n_cparams;
   gint cvals_used;
   GSList *node;
   guint i;
@@ -1889,10 +1897,21 @@ g_object_new_with_custom_constructor (GObjectClass          *class,
    * while their constructor() is running.
    */
 
-  /* Create the array of GObjectConstructParams for constructor() */
-  n_cparams = g_slist_length (class->construct_properties);
-  cparams = g_new (GObjectConstructParam, n_cparams);
-  cvalues = g_new0 (GValue, n_cparams);
+  /* Create the array of GObjectConstructParams for constructor(),
+   * The 1024 here is an arbitrary, high limit that no sane code
+   * will ever hit, just to avoid the possibility of stack overflow.
+   */
+  if (G_LIKELY (class->n_construct_properties < 1024))
+    {
+      cparams = g_newa0 (GObjectConstructParam, class->n_construct_properties);
+      cvalues = g_newa0 (GValue, class->n_construct_properties);
+    }
+  else
+    {
+      cparams = g_new0 (GObjectConstructParam, class->n_construct_properties);
+      cvalues = g_new0 (GValue, class->n_construct_properties);
+      free_cparams = TRUE;
+    }
   cvals_used = 0;
   i = 0;
 
@@ -1933,12 +1952,16 @@ g_object_new_with_custom_constructor (GObjectClass          *class,
     }
 
   /* construct object from construction parameters */
-  object = class->constructor (class->g_type_class.g_type, n_cparams, cparams);
+  object = class->constructor (class->g_type_class.g_type, class->n_construct_properties, cparams);
   /* free construction values */
-  g_free (cparams);
   while (cvals_used--)
     g_value_unset (&cvalues[cvals_used]);
-  g_free (cvalues);
+
+  if (free_cparams)
+    {
+      g_free (cparams);
+      g_free (cvalues);
+    }
 
   /* There is code in the wild that relies on being able to return NULL
    * from its custom constructor.  This was never a supported operation,
diff --git a/gobject/gobject.h b/gobject/gobject.h
index 3dc4f7f480..c67794ae50 100644
--- a/gobject/gobject.h
+++ b/gobject/gobject.h
@@ -369,8 +369,9 @@ struct  _GObjectClass
   /*< private >*/
   gsize                flags;
 
+  gsize         n_construct_properties;
   /* padding */
-  gpointer     pdummy[6];
+  gpointer     pdummy[5];
 };
 
 /**