From 4ab49af7859dc233e6569d66b42755e4791c3b1e Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Fri, 1 May 2026 20:38:38 -0400
Subject: [PATCH] xo-object2: streamline write barriers for DList,DArray muts

---
 xo-alloc2/include/xo/alloc2/alloc/RAllocator.hpp |  8 +-------
 xo-object2/include/xo/object2/DList.hpp          |  2 +-
 xo-object2/src/object2/DArray.cpp                | 10 ----------
 xo-object2/src/object2/DList.cpp                 |  9 ++-------
 xo-reader2/src/reader2/DExpectQListSsm.cpp       |  2 +-
 5 files changed, 5 insertions(+), 26 deletions(-)

diff --git a/xo-alloc2/include/xo/alloc2/alloc/RAllocator.hpp b/xo-alloc2/include/xo/alloc2/alloc/RAllocator.hpp
index e9fa633c..e661e59d 100644
--- a/xo-alloc2/include/xo/alloc2/alloc/RAllocator.hpp
+++ b/xo-alloc2/include/xo/alloc2/alloc/RAllocator.hpp
@@ -80,16 +80,10 @@ namespace xo {
                                                                                                                       lhs_iface, lhs_data,
                                                                                                                       rhs_iface, rhs_data); }
 
+            // see [RAllocator_aux.hpp] for implementation.
             void barrier_assign(void * parent,
                                 obj<AGCObject> * p_lhs,
                                 obj<AGCObject> rhs) noexcept;
-#ifdef NOT_YET
-                this->barrier_assign_aux(parent,
-                                         p_lhs->iface(),
-                                         p_lhs->opaque_data_addr(),
-                                         rhs.iface(),
-                                         rhs.opaque_data());
-#endif
 
             static bool _valid;
         };
diff --git a/xo-object2/include/xo/object2/DList.hpp b/xo-object2/include/xo/object2/DList.hpp
index b5c340c8..fbc64784 100644
--- a/xo-object2/include/xo/object2/DList.hpp
+++ b/xo-object2/include/xo/object2/DList.hpp
@@ -67,7 +67,7 @@ namespace xo {
             void assign_head(obj<AAllocator> mm, obj<AGCObject> h);
             void assign_head_gc(obj<ACollector> gc, obj<AGCObject> h);
             /** assign rest-pointer. Caller responsible for preserving acyclic property! **/
-            void _assign_rest(DList * r);
+            void _assign_rest(obj<AAllocator> mm, DList * r);
 
             /** pretty-printing driver; combine layout+printing **/
             bool pretty(const ppindentinfo & ppii) const;
diff --git a/xo-object2/src/object2/DArray.cpp b/xo-object2/src/object2/DArray.cpp
index aeb03196..49c3d64f 100644
--- a/xo-object2/src/object2/DArray.cpp
+++ b/xo-object2/src/object2/DArray.cpp
@@ -80,14 +80,8 @@ namespace xo {
             if (ix >= size_)
                 return false;
 
-            scope log(XO_DEBUG(true), "need write barrier");
-
             mm.barrier_assign(this, &elts_[ix], x);
 
-            //mm.barrier_assign_aux(this,
-            //                      elts_[ix].iface(), elts_[ix].opaque_data_addr(),
-            //                      x.iface(), x.opaque_data());
-
             return true;
         }
 
@@ -104,10 +98,6 @@ namespace xo {
 
                 mm.barrier_assign(this, &elts_[size_], elt);
 
-                //mm.barrier_assign_aux(this,
-                //                      elts_[size_].iface(), elts_[size_].opaque_data_addr(),
-                //                      elt.iface(), elt.opaque_data());
-
                 ++(this->size_);
 
                 return true;
diff --git a/xo-object2/src/object2/DList.cpp b/xo-object2/src/object2/DList.cpp
index 75bde74c..b8494c34 100644
--- a/xo-object2/src/object2/DList.cpp
+++ b/xo-object2/src/object2/DList.cpp
@@ -141,20 +141,15 @@ namespace xo {
         }
 
         void
-        DList::_assign_rest(DList * rest)
+        DList::_assign_rest(obj<AAllocator> mm, DList * rest)
         {
-            scope log(XO_DEBUG(true), "need write barrier");
-
-#ifdef NOT_YET
             obj<AGCObject,DList> rest_gco(rest);
 
             mm.barrier_assign_aux(this,
                                   nullptr /*lhs iface unused*/,
-                                  &(this->rest_),
+                                  (void**)&(this->rest_),
                                   rest_gco.iface(),
                                   rest);
-#endif
-            this->rest_ = rest;
         }
 
         bool
diff --git a/xo-reader2/src/reader2/DExpectQListSsm.cpp b/xo-reader2/src/reader2/DExpectQListSsm.cpp
index 184bcc41..8ea243ca 100644
--- a/xo-reader2/src/reader2/DExpectQListSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectQListSsm.cpp
@@ -184,7 +184,7 @@ namespace xo {
                     if (this->end_) {
                         /* DExpectQListSsm owns {start_, end_} -> preserves acyclic property */
 
-                        end_->_assign_rest(new_last);
+                        end_->_assign_rest(p_psm->expr_alloc(), new_last);
 
                         this->end_ = new_last;
                     } else {