[gjs] object: Optimize a bit AutoGValueVector usage

[Philip Chimento <pchimento src gnome org>]

commit 8ba49c5f92035016bd6b40d830933ef9a757024a
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Thu May 13 20:18:01 2021 +0200

    object: Optimize a bit AutoGValueVector usage
    
     - Reserve it before using
     - Initialize the GValue only when needed
     - Use move constructor (via emplace) to initialize it
     - Rely on vector destructor to unset it

 gi/object.cpp | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)
---
diff --git a/gi/object.cpp b/gi/object.cpp
index fe2691aa..766f88c1 100644
--- a/gi/object.cpp
+++ b/gi/object.cpp
@@ -1059,15 +1059,14 @@ bool ObjectPrototype::props_to_g_parameters(JSContext* context,
     size_t ix, length;
     JS::RootedId prop_id(context);
     JS::RootedValue value(context);
-    JS::Rooted<JS::IdVector> ids(context, context);
+    JS::Rooted<JS::IdVector> ids(context);
     if (!JS_Enumerate(context, props, &ids)) {
         gjs_throw(context, "Failed to create property iterator for object props hash");
         return false;
     }
 
+    values->reserve(ids.length());
     for (ix = 0, length = ids.length(); ix < length; ix++) {
-        GValue gvalue = G_VALUE_INIT;
-
         /* ids[ix] is reachable because props is rooted, but require_property
          * doesn't know that */
         prop_id = ids[ix];
@@ -1094,14 +1093,13 @@ bool ObjectPrototype::props_to_g_parameters(JSContext* context,
                                                     param_spec->name);
             /* prevent setting the prop even in JS */
 
+        GValue& gvalue = values->emplace_back();
+        gvalue = G_VALUE_INIT;
         g_value_init(&gvalue, G_PARAM_SPEC_VALUE_TYPE(param_spec));
-        if (!gjs_value_to_g_value(context, value, &gvalue)) {
-            g_value_unset(&gvalue);
+        if (!gjs_value_to_g_value(context, value, &gvalue))
             return false;
-        }
 
         names->push_back(param_spec->name);  /* owned by GParamSpec in cache */
-        values->push_back(gvalue);
     }
 
     return true;