According to Brendan Eich ("Mr. SpiderMonkey" himself), using the undocumented

JSPROP_SHARED attribute for properties with getter/setter methods will save us
4-bytes per property in the JS heap (not bad).

src/sbbs3/js_global.c

@@ -73,7 +73,7 @@ static JSBool js_system_get(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 	return(JS_TRUE);
 }
 
-#define GLOBOBJ_FLAGS JSPROP_ENUMERATE|JSPROP_READONLY
+#define GLOBOBJ_FLAGS JSPROP_ENUMERATE|JSPROP_READONLY|JSPROP_SHARED
 
 static struct JSPropertySpec js_global_properties[] = {
 /*		 name,		tinyid,				flags */

src/sbbs3/js_msg_area.c

@@ -293,9 +293,9 @@ static JSBool js_sub_set(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 static struct JSPropertySpec js_sub_properties[] = {
 /*		 name				,tinyid		,flags	*/
 
-	{	"scan_ptr"	,SUB_PROP_SCAN_PTR	,JSPROP_ENUMERATE },
-	{	"scan_cfg"	,SUB_PROP_SCAN_CFG	,JSPROP_ENUMERATE },
-	{	"lead_read"	,SUB_PROP_LAST_READ	,JSPROP_ENUMERATE },
+	{	"scan_ptr"	,SUB_PROP_SCAN_PTR	,JSPROP_ENUMERATE|JSPROP_SHARED },
+	{	"scan_cfg"	,SUB_PROP_SCAN_CFG	,JSPROP_ENUMERATE|JSPROP_SHARED },
+	{	"lead_read"	,SUB_PROP_LAST_READ	,JSPROP_ENUMERATE|JSPROP_SHARED },
 	{0}
 };
 

src/sbbs3/main.cpp

@@ -374,8 +374,8 @@ DLLCALL js_DefineSyncProperties(JSContext *cx, JSObject *obj, jsSyncPropertySpec
 		return(JS_FALSE);
 
 	for(i=0;props[i].name;i++) {
-		if(!JS_DefinePropertyWithTinyId(cx, obj, 
-			props[i].name,props[i].tinyid, JSVAL_VOID, NULL, NULL, props[i].flags))
+		if(!JS_DefinePropertyWithTinyId(cx, obj, /* Never reserve any "slots" for properties */
+			props[i].name,props[i].tinyid, JSVAL_VOID, NULL, NULL, props[i].flags|JSPROP_SHARED))
 			return(JS_FALSE);
 		if(props[i].flags&JSPROP_ENUMERATE) {	/* No need to version invisible props */
 			val = INT_TO_JSVAL(props[i].ver);
@@ -477,7 +477,7 @@ DLLCALL js_DefineSyncProperties(JSContext *cx, JSObject *obj, jsSyncPropertySpec
 
 	for(i=0;props[i].name;i++) 
 		if(!JS_DefinePropertyWithTinyId(cx, obj, 
-			props[i].name,props[i].tinyid, JSVAL_VOID, NULL, NULL, props[i].flags))
+			props[i].name,props[i].tinyid, JSVAL_VOID, NULL, NULL, props[i].flags|JSPROP_SHARED))
 			return(JS_FALSE);
 
 	return(JS_TRUE);